Masterarbeit im Studiengang Environmental Management – Management natürlicher Ressourcen

Impact of wastewater treatment plants on the stream water quality in the upper Stör catchment

Vorgelegt von Staatl. gepr. LMChem. Maria Redeker , im Januar 2011

1. Prüferin: Prof. Dr. Nicola Fohrer 2. Prüferin: Dr. Britta Schmalz

Abteilung Hydrologie und Wasserwirtschaft Institut für Natur und Ressourcenschutz Agrar und Ernährungswissenschaftliche Fakultät ChristianAlbrechtsUniversität zu Kiel Acknowledgements

Diese Arbeit entstand in der Abteilung Hydrologie und Wasserwirtschaft am Institut für Natur und Ressourcenschutz der ChristianAlbrechtsUniversität zu Kiel.

Zuerst möchte ich mich bei Prof. Dr. Nicola Fohrer für die Vergabe des interessanten Themas bedanken, sowie für de Begutachtung der Arbeit und alle wertvollen Anregungen.

Bei Dr. Britta Schmalz bedanke ich mich für die Betreuung, die ständige Diskussionsbereitschaft sowie für wertvolle Anregungen und motivierende Gespräche.

Cristiano Pott danke ich für die gute Zusammenarbeit, die hervorragende inhaltliche und praktische Einarbeitung, sowie viele wertvolle Tips und beantwortete Fragen.

Für die Unterstützung im Labor möchte ich mich bei Monika Westphal, Imke Meyer, Bettina Hollmann, Maya Beyer, Cristiano Pott und Piotr Jamróg bedanken. Monika Westphal danke ich außerdem für aufschlussreiche Diskussionen sowie für Auskünfte zu den Methoden. Paul Zacharias, HansJürgen Voss, Cristiano Pott und Olga Kolychalow danke ich für die Hilfe im Gelände.

Bei Antje Dietrich, Dr. Georg Hörmann und Dr. Claus Schimming bedanke ich mich für hilfreiche Ratschläge zur Auswertung der Ergebnisse.

Bei Herrn Janson und Herrn Haustein vom LLUR, Herrn Nass vom Landkreis Segeberg, Herrn Kienel vom Landkreis Steinburg, Herrn Klenk vom Landkreis Eckernförde, Herrn Seelig vom Landkreis Plön sowie Herrn Kaiser vom Amt bedanke ich mich für die Übermittlung von Daten, für Auskünfte und fachliche Informationen. Ebenso danke ich Herrn Porath von der Firma ROTOX Klärtechnik für die Auskünfte zu den kleinen technischen Kläranlagen.

Herrn Brandt vom Technischen Betriebszentrum Neumünster, Herrn Eberhard von den Gemeindewerken , Frau MarxReese, Klärwärterin in Mörel, und , Herrn Rieper, Klärwerter in , Herrn Nass vom Landkreis Segeberg und Herrn Hopp, Amtsvorsteher vom Amt BokhorstWankendorf danke ich für den Zutritt zu den Kläranlagen, die engagierte Hilfe vor Ort, sowie interessante Führungen und zahlreiche Auskünfte zu den jeweiligen Kläranlagen. Holger Steen vom Landkreis SchleswigFlensburg danke ich für viele wertvolle fachliche Informationen und aufschlussreiche Gespräche.

Dr. Michael Breuer, Katrin Bieger, Frau MarxReese und Herrn Seelig danke ich für die Unterstützung beim Besorgen von Karten. Frau Woike vom Ingenieurbüro Rix+Soll danke ich für die Übermittlung des Gewässsernetzes.

Anna Fr ckiewicz danke ich für viele hilfreiche Auskünfte zu ihrer Masterarbeit. Ebenso danke ich Florian Honsel für Informationen zu seiner Arbeit und die Hilfe bei der Suche nach verschiedenen Informationen.

Olga und Antje danke ich für die spontane Hilfe, Olga, Janine und Rebecca außerdem für die kurzfristigen Einsätze an den Wochenenden und ihre Autos.

Bei meiner Familie und meinen Freunden bedanke ich mich für ihre Unterstützung in jeglicher Hinsicht. Abstract The aim of this thesis was to investigate the impacts of the wastewater treatment plants (WWTPs) in the upper Stör catchment on the water quality of their receiving rivers and ditches by comparing the composition of the effluents with the conditions in the receiving streams. The upper Stör catchment is situated in the centre of SchleswigHolstein in Northern and comprises an area of 468 km 2. There are 23 municipal WWTPs in the upper Stör catchment, 19 were investigated in this thesis. The two largest of them are technical WWTPs with elimination steps for P and N. Five smaller technical WWTPs apply mechanical purification and movingbed biofiltration, whereas the other WWTPs consist of naturally aerated wastewater lagoons. Two parallel sampling campaigns were conducted in the extreme winter months December 2009, January 2010, and February 2010. The results obtained are therefore not representative for the rest of the year, and gained conclusions are only valid for the mentioned period. The first campaign aimed at investigating the water quality of the rivers at the outlets of the sub catchments and is also part of a doctoral thesis (Pott, in prep.) which is currently being developed. The second campaign aimed at assessing the water quality of the streams in the direct vicinity of the WWTP outlets. For the latter one samples were taken from the effluents and from the receiving rivers upstream and downstream of the WWTP outlets. Samples of both campaigns were taken once a month in intervals of four or five weeks. They were analysed for water temperature, electric conductivity, dissolved oxygen, ammonium nitrogen, nitrite nitrogen, nitrate nitrogen, total nitrogen, phosphate phosphorus, total phosphorus, chloride, and sulphate contents. The effluents of the two large WWTPs with N and P elimination had low nutrient but high chloride contents, and the effluents of the lagoons had lower contents than those of the small technical

WWTPs for all parameters except NH 4N, which was, as well as the mostly increasing values from December to February, attributed to dilution effects from rainwater. Whereas the distributions of concentrations in the effluents were well distinguishable, this was not reflected in the magnitude of the impacts the WWTPs exerted on the receiving rivers. They were rather superposed by the size ratio between the single WWTPs and their receiving streams, as well as by the upstream pollutions of the rivers.

Observing the development of NH 4N, PO 4P, and P tot concentrations at selected points from both campaigns revealed highest increases in NH 4N and PO 4P from upstream to downstream of the

WWTPs, followed by gradual decrease further downstream. P tot contents were highest at different points along the streams, which varied from month to month. According to the classification system after LAWA (1998) the adverse effects of the effluents on the

2 streams were on average low for the DO, NO 2N, NO 3N, Cl , and SO 4 contents, which complied with the target class II also downstream of the WWTP outlets. The exception were NO 3N contents (class III), which was due to upstream pollution of the rivers. The parameters of highest concern were NH 4N, N tot , PO 4P, and P tot , which were on average assigned to class IV (excessively contaminated), respectively IIIIV (very heavily contaminated, N tot ) downstream of the WWTPs.

NO 2N contents showed critical pollution (class IIIII) and very heavy contamination (class IIIIV) downstream of single WWTPs. However, upstream contamination was already heavy (class III) in the case of NH 4N and N tot . Also according to the RAKON thresholds (LAWAAO, 2007), the good ecological status is possible to be achieved both upstream and downstream of the WWTPs based on

pH values, DO, and Cl concentrations, but not based on NH 4N, PO 4P, and P tot contents. This demonstrates that although nearly all WWTPs complied with their emission limits for dissolved inorganic N and P tot , which is however not compulsory at low temperatures, they exerted considerable impact on the water quality of the recipients during the sampling period, the ecological consequences of which may be immense.

Table of contents i

Table of contents

1 Introduction...... 1 2 Literature review...... 3 2.1 Water quality of river ecosystems...... 3 2.1.1 Requirements of the European Water Framework Directive...... 3 2.1.2 Current status in Germany...... 4 2.1.3 Processing of nutrients in rivers...... 5 2.1.4 Sources and pathways of nutrients into rivers...... 6 2.1.4.1 Nutrient inputs from diffuse sources...... 7 2.1.4.2 Nutrient inputs from point sources...... 7 2.2 Wastewater treatment plants...... 7 2.2.1 Municipal wastewater...... 7 2.2.2 Sewer systems...... 9 2.2.3 Treatment processes...... 9 2.2.3.1 Mechanical treatment...... 9 2.2.3.2 Biological treatment...... 10 2.2.3.3 Tertiary stage...... 12 2.2.3.3.1 Nitrogen elimination...... 12 2.2.3.3.2 Phosphate elimination...... 15 2.2.4 WWTP types...... 16 2.2.4.1 Sequencing batch reactors...... 16 2.2.4.2 Wastewater lagoons...... 17 3 The upper Stör catchment...... 22 3.1 General description...... 22 3.2 Climate...... 24 3.3 Soils, groundwater situation and land use...... 24 3.4 River network and management practices...... 26 3.5 Wastewater treatment plants in the catchment...... 27 4 Materials and methods...... 30 4.1 Measurement campaigns and selection of sampling points...... 30 4.1.1 Subcatchment campaign...... 30 4.1.2 Wastewater treatment plant campaign...... 32 4.2 Description of the sampling points of the WWTP campaign...... 36 4.3 Weather during the sampling period and effects on the catchment...... 56 4.4 Sampling and measurement of field parameters...... 58 4.4.1 Sampling technique...... 58 4.4.2 Measurement of physicochemical parameters...... 58 4.4.3 Measurement of flow velocity and calculation of discharge...... 59 4.5 Laboratory analyses...... 60

Master thesis – Maria Redeker Table of contents ii

4.5.1 Sample preparation...... 60 4.5.2 Determination of ammonium nitrogen contents...... 61 4.5.3 Determination of orthophosphate phosphorus contents...... 62 4.5.4 Determination of total phosphorus contents...... 62 4.5.5 Determination of nitrite nitrogen, nitrate nitrogen, chloride and sulphate contents...... 63 4.5.6 Determination of total nitrogen contents...... 63 4.5.7 Presentation and evaluation of the results...... 64 4.5.7.1 Time series...... 64 4.5.7.2 Boxandwhiskers plots...... 65 4.5.7.3 Longitudinal river profiles...... 66 4.5.7.4 Discharge of the WWTPs and receiving streams...... 67 4.5.7.5 Comparison with emission limits...... 67 4.5.7.6 Water quality assessment...... 68 5 Results...... 72 5.1 Direct vicinity of the WWTPs...... 72 5.1.1 Water temperature...... 72 5.1.2 pH values...... 75 5.1.3 Dissolved oxygen...... 77 5.1.4 Electric conductivity...... 80 5.1.5 Ammonium nitrogen...... 83 5.1.6 Nitrite nitrogen...... 86 5.1.7 Nitrate nitrogen...... 88 5.1.8 Total nitrogen...... 90 5.1.9 Orthophosphate phosphorus...... 93 5.1.10 Total phosphorus...... 96 5.1.11 Chloride...... 99 5.1.12 Sulphate...... 102 5.2 Longitudinal profiles...... 105 5.2.1 Stör...... 105 5.2.2 Schwale...... 107 5.2.3 Buckener Au...... 109 5.2.4 Fuhlenau...... 111 6 Discussion...... 114 6.1 Effluents...... 114 6.1.1 Physical parameters...... 114 6.1.2 N compounds...... 116 6.1.3 P compounds...... 121 6.1.4 Chloride and sulphate...... 122 6.2 Comparison with emission limits...... 124 6.3 Impacts in the direct vicinity of the WWTPs...... 125 6.3.1 Comparison of parameters...... 125

Master thesis – Maria Redeker Table of contents iii

6.3.2 Comparison of WWTPs...... 128 6.4 Longitudinal profiles...... 138 6.5 Water quality assessment...... 141 6.5.1 Dissolved oxygen...... 142 6.5.2 pH values...... 143 6.5.3 Ammonium nitrogen...... 143 6.5.4 Nitrite nitrogen...... 145 6.5.5 Nitrate nitrogen...... 146 6.5.6 Total nitrogen...... 146 6.5.7 Orthophosphate phosphorus...... 147 6.5.8 Total phosphorus...... 148 6.5.9 Chloride...... 149 6.5.10 Sulphate...... 150 6.5.11 Average water quality over three months...... 150 7 Conclusions and outlook...... 153 References...... 158 Annex...... I

Master thesis – Maria Redeker List of figures iv

List of figures Figure 2.1: Sources and pathways of emissions into surface waters...... 6 Figure 2.2: Scheme of a WWTP with denitrification ...... 14 Figure 2.3: Functional scheme of a naturally aerated lagoon ...... 19 Figure 3.1: Location of the river Stör and the upper Stör catchment...... 22 Figure 3.2: Location of the upper Stör catchment related to districts...... 23 Figure 3.3: The upper Stör catchment...... 23 Figure 3.4: Climate chart of the station Neumünster for the years 1961 – 1990...... 24 Figure 3.5: Location of the upper Stör catchment related to natural zones of SchleswigHolstein.....25 Figure 4.1: Location of the the sampling points of the subcatchment campaign...... 30 Figure 4.2: Location of the sampled WWTPs...... 33 Figure 4.3: Outlet of WWTP L1 and sampling point L1w...... 36 Figure 4.4: Ditch downstream of WWTP L1...... 36 Figure 4.5: Stream network and sampling points at WWTP L1...... 37 Figure 4.6: Führbek with outlet of WWTP L2...... 38 Figure 4.7: Site of the WWTP L4...... 38 Figure 4.8: Stream network at WWTPs L2 and L3...... 39 Figure 4.9: Stream network at WWTP L4...... 40 Figure 4.10: Stream network at the WWTP L5...... 41 Figure 4.11: Outlet of WWTP L5 and two pipes of unknown origin...... 41 Figure 4.12: Buckener Au with entries of ditch 29 and Mühlenbach...... 41 Figure 4.13: Cascade at the outlet of WWTP L6...... 42 Figure 4.14: Manhole with outlet of WWTP L7 and sampling points...... 43 Figure 4.15: Aerial view of the WWTP L8...... 44 Figure 4.16: Sünderbek upstream of WWTP L8...... 44 Figure 4.17: Sünderbek downstream of WWTP L8...... 44 Figure 4.18: White precipitate at the outlet of the WWTP L8 and greyish stain in the water downstream...... 45 Figure 4.19: Last lagoon of WWTP L9 and discharge...... 45 Figure 4.20: Sampling points at WWTP L9 and creek opening into the Stör from the opposite side...... 46 Figure 4.21: Outlet of the WWTP L9...... 46 Figure 4.22: Aerial view of the WWTP L10)...... 47 Figure 4.23: Stream network and sampling points at WWTP L10...... 47 Figure 4.24: Outlet of WWTP L11...... 48 Figure 4.25: Outlet of WWTP L11 with snow cover...... 48 Figure 4.26: Entry of ditch from WWTP L12 into the Dosenbek...... 49 Figure 4.27: Aeration tank with floating bodies at WWTP MB1...... 49 Figure 4.28: Frozen pipe upstream of WWTP MB2...... 51 Figure 4.29: Stream network and sampling points at WWTP MB2...... 51 Figure 4.30: Schwale downstream of entry of ditch 1.12...... 52 Figure 4.31: Entry of ditch 1.12 into Schwale...... 52 Figure 4.32: Visible part of WWTP MB3...... 52 Figure 4.33: Outlet of WWTP MB3...... 52 Figure 4.34: Stream network and sampling points at WWTP MB4...... 53 Figure 4.35: Aasbek and outlet of WWTP MB5...... 54 Figure 4.36: Bünzener Au and outlet of WWTP NP1 at the end of a discharge period...... 55 Figure 4.37: Cascades in the Bullenbek upstream of the bridge at Ehndorfer Weg in Neumünster....56

Master thesis – Maria Redeker List of figures v

Figure 4.38: Temperatures and precipitation during the sampling period at the station ...57 Figure 4.39: Measurement of flow velocity with FlowSens ...... 59 Figure 4.40: Example of a boxandwhiskers plot...... 66 Figure 5.1: Water temperatures in the effluents and receiving streams...... 73 Figure 5.2: Boxandwhiskers plots of the water temperatures upstream, in the effluents and downstream of the WWTPs, and changes from upstream to downstream for the different WWTP types...... 74 Figure 5.3: pH values in the effluents and receiving streams...... 76 Figure 5.4: Boxandwhiskers plots of the pH values upstream, in the effluents and downstream of the WWTPs, and changes from upstream to downstream for the different WWTP types ...... 77 Figure 5.5: Boxandwhiskers plots of the dissolved oxygen contents upstream, in the effluents and downstream of the WWTPs, and changes from upstream to downstream for the different WWTP types...... 78 Figure 5.6: Dissolved oxygen contents in the effluents and receiving streams...... 79 Figure 5.7: EC in the effluents and receiving streams...... 81 Figure 5.8: Boxandwhiskers plots of the EC upstream, in the effluents and downstream of the WWTPs, and changes from upstream to downstream for the different WWTP types ....82 Figure 5.9: NH 4N contents in the effluents and receiving streams...... 84

Figure 5.10: Boxandwhiskers plots of the NH 4N contents upstream, in the effluents and downstream of the WWTPs, and changes from upstream to downstream for the different WWTP types ...... 85 Figure 5.11: Boxandwhiskers plots of the NO 2N contents upstream, in the effluents and downstream of the WWTPs, and changes from upstream to downstream for the different WWTP types ...... 86 Figure 5.12: NO 2N contents in the effluents and receiving streams...... 87

Figure 5.13: NO 3N contents in the effluents and receiving streams...... 89 Figure 5.14: Boxandwhiskers plots of the NO 3N contents upstream, in the effluents and downstream of the WWTPs, and changes from upstream to downstream for the different WWTP types ...... 90 Figure 5.15: N tot contents in the effluents and receiving streams...... 91 Figure 5.16: Boxandwhiskers plots of the Ntot contents upstream, in the effluents and downstream of the WWTPs, and changes from upstream to downstream for the different WWTP types...... 92 Figure 5.17: PO 4P contents in the effluents and receiving streams...... 94 Figure 5.18: Boxandwhiskers plots of the PO4P contents upstream, in the effluents and downstream of the WWTPs, and changes from upstream to downstream for the different WWTP types ...... 95

Figure 5.19: P tot contents in the effluents and receiving streams...... 97 Figure 5.20: Boxandwhiskers plots of the Ptot contents upstream, in the effluents and downstream of the WWTPs, and changes from upstream to downstream for the different WWTP types ...... 98 Figure 5.21: Cl contents in the effluents and receiving streams...... 100 Figure 5.22: Boxandwhiskers plots of the Cl contents upstream, in the effluents and downstream of the WWTPs, and changes from upstream to downstream for the different WWTP types ...... 101 2 Figure 5.23: SO 4 contents in the effluents and receiving streams...... 103 2 Figure 5.24: Boxandwhiskers plots of the SO 4 contents upstream, in the effluents and downstream of the WWTPs, and changes from upstream to downstream for the different WWTP types ...... 104

Master thesis – Maria Redeker List of figures vi

Figure 5.25: Location of the sampling points S6, S7, and S9 and the WWTP L9 at the Stör...... 105 Figure 5.26: Longitudinal profile of NH 4N contents in the river Stör and the effluent of the WWTP L9...... 105 Figure 5.27: Longitudinal profile of PO 4P contents in the river Stör and the effluent of the WWTP L9...... 106 Figure 5.28: Longitudinal profile of P tot contents in the river Stör and the effluent of the WWTP L9...... 106 Figure 5.29: Location of the sampling points S2, S4, S5 and the WWTPs L11 and MB2 relative to the Schwale...... 107

Figure 5.30: Longitudinal profile of NH 4N contents in the river Schwale, the effluent of the WWTP L11 and the entry of the ditch 1.12 transporting effluent from the WWTP MB2...... 107 Figure 5.31: Longitudinal profile of PO 4P contents in the river Schwale, the effluent of the WWTP L11 and the entry of the ditch 1.12 transporting effluent from the WWTP MB2...... 108 Figure 5.32: Longitudinal profile of P tot contents in the river Schwale, the effluent of the WWTP L11 and the entry of the ditch 1.12 transporting effluent from the WWTP MB2...... 108 Figure 5.33: Location of the sampling points S17, S18 and the WWTPs L5, L7, L2 and L3 relative to the Buckener Au...... 109

Figure 5.34: Longitudinal profile of NH 4N contents at the points S18 and S17 in the river Buckener Au and the entry of the ditch 29 transporting effluent from the WWTP L5...110

Figure 5.35: Longitudinal profile of PO 4P contents at the points S18 and S17 in the river Buckener Au and the entry of the ditch 29 transporting effluent from the WWTP L5...110 Figure 5.36: Longitudinal profile of P tot contents at the points S18 and S17 in the river Buckener Au and the entry of the ditch 29 transporting effluent from the WWTP L5...... 111 Figure 5.37: Location of the sampling point S16 and the WWTP L1 relative to the Fuhlenau...... 111 Figure 5.38: Longitudinal profile of NH4N contents at the entry of the Gliner Graben transporting effluent from the WWTP L1 and the point S16 in the river Fuhlenau...... 112 Figure 5.39: Longitudinal profile of PO4P contents at the entry of the Gliner Graben transporting effluent from the WWTP L1 and the point S16 in the river Fuhlenau...... 112 Figure 5.40: Longitudinal profile of Ptot contents at the entry of the Gliner Graben transporting effluent from the WWTP L1 and the point S16 in the river Fuhlenau...... 113 Figure 6.1: Contents of the inorganic nitrogen compounds NH 4N, NO 2N, and NO 3N and N tot in the effluents of the WWTPs...... 116 Figure 6.2: Percental shares of the inorganic nitrogen compounds NH 4N, NO 2N, and NO 3N in N tot ...... 117 Figure 6.3: PO 4P contents and P tot contents in the effluents...... 121 Figure 6.4: Shares of PO 4P in P tot in the effluents...... 121

Master thesis – Maria Redeker List of tables vii

List of tables Table 2.1: Major forms of nitrogen and phosphorus found in natural waters...... 5 Table 2.2: Main components of municipal sewage in Germany...... 8 Table 2.3: Classification of wastewater components with adverse effects on receiving water bodies...... 8 Table 3.1: Percentage of population connected to WWTPs...... 28 Table 3.2: Municipal WWTPs in the upper Stör catchment...... 29 Table 4.1: Overview of the sampling points of the subcatchment campaign...... 31 Table 4.2: Sampling days of the subcatchment campaign and the WWTP campaign...... 32 Table 4.3: Overview of the WWTP campaign sampling points...... 34 Table 4.4: Overview of applied methods, their quantification limits and underlying standard methods...... 61 Table 4.5: Reasons for missing data...... 65 Table 4.6: Classification of water quality according to LAWA (1998)...... 68 Table 4.7: Water quality classification of nutrients, salts and sum parameters according to LAWA (1998)...... 69 Table 4.8: Background levels regarding general physicochemical components in German rivers according to RAKON monitoring (LAWAAO, 2007)...... 70 Table 4.9: Benchmarks regarding general physicochemical components in German rivers according to RAKON monitoring (LAWAAO, 2007)...... 70 Table 6.1: DIN emission limits of the WWTPs and sums of NH 4N, NO 2N and NO 3N contents measured in the effluents...... 124

Table 6.2: P tot emission limits of the WWTPs and P tot contents measured in the effluents...... 124 Table 6.3: Mimima, maxima, and medians of the absolute values of percental deviation of the results measured in the WWTP effluents from the results measured upstream...... 126 Table 6.4: Mimima, maxima, and medians of the absolute values of percental deviation of the results measured downstream of the WWTPs from the results measured upstream...... 127 Table 6.5: Comparison of the percental deviation of selected parameters measured in the effluent of Marlborough WWTP from the values measured upstream with the percental deviation of the same parameters measured downstream of Marlborough WWTP from those measured upstream, based on data after Neal et al. (2008b)...... 128 Table 6.6: Comparison of the proportions of the WWTPs, expressed in connected PE, and the receiving streams, expressed in m 3/s of discharge...... 129 Table 6.7: Percental increases of P tot and DON contents from upstream to downstream of four WWTPs in the Avon catchment compared to connected PE, based on data after Bowes et al. (2005)...... 136

Table 6.8: Percental changes of NO 3N, NH 4N, and PO 4P contents from upstream to downstream of Marlborough WWTP under baseflow conditions prior to and after introduction of P elimination and under stormflow conditions in the subsequent winter, based on data after Neal et al. (2000)...... 137 Table 6.9: Classification of average dissolved oxygen contents upstream and downstream of the WWTPs according to LAWA (1998)...... 142 Table 6.10: Classification of average dissolved oxygen contents upstream and downstream of the WWTPs according to RAKON (LAWAAO, 2007)...... 142 Table 6.11: Classification of average pH values upstream and downstream of the WWTPs according to RAKON (LAWAAO, 2007)...... 143

Table 6.12: Classification of average NH 4N contents upstream and downstream of the WWTPs according to LAWA (1998)...... 143

Master thesis – Maria Redeker List of tables viii

Table 6.13: Classification of average NH 4N contents upstream and downstream of the WWTPs according to RAKON (LAWAAO, 2007)...... 143

Table 6.14: Classification of average NO 2N contents upstream and downstream of the WWTPs according to LAWA (1998)...... 145

Table 6.15: Classification of average NO 3N contents upstream and downstream of the WWTPs according to LAWA (1998)...... 146 Table 6.16: Classification of average N tot contents upstream and downstream of the WWTPs according to LAWA (1998)...... 146 Table 6.17: Classification of average PO 4P contents upstream and downstream of the WWTPs according to LAWA (1998)...... 147 Table 6.18: Classification of average PO 4P contents upstream and downstream of the WWTPs according to RAKON (LAWAAO, 2007)...... 147 Table 6.19: Classification of average P tot contents upstream and downstream of the WWTPs according to LAWA (1998)...... 148

Table 6.20: Classification of average P tot contents upstream and downstream of the WWTPs according to RAKON (LAWAAO, 2007)...... 148 Table 6.21: Classification of average Ptot contents upstream and downstream of the WWTPs according to LAWA (1998)...... 149 Table 6.22: Classification of average Ptot contents upstream and downstream of the WWTPs according to RAKON (LAWAAO, 2007)...... 149 Table 6.23: Classification of average Ptot contents upstream and downstream of the WWTPs according to LAWA (1998)...... 150 Table 6.24: Water quality classification of the investigated parameters according to LAWA (1998) based on the overall arithmetic means of the sampling points upstream and downstream of the WWTPs in the three sampling months...... 151 Table 6.25: Water quality classification of the investigated parameters according to RAKON (LAWAAO, 2007) based on the overall arithmetic means of the sampling points upstream and downstream of the WWTPs in the three sampling months...... 151

Master thesis – Maria Redeker List of abbreviations ix

List of abbreviations BG background level BM benchmark BOD biochemical oxygen demand Cl chloride COD chemical oxygen demand DIN dissolved inorganic nitrogen DIP dissolved inorganic phosphorus DO dissolved oxygen DON dissolved organic nitrogen DOP dissolved organic phosphorus DWD Deutscher Wetterdienst (German Meteorological Sevice) EC electric conductivity IQR interquartile range L wastewater lagoon MB small technical wastewater treatment plant applying mechanical treatment and activation

NH 4N ammonium nitrogen

NO 2N nitrite nitrogen

NO 3N nitrate nitrogen

Ntot total nitrogen PE population equivalents PHB poly hydroxbutyrate PIP particulate inorganic phosphorus PON particulate organic nitrogen POP particulate organic phosphorus

PO 4P orthophosphate phosphorus

Ptot total phosphorus SBR sequencing batch reactor

2 SO 4 sulphate TDN total dissolved nitrogen TDP total dissolved phosphorus TON total oxidisable nitrogen

Master thesis – Maria Redeker List of abbreviations x

WFD Water Framework Directive WW wastewater WWTP wastewater treatment plant NP technical wastewater treatment plant applying mechanical treatment, activation, and tertiary nitrogen and phosphate elimination Q1 1 st quartile Q3 3 rd quartile

Master thesis – Maria Redeker 1. Introduction 1

1 Introduction Apart from physical alterations affecting the hydromorphology of rivers, their water quality is affected by the input of chemical substances, at which the nutrients nitrogen (N) and phosphorus (P) play a major role (Feldwisch & Frede, 1999). Enhanced nutrient availability causes various problems, such as toxic algal blooms, oxygen depletion, fish kills, loss of biodiversity, aquatic plant beds and coral reefs. Thus, nutrient enrichment seriously degrades aquatic ecosystems, but also impairs the use of water for anthropogenic purposes such as drinking, industry, agriculture, and recreation (Carpenter, 1998). Besides diffuse sources, such as agricultural activities, erosion, or surface runoff, effluents from wastewater treatment plants (WWTPs) contribute a significant input of nutrients (Neal et al., 2005; Pieterse et al., 2003), usually in highly bioavailable form, which are accompanied by considerable loads of readily degradable organic material (Mainstone & Parr, 2002). WWTPs appear to be the primary ecological risk factor for P inputs in many lowland rivers. Especially sewage effluents from WWTPs without nutrient elimination steps in smaller settlements discharging into ecologically sensitive tributaries are of primary concern (Jarvie et al., 2006). For an improvement of the current status of water bodies, the European Commission has adopted the Water Framework Directive (WFD; EC, 2000), which demands a holistic basin wide approach to water protection (Neal & Jarvie, 2005) and aims at the achievement of a “good ecological status” for all water bodies until the year 2015. This comprises for surface waters a “good chemical status”. One of the major requirements is the reduction of nutrient inputs into water bodies. To achieve this, it is important to identify the contributing processes and sources (Pieterse, 2003). There have been a number of studies identifying the contribution of point sources to the nutrient status of river ecosystems in terms of absolute values, i.e. loads (e.g., Benedetti et al., 2008; Pieterse et al., 2003; Withers et al., 2009; Wood et al., 2005) or by characterising the behaviour of certain N and P compounds, e.g. respective to discharge or to tracers, such as boron or chloride (e.g., Howden et al., 2008; Jarvie et al., 2006; Neal et al., 2008a). Neal et al. (2005) compared the composition, in terms of concentrations, of the effluent from six WWTPs with the upstream water quality in the receiving river Dun in UK. In two further studies the water quality along the river Kennet in UK was investigated with the aim to examine the impact of effluent from a WWTP on the receiving water and the downstream water quality changes (Neal et al., 2000, 2008b). However, concerning catchmentwide investigation of water quality at sewage disposal points and its changes from upstream to downstream, which is

Master thesis – Maria Redeker 1. Introduction 2 important to define the conditions for the existence of life and which, in case of impaired conditions, requires a certain distance from the point of discharge to recover from the impact, there still appears to be need for research.

The Stör catchment has been investigated in a number of scientific projects, diploma and doctoral theses, which focused on the modelling of discharge (Dobslaff, 2005), nutrient inputs and retention (Venohr, 2000), and on the assessment and modelling of the water and nutrient balance (Jelinek, 1999). Both latter theses were based on data from the socalled “StörProjekt” (Ripl et al., 1996), which was part of a series of research projects concerning the “modelbased development of ecologically defined rehabilitation concepts using the example of small running waters” funded by the Federal Ministry of Education and Research (Bundesministerium für Bildung und Forschung, BMBF) and aimed at the development of a management concept to reduce nutrient emissions. Recent work deals with the investigation of water quality in terms of nutrients and physicalchemical parameters in the upper Stör catchment along the river Stör and its main tributaries (Fr ckiewicz, 2010) and in the subcatchments (Pott, in prep.).

The main aim of this thesis is to investigate the impacts of the municipal WWTPs, i.e. point sources, in the upper Stör catchment on the water quality of their receiving rivers and ditches by comparing the composition of the effluents with the conditions in the receiving streams. Based on two campaigns conducted in three winter months of 2009/2010, changes in the direct vicinity of WWTP outlets are assessed and compared to the composition of the effluents. In addition, they are compared to selected points further upstream and downstream in the receiving rivers. To determine the ecological status upstream and downstream of the WWTPs, the water quality is assessed according to the classification after LAWA (1998) and the RAKON monitoring guidance (LAWAAO, 2007). The sampling took place under extreme conditions in the winter months of 2009/2010 and therefore does not reflect the typical conditions, but rather a “worst case” situation concerning the performance of the WWTPs. A second thesis is currently being developed on the basis of data sampled in the summer months of 2010 (Honsel, in prep.).

Master thesis – Maria Redeker 2. Literature review 3

2 Literature review

2.1 Water quality of river ecosystems Water quality comprises the physical, chemical, and biological characteristics of a water body, which acquires these characteristics from a suite of complex interactions among the water, atmosphere, soils, and lithology and can be affected by human activities (Peters et al., 2005). The chemical characteristics of water bodies comprise the nutrients, which are the elements essential for life and whose supply potentially limits metabolic processes in streams. N and P are, together with carbon and silicon, the nutrients most heavily utilised by the river biota (Allan, 1995). Both may limit the growth rate or biomass yield of aquatic plants and thus cause eutrophication when they reach water bodies in elevated concentrations. In water bodies without anthropogenic impact especially P is present only in low amounts and thus more often than N the limiting factor for plant growth. In brooks which are extremely low in nutrients, already small P inputs implicate enhanced bacterial and algal production (Uhlmann & Horn, 2001). The primary effect of enhanced nutrient availability is thus an increased yield of aquatic plants, which leads to a shift in the species composition, as less sensitive, generalist species displace more sensitive, often endangered, species which are adapted to low nutrient availability. The quick development of certain species causes algal blooms. The secondary effect is the depletion of oxygen when dead algae are decomposed, which in turn causes a further deterioration of water quality and eventually the extinction of aquatic communities (Feldwisch & Frede, 1999). In addition, nutrients can have direct toxic effects on aquatic organisms: ammonium is under alkaline conditions (pH > 8) and high temperatures converted to ammonia, which is toxic to fish and can be lethal at concentrations from 0.3 mg/L (Ellis, 1989, cited in Heathwaite, 1993).

Chronic toxicity can emerge at concentrations as low as 0.02 mg/L to 0.3 mg/L NH 3N and induce intoxication and necrosis in the gills. Also nitrite, which occurs as an intermediate in nitrification and denitrification processes, has toxic effects on fish and invertebrates (Uhlmann & Horn, 2001).

2.1.1 Requirements of the European Water Framework Directive The "Directive 2000/60/EC of the European Parliament and of the Council establishing a framework for the Community action in the field of water policy" or, in short, the EU Water

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Framework Directive (WFD), claims a “good status” until 2015 for all water bodies (inland surface waters, transitional waters, coastal waters and groundwater), which comprises in the case of rivers, i.e. surface water bodies, both a good ecological and a good chemical status, which are in turn defined by certain quality elements. According to Article 4 associated with Annex V of the WFD, the good ecological status is given if both biological and hydromorphological quality elements show low levels of distortion resulting from human activity, but deviate only slightly from those normally associated with the surface water body type under undisturbed conditions. To reach a good chemical status, temperature, oxygen balance, pH, acid neutralising capacity and salinity as well as nutrients must not reach levels outside a range which ensures the functioning of the type specific ecosystem and the achievement of the values specified for the biological quality elements, whereas nutrients are mentioned separately.

2.1.2 Current status in Germany By the end of 2004 9,000 German river water bodies were identified and assessed for their ecological and chemical status (BMU, 2005). The assessment showed that 61 % of the investigated water bodies were at risk of failing to achieve a good ecological status by 2015. 24% of the water bodies were possibly at risk of failing the WFD objectives, while only 15% were likely to achieve them. For the chemical status results were more positive. Approximately 63% of the water bodies assessed will probably meet the environmental objectives of the Directive, 28% were possibly at risk of failing the objectives, in some cases owing to a lack of data or the fact that the assessments did not include measuring data, and 9% of the water bodies assessed were at risk of failing the objectives (BMU, 2005). Primary reasons for failing the objectives were physical alterations affecting the hydromorphology and river continuity, as well as inputs of nutrients and other pollutants (BMU, 2005). The Stör as well as all of its major tributaries are at risk of failing to achieve the objectives, with exception of one water body. Also in the Stör catchment the major deficits concern morphological alterations, whereas data are insufficient to estimate the physicalchemical status for most of the water bodies. In the upper Stör catchment four out of ten water bodies are likely to achieve the target water class, while two water bodies are at risk to fail it, and for the rest of the water bodies there are insufficient data available to allow for an assessment. Six water bodies are at risk not to achieve a good overall ecological status, whereas for the rest there are not enough data available to allow for an estimation (MLUR, 2004).

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2.1.3 Processing of nutrients in rivers Nutrients occur in water bodies in various chemical forms as ions or dissolved gases in solution. The major forms of N and P found in natural waters are listed in Table 2.1.

Table 2.1: Major forms of nitrogen and phosphorus found in natural waters (Allan, 1995 after Meybeck, 1982) Nitrogen dissolved inorganic nitrogen (DIN): + NO 3 , NO 2 , NH 4 total dissolved nitrogen (TDN) total nitrogen dissolved organic nitrogen (DON) particulate organic nitrogen (PON) Phosphorus dissolved inorganic phosphorus (DIP): 3 PO 4 total dissolved phosphorus (TDP) dissolved organic phosphorus (DOP) total phosphorus particulate organic phosphorus (POP) particulate inorganic phosphorus (PIP)

They are transformed into the particulate phase by physical and chemical processes, as well as by metabolic activities. More precisely, these processes include adsorption, flocculation, chemical precipitation, assimilation and excretion (Allan, 1995). The principal pathways of cycling differ among the nutrients. Phosphorus is subject to a number of biological processes, such as assimilation of DIP by plants and microbes into cellular constituents, thereby being transformed into POP; release during cell lysis or excretion of DIP and DOP; and bacterial mineralisation of DOP to DIP. In addition, the availability of P is influenced by physicalchemical transformations, i.e. by abiotic processes. These include,

3 depending on DIP concentrations, sorption and desorption of PO 4 ions onto and from charged clays and organic particles, as well as under aerobic conditions complexing reactions with metal oxides and hydroxides to form insoluble precipitates, which are released under anaerobic conditions.

+ Nitrogen transforming processes include assimilation of DIN, preferentially NH 4 , by autotrophs, bacteria and funghi; nitrogen fixation by bacteria and cyanobacteria, which thereby

+ convert N 2 gas into NH 4 and incorporate it into biomass; excretion of respectively

+ + decomposition to NH 4 ; sorptiondesorption reactions of NH 4 with clays and humic materials,

+ which to some extent buffer NH 4 concentrations; and nitrificationdenitrification pathways, which result in a loss of N, in the form of N 2, from the system (Allan, 1995).

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2.1.4 Sources and pathways of nutrients into rivers Nutrients in water bodies originate both from natural and anthropogenic sources. Natural pathways of nutrients into the water bodies include on the one hand release from rocks and soils by weathering and subsequent transport in solution by runoff, and on the other hand wet and dry precipitation of winderoded terrestrial dust and salts originating in sea spray (Allan, 1995). Natural background loads amount to 5 kg/(ha·a) for nitrogen and to 0.05 0.1 kg/(ha·a) for phosphorus, which lead to concentrations below 2.5 mg/L and 0.05 mg/L for nitrogen and phosphorus, respectively (Feldwisch & Frede, 1999). Anthropogenic inputs into German surface waters accounted for 465 kt/a of N and 23 kt/a of P in 2005 (UBA, 2006). The principal anthropogenic sources of emissions into water bodies are agriculture, municipal WWTPs, power plants, transport and industrial plants. They can be subdivided into point sources and diffuse sources, as shown in Figure 2.1 and described in the following sections.

Figure 2.1: Sources and pathways of emissions into surface waters (UBA, 2006 after Fuchs & Scherer, 2002)

Most of the phosphorus loading to inland surface waters is attributable to discharges from point sources, especially municipal sewage and industrial effluent, whereas nitrogen loading originates primarily from agricultural activity, especially from the use of nitrogen fertilisers and manure (Thyssen, 1999).

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2.1.4.1 Nutrient inputs from diffuse sources Diffuse sources comprise the inputs from widespread areas, which are not well locatable (Feldwisch & Frede, 1999), such as atmospheric deposition, erosion, runoff, groundwater, drainage, and sealed urban surfaces (Thyssen, 1999). Inputs from diffuse sources are often intermittent and linked to seasonal agricultural activity or irregular events, such as heavy precipitation or major construction (Carpenter et al., 1998). In 2005 diffuse sources had a share of 82 % in total N input, at which groundwater made up the main pathway (48 % of total N input). Compared to 1985 N inputs from diffuse sources were reduced by 24 % (UBA, 2006). The share of diffuse sources in total P inputs accounted for 65 % in 2005. The main pathways were erosion (22 % of total P input) and groundwater (20 % of total P input). P inputs from diffuse sources was reduced by 29 % compared to 1985 (UBA, 2006). Agricultural inputs accounted for ca. 70 80 % of total N inputs and ca. 55 % of total P inputs into surface waters in 2005 (UBA, 2006).

2.1.4.2 Nutrient inputs from point sources Point sources are well locatable and include the direct inputs from municipal sewage systems and industrial dischargers (Thyssen, 1999). Inputs from point sources tend to be continuous, with little variability over time (Carpenter et al., 1998). They had a share of 18 % in total N inputs in 2005. Compared to 1985 N inputs from point sources were reduced by 76 %, mainly due to improved performance of WWTPs. With a share of 35 % point sources constituted the dominant pathway of total P inputs in 2005, although they had been reduced compared to 1985 by 86 % (UBA, 2006).

2.2 Wastewater treatment plants

2.2.1 Municipal wastewater Municipal wastewater (WW) is a mixture of a high number of substances (Koppe et al., 1999). The main components are domestic WW (sewage from private households, municipal establishments, and smaller trade companies), sewage from greater commercial and industrial companies, hospitals, and barracks, and “imported” water (water redirected from springs and brooks in the 1 st half of the 20 th century, drainages, and groundwater which may intrude at leaky points of the sewer system) (Mudrack & Kunst, 2003; Koppe et al., 1999). Domestic WW has five main components, which are listed together with their usual variety in Table 2.2 (Koppe et al., 1999).

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Table 2.2: Main components of municipal sewage in Germany (Koppe et al., 1999) Specific daily amount of Component sewage per person (L/d) drinking, cooking, and dishwasher water 3 – 10 urine and feces 1 – 3 toilet water, WC 10 – 10 cleaning and washing water 5 – 50 washing, bathing, and shower water 5 – 500

WW contains various substances which exert adverse effects on water bodies. They can be grouped as oxygen depleting substances, nutrients, toxic substances, and endocrine effective substances (Table 2.3).

Table 2.3: Classification of wastewater components with adverse effects on receiving water bodies (after Mudrack & Kunst, 2003) oxygen depleting endocrine effective Group nutrients toxic substances substances substances xenobiotics, Example BOD , COD * N, P heavy metals 5 synthetic hormones Adverse impaired oxygen excessive primary hormonelike effects, intoxication effect balance of waters production impaired health * BOD: biochemical oxygen demand; COD: chemical oxygen demand

BOD 5 and COD are measures for the content of oxygen depleting organic carbon (C) compounds. BOD 5 is the mass of oxygen required for aerobic decomposition of biologically oxidisable WW constituents over a period of five days at 20 °C. COD is the mass of oxygen equivalent to the mass of potassium dichromate which reacts under defined conditions with the oxidisable constituents (Mehlhart, 1997). Depending on the structure and size of the connected municipalities, the different lifestyles of the inhabitants and the shares of industries, different amounts of WW can arise (Mudrack & Kunst, 2003). The typical range of domestic wastewater discharge in Germany is 100 – 150 L/d per inhabitant (ATVDVWK, 2003). The water supply to German households was 122 L/d per inhabitant (Statistisches Bundesamt, 2011), whereas not all water delivered to households is discharged as wastewater. Discharge and concentrations of municipal sewage show strong variations and typical patterns in course of a day, with minima at night and maxima in the morning. As the minima and

Master thesis – Maria Redeker 2. Literature review 9 maxima of both coincide, even stronger variations arise for the pollutant loads (Mudrack & Kunst, 2003).

2.2.2 Sewer systems In combined sewer systems rainwater runoff is collected together with the WW. As the rainwater discharge may amount to 100fold of the WW, storage structures such as rainwater retention basins have to be included into the system at appropriate positions to keep the sewer cross sections in technically and economically feasible dimensions. If the discharge surmounts a certain value, part of the combined sewage is discharged via these structures into the next water body, which experiences thereby a certain burden, depending on the amount and pollution of the discharged water (Mudrack & Kunst, 2003). In separate sewer systems WW and rainwater are collected separately. The WW is directed to the WWTP, whereas rainwater and unpolluted water of other origin is discharged directly into the receiving water body, assuming that the pollution of the rainwater is so low that a treatment prior to discharge is not required. However, in the case of polluted surfaces, faulty connections of WW pipeworks or especially high demands on the water quality, a purification of the rainwater may be necessary (Mudrack & Kunst, 2003).

2.2.3 Treatment processes Treatment processes of municipal WWTPs comprise at least a mechanical and a biological stage. An additional stage may be adopted for the elimination of N and P compounds.

2.2.3.1 Mechanical treatment In the mechanical stage solid material is removed from the wastewater. Large particles are removed by screens or reduced in size by grinding devices. Inorganic solids are removed in grit channels, and much of the organic suspended solids is removed by sedimentation (Halling Sørensen & Jørgensen, 1993). The first stage consists of screening plants for the removal of coarse particles. A subsequent grit chamber is passed by the sewage with reduced velocity, allowing settling particles to sediment. In a grease trap grease and other floating particles are dragged together and skimmed from the surface, emulsified grease is precipitated as foam via aeration (Schwoerbel & Brendelberger, 2005). Also fine suspended particles are thereby swirled up and can be removed with the grease (Schönborn, 2003). The following primary sedimentation tank allows for slow sedimentation of finer organic particles within a period of about 2 h. Sedimented sludge is

Master thesis – Maria Redeker 2. Literature review 10 removed from the tank (Schwoerbel & Brendelberger, 2005; Schönborn, 2003). Suspended solids which do not settle within this period reach the biological stage (Schönborn, 2003).

2.2.3.2 Biological treatment The biological treatment processes are an intensified form of the self purification processes proceeding in natural waters. The aim is an extensive mineralisation of the organic substances contained in wastewater (Schwoerbel & Brendelberger, 2005), by which carbohydrates, proteins and fats are degraded to carbon dioxide, water, sulphate, nitrate, and phosphates (Schönborn, 2003). The microorganisms thereby gain energy, which they store in the form of ATP (Mudrack & Kunst, 2003). Two usually applied processes are the activated sludge process and treatment with trickling filters.

Activated sludge process The activated sludge process is based on the mechanisms proceeding in river ecosystems. Dissolved organic matter is converted into settleable biomass via uptake and metabolisation by bacteria, which thereby coagulate to flocs, settle and can be removed (Schönborn, 2003). It takes place in a socalled activation tank, a reactor in which the pretreated WW is aerated. Thereby the degrading organisms are suspended in the WW and prevented from sedimentation (Schwoerbel & Brendelberger, 2005). A high number of species is involved in the process, often several hundreds. Most bacteria are small and compact, while only few filamentous bacteria are involved. The flocs have diameters of 50 to > 800 µm and embed inorganic compounds (ca. 30 %). Also the nonsettleable particles and colloidal substances originating from the primary settling tank can form aggregates and settle (Schönborn, 2003). Bacteria in the outer layers of activated sludge flocs are very active, whereas those in the core zone show less activity. A minimum oxygen concentration of 0.1 mg/L is required in the core zone. Also bacteriovorous protozoa and metazoa are present in the flocs. Due to the bacteriovory the bacteria are kept in the exponential growth phase, which means that their production is stimulated. Ciliates (a group of protozoans) consume both bacteria and flagellates, so that the system tend to an equilibrium between bacteria, zooflagellates, and ciliates, at which the zooflagellates are extremely bacteriovorous (Schönborn, 2003). Also a nitrification is desired already in the activated sludge process. As nitrifying bacteria have relatively long generation times, the sludge age, i.e. the detention time of sludge in the

Master thesis – Maria Redeker 2. Literature review 11 tank, has to account for at least about 8 10 days and the oxygen depletion must be low (Schönborn, 2003). A secondary sedimentation basin is connected downstream of the aeration basin. It serves for sedimentation of the sludge flocs and thereby clearing of the treated water. Settling in a separate tank allows for the withdrawal of a high amount of biomass. Part of the sludge, the so called return sludge, is returned to the aeration tank to ensure a consistent concentration of biomass and a compensation of variations in concentration (Schönborn, 2003). If nitrification occurs in the aeration tank, a strong denitrification may arise in the anaerobic sludge of the secondary sedimentation basin. Ascending molecular nitrogen swirls up the sedimented sludge, which is unfavourable for the settling process. Therefore often a denitrification basin is installed between the aeration tank and the secondary sedimentation basin. If the core zones of the flocs are anaerobic, denitrification may already arise in the aeration basin (Schönborn, 2003). If filamentous bacteria become dominant in the aeration tank, the sludge bulks instead of forming flocs, which means failure of the treatment process. In recent times, also foam formation emerges at the surface of the aeration and secondary sedimentation tanks due to massreproduction of certain actinomycetes, which trap bubbles of air and nitrogen and arise due to surfaceactive substances in the WW. This foam has to be skimmed and may not be used as return sludge (Lemmer, 1992, cited in Mudrack & Kunst, 2003).

Trickling filters Trickling filters simulate the microbenthic system. The towertype trickling filters are round or rectangular containers with a diameter (or width, respectively) of 7 8 m and a height of 4 5 m. They are filled with a porous material, which constitutes an interstitial. Water from the primary sedimentation tank is sprayed above this porous material. Trickling filters are not aerated artificially, but by the air intruding to the container from above and below. In the enormous pore volume a bacterial mat develops, on which a speciesrich system establishes. Organic pollutants are decomposed rapidly, the BOD 5 is reduced by about 80 %. Throughput time is often less than one hour. The microorganisms are consumed by many protozoans, rotatoria, and nematodes. These organisms in turn are grazed by large oligochaetes. This causes a bioturbation in the bacterial mat and allows for a deep intrusion of oxygen. This system of intensive energy flow and grazing stimulate the degradation performance of the microorganisms; both microorganisms

Master thesis – Maria Redeker 2. Literature review 12 and their predators are kept in the exponential growth phase. Simultaneously the sprayed water clears the pores and carries detached parts of the bacterial mat. Disturbance may arise when the pollution of the wastewater is too high, as the bacterial mat may obtain densities and heights which do not allow for sufficient clearing by the sprayed water. The pores then get clogged, oxygen does not intrude sufficiently deep, and the base of the mat becomes anoxic. Big parts of the mat detach and thereby cause again growth, which connotes a homoeostasis of the system within certain borders. However, the performance of the system decreases. In the lowest zone of the passage nitrification processes arise. While in the 3 rd , anaerobic zone

+ substances such as NH 4 are abundant, the lower zone is oxic, as air intrudes from below, and nitrification processes arise. If the water is returned into the biofilter and the bacterial mat is relatively dense, denitrification can take place in its anoxic basis (Schönborn, 2003).

Biofiltration Trickle filters are a method of biofiltration. Further examples for biofiltration are fixedbed reactors, where water is continuously or periodically led over a carrier material, rotating contactors, or movingbed reactors, where the substrate consists of small floating bodies which are kept floating by mixing and aeration.

2.2.3.3 Tertiary stage As the pure mechanical and biological treatment processes were not designed for the elimination of N and P compounds, a further treatment stage has to be applied for their removal.

2.2.3.3.1 Nitrogen elimination Domestic WW contains about 30 50 mg/L N (Schwoerbel & Brendelberger, 2005). The major portion of N compounds in municipal WW are reduced N compounds such as ammonia, urea, amines, amino acids, or protein, whereas oxidised N compounds such as nitrate or nitrite are usually not present in relevant amounts. The ammonia in raw municipal WW is mainly derived from urine and is formed in the sewer system by enzymatic cleavage of urea with ureases:

NH 2CONH 2 + H 2O CO 2 + 2 NH 3 (eq. 1).

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The residence time of the water in the sewer is not long enough for a significant contribution of ammonia from other sources, such as proteolysis and deamination of the amino acids (Gallert & Winter, 1999). About 25 30 % of the N present in WW are converted into bacterial biomass and removed from the system with the surplus sludge. If the rest is not degraded further than to ammonium, the effluent contains high ammonium contents, which pollute the receiving waterbody (Schwoerbel & Brendelberger, 2005). Biological N elimination is realised, as in natural water bodies, by nitrification and denitrification (Schönborn, 2003). Nitrification by autotrophic nitrifyers consists of two steps, namely nitritation (equation 2) and nitration (equation 3). The former one describes the oxidation of ammonium to nitrite by ammonium oxidisers (e.g., Nitrosomonas ), the latter one the oxidation of nitrite to nitrate by nitrite oxidising bacteria (e.g., Nitrobacter ):

+ + NH 4 + 1.5 O 2 NO 2 + 2 H + H 2O (eq. 2),

NO 2 + 0.5 O 2 NO 3 (eq. 3). These processes constitute the energyyielding processes for autotrophic growth of the nitrifying bacteria (Gallert & Winter, 1999), which use reduced inorganic N compounds as electron donor and O 2 as ele ctron acceptor. The C source required for cell growth is CO 2

+ (Mehlhart, 1997). Since high NH 4 concentrations have toxic effects on Nitrobacter , the role of

+ Nitrosomonas is not only to supply NO 2 , but also to degrade high concentrations of NH 4 (Mudrack & Kunst, 2003). The energy yield of nitrifying bacteria is very low. Nitrosomonas requires oxidation of 30 g

NH 3 to form 1 g of cell dry mass. Therefore nitrifying bacteria have, compared to the heterotrophic bacteria present in the activated sludge, a low growth rate, which in addition strongly depends on temperature. They will develop only in a biocoenosis which allows for a certain minimum residence time. This residence time is in the activated sludge process identical with the sludge age, which depends on the nutrient supply (BOD 5) of the activated sludge: an increased BOD 5 causes increased development of biomass, which in turn requires an increased withdrawal of excess sludge and thereby results in a reduced sludge age. This dependence is determined by growth of the heterotrophic bacteria, which consume the organic substances present in WW. Nitrifiers depend on the sludge age of the heterotrophic bacteria and can only survive if it exceeds their doubling time (Mudrack & Kunst, 2003).

Denitrification is the reduction of the oxidised N compounds NO 3 and NO 2 to molecular N 2. This process is catalysed by heterotrophic aerobic bacteria which are able to switch their

Master thesis – Maria Redeker 2. Literature review 14 oxidative metabolism from oxygen respiration (equation 4) to nitrate respiration (equation 5). Similar to oxygen respiration they require a complex C source as an electron source (in the given examples, methanol; however a variety of compounds have been evaluated to serve as C source for denitrification (several authors, cf. HallingSørensen & Jørgensen, 1993)) (Gallert & Winter, 1999; Mudrack & Kunst, 2003):

2 CH 3OH + 3 O 2 2 CO 2 + 4 H 2O (eq. 4)

5 CH 3OH + 6 NO 3 5 CO 2 + 7 H 2O + 3 N 2 + 6 OH (eq. 5). As the energy yield from nitrate respiration is about 10 % lower than that from oxygen respiration, the organisms preferentially use free oxygen for respiration and switch to nitrate oxidation only under anoxic conditions (Mudrack & Kunst, 2003).

Denitrification starts with the reduction of NO 3 to NO 2 by membranebound nitrate reductase A (a). A membranebound nitrite reductase (b) catalyses the formation of NO, and eventually the NO reductase (c) and N 2O reductase (d) form N 2 (Gallert & Winter, 1999):

e2 e e e (eq. 6). NO 3 a NO 2 b NO c 0.5N 2O d N5.0 2 To avoid flotation and drifting of activated sludge in the secondary sedimentation tank, in practice a denitrification tank, which is stirred instead of aerated to allow for anoxic conditions, is installed upstream of the aeration tank (Figure 2.2). Thereby the entire load of inflowing

+ nutrients is available as electron donors. NH 4 containing compounds pass this tank unchanged

and are nitrified in the aeration basin. The emergent NO 3 is returned to the denitrification basin together with the return sludge and additionally in an internal recirculation of the water in the aeration tank. By 4fold recirculation about 80 % of the nitrate can be denitrified (Mudrack & Kunst, 2003).

influent DT AT ST effluent NH + + - - 4 NH 4 NO 3 NO 3 - NO 3 N 2

internal recirculation return sludge

Figure 2.2: Scheme of a WWTP with denitrification (DT: denitrification tank, AT: aeration tank, ST: secondary sedimentation tank) (after Mudrack & Kunst, 2003)

As oxygen deficiency prevents the growth of nitrifiers in the denitri fication tank, the sludge age required for nitrification and denitrification increases to 9 17 days (Imhoff, 1993).

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Further advantages of denitrification are the yield of oxidation equivalents, which correspond to 2.9 g O 2 / g NO 3N, or 63 % of the 4.6 g O 2 required for nitrification of 1 g NH 4N, and the consumption of protons, which accounts for 50 % of the protons released by nitrification (Mudrack & Kunst, 2003).

2.2.3.3.2 Phosphate elimination Wastewater contains on average 10 mg/L phosphates, about half of which are orthophosphates. However, only orthophosphate is available for elimination (Schönborn, 2003). The elimination of P compounds can be achieved by chemical and biological processes. In the chemical elimination, phosphates are precipitated with salts, such as ferrous or ferric sulphate, aluminium sulphate, aluminium chloride, or calcium hydroxide. The precipitation is often conducted downstream of the secondary stage (postprecipitation), but is possible also upstream (preprecipitation) or in the aeration tank (simultaneous precipitation). Post precipitation has the highest efficiency, as also the particles passing the secondary sedimentation tank can settle. However, this method requires a separate tank. Preprecipitation has the disadvantage that too much P is eliminated from the activation tank, so that filamentous bacteria may become predominant and bulking sludge develops. Simultaneous precipitation requires the least space, prevents formation of bulking sludge, and improves the settleability of the sludge flocs (Höll, 2002; Schönborn, 2003). Biological phosphate elimination is based on the capability of certain bacteria to assimilate orthophosphate in excess of their current demand and store it as polyphosphate granula (voluntin) (Mudrack & Kunst). As an essential nutrient for the bacterial metabolism, P is permanently assimilated during the activated sludge process and eliminated to a certain extent with the surplus sludge (Höll, 2002). Many bacteria store phosphates as polyphosphate only in the case of P shortage. Certain bacteria are also capable to assimilate and store phosphate without the requirement of precedent deficit (“luxury uptake”). However, stress such as growth limitation by shortage of a nutrient (e.g., nitrogen, sulphur) (Mudrack&Kunst, 2003) or the change from aerobic to anaerobic conditions (Schönborn, 2003) appears to stimulate phosphate uptake. Technically, in an anaerobic tank upstream of the aeration tank (often combined with the primary sedimentation tank) facultative anaerobic bacteria ferment readily degradable polymers to organic acids (e.g., acetic acid). They serve as substrate for the present aerobic phosphateassimilating bacteria to build up storage materials, such as poly hydroxybutyrate (PHB). The required energy is gained from breakdown of the polyphosphate storage, which is

Master thesis – Maria Redeker 2. Literature review 16 linked to a redissolution of orthophosphate. Owing to the ability to grow under anaerobic conditions and synthesis of storage materials, these organisms have a competitive advantage over other aerobic bacteria, allowing for an accumulation of these species in the biocoenosis of the activated sludge (Schönborn, 2003; Mudrack & Kunst, 2003). In the aerobic stage an enormous reaccumulation of orthophosphate to fill up the polyphosphate storage sets in. The uptake rate is directly proportional to the rate of preliminary redissolution and uptake exceeds the redissolution. The required energy is gained from PHB and external organic substances, so that the amount of storage material within the cell decreases (Schönborn, 2003; Mudrack & Kunst, 2003). In the secondary sedimentation tank the polyphosphate storing bacteria settle and are removed with the excess sludge. However, stipulated P contents in the effluents cannot be achieved by exclusive application of biological P elimination. Primarily it serves to reduce the amount of precipitants and thus to avoid an increase in salinity in the effluents (Höll, 2002).

2.2.4 WWTP types Apart from the continuous flow systems, which consist of several tanks arranged in series, several variations of WWTP designs exist. In this section two variations which are applied in the upper Stör catchment are presented.

2.2.4.1 Sequencing batch reactors Sequencing batch reactors (SBRs) are a fillanddraw version of the activated sludge process. Metabolic reactions and solidliquid separation are executed in one tank in a well defined and continuously repeated time sequence, whereas in the continuous flow the sequence of processes rather space oriented. The wastewater is batchwise introduced into the tank, treated for a defined period of time, and eventually removed from the tank (Morgenroth & Wilderer, 1999). The first activated sludge plants ever built worked according to the principles of an SBR (Ardern & Lockett, 1914). However, for the lack of proper control technology and clogging of the aerators, they were soon converted into continuous flow systems. Today, with improved technical means, both systems are equally applicable and competitive (Morgenroth & Wilderer, 1999). The SBR process is characterised by a series of process phases, namely fill, react, settle, and decant, each lasting for a defined time period. In sum, they make up a process cycle which is progressively repeated. As filling only makes up a fraction of the cycle time, usually more than

Master thesis – Maria Redeker 2. Literature review 17 one SBR is used to handle the continuous inflow of wastewater. SBR plants consist of a number of SBRs operated in parallel. Optional components are an influent holding tank upstream of the SBRs, and an effluent buffer tank downstream. The latter is applied to smooth the variations in the effluent flow range, which is of especial significance for large SBR plants discharging into small water bodies (Morgenroth & Wilderer, 1999). SBRs can be operated according to the respective process objective by different combinations and numbers of fill, mix, aeration, settle and draw phases. For denitrification and biological P elimination periods without oxygen supply are required, but mass transfer of wastewater components, such as organic material and nitrate, needs to be ensured, which is realised by mixing without aeration. Oxygen is introduced by aeration for the oxidation of organic and inorganic WW compounds. In addition it provides sufficient mixing and removal of reaction products, such as CO 2, from the water (Morgenroth & Wilderer, 1999). The duration of the phases is controlled by a timer which can easily be adjusted to the current situation. Thus the system offers a greater flexibility of changing operation conditions than the continuous flow system. The basic process characteristics during every single cycle can be monitored by online measurements. A combination of both can directly be used to optimize the operation, e.g. to extend the duration of aeration in case of a peak load of N for achieving complete nitrification, or to reduce aeration time if all ammonia has been oxidised before the termination of the aerobic phase in order to save energy (Morgenroth & Wilderer, 1999).

2.2.4.2 Wastewater lagoons WW lagoons are a method of seminatural WW treatment. In contrast to the relatively compact technical WW treatment methods, they belong to the largescale methods (ATV, 1985). In Germany the application of WW lagoons is usually restricted to rural areas with only few thousand population equivalents (PE) connected (Mudrack & Kunst, 2003). They are artificial basins applied for a biological treatment of WW, which depending on the groundwater table and the permeability of the soil are sealed artificially (Lorch, 1997). As the technical treatment methods, the functioning of WW lagoons is based on the self purification processes of natural water bodies, and mainly differs in the intensity of the microbial processes. WW lagoons are limnic ecosystems (Lorch, 1997), which can be regarded as closely analogous to nutrientrich shallow natural water bodies. Diverse variations of lagoon WW treatments are in use, which can be classified by various aspects. An established classification according to the German Association for Water, Wastewater and Waste (Deutsche Vereinigung für Wasserwirtschaft, Abwasser und Abfall,

Master thesis – Maria Redeker 2. Literature review 18

ATV) distinguishes settling lagoons, naturally and technically aerated lagoons, and polishing lagoons: Settling lagoons serve for sedimentation and decomposition of settleable WW

components. Due to high concentrations of BOD 5, oxygen depletion exceeds oxygen uptake. Thus both water and sludge are anaerobic. The retention time accounts for at

least 1 day and the reduction of BOD 5 30 % 60 %. Usually they are applied as preliminary stage in a multiplestage lagoon WWTP (Mudrack & Kunst, 2003). Naturally aerated lagoons are supplied with oxygen by natural aeration, i.e. by physical and biological processes, via the waterair interface. The oxygen content thus depends on climatic conditions. The upper part of the water body is usually aerobic, while the lower part and the sludge are usually anaerobic. For sufficient oxygen supply the maximum depth of naturally aerated lagoons should be 1 – 1.5 m. They have usually less than 1,000 PE connected (Lorch, 1997). The retention time of the water in naturally aerated lagoons accounts for several days or weeks (ATV, 1985). Physical oxygen input occurs via the waterair interface, depending on disturbance of the surface by wind, surface/volume ratio, temperature, and oxygen saturation. Biogenous oxygenation is given by photosynthesis, which depends on light availability and therefore takes place only during the day. In the absence of light respiration of the autotrophic organisms prevails and contributes to oxygen depletion. Ice cover in winter prevents physical oxygen supply. However, the transmittance of clear ice allows for photosynthesis by (the reduced amount of) autotrophic organisms, as long as the ice sheet is not covered by snow (Mudrack & Kunst, 2003). Technically aerated lagoons allow for a smaller surface and a greater depth (up to 3.5 m) than naturally aerated lagoons, for a shorter retention time, and can have up to 5,000 PE connected. They are aerated e.g. by surface aerators, at which simultaneously the water is revolved without swirling up sludge (Lorch, 1997). Appropriately designed aerated WW lagoons allow for a yearround highly efficient WW and sludge treatment (Mudrack & Kunst, 2003). For the settlement of suspended particles a sedimentation zone or lagoon is required (Neumann, 1987). Polishing lagoons are installed for further purification of biologically treated WW concerning suspended particles, residual organic pollution, inorganic nutrients, and hygienic aspects (Neumann, 1987). Usually they are designed as unaerated lagoons. To

Master thesis – Maria Redeker 2. Literature review 19

avoid redissolution of phosphates from settled sludge, they should be aerobic down to the watersludge interface (Mudrack & Kunst, 2003). An overview of the mechanisms in a naturally aerated lagoon is given in Figure 2.3.

wind

precipitation irradiation evaporation raw WW (physical

aeration) day night

c i

photolithotrophic organisms b o

CO 2, H 2O, r e

biogenic aeration min. nutrients a dissolved organic

substances chemoorganotrophic organisms

c

i b

particulate matter o

r

e

a n

anaerobic bacteria org. acids, CO 2, CH 4, H 2, H 2S, NH 3 a

Figure 2.3: Functional scheme of a naturally aerated lagoon (after Neumann, 1987)

Purification mechanisms take place at the watersludge and waterair interfaces, as well as within the water body. Organic and inorganic solids settle to the sediment, where the organic constituents are degraded by anaerobic and possibly aerobic processes, and intermediates are released into the water. Oxygen is taken up at the waterair interface by physical aeration, and gaseous and volatile degradation products, such as carbon dioxide, methane, and under certain conditions hydrogen sulphide and ammonia, are emitted. Transformations within the water and at sediment interfaces can be of physicalchemical and biological/biochemical nature. The former ones comprise neutralisation, reductionoxidation, precipitation, flocculation, and sorption processes, the latter ones dissimilatory and assimilatory processes (Neumann, 1987). The biological processes are mediated by the following groups of organisms: Aerobic and anaerobic heterotrophic microorganisms degrade organic substances, partly under oxygen depletion, to build up cellular constituents and to gain energy. Autotrophic organisms (e.g. phytoplancton, algae, macrophytes, reeds) assimilate inorganic compounds (e.g. ammonium, nitrate, phosphate, carbon dioxide) released from heterotrophic decomposition and thereby eliminate nutrients from the water; they gain energy from photosynthesis and therewith provide oxygen for the aerobic heterotrophic organisms. The elimination of carbon dioxide may lead to

Master thesis – Maria Redeker 2. Literature review 20 a biogenous decalcification, which in turn causes a strong increase of pH. Metazoa (e.g. zooplankton, daphniae, insect larvae, fish) provide biological filtration, assimilate readily degradable organic compounds from the sludge and act as top predators (Neumann, 1987; Mudrack & Kunst, 2005). Dead biomass settles to the sediment, where it is subject to degradation processes (Neumann, 1987). Due to complex interactions in the system, the physical, chemical, and biological processes can not be clearly separated, and interdependences exist between the different mechanims. Also aerobic, facultative aerobic and anaerobic zones do not exhibit defined borders. The significance of the different factors and the composition of the biocoenosis depend on the kind and intensity of pollutions (Neumann, 1987), but also on external conditions such as temperature, light availability, and oxygen supply. Due to their long retention time also organisms with long generation times can develop, and thereby an adaptation to slowly degradable substances is possible (Mudrack & Kunst, 2003). Mechanisms discussed for N removal in WW lagoons are nitrification and denitrification, ammonia volatilisation, sedimentation of organic nitrogen via biological uptake and with particulate WW constituents, although disagreement exists concerning the main route (e.g., Maynard et al., 1999; Lai & Lam, 1995). Nitrification and denitrification do not appear to play a major role, because of the lack of sufficient surface area for the attachment of nitrifying bacteria, and as low concentrations of nitrite and nitrate are observed in the effluents (Ferrara & Avci, 1982; Reed, 1985; Toms et al., 1975), although Lai & Lam (1995) found those processes to be the major N removal pathway in a system of eight lagoons in Australia, and also Santos and Oliveira (1987) concluded that nitrification occurred in a tertiary lagoon in Portugal. Several studies cited in Maynard et al. (1999) have concluded that ammonia volatilisation at pH values > 10 is the main pathway, whereas Ferrara & Avci (1982) found sedimentation of organic nitrogen via biological uptake to be the main mechanism, and Reed (1985) assumed volatilization to dominate under warmer conditions in summer, and benthic deposition under colder conditions in winter. However, it is generally believed that the efficiency of N removal is related to temperature, pH, and detention time (Lai & Lam, 1995). Removal mechanisms for P in WW lagoons comprise deposition of inorganic P with particulate matter, uptake of inorganic P from the water column by algae and bacteria converting it to organic P, and deposition of organic P with biomass (Houng & Gloyna, 1984). Toms et al. (1975), Houng & Gloyna (1984), and Mara & Pearson (1986, cited in Maynard et al., 1999) found P removal to be preliminary governed by the presence of algae, at which Toms et al. (1975) concluded the major mechanism to be the precipitation of P as hydroxyapatite as a

Master thesis – Maria Redeker 2. Literature review 21

result from increased pH values caused by the photosynthetic uptake of CO 2 from bicarbonate, rather than the uptake by algae itself. However, P may be released from the sediments in the case of P shortage in the water column and under anaerobic conditions at the sedimentwater interface (Houng & Gloyna, 1984). Advantages of unaerated lagoons are the low financial and technical effort, the low requirements for maintenance work, good performance and a high process stability, the high buffer capacity concerning peak loads and variations in the amount of inflowing water, the simultaneous treatment of rainwater, and that the effort for sludge treatment merely consists in clearance in annual or perennial periods. Disadvantages are the required space, insufficient nitrification, denitrification and P elimination, and limited opportunity for operational measures to optimise the performance (Mudrack & Kunst, 2003; Lorch, 1997).

Master thesis – Maria Redeker 3. The upper Stör catchment 22

3 The upper Stör catchment

3.1 General description The river Stör is a North German lowland river. It has a total length of about 83 km and is thus the largest tributary of the river Elbe in the federal state SchleswigHolstein. Its catchment has a total area of about 1,780 km 2. The Stör originates near Willingrade, about 10 km southeast of the town Neumünster and opens into the Elbe near Glückstadt, about 15 km southwest of the town Itzehoe (Figure 3.1). Its width varies from 0.5 m in Willingrade to ca. 10 m in Kellinghusen and 150 m in the estuary. The downstream section up to the village Kellinghusen is influenced by the tide (MLUR, 2004).

Figure 3.1: Location of the river Stör and the upper Stör catchment (Landesvermessungsamt SchleswigHolstein, 2005; modified)

The upper Stör catchment is the catchment of the tidalfree part of the Stör, from its origin near Willingrade to the gauge in Willenscharen. It is situated in the centre of the federal state SchleswigHolstein (Figure 3.1), has an area of 468 km 2 and belongs, as a part of the Stör catchment, to the Elbe river basin. It is dominated by rivers of the types 14 (small sand dominated lowland rivers), 16 (small graveldominated lowland rivers), and 19 (small streams in riverine floodplains) according to the German classification (LAWA, 2003).

Master thesis – Maria Redeker 3. The upper Stör catchment 23

The catchment covers parts of the districts RendsburgEckernförde, Plön, Segeberg, and Steinburg as well as the city of Neumünster, which is situated in the centre of the catchment (Figure 3.2).

Figure 3.2: Location of the upper Stör catchment related to districts (Landesvermessungsamt SchleswigHolstein, 2005)

The upper Stör catchment expands from north to south over 19 km from to Willenscharen, and from west to east over 35 km from to Trappenkamp (Figure 3.3).

Figure 3.3: The upper Stör catchment (LANU, 2003)

Master thesis – Maria Redeker 3. The upper Stör catchment 24

3.2 Climate The climate in the upper Stör catchment, as in whole SchleswigHolstein, can be described as moderately maritime (Riedel, 1987) and is mainly influenced by the Azores highpressure system and the Islandic lowpressure system. It is characterised by mainly westerly winds and advection. In summer convective conditions may arise (Jelinek, 1999).

100 18

90 16

80 14 70 12 60 10 50 8 40 °C / T 6 30 precipitationmm / 20 4

10 2

0 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

precipitation temperature

Figure 3.4: Climate chart of the station Neumünster for the years 1961 – 1990 (DWD, 2006, 2007)

Figure 3.4 shows the climate chart for the station Neumünster of the DWD (Deutscher Wetterdienst, German Meteorological Service), which is situated approximately in the centre of the catchment, for the years 1961 – 1990. The average temperature in the mentioned period accounted for 8.4 °C and the average annual precipitation for 875 mm (DWD, 2006, 2007). Evaporation in the catchment depends on the type of land use and varies between 380 mm/a to 400 mm/a on arable land and grassland and 600 mm/a to 700 mm/a on coniferous woodland (Jelinek, 1999). December, January, and February were the coldest months in the given period, with average temperatures of 1.6 °C, 0.2 °C, and 0.8 °C. February represented the month with the lowest average monthly precipitation (48 mm) (DWD, 2006, 2007).

3.3 Soils, groundwater situation and land use The upper Stör catchment extends into three of the four natural zones of SchleswigHolstein (Figure 3.5). The central and main part of the area belongs to the Low Geest (Niedere Geest), the western part to the High Geest (Hohe Geest), and the eastern part to the Eastern Upland (Östliches Hügelland).

Master thesis – Maria Redeker 3. The upper Stör catchment 25

Figure 3.5: Location of the upper Stör catchment related to natural zones of SchleswigHolstein (Landesvermessungsamt SchleswigHolstein, 2005)

The Eastern Upland has the most pronounced relief and contains mainly boulder clay, sandy soils and gravel (Fränzle, 1981). The High Geest has less pronounced relief and contains mainly Podsol and Braunerde, according to the German nomenclature (AdhocArbeitsgruppe Boden, 2005). The Low Geest is characterised by sandy soils, with mainly EisenHumus Podsol, GleyPodsol, and PodsolGley soils (Finnern, 1997) (Annex, Figure 2). Lowland catchments like the upper Stör catchment are characterised by nearsurface groundwater levels, which can be explained mainly by low slopes and a positive water budget throughout the year (Kluge & Jelinek, 1999). The saturated zone is subject to seasonal variation. In winter groundwater is recharged due to low evapotranspiration. As the shallow groundwater is fed by infiltration, variation in groundwater levels is mainly influenced by precipitation. Shallow groundwater occurs especially in glacial outwash plains of the Low Geest (Venohr, 2000). The Eastern Upland and the High Geest have higher depths to ground water. In push moraines of the High Geest they can account for 10 m and more, whereas in the crests in the southeast of the catchment they can amount to more than 40 m (Dobslaff, 2005). The geology in the eastern upland is very heterogeneous. Aquifers can therefore occur in very different depths, and both waterlogging and zones of deeper groundwater levels exist (Kluge, 2002 cited in Dobslaff, 2005).

Master thesis – Maria Redeker 3. The upper Stör catchment 26

The landscapes in the upper Stör catchment developed mainly under anthropogenic impacts and have changed a lot in course of the centuries (Ripl, 1996). Land use is dominated by agriculture, with about 77 % of the surface. About 49 % of the area are used as arable land, about 28 % as grassland and pasture. About 12 % are covered with forest, the main share of which is made up by the Staatsforst Neumünster forests and the nature park Aukrug. Urban area accounts for 10 %, of which the main part is made up by the city of Neumünster with nearly 800,000 citizens. The Einfelder See is the only lake with a significant size in the catchment and accounts for less than 1 % of the area. Also the bog Dosenmoor, remnants of the Großes Moor in the east of Nortorf, and other small wetlands only have a minor share (2 %) (Corine Landcover, EEA 2006; cf. Annex, Figure 1).

3.4 River network and management practices The river network of the catchment has a total length of more than 600 km. Drainage ditches account for about half of the length, rivers and streams for about 47 %. The rest consists of partly piped gap closures, small reservoirs and ponds (Basisgewässernetz LANU SH, 2003, 1:25,000). Bünzener Au and Schwale are the largest tributaries of the Stör (Figure 3.3). Other significant tributaries under consideration in this thesis are Buckener Au and Fuhlenau. Schwale originates in the eastern upland near Gönnebek and opens into the Stör between Neumünster and Padenstedt after about 20 km. It is one of the streams which have no or only slight morphological deficits and therefore indicate a good ecological state (MLUR, 2004). It is classified as type 16 and as type 14 in the last kilometres. The vicinity of the Schwale is primarily of agricultural use, and in its last 6 km it passes the city of Neumünster. Bünzener Au is the main water course in the western part of the catchment, draining about 44 % of the area (Dobslaff, 2005). It originates at the junction of Buckener Au and Fuhlenau in the north of AukrugInnien and opens into the Stör about 2.5 km upstream of the gauge in Willenscharen. It is classified as type 14. The Buckener Au has a length of about 11 km and classified as type 19. Its catchment area covers approximately 60 km 2 and is mainly used agriculturally (73 %). It is traversed by several smaller streams and ditches (Martini, 2000). The Buckener Au originates near Nienjahn at the western edge of the upper Stör catchment and is followed up by the Bünzener Au. It is one of few streams in the catchment with still existent natural morphological structures (MLUR, 2004). In a renaturation project from 1987 to 1991 nearnatural structures were also reconstructed (Martini, 2000).

Master thesis – Maria Redeker 3. The upper Stör catchment 27

Fuhlenau has a length of about 6 km and is classified as type 16. It originates near the Bargstedter Moor, about 3 km northwest of the village . It opens into the Bünzener Au at the point where it follows up the Buckener Au. During the past century the landscape and the river network were subject to significant changes by hydraulic engineering. An increasing need for agricultural land use due to growing population lead to straightening, deepening and canalising of many river sections, construction of drainage systems, and extension of ditch systems. The functioning of the ecosystem was thereby altered considerably, in a way that the water table decreased and the water balance became more dynamic. Beginning in the 1980s renaturation measures were decided and implemented. One of the first measures in the upper Stör catchment was the renaturation of the upper Buckener Au, in which near natural conditions of the river were reconstructed by flattening and widening of river profiles, removal of canalised sections, construction of sand traps, and planting of trees (e.g., black alder) (Martini, 2000). The Bearbeitungsgebietsverband Nr. 13 Oberlauf Stör (13 th Area of Operation Upper Stör) set up in a rough concept an array of water management measures for the Stör catchment, which aims at the improvement of chances to achieve a good ecological status, which is one of the major goals of the WFD. The measures were to be implemented until 2009. They were set up separately for single rivers in the catchment and include the regeneration of river continuity, reduction of nutrient loss by establishing riparian vegetation, improvement of the ecological and river channel structures, reduction of maintenance, increase of the water table, the compensation of nutrient loss, and the acquisition of land for the extensive use as permanent grassland and for development of deciduous woods (BGV Oberlauf Stör, 2005).

3.5 Wastewater treatment plants in the catchment In the districts parts of which belong to the upper Stör catchment between 89.9 % and 99.8 % of the population are connected to WWTPs (Table 3.1).

Master thesis – Maria Redeker 3. The upper Stör catchment 28

Table 3.1: Percentage of population connected to WWTPs (MLUR, 2005) Percentage of population District connected to WWTPs Neumünster (city) 99.8 % Plön 92.2 % RendsburgEckernförde 91.3 % Segeberg 95.5 % Steinburg 89.9 %

There are 23 municipal WWTPs with a design capacity of > 50 PE in the upper Stör catchment. At the end of 2008 they had a total design capacity of 394,985 PE and 121,679 PE actually connected (LLUR, 2009). An overview of the WWTPs in the catchment is given in Table 3.2. The majority of WWTPs in the catchment apply WW lagoons as treatment technology, of which four are aerated technically, whereas 12 function with natural aeration. They have each between 34 and 1,140 PE connected. There are five smaller technical WWTPs which apply mechanical treatment and activation and have between 92 and 223 PE connected. The two major WWTPs in Neumünster and AukrugBünzen with design capacities of 380,000 PE respectively 7,000 PE and actually connected 110,816 PE respectively 4,000 PE are technical WWTPs which apply in addition to mechanical treatment and activation also nitrification, denitrification, biological and chemical P elimination processes. Most of the WWTPs thus fall within the size category 1. Only the WWTPs in Neumünster, AukrugBünzen, and Gnutz fall within the size categories 5, 3, and 2, respectively. The WW lagoons are connected to combined sewer systems, while the municipalities with technical WWTPs are provided with separate sewer systems. Further information about the single WWTPs is given in section 4.2.

Master thesis – Maria Redeker 5. Results Table 3.2: Municipal WWTPs in the upper Stör catchment (modified after LLUR, 2009) design volume of combined / WWTP size connected treatment location receiving stream capacity wastewater 2008 separate sewer no. category PE technology** (PE) (m 3) system L1 Gnutz Fuhlenau 2 1,200 1,140 l 141,300 c L2 Mörel Ost Führbek 1 260 224 la *** c L3 Mörel West Führbek 1 70 34 l *** c L4 Tappendorf Grenzgraben 1 410 342 l *** c L5 Grauel ditch 29 1 360 230 l *** c L6 Poyenberg Poyenberger Bek 1 400 409 l 33,911 c

Master thesis Maria– Redeker L7 AukrugHomfeld Steenbek 1 300 365 l 58,000 c L8 Groß Kummerfeld Sünderbek 1 790 831 l 112,600 c L9 Kleinkummerfeld Stör 1 360 394 l 53,550 c L10 Kleink.Bahnhof ditch H 4 1 220 171 l 31,425 c L11 Gönnebek Nord Schwale 1 220 211 l 35,840 c L12 Negenharrie Dosenbek 1 690 314 l *** c MB1 Wittbek 1 200 126 m/b 4,769 s MB2 Petersberg ditch 1.12 1 150 103 m/b *** s MB3 Hollenbek ditch 1.6 1 340 223 m/b *** s MB4 Schipphorst ditch 1.6 1 150 150 m/b *** s MB5 Hüttenwohld ditch 1.4 1 140 92 m/b *** s NP1 AukrugBünzen Bünzener Au 3 7,000 4,000 m/b/n/d/biop/p 248,068 s NP2 Neumünster Bullenbek 5 380,000 110,816 m/b/n/d/biop/p 9,317,621 s * Bokhorst ditch 1.4.1.1 1 550 473 la *** s * Gönnebek Süd Sünderbek 1 400 400 la 58,300 c * Willingrade Stör 1 600 524 la 59,500 c * BraakSiedlung ditch H 9 1 175 107 l 14,000 c * not sampled within the frame of this thesis ** l: naturally aerated WW lagoons, la: technically aerated WW lagoons, m: mechanical treatment, b: activation, n: nitrification, d: denitrification, biop: biological P elimination, p: chemical P elimination *** not specified 29 4. Materials and methods 30

4 Materials and methods

4.1 Measurement campaigns and selection of sampling points In the frame of this thesis two different measurement campaigns were realised in the months December 2009, January 2010, and February 2010. The first campaign aimed at the water quality at the outlets of the subcatchments of the upper Stör catchment, the second campaign, which constitutes the main focus of this thesis, at the impacts of wastewater treatment plants on the stream water quality in the catchment.

4.1.1 Subcatchment campaign This campaign was conducted in collaboration with a doctoral thesis which is being developed in the Department of Hydrology and Water Resources Management at the ChristianAlbrechts University Kiel since August 2009. The results of the subcatchment campaign presented in this thesis are also part of the mentioned doctoral thesis (Pott, in prep.). In the frame of the mentioned doctoral thesis, water samples are taken once a month at the outlets of the subcatchments of the upper Stör catchment within a period of two years. Sampling days in the scope of this Master thesis were December 16, 2009, January 13, 2010, and February 17, 2010.

Figure 4.1: Location of the the sampling points of the subcatchment campaign

Master thesis – Maria Redeker 4. Materials and methods 31

Sampling points had been chosen at the outlets of each subcatchment. To allow for comparison with data from earlier projects (Dobslaff, 2005; Ripl, 1996), the position of the sampling points from those projects had been largely adopted. Another criterion to define the exact position of the sampling points was their accessibility. The position of the sampling points is depicted in Figure 4.1 and summarized in Table 4.1. They are numbered in the order of sampling.

Table 4.1: Overview of the sampling points of the subcatchment campaign Sampling point River Location S1 Dosenbek downstream of Naturschutzgebiet Dosenmoor S2 Schwale gauge Brachenfeld, upstream entry of Dosenbek downstream gauge Tungendorf, Brachenfelder S3 Dosenbek Gehölz S4 Schwale Bönebüttel, bridge at road K16 between Neuenrade and Husbergermoor, ca. S5 Schwale 1 km downstream entry of ditch 1.12 S6 Stör upstream entry of Sünderbek S7 Stör Neumünster near Kiebitzweg S8 Padenstedter Au Padenstedt, bridge at road K12 gauge Padenstedt, downstream entry of S9 Stör Padenstedter Au MLUR measuring point Aalbek, , S10 Aalbek bridge at K34 MLUR measuring point , S11 Bredenbek Dithmarsische Berge S12 Mitbek Gauge BökenHöllenau, AukrugBöken S13 Mitbek upstream connection with Höllenau S14 Höllenau , bridge at road K46 S15 Himmelreichbach forest Gehege Himmelreich, upstream pasture S16 Fuhlenau near Gnutz, ca. 1 km downstream of WWTP near Waldesruh, upstream entry of stream at S17 Buckener Au bridge at road K81 S18 Buckener Au near Grauel, upstream entry of Poyenberger Bek S19 Wischbek upstream entry into Bünzener Au S20 Bünzener Au gauge Sarlhusen, upstream of entry into Stör S21 Stör gauge Willenscharen

Master thesis – Maria Redeker 4. Materials and methods 32

4.1.2 Wastewater treatment plant campaign In this campaign the same water quality parameters as in the subcatchment campaign were assessed in the effluents of wastewater treatment plants as well as in the direct vicinity (upstream and downstream) in the receiving rivers and ditches. This should serve as a basis on which to estimate the impacts of point sources on the overall water quality in the catchment. As the WWTP campaign made up the main part of work of the thesis, the sampling points and results from this campaign will be described more detailed. However, for their discussion against the background of the stream water quality, part of the results from the subcatchment campaign will be included. Sampling for this campaign was planned to take place once a month within two days before and two days after the sampling days of the subcatchment campaign. For organizational reasons and due to limited time at daylight, in December 2009 and January 2010 the sampling periods had to be extended (see details at the description of the individual WWTPs in section 4.2). Table 4.2 gives an overview of the sampling days of the WWTP campaign compared to those of the subcatchment campaign.

Table 4.2: Sampling days of the subcatchment campaign and the WWTP campaign Sampling days sub-catchment campaign Sampling days WWTP campaign 14.15.12.2009, 16.12.2009 17.20.12.2009 11.12.01.2010, 13.01.2010 14.16.01.2010, 28.01.2010 15.16.02.2010, 17.02.2010 18.19.02.2010

The locations of the WWTPs in the catchment are depicted in Figure 4.2. Nomenclature for the different WWTP types is as follows: wastewater lagoons: L, WWTPs applying mechanical purification and activation: MB, WWTPs applying tertiary treatments for further nitrogen and phosphorus elimination: NP, each followed by consecutive numbers for the single WWTPs.

Master thesis – Maria Redeker 4. Materials and methods 33

Figure 4.2: Location of the sampled WWTPs

In order to allow for an estimation of the water quality of the effluents from the WWTPs, but also their effect on the water quality of the receiving rivers and ditches, at each WWTP at least three sampling points were chosen: the first one in the river or ditch just upstream of the WWTP outlet (symbol: a), the second one from the effluent of the WWTP (symbol: w) and the third one downstream of the outlet (symbol: b), where the effluent water appeared well mixed with the stream water, but no inflow from other sources was obvious. At three sites where a WWTP discharges into a ditch or small stream which opens into one of the rivers sampled in the subcatchment campaign, further sampling points were defined near the entry into that river (in the river upstream of the entry, symbol: Ra; in the tributary just upstream of the entry, symbol: Rw; in the river downstream of the entry, symbol: Rb). To reflect different situations, tributaries with different distances from the WWTPs and different numbers of branchings were chosen (L1, L5, MB2; cf. section 4.2). Table 4.3 gives an overview of the sampling points from this campaign. Technical data of the WWTPs are listed in Table 3.2.

Master thesis – Maria Redeker 4. Materials and methods 34

Table 4.3: Overview of the WWTP campaign sampling points WWTP Location, Sampling Symbol Location of sampling point no. receiving days of stream sampling point L1 Gnutz 20.12.2009, L1a manhole at ditch 9.1.1 upstream WWTP ditches 12.01.2010, outlet Fuhlenau 15.02.2010 L1w WWTP effluent L1b ditch 9.1.1 downstream WWTP L1Ra Fuhlenau upstream entry of Gliner Graben L1Rw Gliner Graben upstream entry into Fuhlenau L1Fb Fuhlenau downstream entry of Gliner Graben L2 Mörel Ost 15.12.2009, L2a Führbek upstream WWTP outlet Führbek 12.01.2010, L2w WWTP effluent 15.02.2010 L2b Führbek downstream WWTP outlet L3 Mörel-West 15.12.2009, L3a, inflows to manhole receiving WWTP Möradgraben L3a1 effluent Führbek L3w WWTP effluent discharged into manhole L3b Möradgraben in 1 st manhole downstream manhole receiving WWTP effluent L4 Tappendorf 15.12.2009 L4a Grenzgraben in manhole upstream sewage Grenzgraben disposal point L4w effluent from sewage disposal point at Grenzgraben L4b 1 st open point of Grenzgraben L5 Grauel 15.12.2009, L5w WWTP effluent ditch 29 14.01.2010, L5Ra Buckener Au upstream entry of ditch Buckener Au 15.02.2010 L5Rw ditch upstream entry into Buckener Au L5Rb Buckener Au downstream entry of ditch, upstream entry of Mühlenbach from opposite side L6 Poyenberg 19.12.2009, L6a Poyenberger Bek upstream WWTP outlet Poyenberger 12.01.2010, L6w last pool of cascade at WWTP outlet Bek 18. 02.2010 L6b Poyenberger Bek downstream WWTP outlet L7 Aukrug- 14.12.2009, L7a Steenbek upstream WWTP outlet, in same Homfeld 28.01.2010, manhole Steenbek 18.02.2010 L7w WWTP effluent L7b Steenbek downstream WWTP outlet, in the same manhole

Master thesis – Maria Redeker 4. Materials and methods 35

L8 Groß 18.12.2009, L8a Sünderbek upstream WWTP outlet Kummerfeld 16.01.2010, L8w WWTP effluent Sünderbek 16.02.2010 L8b Sünderbek downstream WWTP outlet L9 Kleinkummer- 18.12.2009, L9a Stör upstream WWTP outlet feld 16.01.2010, L9w official discharge in last lagoon Stör 16.02.2010 L9b Stör downstream WWTP outlet, upstream creek entering from opposite side L10 Kleinkummer- 18.12.2009, L10a ditch H2 upstream WWTP site feld Bahnhof 16.01.2010 L10w official discharge in last lagoon ditches Stör L10b ditch H2 downstream WWTP site L11 Gönnebek 18.12.2009, L11a Schwale upstream WWTP outlet Nord 15.01.2010, L11k WWTP effluent Schwale 16.02.2010 L11b Schwale downstream WWTP outlet L12 Negenharrie 17.12.2009, L12a Dosenbek upstream effluent ditch Dosenbek 15.01.2010, L12k effluent ditch upstream entry into Dosenbek 19.02.2010 L12b Dosenbek downstream effluent ditch MB1 Heinkenborstel 19.12.2009, MB1a ditch upstream WWTP outlet ditch Wittbek 12.01.2010, MB1w WWTP effluent 15.02.2010 MB1b ditch downstream WWTP outlet MB2 Petersberg 17.12.2009, MB2a ditch 1.12 upstream WWTP outlet ditch 1.12 15.01.2010, MB2w WWTP effluent Schwale 16.02.2010 MB2b ditch 1.12 downstream WWTP outlet MB2Ra Schwale upstream entry of ditch 1.12 MB2Rw ditch 1.12 upstream entry into Schwale MB2Rb Schwale downstream entry of ditch 1.12 MB3 Hollenbek 15.01.2010, MB3a ditch 1.6 upstream WWTP outlet ditch 1.6 19.02.2010 MB3w WWTP effluent Schwale MB3b ditch 1.6 downstream WWTP outlet MB4 Schipphorst 28.01.2010, MB4a ditch 1.6 upstream entry of pipework ditch 1.6 19.02.2010 MB4k WWTP effluent Schwale MB4b 1 st open intercept of ditch 1.6 downstream of WWTP outlet MB5 Hüttenwohld 17.12.2009, MB5a Aasbek upstream WWTP outlet Aasbek 15.01.2010, MB5k WWTP effluent 19.02.2010 MB5b Aasbek downstream WWTP outlet

Master thesis – Maria Redeker 4. Materials and methods 36

NP1 Aukrug- 14.12.2009, NP1a Bünzener Au upstream WWTP outlet Bünzen 14.01.2010, NP1w WWTP effluent Bünzener Au 18.02.2010 NP1b Bünzener Au downstream WWTP outlet NP2 Neumünster 14.12.2009, NP2a Bullenbek upstream ditch from polishing Bullenbek 14.01.2010, lagoon 18.02.2010 NP2w ditch connecting polishing lagoon with Bullenbek NP2b Bullenbek downstream ditch from polishing lagoon

4.2 Description of the sampling points of the WWTP campaign In the following section the sampled WWTPs and the receiving streams are described briefly. The mentioned depths and widths of the streams refer to the values measured in February 2010.

L1: Gnutz The WWTP L1 is situated about 700 m west of the village Gnutz near the river Fuhlenau. It consists of 3 lagoons. The site is surrounded by pastures and a maize field and bordered on three sides by a line of trees. The outlet of the WWTP is situated at the ditch 9.1.1, next to a manhole connecting a more elevated part of the ditch upstream with the lower one downstream (Figures 4.3, 4.4). In the sampling period the outlet was about at the level of the water table, behind some bigger stones. The water is discharged into the Fuhlenau via the ditches 9.1 and 9 (Gliner Graben), as Figure 4.5 shows.

WWTP outlet manhole

Figure 4.4: Ditch downstream of WWTP L1

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Sample L1a was taken from the manhole connecting the two ditches, sample L1w from between the stones at the outlet. Some meters downstream of the WWTP outlet, brownish surfacerunoff water was observed. Sample L1b was taken upstream of this point. Samples L1Ra, L1Rw, and L1Rb were taken where indicated in Figure 4.5.

Figure 4.5: Stream network and sampling points at WWTP L1 (Landesvermessungsamt, 2003; BG13)

L2: Mörel Ost The WWTP is situated about 1 km east of the centre of the village Mörel at the road Wiesenweg (Figure 4.8). It consists of 4 lagoons, one of which is aerated periodically. In January and February 2010, when the lagoons were frozen, the aeration did not function (MarxReese, 2010). The site is surrounded by pastures, and at the northeast side it is separated from the road by a line of trees. The WWTP discharges into the stream Führbek, on the opposite side of the road. At the outlet the Führbek was about 1 m wide and 15 cm deep. Both banks are vegetated with shrubs (Figure 4.6). In this reach, one side of the Führbek neighbours to the road, the other one to a pasture and a maize field.

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WWTP outlet Figure 4.6: Führbek with outlet of WWTP L2 (15.2.2010)

L3: Mörel West The WWTP consists of four lagoons. It is situated on an arable field about 700 m southeast of the village Mörel. The northern side is bordered by a line of trees (Figure 4.7).

Figure 4.7: Site of the WWTP L4 (15.12.2009)

It discharges subterraneously into the ditch 18.2 (Möradgraben), which connects subterraneously with the ditch 18.2.1 and opens into the river Führbek, about 800 m downstream of the WWTP L2. Another 1 km downstream the Führbek discharges into the Buckener Au (Figure 4.8).

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Figure 4.8: Stream network at WWTPs L2 and L3 (Landesvermessungsamt, 2003; BG13)

Apart from the WWTP a source with unknown origin discharges into the Möradgraben at the same point, which is accessible by a manhole. As also the Möradgraben enters via a pipe, it was not possible to find out which pipe was from the ditch and which from the other source. Samples were taken in the manhole from the WWTP outlet (L3w) and from both other pipes entering from upstream (L3a and L3a1). Sample L3b was taken from the water jet entering the next manhole downstream. Due to bad accessibility in the snow period this site was not sampled in January and February 2010.

L4: Tappendorf The WWTP consists of three lagoons and is situated between pastures and maize fields about 700 m southeast of the village Tappendorf. Two edges of the WWTP site each border with a line of trees. The WWTP discharges subterraneously via a channel of about 450 m length into the ditch 14 (Grenzgraben). The Grenzgraben discharges into the river Buckener Au about 1.5 km downstream of the sewage disposal point (Figure 4.9).

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Figure 4.9: Stream network at WWTP L4 (Landesvermessungsamt, 2003; BG13)

Samples were taken in the manhole at the sewage disposal point from the channel transporting the effluent (L4w) and from the Möradgraben entering from upstream (L4a). Sample L4b was taken from the next open intercept of the Möradgraben about 300 m downstream. Because of the long distances between the sampling points and the WWTP, influences from possible other sources can not be excluded. Results from this site thus have been included in the overview of results, but not in the further evaluation. Due to bad accessibility in the snow period, also this site was only sampled in December 2009.

L5: Grauel The WWTP consists of five lagoons and is situated about 300 m east of the village Grauel. It is surrounded by a row of trees, and the vicinity consists of agricultural land and a small forest in the northwest. The WWTP discharges into the ditch 29, which has its origin at the WWTP outlet. Also two other pipes of unknown origin become superficial at that point (Figure 4.11), and plant residues were present at each of the sampling days. About 120 m downstream another pipe, possibly a drainage, discharges into the ditch, and another 300 m downstream the ditch opens into the river Buckener Au, which at that point was 2.2 m wide and 25 cm deep (Figure 4.10). In January 2010 the ditch was partly, in February 2010 almost completely covered by snow.

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Figure 4.10: Stream network at the WWTP L5 (Landesvermessungsamt, 2003; BG13)

In December 2009 the banks of the Buckener Au were vegetated with grasses and some single trees next to the outlet of the ditch, which were mowed respectively cut until the sampling day in January 2010. About 10 m downstream of the outlet of the ditch, the creek Mühlenbach opens into the Buckener Au from the opposite side (Figure 4.12).

Figure 4.11: Outlet of WWTP L5 and Figure 4.12: Buckener Au with entries of two pipes of unknown origin (14.1.2010) ditch 29 (front, left) and Mühlenbach (back, right) (14.1.2010)

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Sample L5w was taken in the ditch 29 just downstream of the WWTP outlet from the main stream, aiming to exclude water originating from the two other pipes. Further samples were taken from the end of the ditch (L5Rw), from the Buckener Au upstream of the ditch entry (L5Ra) and just upstream of the entry of the Mühlenbach (L5Rb).

L6 Poyenberg The WWTP is situated about 700 m northwest of the village Poyenberg. It consists of three lagoons and is surrounded by pastures. The site is bordered in the south and southwest by a line of trees. The WWTP discharges into the river Poyenberger Bek via a cascade of small basins (Figure 4.13). The Poyenberger Bek was 1.1 m wide and 18 cm deep at that point and discharges into the Buckener Au about 600 m downstream. Sample L6w was taken from the last basin of the cascade, samples L6a and L6b upstream and downstream from the Poyenberger Bek.

Figure 4.13: Cascade at the outlet of WWTP L6

L7 Aukrug-Homfeld The WWTP consists of 4 lagoons, at the edges of which some grass or reeds were present. It is situated between paddocks 600 m north of the village Homfeld in the township Aukrug. 3 sides of the WWTP site are surrounded by willow trees. A small forest borders to the WWTP site in the west. The WWTP discharges subterraneously into the river Steenbek, which originates about 600 m upstream and up to the sewage disposal point is canalised.

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Samples were taken in the manhole of the WWTP outlet as indicated in Figure 4.14.

L7a L7b

L7w

Figure 4.14: Manhole with outlet of WWTP L7 and sampling points

During the sampling week in January 2010 the discharge pipe in the last lagoon was blocked with plant material so that the amount and composition of the discharged effluent deviated from the usual conditions. The January samples were therefore taken two weeks later.

L8 Groß Kummerfeld The WWTP consists of three lagoons and is situated ca. 1 km west of the village Groß Kummerfeld. The last and most western lagoon is almost entirely surrounded by forest, the rest of the WWTP site is bordered with a line of trees in the south and east, and some bushes are growing on the banks of the first and second lagoon. The northern part of the site is opened to agricultural land. The WWTP discharges over a short slope into the river Sünderbek about 1 km upstream of its connection with the river Stör. The WWTP outlet is situated in the forested area (Figures 4.15, 4.16, 4.17). Samples were taken from the slope (L8w), from the Sünderbek 1 2 m upstream of the outlet (L8a), and about 20 m downstream of the outlet (L8b).

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Sünderbek WWTP outlet

Figure 4.15: Aerial view of the WWTP L8 (photography: district Segeberg)

Figure 4.16: Sünderbek upstream of Figure 4.17: Sünderbek downstream of WWTP L8 (16.2.2010) WWTP L8 (16.2.2010)

In February 2010 a white precipitate on the slope below the outlet and a greyish stain in the water downstream were observed (Figure 4.18).

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Figure 4.18: White precipitate at the outlet of the WWTP L8 and greyish stain in the water downstream (16.2.2010)

L9 Kleinkummerfeld The WWTP is situated between the village Kleinkummerfeld and the Staatsforst Neumünster at the road K114. It consists of three lagoons, which are surrounded by a line of trees. In the northeast it borders to a small part of the forest. The southern vicinity is used agriculturally. Due to a high groundwater table the lagoons could not be sealed, but it is assumed that due to osmotic pressure groundwater will rather intrude than receive wastewater (Nass, 2011). There are drainages installed to redirect the groundwater, but due to consistently low monitoring values, especially concerning P contents, groundwater is suspected to intrude (Nass, 2009, 2010b). On the last lagoon no ice sheet developed throughout the sampling period (Figure 4.19).

discharge

Figure 4.19: Last lagoon of WWTP L9 and discharge (16.2.2010)

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The WWTP discharges into the river Stör about 4 km downstream of its origin. About 300 m upstream of the WWTP the Stör was 5.7 m wide and 35 cm deep. At the WWTP it is shaded by the forest, and the soil during the sampling period was swampy. Aquatic plants were growing in the river, and organic material was observed on the bed. The effluent of the WWTP is discharged at level of the water table (Figure 4.21), where it immediately mixes with the water from the Stör. Therefore the sample L9w was taken from the official discharge of the WWTP in the last lagoon (Figure 4.19). Sample L9a was taken from the Stör just upstream of the WWTP outlet. Sample L9b was taken about 60 m downstream in the Stör, just upstream of the entry of a small creek from the opposite side (Figure 4.20).

Figure 4.20: Sampling points at WWTP L9 and creek opening into the Stör from the opposite side (Landesvermessungsamt, 2003; BG13, modified)

Figure 4.21: Outlet of the WWTP L9 (18.12.2009)

L10 Kleinkummerfeld Bahnhof The WWTP is situated about 1 km southeast of the village Kleinkummerfeld near the road B 205 between a pasture and arable fields. Also this WWTP is not sealed, groundwater is

Master thesis – Maria Redeker 4. Materials and methods 47 redirected via a circumferential ditch (Nass, 2009). The WWTP consists of three lagoons and discharges into the ditch H2 via the circumferential ditch, which was vegetated with reeds. Also the edges of the lagoons were vegetated with reeds. The ditch H2 received also water from a rainwater retention basin just upstream of the site. After about 1.6 km it opens into the Stör via the ditch H about 600 m upstream of the WWTP L9 (Figure 4.23).

discharge sewage disposal point

rain retention basin

Figure 4.22: Aerial view of the WWTP L10 (photography: district Segeberg)

Figure 4.23: Stream network and sampling points at WWTP L10 (Landesvermessungsamt, 2003; BG13, modified)

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As the sewage disposal point in the ditch was hidden between the reeds, the sample L10w was taken from the official discharge of the WWTP in the last lagoon. Samples L10a and L10b were taken from the ditch H2 upstream and downstream of the WWTP site.

L11 Gönnebek Nord The WWTP is situated at the northwestern edge of the village Gönnebek at the Schwale, next to the bridge at the road Ruesch. It consists of three lagoons, which are surrounded by trees at three sides. The vicinity consists of maize fields and a paddock. The outlet of the WWTP is situated in the bank between the wastewater lagoons and the river Schwale, discharging the effluent water over a slope (Figure 4.24).

Figure 4.24: Outlet of WWTP L11 Figure 4.25: Outlet of WWTP L11 with snow cover (29.8.2010) (16.2.2010) The Schwale at that point was about 1 m wide and 5 cm deep. It neighbors with a maize field and upstream with the village and a paddock. The bank between the WWTP and the Schwale is vegetated with trees. Samples were taken from the slope (L11w), from the Schwale upstream (L11a) of the outlet and about 10 m downstream, just upstream of the bridge (L11b). In February 2010 the slope was covered with snow, which had to be removed in order to access the effluent water (Figure 4.25).

L12: Negenharrie The WWTP is situated between arable fields about 200 m south of the settlement Fiefharrie. It consists of three lagoons bordered by a line of trees in the south. Because of a high groundwater table the site is surrounded by a circumferential drainage system (Rieper, 2009).

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The WWTP discharges via a ditch into the Dosenbek, which has its origin about 600 m upstream of the WWTP and was about 80 cm wide and 8 cm deep at the entry of the effluent ditch. Both the effluent ditch and the Dosenbek were vegetated by grass and small water plants during the sampling period.

MB1 Heinkenborstel The WWTP MB1 is situated about 200 m south of the village Heinkenborstel at the road Westerholz. It consists of three sedimentation tanks and two aeration tanks with movingbed biofilm substrate (Figure 4.27). From the second aeration tank the water is released into a reservoir and pumped out into the ditch when the water table reaches a certain level (usually in time lags of a few minutes) (Eberhard, 2010b).

Figure 4.27: Aeration tank with floating bodies at WWTP MB1

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The WWTP discharges into a small ditch, which flows parallel to the road and after about 350 m connects with the river Wittbek. The outlet of the WWTP in the sampling period was only slightly above the water table. The ditch is partially shaded by trees. At the sampling day in February 2010 it was largely covered with snow upstream of the WWTP. Samples were taken from the outlet pipe (MB1w), from the ditch upstream of the outlet (MB1a) and some meters downstream (MB1b). As at the other WWTPs of this type, the sample downstream of the outlet pipe was taken in the middle of a discharge period, when the effluent water was mixed well with the stream water. Usually the samples from the outlet and downstream were not taken in the same discharge period.

MB2 Petersberg The WWTP MB2 is situated at the road Grüner Weg of the village Griesenbötel in the township Rendswühren. At the WWTPs MB2, MB3, MB4, and MB5 the wastewater is collected after primary settlement in a buffer tank to compensate peak loads. From the buffer tank it is pumped continuously through the WWTP, consisting of movingbed biofilm reactors, which are aerated alternately and intermittently six times per hour, and secondary sedimentation tanks for the removal of floating and settling particles. An intermittent discharge results from the volume of the air which displaces part of the water in the aeration tank in periods of full load and from sludge returning, which causes periodically lower volume in the secondary sedimentation tanks (Porath, 2010). The WWTP discharges into the ditch 1.12, which about 1.3 km downstream opens into the river Schwale (Figure 4.29). About 5 m upstream of the WWTP outlet the ditch passes under a road through a concrete pipe. The pipe was frozen and blocked entirely at the sampling days in January and February 2010 (Figure 4.28), so that the ditch in this reach was only fed by the WWTP effluent. The ditch 1.12 passes mainly agricultural area and is only partly shaded by trees.

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Figure 4.28: Frozen pipe upstream of WWTP MB2 (15.1.2010)

Figure 4.29: S tream network and sampling points at WWTP MB2 (Landesvermessungsamt, 2003; BG 13)

At its entry into the river Schwale, the ditch 1.12 was about 1.3 m wide and 8 cm deep. The Schwale, which originates about 4.5 km upstream, was about 2.1 m wide and 15 cm deep. In the vicinity of the entry bigger stones surmount the water surface (Figures 4.30, 4.31), causing a high flow velocity. In February 2010 strong turbulences were observed. Samples at the WWTP were taken from the outlet (MB2w), from the ditch upstream of the WWTP but downstream of the road (MB2a), and from the ditch downstream of the outlet (MB2b). Samples at the entry of the ditch into the Schwale were taken from the end of the ditch (MB2Rw), and from the Schwale upstream (MB2Ra) and downstream of the stones (MB2Rb).

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Figure 4.30: Schwale downstream of entry of ditch 1.12 (15.1.2010) Figure 4.31: Entry of ditch 1.12 into Schwale (15.1.2010)

MB3 Hollenbek The WWTP MB3 is situated at the southwestern edge of the village Hollenbek at the road Wiesenweg. It discharges into the ditch 1.6, which was about 1.45 m wide and 8 cm deep at that point and opens into the river Schwale about 1.8 km downstream. On one side it neighbors with the settlement and on the other side with the road and a field. The WWTP MB4 in Schipphorst is located about 2.5 km upstream. In between the ditch passes arable fields and pastures as well as the village Hollenbek.

Figure 4.32: Visible part of WWTP MB3 (17.11.2009) Figure 4.33: Outlet of WWTP MB3 (19.2.2010)

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The visible part of the WWTP and the outlet are depicted in the Figures 4.32 and 4.33. For administrative reasons this site was not sampled in December 2009.

MB4 Schipphorst The WWTP MB4 is situated in the southern part of the village Schipphorst in the township Rendswühren at the road K6. It discharges subterraneously into the ditch 1.6, which is piped from about 300 m upstream to about 550 m downstream of the WWTP. In the first piped meters another pipework (1.6.14a) flows into the ditch 1.6 (Figure 4.34). Sample MB4w was taken from the water jet from the WWTP outlet. As the ditch was not accessible via the manhole, sample MB4a and MB4b had to be taken upstream and downstream of the piped section of the ditch.

Figure 4.34: Stream network and sampling points at WWTP MB4 (Landesvermessungsamt, 2003; BG13)

The long distance of the nearest accessible points upstream and downstream of the WWTP admits considerable uncertainties. Influences from possible other sources such as drainages or from farmyards nearby cannot be ascertained, especially the conditions of the channel flowing in just downstream of the point MB4a cannot be considered at all. The results obtained at this location are therefore not useful to assess a direct impact of the WWTP on the ditch 1.6. Thus they have indeed been included in the overview of the results, but not considered in the further evaluation. The only sampling at this WWTP took place in January 2010, for organisational reasons two weeks later than scheduled.

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MB5 Hüttenwohld The WWTP MB5 is situated at the road K6 at the northern edge of the village . It discharges into the river Aasbek about 1.5 km downstream of its origin in the forest. At that point the Aasbek was about 90 cm wide and 13 cm deep. One bank is vegetated with trees, behind which a maize field is situated. On the side of the WWTP it neighbours with the settlement.

NP1 Aukrug-Bünzen The WWTP NP1 is located in the north of the village Bünzen in the township Aukrug at the river Bünzener Au. Mechanical treatment is realised with rods, an aerated grit chamber and a grease trap. Biological and tertiary treatment steps, as well as secondary sedimentation take place in two SBRs, which work in cycles of 8 h duration and are charged alternately in intervals of 4 h. Chemical phosphate elimination is realised with iron(III) chloride sulphate prior to sludge sedimentation, whereas the amount of added iron(III) chloride sulphate depends on the content of phosphate remaining after aeration. Due to the working cycles of the SBRs, effluent is discharged in intervals of about 4 h, with a duration of about 50 min each (Eberhard, 2010a). The WWTP discharges from the SBRs into the Bünzener Au about 600 m downstream of the entry of the river Mitbek. 600 m downstream of the WWTP, the Bünzener Au was 7.7 m wide

Master thesis – Maria Redeker 4. Materials and methods 55 and 65 cm deep. In the vicinity of the WWTP the land is used agriculturally, and the village Innien is located about 500 m upstream.

outlet

Figure 4.36: Bünzener Au and outlet of WWTP NP1 at the end of a discharge period (18.2.2010)

NP2 Neumünster The WWTP NP2 is the largest WWTP in the upper Stör catchment. It is situated in the west of the town Neumünster and discharges into the stream Bullenbek. Mechanical treatment in the WWTP is realised by a coarse screen with rod separation of 40 mm, two parallel drum screens with a rod separation of 5 mm, a combined aerated grit chamber and grease trap, and a primary settling tank. Biological and tertiary treatment as well as secondary sedimentation take place in a continuous flow system. Upstream of the aeration tank an anaerobic tank is installed, which is fed with a 1:1 volume mixture of the wastewater from the aeration tank and denitrified return sludge. Nitrification, denitrification and biological phosphate elimination are realised in three parallel aeration tanks with circulating flow, with both aerated and unaerated zones (Stadt Neumünster, 2010). Chemical phosphate elimination is in summer realised with iron(III) chloride sulphate if required, whereas the amount added depends on the phosphate content remaining after biological phosphate elimination. In winter chemical phosphate elimination occurs as a side effect from the addition of polyaluminium chloride, which is done to avoid foaming in the aeration tanks. The added amount of polyaluminium chloride is in excess of the phosphate present (Brandt, 2010 ).

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Secondary settlement is realised in four parallel tanks where the activated sludge settles down and is scraped into a funnel. Return sludge is denitrified and recycled, while surplus sludge is dewatered and processed to manure. From the secondary sedimentation tanks the water is discharged via a polishing lagoon, where it remains for 45 days, into the Bullenbek, which opens about 700 m downstream into the Stör. Sample NP2w was taken from a ditch connecting the polishing lagoon with the Bullenbek, sample NP2a from the Bullenbek upstream of the ditch. Sample NP2b was taken about 70 m downstream of the ditch, downstream of the bridge at the road Ehndorfer Weg, as upstream of the bridge an enclosed land property inhibits access. Results at the point NP2b therefore may be influenced by the road, by some water cascades which were observed upstream of the bridge (Figure 4.37) and possible other factors which could not be ascertained.

Figure 4.37: Cascades in the Bullenbek upstream of the bridge at Ehndorfer Weg in Neumünster

4.3 Weather during the sampling period and effects on the catchment Apart from spatial and technical characteristics, the results obtained at the different sampling points are influenced by the weather conditions prevailing at the sampling days and the previous days and weeks. Figure 4.38 shows the mean daily temperatures and sums of daily precipitation for the period from November 1, 2009, to February 28, 2010 of the station Padenstedt (DWD, 2010), which is located in the south of the catchment and follows up the station Neumünster. Freezing, apart from December 2, set in at the beginning of the sampling period in December 2009. Also the first snow fell during the mentioned sampling series in December. Apart from

Master thesis – Maria Redeker 4. Materials and methods 57 short periods, often only single days, with temperatures above 0 °C, temperatures remained negative throughout the sampling period. Until the sampling series in January 2010, ice sheets had developed on most WW lagoons and by the sampling period in February 2010 were nearly completely covered with snow. The only WW lagoon which was also in February only partly covered by ice and snow was L9. According to the course of the temperature curve in Figure 4.38, major defrosting probably has not taken place in between. Thus, especially the effluents of the WW lagoons in the December 2009 sampling period were still influenced by warmer temperatures and therefore higher microbial activities, whereas until the sampling period in January 2010 or latest in February 2010 the effluents from the WW lagoons were influenced by low temperatures and oxygen deficiency due to the covered water airinterface during their complete detention time. Also the influence of rainwater on the WW lagoon effluents is assumed to have been lower in January and February 2010, as due to the ice sheet on the surface no direct input into the lagoons was possible. In addition, as precipitation was in form of snow, only thawed water, e.g. from road runoff, reached the lagoons via the combined sewer system. However, two periods of higher precipitation may have influenced the sewage at the end of December 2009 and the beginning of February 2010. Especially, as the precipitation in December 2009 coincided with positive temperatures and therefore may have caused considerable runoff. Perceptible thawing started during the last one or two sampling days in February 2010.

30

25

20

15

10

5 sampling days 0 precipitation

T / °C, pcp / mm pcp / °C, / T temperature -5

-10

-15 01.11.2009 18.11.2009 14.12.2009 11.01.2010 28.01.2010 15.02.2010 28.02.2010 date

Figure 4.38: Temperatures and precipitation during the sampling period at the station Padenstedt (DWD, 2010)

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4.4 Sampling and measurement of field parameters At each sampling point, samples were taken for the immediate measurement of physicochemical parameters and for the later measurement of nutrient contents in the laboratory. Additionally, in the February 2010 sampling series of the WWTP campaign, the flow velocities and cross sectional areas of the rivers and ditches receiving the WWTP effluents were measured near the points of disposal. This should allow for an estimation of discharge of the concerning rivers and ditches with the aim to estimate the proportions between the WWTPs and the streams into which they discharge.

4.4.1 Sampling technique Samples from rivers and ditches were taken with a 2 L beaker from the middle of the stream next to the surface, attempting to avoid swirling up sediments. Samples from WWTP effluents were taken just before entering the receiving stream, according to the given conditions at the individual outlets. Where water was discharged via pipes or otherwise in a free fall, water was taken from the water jet. Where water was discharged flowing above a surface, water was collected laying the beaker on that surface with opening above, so water could flow into the beaker. Due to strong water jets and due to the increased contact zone with the air when water flows above a surface, oxygen contents in the samples may be higher than in the WWTPs themselves. However, this reflects the situation of the effluent waters at the point of entering the receiving stream. Before taking the sample itself, the beaker was rinsed with water from the respective sampling point to avoid contamination from residues in the beaker. Samples were filled into one polyethylene bottle of 50 mL (for later determination of total nitrogen), 100 mL (for later determination of total phosphorus), and 250 mL (for later determination of the other parameters) each, which had been rinsed with sample water before. Bottles were stored in a cooler during transport.

4.4.2 Measurement of physicochemical parameters Dissolved Oxygen (DO) content, electric conductivity (EC), pH values and water temperature (T) were measured with the respective probes of a Multi 340i combined pH / dissolved oxygen / electric conductivity measuring instrument manufactured by WTW. Temperature was read from the pH probe. In February 2010, the pH probe did not work steadily with low ambient temperatures in the field, and due to the measurement of flow velocities the time for work during daylight was

Master thesis – Maria Redeker 4. Materials and methods 59 limited. Therefore in February 2010 only DO contents and water temperature were measured in the field. PH values and EC were measured in the laboratory in the 250 mL bottles prior to filtration (see Chapter 4.5.1). Water temperatures in the field in this case were read from the oxygen probe.

4.4.3 Measurement of flow velocity and calculation of discharge Flow velocities were measured with a FlowSens single axis electromagnetic flow meter manufactured by SEBA Hydrometrie (Figure 4.39). The functional unit of FlowSens is a sensor head which measures flow velocity via electromagnetic induction. It is based on Faraday's Law, which means that a conductor (in this case water) moving in a magnetic field (produced by a coil in the sensor) generates a voltage, which is measured by a pair of electrodes (SEBA Hydrometrie, instruction sheet).

Figure 4.39: Measurement of flow velocity with FlowSens (photography: SEBA Hydrometrie, instruction sheet)

To obtain a preferably representative value for the discharge ( Q), which is related to the stream cross section ( A) and the mean flow velocity v by Q v A (eq. 7), flow velocities v are usually measured in different distances from the bank at different heights each. For calculation of the cross sectional area, the river width and the water depth at each distance are recorded. This was realised in the bigger streams which were accessible by a bridge (Bünzener Au, about 600 m downstream of the WWTP in AukrugBünzen (NP1) while no water was being discharged, and Stör, about 300 m upstream of the WWTP in Kleinkummerfeld (L9)). In the smaller and in the worse accessible streams flow velocity was measured only at one distance

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(where possible in the middle of the stream) and, according to the water depth, in one, two or three heights (for details see Annex D, Table 17). In most cases the water depth was recorded at 3 equally distributed distances from the bank to obtain a better approximation to the cross sectional area. Flow velocity measurement took place for 30 s at each measurement point of a cross section. Average velocity and standard deviation were read from the digital control unit. Cross sectional areas, mean flow velocities and discharges in each measured cross section were calculated by the software Flügel (Brecht, 2005) from the measured stream width, water depths and flow velocities. In the ditch next to the WWTP in Heinkenborstel (MB1) and in the river Schwale next to the WWTP in Gönnebek (L11) the water was too shallow for the use of FlowSens. In these cases a small piece of ice was laid on the middle of the stream and its floating time over a certain distance was recorded (Annex D, Table 17). This step was repeated 3 times to allow for the calculation of a mean value and standard deviation. Mean flow velocity was calculated as L v k (eq. 8) t where L is the distance, t the travel time and k a correction factor for the roughness of the bed. k varies between 0.8 for rough beds and 0.9 for smooth beds, but most commonly 0.85 is used, unless a singularly rough or smooth bed is measured (Gore, 1996). Discharge was then calculated according to equation 7.

4.5 Laboratory analyses Samples were prepared and analysed in the laboratory of the Department of Hydrology and Water Resources Management at ChristianAlbrechtsUniversity Kiel. Determined parameters were ammonium nitrogen (NH 4N), nitrite nitrogen (NO 2N), nitrate nitrogen (NO 3N), total

nitrogen (N tot ), orthophosphate phosphorus (PO 4P), total phosphorus (P tot ), chloride (Cl ), and

2 sulphate (SO 4 ).

4.5.1 Sample preparation Samples bottled for the determination of total nitrogen and total phosphorus contents were directly transferred from the cooler to the freezer and stored at 18 °C. Samples from the 250 mL bottles were vacuum filtered with 0.45 µm cellulose acetate filters manufactured by Sartorius. Filtered samples were each transferred to a 100 mL polyethylene bottle (for later determination of NH 4N and PO 4P contents) and to a 50 mL polyethylene

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2 bottle (for later determination of Cl , SO 4 , NO 3N and NO 2N contents). 50 µL of 1 N NaOH

solution were added to the samples in the 50 mL bottles to stabilize the NO 2 ions. All bottles were transferred to the freezer and stored at 18 °C. For each analysis the respective bottles were defrosted over night at ambient temperature. Analyses were carried out according to the laboratory script (Westphal et al., 2009), following the standard methods which are given in Table 4.4 together with the respective quantification limits. The reagents used for analyses are listed in the Annex C.

Table 4.4: Overview of applied methods, their quantification limits and underlying standard methods Parameter Method Quantification limit Standard method

NH 4N Spectrophotometry 0.024 mg/L DEV E5 / DIN 38406

NO 2N Ion chromatography 0.016 mg/L DEV D19

NO 3N Ion chromatography 0.033 mg/L DEV D19 Luminescence N 0.522 mg/L DIN 38409, EN 12260 tot spectrometry

PO 4P Spectrophotometry 0.005 mg/L DEV D11, DIN 1189 DEV E5 / DIN 38411, P Spectrophotometry 0.010 mg/L tot DEV H36 Cl Ion chromatography 0.165 mg/L DEV D19

SO 4 Ion chromatography 0.185 mg/L DEV D19

4.5.2 Determination of ammonium nitrogen contents 5 mL of the defrosted membrane filtered sample were mixed with 0.2 mL of a sodium nitroprusside dihydrate / sodium salicylate solution and 0.2 mL of an oxidising solution. 3 replicates of each sample were prepared and measured against a blank with distilled water instead of sample (also 3 replicates). Due to alkaline conditions dichloroisocyanuric acid sodium salt is converted to hypochlorite. The equilibrium of ammonium and ammonia is shifted to ammonia, which reacts with sodium hypochlorite to form monochloroamine. Nitroprusside catalyses the reaction of sodium salicylate with monochloroamine to quinone chloroimine, which forms with further salicylate the yellow associated indophenol which dissociates in alkaline media to a blue dye (Bolleter et al., 1961). The extinction of the dye was detected after 90 min with a Shimadzu UV1602 UVvisible spectrophotometer with ASC5 auto sample changer at 690 nm. Concentrations were quantified

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by external calibration with ammonium chloride standards in the range of 0.05 – 0.8 mg NH 4 N/L.

The actual NH 4N concentration cr of each replicate was calculated by

cr cr ,meas c B , meas F dil F reag (eq. 9) where cr,meas is the NH 4N concentration of the measured solution as put out by the photometer software, c B, meas the arithmetic mean of the NH 4N concentrations of the 3 blank solutions as put out by the photometer software, Fdil the dilution factor of the sample and Freag the correction factor for the reagents (volume of added reagents divided by 5 mL).

When cr,meas exceeded 0.8 mg/L, the determination was repeated with a dilution, usually by the factor 10 or 25, in single cases 50, 100 or 200, before adding the reagents. From the 3 replicates, 2 with the lowest difference (< 5 %, otherwise the sample was remeasured) of NH 4N concentrations were chosen and the final NH 4N concentration was calculated as their arithmetic mean.

4.5.3 Determination of orthophosphate phosphorus contents 5 mL of the defrosted membrane filtered sample were mixed with 0.2 mL of an ammonium heptamolybdate / antimony potassium tartrate solution and 0.1 mL of a 10 % w/v ascorbic acid solution. 3 replicates of each sample were prepared and measured against a blank with distilled water instead of sample (also 3 replicates). In acidic conditions orthophosphate ions react with molybdate and antimony ions to form an antimonyphosphomolybdate complex, which is reduced by ascorbic acid to a coloured molybdenum blue complex. The extinction of this complex was detected after 30 min with a Shimadzu UV1602 UVvisible spectrophotometer with ASC5 auto sample changer at 880 nm. Concentrations were quantified by external calibration with monopotassium phosphate standards in the range of 0.05 – 0.8 mg PO 4P/L.

Actual PO 4P concentrations of the replicates and final PO 4P concentrations of the samples were calculated analogous to the NH 4N concentrations as described above (Chapter 4.5.2). Also dilutions were prepared as described above (Chapter 4.5.2).

4.5.4 Determination of total phosphorus contents 10 mL of the wellmixed defrosted unfiltered sample was digested for 1 h under pressure and heat supply with 10 mL of an aqueous oxidising solution. Organic phosphorus compounds thereby are oxidised to orthophosphate ions. 3 replicates of each sample were prepared plus a blank with distilled water instead of sample (also 3 replicates).

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When cooled down, total phosphorus contents of the samples were determined as orthophosphate contents of the digested samples as described in Chapter 4.5.3.

Actual P tot concentrations of the replicates and final P tot concentrations of the samples were calculated analogous to the NH 4N concentrations as described above (Chapter 4.5.2), but the dilution factor was multiplied by 2 and a difference of 10 % was tolerated between the 2 chosen replicates to calculate the mean value. Dilutions were prepared with factors 5 or 10.

4.5.5 Determination of nitrite nitrogen, nitrate nitrogen, chloride and sulphate contents 2.4 mL of the defrosted membrane filtered sample with added NaOH were diluted with 9.6 mL of ultrapure water and analysed by the laboratory staff with a modular ion chromatography system manufactured by Metrohm. The ions contained in the sample are extracted by diffusion through a 0.2 µm dialysis membrane into an acceptor solution. 20 µL of the acceptor solution are injected into a Metrosep A Supp 4 column (column packing: polyvinyl alcohol with quaternary ammonium groups, particle size: 9 µm, dimensions: 250 mm x 4 mm) and eluted by an aqueous solution containing 1 mmol/L Na 2CO 3 and 4 mmol/L NaHCO 3 with a flow of 1 mL/min. Ion contents are detected by a conductivity detector. They are identified by their retention times and quantified by the peak areas by external calibration with 4 standard solutions in the range of 1 – 20 mg/L of each ion. When a concentration in the diluted sample was above 20 mg/L, the determination was repeated with a higher dilution. When a concentration was below the detection limit, the sample was analysed undilutedly.

2 Results were given by the device software as NO 2 , NO 3 , Cl , and SO 4 after back calculation

of the dilutions. To obtain the values for NO 2N and NO 3N, the results for NO 2 and NO 3 were multiplied by 0.304 and 0.226, respectively.

4.5.6 Determination of total nitrogen contents 100 µL of the wellmixed defrosted unfiltered sample were injected into a DIMATOC 100 element analyser with automatic sample changer (manufactured by DIMATEC) and combusted at 850 °C in an oxygen stream. The nitrogen dioxide (NO 2) gas resulting from combustion of the nitrogen compounds is converted at 330 °C to nitric oxide (NO), which is excited by ozone and detected by luminescence spectrometry. N tot concentrations were quantified by external calibration with 6 ammonium sulphate solutions in the range of 0.5 – 20 mg N/L.

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According to experience of the laboratory, samples with N tot concentrations of up to about 150 mg N/L can be measured under these conditions undilutedly without a loss of accuracy.

Therefore samples were not diluted for N tot determination. Each sample was injected 3 times (from the same vial) and the arithmetic mean of the results was calculated by the device software.

4.5.7 Presentation and evaluation of the results Management, evaluation and presentation of the results were realised with the software programmes OpenOffice.org Calc, version 3.2.1, and R, version 2.10.1.

4.5.7.1 Time series Water quality parameters are presented in short time series arranged by the single WWTPs. Three time series per WWTP marked in different colours represent the three sampling positions (upstream, effluent, and downstream of the WWTPs). For the parameters NH 4N,

PO 4P, and P tot , error bars represent the standard deviation of the results of the two replicates chosen for the calculation of the arithmetic mean (see sections 4.5.2, 4.5.3, and 4.5.4). As for

2 the determination of NO 2N, NO 3N, Cl , and SO 4 only one replicate was measured each, no standard deviation could be calculated. In the frame of quality assurance of the laboratory a sample of known composition is regularly measured with the samples. The percental standard deviation of this sample was applied as measurement uncertainty for the mentioned parameters. It is important to note that the lines connecting the results of the three sampling days per WWTP are displayed for presentation clarity, but do not imply statements about the development in between. Tables of the single results are included in the Annex D. In addition, the differences between the results obtained upstream and downstream of the single WWTPs are represented in the form of column diagrams. Error bars in the column

2 diagrams of the parameters NH 4N, NO 3N, PO 4P, P tot , Cl , and SO 4 represent the range of possible differences given by the sum of measurement uncertainties of the respective samples from upstream and downstream. The WWTP L3 with two inflowing pipes upstream of the WWTP outlet (see section 4.2) is not included in the difference diagrams. Missing data arise from the reasons listed in Table 4.5.

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Table 4.5: Reasons for missing data reason months parameters samples DO MB1a,w,b defective probes December 2009 EC L7a,w,b December 2009 all MB1w accessibility January 2010, L3a,w,b, L4a,w,b, all February 2010 L10a,w(Feb),b

samples lost December 2009 N tot , P tot MB1b December 2009 all MB3a,w,b, MB4a,w,b other February 2010 all MB4a,w,b

4.5.7.2 Box-and-whiskers plots The distributions of the results of the single parameters are depicted in the form of boxand whiskers plots, which are also used for the comparison between the results of the different WWTP types. For each sampling position, the results from all three months at all WWTPs of one type have been summarized to one distribution, so that three distributions have resulted for every sampling position. Boxandwhiskers plots are a method for graphical display of the statistical parameters of a distribution, such as the median, 1 st and 3 rd quartile (Q1 and Q3), and outliers (Figure 4.40). The central horizontal line represents the median, or 2 nd quartile (Q2), the upper and lower ends of the box the 1 st and the 3 rd quartile (Q1 and Q3) of the distribution. The box thus represents the central 50 % of observations. The distance between Q1 and Q3 is referred to as interquartile range (IQR). The whiskers (vertical lines) represent a range of inconspicuous spread, which is, according to experience from exploratory data analysis, set to 1.5 IQR. The ends of the whiskers represent the lowest respectively the highest observation within this range. Observations beyond 1.5 IQR are considered as outliers and depicted as single dots. The distance between minimum and maximum is referred to as range (Sachs & Hedderich, 2009).

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Figure 4.40: Example of a boxandwhiskers plot

Q1 and Q3 are usually indicated in distributions with n > 12 (Sachs & Hedderich, 2009). In the present thesis the majority of distributions has n < 12, and especially in case of the technical WWTPs with tertiary N and P elimination the quartiles had to be determined by interpolation. For comparability of the different distributions the indication of Q1 and Q3 has anyhow been included. For better visualisation of the distributions, which are not in all cases unimodal, the boxand whiskers plots have been overlaid with stripcharts, which represent the single observations, in this thesis as red dots. The results of the WWTPs L3, L4, L10, and MB4 have not been included in the construction of the boxandwhiskers plots, as they were only sampled in one month. As the NH 4N contents measured at the effluent of L8 were unfeasibly low (Nass, 2010), and in the past 5 years a value in this magnitude had only been detected once at that site (UWB Segeberg, 2010), also the results from the effluent at L8 have not been incorporated in the boxandwhiskers plots.

4.5.7.3 Longitudinal river profiles

For four rivers, results of the parameters NH 4N and PO 4P, as characteristic wastewater parameters and P tot , which is more than PO 4P influenced also by diffuse sources, from both campaigns are presented in common diagrams as longitudinal profiles, whereas the results measured in the rivers are represented as dots, and those measured in the effluents, respectively at the entries of ditches transporting the effluents, as columns. Tables with the results are listed in the Annex D (Tables 14 16).

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4.5.7.4 Discharge of the WWTPs and receiving streams To investigate a possible relation between the size of the WWTPs and the magnitude of their impact on the stream water quality, the ratio of dimensions of the WWTPs and the receiving streams, regarding their discharge, should have been calculated and the difference of the single water quality parameters plotted against the mentioned proportions. However the measurement of the discharge of the WWTPs was technically not realisable with the available means, as the discharge was too high for a volumetric analysis. Also a calculation of discharge differences between upstream and downstream of the WWTPs via flow velocity measurement was in the necessary exactness not realisable, as in the snow period the rivers were not adequately accessible, and often the banks were covered with snow, prohibiting exact measurements of the stream width and flow velocities near the banks. The only WWTP with exact records of current discharges is the WWTP NP1. As a substitute for discharge from the WWTPs the number of connected PE was consulted. It is important to note that this figure does not account for possible external connections or, in case of combined combined sewer systems, the amount of precipitation. It should also be noted that due to the low number of measuring points per cross section also the results obtained for discharge are very rough approximations. Thus, both dimensions do not reflect exact values, but still can be used for an approximate comparison. For the described lack of exactness the comparison was only realised qualitatively by comparing the number of PE connected to a WWTP with the calculated discharge in form of a table. The calculation of discharges of the rivers and ditches receiving the effluents of the WWTPs is summarised in form of a table in the Annex D. The differences observed between the upstream and downstream sampling points in form of the column diagrams mentioned in section 4.5.7.1 were qualitatively compared with the table and with another set of column diagrams representing the differences of the single parameters between the effluents and the upstream sampling positions, which can also be found in the Annex E.

4.5.7.5 Comparison with emission limits The Council Directive 91/271/EEC concerning urban wastewater treatment (EC, 1991) stipulates N tot and P tot emission limits for WWTPS in sensitive areas with > 10,000 PE, which concerns in the upper Stör catchment the WWTP NP2. The German Wastewater Ordinance

(AbwV, 2004) sets a general threshold of 10 mg/L for NH 4N contents in the effluents of WWTPs of size categories 3 and higher, which concerns in addition the WWTP NP1, as well as thresholds for DIN and P tot for WWTPs of the size categories 4 and 5. Both do not set

Master thesis – Maria Redeker 4. Materials and methods 68 requirements for WWTPs of the size categories 1 and 2, i.e. < 5,000 PE, concerning N and P. In addition to the legal requirements the water authorities of the districts may set individual emission limits in the discharge permissions for the WWTPs. However, the determination of these values is often guided by the monitoring data from the respective WWTPs. Alike the legal emission limits they are for technical reasons valid at water temperatures > 12 °C and for the individual measurements (Haustein, 2011). For all of the investigated WWTPs emission limits for N tot and P tot exist. As the emission limits are valid for individual measurements, the results of the single measurements of the effluent samples taken in the scope of this thesis were compared with their respective emission limits. The limit was regarded as exceeded if the calculated concentration minus the measurement uncertainty was above the limit. For the purpose of clarity, measurement uncertainties were indicated only where the limits are exceeded.

Measurement uncertainties were in case of P tot contents given by the standard deviations of two replicates. In the case of DIN, they were given by the sum of the measurement uncertainties of

NH 4N and NO 3N (cf. section 4.5.7.1).

4.5.7.6 Water quality assessment For estimation of the pollution of the streams at the sampled points the classification system of the German Working Group on water issues of the Federal States and the Federal Government (LAWA, 1998) and the LAWAAO Framework Concept Monitoring RAKON (LAWAAO, 2007) were consulted. The classification according to LAWA (1998) distinguishes four main and three subclasses of water quality, from “unpolluted to very lightly polluted” (class I) to “excessively contaminated” (class IV), as indicated in Table 4.6.

Table 4.6: Classification of water quality according to LAWA (1998) I unpolluted to very lightly polluted III lightly polluted II moderately poluted IIIII critically polluted III heavily contaminated IIIIV very heavily contaminated IV excessively contaminated

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The thresholds of the single classes concerning nutrients, salts, and sum parameters are listed in Table 4.7.

Table 4.7: Water quality classification of nutrients, salts and sum parameters according to LAWA (1998) compound unit water quality class I I-II II II-III III III-IV IV

Ntot mg/L 1 1.5 3 6 12 24 > 24

NO 3N mg/L 1 1.5 2.5 5 10 20 > 20

NO 2N mg/L 0.01 0.05 0.1 0.2 0.4 0.8 > 0.8

NH 4N mg/L 0.04 0.1 0.3 0.6 1.2 2.4 > 2.4

Ptot mg/L 0.05 0.08 0.15 0.3 0.6 1.2 > 1.2

PO 4P mg/L 0.02 0.04 0.1 0.2 0.4 0.8 > 0.8

O2 mg/L > 8 > 8 > 6 > 5 > 4 > 2 2 Cl mg/L 25 50 100 200 400 800 > 800

2 SO 4 mg/L 25 50 100 200 400 800 > 800 TOC mg/L 2 3 5 10 20 40 > 40 AOX µg/L “0” 10 25 50 100 200 > 200

The system has been applied to the arithmetic means of the sampling points upstream and downstream of each WWTP. It had been designed for the classification of natural water bodies, but for comparability it has also been applied to the ditches and pipeworks investigated in the frame of this thesis.

The RAKON concept proposes the classification of water quality based on two thresholds, which are neither legally binding, nor values to cause remediation measures. They describe the transition from "very good" to "good" status (background levels) and the transition from "good" to "moderate" status/condition (benchmarks). These thresholds consider the different river types in assigning individual background levels and benchmarks to each type. An overview of background values and benchmarks for the river types investigated in the scope of this thesis is given in Tables 4.8 and 4.9.

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Table 4.8: Background levels regarding general physicochemical components in German rivers according to RAKON monitoring (yellow: according to exemplary ordinance, green: additionally impactrelevant) (LAWAAO, 2007)

- Parameter O 2 TOC BOD 5 Cl pH P tot PO 4-P NH 4-N unit mg/L mg/L mg/L mg/L mg/L mg/L mg/L minimum statistical mean mean mean – mean mean mean parameter value value value maximum value value value value LAWA water types 14, 16 (brooks of > 9 5 2 50 0.05 0.02 0.04 lowlands) 19 (organic rivers of > 8 7 3 50 0.05 0.02 0.04 lowlands)

Table 4.9: Benchmarks regarding general physicochemical components in German rivers according to RAKON monitoring (yellow: according to exemplary ordinance, green: additionally impactrelevant) (LAWAAO, 2007)

- Parameter O 2 TOC BOD 5 Cl pH P tot PO 4-P NH 4-N unit mg/L mg/L mg/L mg/L mg/L mg/L mg/L minimum statistical mean mean mean – mean mean mean parameter value value value maximum value value value value LAWA water types 14, 16 (brooks of > 7 7 4 200 6.5 – 8.5 0.1 0.07 0.3 lowlands) 19 (organic rivers of > 6 10 6 200 5 – 8 0.15 0.1 0.3 lowlands)

Also the RAKON concept has been applied to the arithmetic means of the sampling points upstream and downstream of each WWTP. Not all the recipients of the WWTP effluents are assigned to one of the water types. In these cases the thresholds of the next receiving river assigned to a water type were applied. The compliance of the samples with the thresholds are indicated in tables as follows: “BG” and blue colour for values which comply with the background level “BM” and green colour for values which comply with the benchmark “” and yellow colour for values which do not comply with the thresholds.

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It should be noted that at L3, L4, L10, and MB4 samples were available from only one month each and therefore might not be representative for the whole sampling period. Also for MB2a only the results from December 2009 were included in the evaluation.

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5 Results In the following chapter the results of the investigations described in Chapter 4 are presented. The first section focuses on the water quality parameters measured in the effluents of the WWTPs and in the direct vicinity in the receiving rivers and ditches upstream and downstream of the WWTPs. In the second section longitudinal profiles of the rivers Stör, Schwale, Buckener Au, and Fuhlenau are synthesized from the available sampling points from both campaigns conducted in the scope of this thesis.

5.1 Direct vicinity of the WWTPs

5.1.1 Water temperature The water temperatures in the rivers and ditches upstream of the WWTPs ranged from 0.1 °C at MB5 in January to 6.7 °C at L4 and L10 in December each. No general development in course of the months can be observed (Figure 5.1a). As shown in Figure 5.2, the distribution of water temperatures upstream of the wastewater lagoons was highest with a median of 4.9 °C and most values above 4 °C. Upstream of the small technical WWTPs lowest, with a median of 1.7 °C and most values below 3 °C. Upstream of the technical WWTPs with tertiary N and P elimination the temperatures were similar to those upstream of the lagoons, but the median was a bit lower (3.9 °C) and the range slightly narrower. The water temperatures of the WWTP effluents ranged from 0.2 °C at L11 in February to 10.2 °C at NP1 in December. For the wastewater lagoons the water temperature was lower in the effluents than upstream, whereas for the technical WWTPs it was generally higher in the effluents than upstream, with exception of NP2, where the effluent is discharged via a polishing lagoon (see section 4.2), in December. Effluent temperatures generally decreased from December to February at most WWTPs. In the effluents of the wastewater lagoons they were roughly between 1.5 °C and 4.5 °C in December, whereas in February in all except 2 WWTPs (L9 and L12) effluent temperatures were below 1 °C. The lowest temperatures were recorded at the wastewater lagoons, with a median of 1.6 °C and a maximum of 4.3 °C. Highest temperatures were measured at the small technical WWTPs, with a median of 7 °C and a minimum of 5.4 °C. Effluent temperatures of the technical WWTPs applying tertiary N and P elimination were intermediate. They had a median of 5.8 °C.

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7 10

6 8 5 6 4 4 3 T / °C

T / °C 2 2

1 0

0 -2 Master thesis Maria– Redeker Feb. 10 Feb. 10 Feb. 10 Feb. 10 Feb. 10 Feb.10 Feb. 10 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Feb. 10 Feb. 10 Feb. 10 Feb. 10 Feb. 10 Feb. 10 Feb. 10 Feb. 10 Feb. 10 Feb. 10 Feb. 10 Feb. 10 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 L1Jan.10 L2Jan.10 L3Jan.10 L4Jan.10 L5Jan.10 L6Jan.10 L7Jan.10 L8Jan.10 L9Jan.10 L10 Jan. 10 L11 Jan. 10 L12 Jan. 10 NP1 Jan.10 NP1 NP2 Jan. 10 NP2 Jan. MB5 Jan.MB510 MB4 Jan.MB410 MB3 Jan.MB310 MB2 Jan.MB210 MB1 Jan.MB110 WWTP no. and month WWTP no. and month

sampling position: upstream upstream effluent downstream

b) 1 5

0 4

-1 3

-2 2 diff Tdiff /°C diff Tdiff °C / -3 1

-4 0

-5 -1 L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 WWTP no. WWTP no. difference downstream – upstream Dec. 2009 Jan. 2010 Feb. 2010

Figure 5.1: Water temperatures in the effluents and receiving streams. a) Time series. WWTPs are listed by WWTP type and number. Different colours represent the different sampling positions (upstream, effluent, and downstream of the WWTPs, see legend). Three points per time series are dedicated to the

sampling days in December 2009, January 2010, and February 2010. b) Differences between the sampling points from upstream to downstream of the WWTPs 73 at the sampling days in December 2009, January 2010, and February 2010. 5. Results 74

Figure 5.2: Boxandwhiskers plots of the water temperatures upstream, in the effluents and downstream of the WWTPs, and changes from upstream to downstream for the different WWTP types (L = wastewater lagoons, MB = mechanic and biological treatment, NP = additional tertiary N and P elimination). See section 4.5.7.2 for remarks about the boxandwhiskers plots.

Water temperatures measured downstream of the WWTPs roughly followed the trends of the points upstream. They were largely between the respective temperatures measured upstream and in the effluents and ranged from 0.1 °C (MB5, in January) to 6.9 °C (NP2, in December). Medians downstream of the lagoons, small technical WWTPs and technical WWTPs with tertiary N and P elimination were 4.7 °C, 3.5 °C, and 3.7 °C, respectively. The distributions were more similar to each other than upstream and in the effluents and showed higher variation concerning the IQRs. All three distributions overlap to a great extent. In line with the observations from Figure 5.1a, it can be recognised in Figure 5.1b that at the wastewater lagoons the differences of water temperatures from upstream to downstream were largely negative, with the largest reduction at L10, whereas at the small technical WWTPs they were largely positive and had higher absolute values. At the technical WWTPs with tertiary N and P elimination the changes were minor than at the two other WWTP types, and included both positive and negative values. The medians of the differences were 0.3 °C, +1.0 °C, and ±0 °C, respectively. The widest range occurred at the small technical WWTPs, while the narrowest one can be observed at the technical WWTPs with tertiary N and P elimination. Also in the differences of water temperatures no general development is visible over the months.

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5.1.2 pH values pH values upstream of the WWTPs ranged from 6.54 at L10 in December to 8.46 at L7 in January. Greatest variations between the months can be observed at L7 and L2. In the most rivers and ditches pH values increased slightly from December to February (Figure 5.3a). Medians did not differ much from each other, with values of 7.29 upstream of the lagoons, 7.43 upstream of the small technical WWTPs and 7.36 upstream of the technical WWTPs with tertiary N and P elimination. The greatest variation (from 6.56 to 8.46) can be observed upstream of the lagoons, and the least (from 7.00 to 7.48) upstream of the technical WWTPs with N and P elimination (Figure 5.4). In the effluents pH values ranged from 6.68 at NP1 in December to 8.00 at L7 in January. Between the months greatest variations occurred, as upstream, at L7. However no general development can be recognised from December to February. In the effluents of the technical WWTPs pH values were largely lower than in the receiving rivers and ditches, with the exception of MB1. The lowest distribution with a median of 7.06 was that at the technical WWTPs with tertiary N and P elimination. Those at the wastewater lagoons and small technical WWTPs had a similar heights with medians of 7.31 and 7.38, respectively, whereas the widest range (from 6.73 to 8.00) can be observed at the lagoons. The pH values downstream of the WWTPs ranged from 6.4 at L6 to 8.79 at MB4, both in January. The latter value was exceptionally high compared to the other values recorded downstream of the WWTPs. At most points pH values were below 7.8. They were largely between the values of the corresponding rivers upstream and the effluents. In some cases they were obviously beyond that scope, especially at MB4, NP1, and L7 in January, and at L2 in December. The medians accounted for 7.31 downstream of the wastewater lagoons, 7.56 downstream of the small technical WWTPs and 7.32 downstream of the technical WWTPs with tertiary N and P elimination. The widest range (6.40 – 7.83) can, as upstream and in the effluents, again be observed downstream of the lagoons and the narrowest one (7.32 – 7.55) at the small technical WWTPs.

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8.5 8.5

8 8

7.5 7.5

pH 7 pH 7

6.5 6.5

6 6 Master thesis Maria– Redeker Feb. 10 Feb. 10 Feb. 10 Feb. 10 Feb. 10 Feb. 10 Feb. 10 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec. 09 Dec.09 Dec. 09 Dec. 09 Dec. 09 Dec.09 Dec.09 Dec. 09 Dec. 09 Dec.09 Dec. 09 Dec. 09 Dec. 09 Dec.09 L1 Jan. 10 L1Jan. L2 Jan. 10 L2Jan. L3 Jan. 10 L3Jan. L4 Jan. 10 L4Jan. L5 Jan. 10 L5Jan. L6 Jan. 10 L6Jan. L7 Jan. 10 L7Jan. L8 Jan. 10 L8Jan. L9 Jan. 10 L9Jan. L10 Jan. 10 Jan. L10 L11 Jan. 10 Jan. L11 L12 Jan. 10 Jan. L12 NP1 Jan. 10 NP1 Jan. NP2 Jan. 10 NP2 Jan. MB5 Jan.MB510 MB4 Jan.MB410 MB3 Jan.MB310 MB2 Jan.MB210 MB1 Jan.MB110 WWTP no. and month WWTP no. and month sampling position: upstream upstream effluent downstream

b) 1 1

0.8 0.8

0.6 0.6

0.4 0.4

0.2 0.2 diff pH diff diff pH diff 0 0

-0.2 -0.2

-0.4 -0.69 -0.4 L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 WWTP no. WWTP no. difference downstream – upstream Dec. 2009 Jan. 2010 Feb. 2010

Figure 5.3: pH values in the effluents and receiving streams. a) Time series. WWTPs are listed by WWTP type and number. Different colours represent the different sampling positions (upstream, effluent, and downstream of the WWTPs, see legend). Three points per time series are dedicated to the sampling days

in December 2009, January 2010, and February 2010. b) Differences between the sampling points from upstream to downstream of the WWTPs at the 76 sampling days in December 2009, January 2010, and February 2010. 5. Results 77

Figure 5.4: Boxandwhiskers plots of the pH values upstream, in the effluents and downstream of the WWTPs, and changes from upstream to downstream for the different WWTP types (L = wastewater lagoons, MB = mechanic and biological treatment, NP = additional tertiary N and P elimination). See section 4.5.7.2 for remarks about the boxandwhiskers plots.

The differences between the pH values measured upstream and downstream of the WWTP effluents (Figure 5.3b) ranged from 0.69 at L7 in January to +0.85 at L3 in December. In most cases they were relatively small (+/ 0.2 pH units or less), and usually less pronounced at the wastewater lagoons than at the small technical WWTPs. Stronger changes occurred at L10 in December and at L7 and MB1 in January. At all WWTP types both negative and positive changes can be observed, which were largely most pronounced in January. The medians for the pH value changes were close to 0 for all WWTP types (0.03, 0.01, and 0.03 at the lagoons, small technical WWTPs and technical WWTPs with tertiary N and P elimination). If outliers are not regarded, the widest range (from 0.33 to +0.38) emerged at the small technical WWTPs.

5.1.3 Dissolved oxygen Upstream of the WWTPs dissolved oxygen contents ranged from 2.5 mg/L at L10 to 15.6 mg/L at L2, both in December. Variation over the months was quite different and reached from relatively stable values upstream of L1 to variations over nearly 8 mg/L upstream of L7. However, no common increase or decrease of values from December to February can be recognized (Figure 5.6a). The medians accounted for 3.9 mg/L, 4.8 mg/L, and 4.4 mg/L upstream of the lagoons, small technical WWTPs and technical WWTPs with tertiary N and P

Master thesis – Maria Redeker 5. Results 78 elimination. The ranges decreased in the mentioned order, but overlapped nearly completely (Figure 5.5). In the effluents oxygen contents ranged from 0.5 mg/L at L10 in December to 12.8 mg/L at L2 in February. In all samples they were below the oxygen contents measured upstream. The highest and lowest contents were recorded in the effluents of the wastewater lagoons, the contents recorded at the technical WWTPs were in an intermediate reach (between 3.9 mg/L at NP1 in February and 8.7 mg/L at MB2 in February; most values were below 5 mg/L). Accordingly the distribution at the lagoons had the widest range, and it was relatively symmetric, whereas the distributions at the technical WWTPs had narrower ranges. They were positively skewed. Medians at the lagoons, small technical WWTPs and technical WWTPs with tertiary N and P elimination accounted for 3.9 mg/L, 4.8 mg/L, and 4.4 mg/L, respectively. Also in the effluents no common trend can be observed over the months. Downstream of the WWTPs oxygen contents ranged from 4.1 mg/L at L7 to 14.0 mg/L at L3, both in December. With few exceptions they were between the respective ones upstream and in the effluents. With medians of 7.4 mg/L, 9.3 mg/L, and 10.2 mg/L the distributions downstream of the lagoons, small technical WWTPs and technical WWTPs with tertiary N and P elimination were similar to those upstream, but shifted a bit lower. Downstream of the wastewater lagoons, oxygen contents showed less, downstream of the technical WWTPs with tertiary N and P elimination more variation than upstream.

Figure 5.5: Boxandwhiskers plots of the dissolved oxygen contents upstream, in the effluents and downstream of the WWTPs, and changes from upstream to downstream for the different WWTP types (L = wastewater lagoons, MB = mechanic and biological treatment, NP = additional tertiary N and P elimination). See section 4.5.7.2 for remarks about the boxandwhiskers plots.

Master thesis – Maria Redeker 5. Results

a) 16 16 14 14

12 12

10 10

8 8

6 6

4 4 c(O2)/mg/L c(O2)/mg/L 2 2

0 0 Master thesis Maria– Redeker Feb. 10 Feb.10 Feb. 10 Feb. 10 Feb. 10 Feb. 10 Feb.10 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Feb. 10 Feb. 10 Feb. 10 Feb. 10 Feb.10 Feb. 10 Feb.10 Feb. 10 Feb.10 Feb. 10 Feb.10 Feb. 10 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 L1Jan.10 L2Jan.10 L3Jan.10 L4Jan.10 L5Jan.10 L6Jan.10 L7Jan.10 L8Jan.10 L9Jan.10 L10 Jan. 10 L11 Jan. 10 L12 Jan. 10 NP1 Jan. 10 NP1 Jan. NP2 Jan.10 NP2 MB5 Jan. Jan. MB510 MB4 Jan. Jan. MB410 MB3 Jan.MB310 MB2 Jan. Jan. MB210 MB1 Jan.MB110 WWTP no. and month WWTP no. and month sampling position: upstream upstream effluent downstream

b) 4 4

3 3

2 2

1 1

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-1 c(O2)diff mg/L / diff c(O2)diff mg/L / -1

-2 -2

-3 -3

-4 -4 L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 WWTP no. WWTP no. difference downstream – upstream Dec. 2009 Jan. 2010 Feb. 2010

Figure 5.6: Dissolved oxygen contents in the effluents and receiving streams. a) Time series. WWTPs are listed by WWTP type and number. Different colours represent the different sampling positions (upstream, effluent, and downstream of the WWTPs, see legend). Three points per time series are dedicated to the

sampling days in December 2009, January 2010, and February 2010. b) Differences between the sampling points from upstream to downstream of the WWTPs 79 at the sampling days in December 2009, January 2010, and February 2010. 5. Results 80

The differences of dissolved oxygen concentrations between upstream and downstream of the WWTPs reached from 3.6 mg/L (NP2 in February) to +4.0 mg/L (L3 in December), at which the positive values comply with the cases in which the concentrations downstream of the WWTPs were higher than both upstream and in the effluents. At all WWTP types different magnitudes of reductions occurred, except at the technical WWTPs with tertiary N and P elimination, where at NP1 only small differences can be observed, while at NP2 the largest reductions (besides at L1) can be recognised. The medians had values of 0.9 mg/L, 0.7 mg/L, and 1.5 mg/L at the lagoons, small technical WWTPs and technical WWTPs with tertiary N and P elimination. In agreement with the observations from Figure 5.6b, the widest ranges were those at the lagoons (3.4 mg/L to +1.5 mg/L) and at the technical WWTPs with tertiary N and P elimination (3.6 mg/L to +0.2 mg/L).

5.1.4 Electric conductivity The electric conductivities in the rivers and ditches ranged from 347 µS/cm upstream of L10 to 1564 µS/cm upstream of MB2, where in January and February the ditch was frozen under the small bridge upstream of the WWTP (see section 4.2). Disregarding that point, the highest EC upstream of the WWTPs was 825 µS/cm at MB1 in February. Compared with EC in the effluents in most of the streams the EC was quite stable over the months (Figure 5.7a). The medians accounted for 528 µS/cm, 652 µS/cm, and 495 µS/cm, respectively upstream of the wastewater lagoons, the small technical WWTPs and the technical WWTPs with tertiary N and P elimination (Figure 5.8). In the effluents EC ranged from 298 µS/cm at L2 to 1577 µS/cm at MB2, both in December. The wastewater lagoons mostly had values below 800 µS/cm, while at the technical WWTPs the values were largely above. At most WWTPs, EC increased from December to February. While at the wastewater lagoons in December and partly in January the effluents had a lower EC than the receiving rivers and ditches, at the technical WWTPs all EC values were above those in the corresponding streams. Medians were 572 µS/cm at the lagoons, 1232 µS/cm at the small technical WWTPs and 1010 µS/cm at the technical WWTPs with tertiary N and P elimination, whereas the latter was nearly consistent with the maximum at the lagoons and the minimum at the small technical WWTPs. All three distributions showed more variation than those upstream and mainly increased from December to February.

Master thesis – Maria Redeker 5. Results

a) 1200 1600

1400 1000 1200 800 1000

600 800

600 400 400 EC / S/cm EC / EC / S/cm EC / 200 200

0 0 Master thesis Maria– Redeker Feb.10 Feb. 10 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Feb. 10 Feb.10 Feb.10 Feb.10 Dec. 09 Dec. Dec.09 Dec.09 Dec. 09 Dec.09 Dec.09 Dec. 09 Dec. 09 Dec. Dec.09 Dec.09 Dec. 09 Dec.09 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Dec. 09 Dec. 09 Dec. Dec.09 Dec. 09 Dec.09 Dec.09 Dec. 09 L9 Jan. 10 L9Jan. L8 Jan. 10 L8Jan. L7 Jan. 10 L7Jan. L6 Jan. 10 L6Jan. L5 Jan. 10 L5Jan. L4 Jan. 10 L4Jan. L3 Jan. 10 L3Jan. L2 Jan. 10 L2Jan. L1 Jan. 10 L1Jan. L12 Jan. 10 L12Jan. L11 Jan. 10 L11Jan. L10 Jan. 10 L10Jan. NP1 Jan. Jan. 10 NP1 NP2 Jan. Jan. 10 NP2 MB5 Jan. 10 Jan. MB5 MB4 Jan. 10 Jan. MB4 MB3 Jan. 10 Jan. MB3 MB2 Jan. 10 Jan. MB2 MB1 Jan. 10 Jan. MB1 WWTP no. and month WWTP no. and month sampling position: upstream upstream effluent downstream

b) 400 600

300 500

400 200 300 100 200 diff EC / EC / S/cm diff diff EC / EC / S/cm diff 0 100

-100 0

-200 -100 L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 WWTP no. WWTP no. difference downstream – upstream Dec. 2009 Jan. 2010 Feb. 2010

Figure 5.7: EC in the effluents and receiving streams. a) Time series. WWTPs are listed by WWTP type and number. Different colours represent the different sampling positions (upstream, effluent, and downstream of the WWTPs, see legend). Three points per time series are dedicated to the sampling days in December 2009, January 2010, and February 2010. b) Differences between the sampling points from upstream to downstream of the WWTPs at the sampling days in December 2009, January 2010, and February 2010. 81 5. Results 82

Figure 5.8: Boxandwhiskers plots of the EC upstream, in the effluents and downstream of the WWTPs, and changes from upstream to downstream for the different WWTP types (L = wastewater lagoons, MB = mechanic and biological treatment, NP = additional tertiary N and P elimination). See section 4.5.7.2 for remarks about the boxandwhiskers plots. EC downstream of the WWTPs in all cases was between the respective values upstream and in the effluents or only slightly beyond. Values ranged from 386 µS/cm at L6 in December to 1564 µS/cm at MB2 in January. They were in a similar range at all WWTPs (ca. 400 – 800 µS/cm), except for MB1, MB2, and NP2, where higher values were recorded. The distributions downstream of the wastewater lagoons, the small technical WWTPs and technical WWTPs with tertiary N and P elimination had medians of 520 µS/cm, 897 µS/cm, and 689 µS/cm respectively. Disregarding two outliers at the small technical WWTPs, the widest range can be observed at the technical WWTPs with tertiary N and P elimination (446 µS/cm 1246 µS/cm), while those at the other WWTP types were only half as wide and overlapped in about 50 % of their width. The changes in EC from upstream to downstream of the single WWTPs are shown in Figure 5.7b. They ranged from 136 µS/cm at L1 in December to +570 µS/cm at NP2 in February. The absolute values of the changes were smallest at the wastewater lagoons and greatest at the technical WWTPs with tertiary N and P elimination. While at the technical WWTPs EC almost exclusively increased (except at MB2 in February), at the wastewater lagoons also reductions occurred in December and January. The distribution of EC changes at the wastewater lagoons had the lowest median (+5 µS/cm) and the smallest range (136 µS/cm to +107 µS/cm), whereas the IQR ranged only from 5 µS/cm to +18 µS/cm. While the minima were near 0 at both types of technical WWTPs (6 µS/cm at the small ones, +2 µS/cm at those with tertiary N

Master thesis – Maria Redeker 5. Results 83 and P elimintaion), the maximum and therefore also median were highest at the latter ones (570 µS/cm, respectively 194 µS/cm).

5.1.5 Ammonium nitrogen

NH 4N contents in the rivers and ditches upstream of the WWTPs ranged from below the quantification limit (0.01 mg/L at MB2 in December) to 12 mg/L at L1 in February (Figure

5.9a). Except for that point all rivers and ditches had NH 4N contents below 2.3 mg/L, in most cases also below 1 mg/L. NH 4N contents upstream the WWTPs were relatively stable over the months compared to the contents in the effluents. The highest variation (decrease of 1.6 mg/L from December to January and February) occurred at L7. The medians upstream of the wastewater lagoons, small technical WWTPs and technical WWTPs with tertiary N and P elimination accounted for 0.28 mg/L, 0.49 mg/L, and 0.30 mg/L, respectively. The distribution upstream of the lagoons had the widest range (0.03 mg/L 12 mg/L), but was strongly positively skewed, with most values below 0.5 mg/L. The narrowest range was that of the distribution upstream of the technical WWTPs with tertiary N and P elimination (0.21 mg/L – 0.44 mg/L) (Figure 5.10).

In the effluents of the WWTPs the NH 4N contents varied stronger than in the receiving rivers and ditches, both between the different WWTPs and at the single WWTPs between the months. At most of the WWTPs the values increased from December to February. The greatest variations occurred at part of the wastewater lagoons and at MB3. The NH 4N contents in the effluents ranged from 0.03 mg/L at MB5 in December to 46 mg/L at MB1 in January. At the wastewater lagoons they were distributed over the whole range between 0.4 mg/L and 34 mg/L, whereas at the small technical WWTPs were largely below 7.4 mg/L (only MB1 and the February sample of MB3 had values around 45 mg/L and 30 mg/L, respectively). At the technical WWTPs with tertiary N and P elimination all NH 4N contents were below 1.5 mg/L. Medians accounted for 14 mg/L, 2.4 mg/L, and 0.49 mg/L respectively, and the distributions were strongly positively skewed.

Master thesis – Maria Redeker 5. Results a) 40 50 8 45 35 7 40 30 6 35 25 30 5 20 25 4 20 15 3

c(NH4N) / / mg/L c(NH4N) 15 10 2 10 5 5 1

0 0 0 Master thesis Maria– Redeker Feb. 10 Feb. 10 Feb. 10 Feb. 10 Feb. 10 Feb. 10 Feb. 10 Dec.09 Dec.09 Dec. 09 Dec.09 Dec. 09 Dec.09 Dec.09 Feb. 10 Feb. 10 Feb.10 Feb. 10 Feb. 10 Feb. 10 Feb.10 Feb. 10 Feb. 10 Feb.10 Feb.10 Feb. 10 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 L1Jan.10 L2Jan.10 L3Jan.10 L4Jan.10 L5Jan.10 L6Jan.10 L7Jan.10 L8Jan.10 L9Jan.10 L10 Jan. 10 L11 Jan. 10 L12 Jan. 10 NP1 Jan. 10 NP1 Jan. NP2 Jan. 10 NP2 Jan. MB1 Jan.MB110 Jan.MB210 MB3 Jan.MB310 Jan.MB410 MB5 Jan.MB510 WWTP no. and month WWTP no. and month WWTP no. and month sampling position: upstream upstream effluent downstream

b) 5 12.0 30 1.2 4.5 25 1 4 3.5 0.8 20 3 0.6 2.5 15 0.4 2 10 diff c(NH4N) / mg/L c(NH4N) / diff 1.5 0.2 1 5 0 0.5 0 0 -0.2 L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 MB1 MB3 MB2 MB4 MB5 NP1 NP2 WWTP no. WWTP no. WWTP no. difference downstream – upstream Dec. 2009 Jan. 2010 Feb. 2010

Figure 5.9: NH 4N contents in the effluents and receiving streams. a) Time series. WWTPs are listed by WWTP type and number. Different colours represent the different sampling positions (upstream, effluent, and downstream of the WWTPs, see legend). Three points per time series are dedicated to the sampling

days in December 2009, January 2010, and February 2010. b) Differences between the sampling points from upstream to downstream of the WWTPs at the 84 sampling days in December 2009, January 2010, and February 2010. 5. Results 85

Figure 5.10: Boxandwhiskers plots of the NH 4N contents upstream, in the effluents and downstream of the WWTPs, and changes from upstream to downstream for the different WWTP types (L = wastewater lagoons, MB = mechanic and biological treatment, NP = additional tertiary N and P elimination). See section 4.5.7.2 for remarks about the boxandwhiskers plots. *For the purpose of clarity, three outliers at 11.6 mg/L, 11.2 mg/L, and 10.5 mg/L are not depicted.

Downstream of the WWTPs the NH 4N contents ranged from 0.26 mg/L at NP1 in December to 28 mg/L at MB1 in January. Downstream of the wastewater lagoons NH 4N contents were largely below 6.4 mg/L, with exception of L1 and L10, which had considerably higher values

(12 mg/L up to 24 mg/L). Downstream of the technical WWTPs NH 4N contents were lower, with values below 1.5 mg/L, except for MB1b and MB3b (in February), which had NH 4N contents between 12 mg/L and 28 mg/L. Also downstream of the WWTPs NH 4N contents largely increased over the months. The medians downstream of the wastewater lagoons, small technical WWTPs and technical WWTPs with tertiary N and P elimination accounted for 2.2 mg/L, 0.90 mg/L, and 0.55 mg/L, respectively. As upstream and in the effluents, the distributions were strongly positively skewed.

The changes of NH 4N contents from upstream to downstream of the WWTPs are depicted in Figure 5.9b. They reflect quite well the situation at the effluents: At the wastewater lagoons the values of the differences were distributed relatively evenly within a range from +0.18 mg/L at L3 in December to +4.85 mg/L at L7 in February. At the technical WWTPs most differences were between 0.02 mg/L and +1.03 mg/L. Stronger changes (between +11 mg/L and +26 mg/L) occurred at L1 and MB3 in February, and at MB1 in all three months. At most WWTPs the changes of NH4N contents increased over the months. The medians of changes were +1.15 mg/L, +0.58 mg/L, and 0.23 mg/L at the wastewater lagoons, small technical WWTPs and technical WWTPs with tertiary N and P elimination.

Master thesis – Maria Redeker 5. Results 86

5.1.6 Nitrite nitrogen

At the wastewater lagoons and the technical WWTPs with tertiary N and P elimination NO 2N was detected at all three sampling positions only in single samples, with contents up to 0.22 mg/L (Figure 5.12a). In contrast in the effluents of each of the small technical WWTPs considerable contents (up to 0.8 mg/L) occurred at least in one month. A conspicuously high value (4.7 mg/L) was found at MB2 in January. Upstream and downstream of the small technical WWTPs, NO 2N was also detected only in single samples, with contents up to 0.52 mg/L, if MB2 is not regarded.

Accordingly, the changes of NO 2N contents from upstream to downstream had higher absolute values at the technical WWTPs than at the wastewater lagoons (Figure 5.12b). While at two wastewater lagoons the contents decreased, they mainly increased at the technical WWTPs.

Figure 5.11: Boxandwhiskers plots of the NO 2N contents upstream, in the effluents and downstream of the WWTPs, and changes from upstream to downstream for the different WWTP types (L = wastewater lagoons, MB = mechanic and biological treatment, NP = additional tertiary N and P elimination). See section 4.5.7.2 for remarks about the boxandwhiskers plots. *For the purpose of clarity, outliers upstream, in the effluent, and downstream of the small technical WWTPs at 4.41 mg/L, 4.70 mg/L, and 3.81 mg/L, respectively are not displayed. In the boxandwhiskers plots (Figure 5.11) the statistical parameters of most distributions were equal to 0, except for single outliers. The effluents of the small technical WWTPs had the only distributions where the statistical parameters were different higher. The median accounted for 0.00 mg/L, 0.32 mg/L, and 0.47 mg/L for the NO 2N contents upstream, in the effluents and downstream, and was ±0.00 for the differences between the concentrations upstream and downstream. It should be noticed that for better visibility the outliers from MB2 in January (around 4 mg/L) are not depicted.

Master thesis – Maria Redeker 5. Results a) 0.6 5 4.5 0.5 4 3.5 0.4 3 0.3 2.5 2

0.2 c(NO2N)/ mg/L 1.5 c(NO2N) / mg/L c(NO2N) / 1 0.1 0.5 0 0 Master thesis Maria– Redeker Feb. 10 Feb.10 Feb.10 Feb. 10 Feb. 10 Feb.10 Feb.10 Feb. 10 Feb.10 Feb.10 Feb. 10 Feb. 10 Feb.10 Feb. 10 Feb. 10 Feb.10 Feb.10 Feb. 10 Feb. 10 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 L1Jan.10 L2Jan.10 L3Jan.10 L4Jan.10 L5Jan.10 L6Jan.10 L7Jan.10 L8Jan.10 L9Jan.10 L10 Jan. 10 L11 Jan. 10 L12 Jan. 10 NP1 Jan.10 NP1 NP2 Jan.10 NP2 MB5 Jan. Jan. MB510 MB4 Jan.MB410 MB3 Jan.MB310 MB2 Jan. Jan. MB210 MB1 Jan. Jan. MB110 WWTP no. and month WWTP no. and month sampling position: upstream upstream effluent downstream

b) 0.02 0.3 0.2 0.01 0.1 0 0 -0.1 -0.01 -0.2 -0.02 -0.3

diff c(NO2N)/mg/L diff -0.03 c(NO2N)/mg/L diff -0.4 -0.5 -0.04 -0.6 -0.05 -0.7 L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 WWTP no. WWTP no. difference downstream – upstream Dec. 2009 Jan. 2010 Feb. 2010

Figure 5.12: NO 2N contents in the effluents and receiving streams. a) Time series. WWTPs are listed by WWTP type and number. Different colours represent the different sampling positions (upstream, effluent, and downstream of the WWTPs, see legend). Three points per time series are dedicated to the sampling days

in December 2009, January 2010, and February 2010. b) Differences between the sampling points from upstream to downstream of the WWTPs at the sampling 87 days in December 2009, January 2010, and February 2010. 5. Results 88

5.1.7 Nitrate nitrogen

NO 3N contents in the rivers and ditches ranged from 0.06 mg/L upstream of L10 to 21.7 mg/L upstream of MB2, both in December. At most of the points the values decreased from December to February (Figure 5.13a). The medians accounted for 3.24 mg/L, 8.42 mg/L, and 2.40 mg/L upstream of the wastewater lagoons, the small and the technical WWTPs and the technical WWTPs with tertiary N and P elimination. The distribution upstream of the small technical WWTPs had the widest range (12.56 mg/L), whereas the distribution upstream of the technical WWTPs with tertiary N and P elimination had the narrowest (4.00 mg/L). All three distributions were slightly positively skewed (Figure 5.14).

In the effluents NO 3N contents ranged from below the detection limit in several samples to 29.1 mg/L at MB4 in February. The lowest values (<1 mg/L) were detected in the effluents of the lagoons and NP1, and the highest values (> 15 mg/L) in those of the small technical

WWTPs. In the effluents of the small technical WWTPs NO 3N contents showed high variation over the months at the single WWTPs (up to nearly 20 mg/L) and largely decreased, while they were relatively stable at the other WWTP types. At the wastewater lagoon effluents all NO 3N contents were below those upstream of the respective WWTPs, while at the technical WWTPs both higher and lower values occurred. The medians accounted for 0.11 mg/L at the lagoons, 10.7 mg/L at the small technical WWTPs, and 2.95 mg/L at the technical WWTPs with tertiary N and P elimination. The narrowest range (0 mg/L – 2.90 mg/L) can be recognised at the wastewater lagoons, whereas the widest one (1.57 mg/L –

22.7 mg/L) occurred at the small technical WWTPs. At both technical WWTPs the NO 3N contents are split up into two groups, which concentrate in the upper and lower quarters of the ranges.

NO 3N contents downstream of the WWTPs ranged from 0.04 mg/L at L1 to 18.8 mg/L at MB2, both in February. Not in all cases were they between the values measured upstream and in the effluents of the respective WWTPs, which can however, except for L11 in January, be explained by the measurement uncertainty. Their medians were 3.10 mg/L, 10.7 mg/L and 2.10 mg/L downstream of the wastewater lagoons, the small technical WWTPs and the technical WWTPs with tertiary N and P elimination. The ranges accounted for 14.1 mg/L, 15.5 mg/L, and 2.34 mg/L, respectively. All distributions were slightly positively skewed.

Master thesis – Maria Redeker 5. Results a) 16 30

14 25 12 20 10

8 15

6

c(NO3N) / / mg/L c(NO3N) 10

c(NO3N) / mg/L / c(NO3N) 4 5 2

0 0 Master thesis Maria– Redeker Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 L1 Jan. 10 L1Jan. L2 Jan. 10 L2Jan. L3 Jan. 10 L3Jan. L4 Jan. 10 L4Jan. L5 Jan. 10 L5Jan. L6 Jan. 10 L6Jan. L7 Jan. 10 L7Jan. L8 Jan. 10 L8Jan. L9 Jan. 10 L9Jan. NP1 Jan. 10 Jan. NP1 NP2 Jan. 10 Jan. NP2 MB1 Jan. 10 Jan. MB1 MB2 Jan. 10 Jan. MB2 MB3 Jan. 10 Jan. MB3 MB4 Jan. 10 Jan. MB4 MB5 Jan. 10 Jan. MB5 L10 Jan. L10Jan. 10 L11 Jan. L11Jan. 10 L12 Jan. L1210 Jan. WWTP no. and month WWTP no. and month sampling position: upstream upstream effluent downstream

b) 8 8

6 6

4 4

2 2

0 0

-2 -2 diff c(NO3N) / / mg/L c(NO3N) diff diff c(NO3N) /mg/L c(NO3N) diff -4 -4

-6 -6

-8 -8 L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 WWTP no. WWT P no. difference downstream – upstream Dec. 2009 Jan. 2010 Feb. 2010

Figure 5.13: NO 3N contents in the effluents and receiving streams. a) Time series. WWTPs are listed by WWTP type and number. Different colours represent the different sampling positions (upstream, effluent, and downstream of the WWTPs, see legend). Three points per time series are dedicated to the sampling days in December 2009, January 2010, and February 2010. b) Differences between the sampling points from upstream to downstream of the WWTPs at the sampling days in December 2009, January 2010, and February 2010. 89 5. Results 90

Figure 5.14: Boxandwhiskers plots of the NO 3N contents upstream, in the effluents and downstream of the WWTPs, and changes from upstream to downstream for the different WWTP types (L = wastewater lagoons, MB = mechanic and biological treatment, NP = additional tertiary N and P elimination). See section 4.5.7.2 for remarks about the boxandwhiskers plots.

The differences in NO 3N contents between upstream and downstream of the single WWTPs ranged from 4.47 mg/L at MB2 in December to +5.83 mg/L at NP2 in February (Figure

5.13b). At the lagoons positive differences reflect the cases where downstream the NO 3N contents were higher than both upstream and in the effluents. The largest reduction can be recognised at L11. At the small technical WWTPs in the most cases NO 3N contents were also reduced, but in a greater extent than at the wastewater lagoons. Strongest reductions can be observed at MB1 and MB2. At NP1 in December and January the NO 3N contents were slightly reduced and in February slightly elevated, while at NP2 the strongest increases of NO 3 N contents occurred. Accordingly, the distribution at the technical WWTPs with tertiary N and P elimination had the highest median (+1.73 mg/L) and contained mainly positive values. The distribution at the small technical WWTPs had the lowest median (0.93 mg/L) and predominantly spread in the negative range. The distribution at the wastewater lagoons had a median of 0.30 mg/L and contained slightly more negative than positive values. All three distributions had similar ranges between 5.74 mg/L and 7.13 mg/L.

5.1.8 Total nitrogen In the rivers and ditches upstream of the WWTPs, disregarding the ditch 1.12 at MB2 in

January and February, N tot contents ranged from 0.92 mg/L at NP2 in February to 22.4 mg/L at MB2 in December. Compared to the effluents they were relatively stable over the months and showed a slight decrease at most sites (Figure 5.15a).

Master thesis – Maria Redeker 5. Results a) 45 80

40 70

35 60 30 50 25 40 20 30 15 c(Ntot) / mg/L c(Ntot) / 20 c(Ntot) / mg/L c(Ntot) / 10

5 10

0 0 Master thesis Maria– Redeker Feb. 10 Feb. 10 Feb.10 Feb. 10 Feb. 10 Feb. 10 Feb. 10 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Feb. 10 Feb. 10 Feb. 10 Feb.10 Feb. 10 Feb. 10 Feb. 10 Feb. 10 Feb. 10 Feb.10 Feb. 10 Feb. 10 Dec.09 Dec. 09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 L1 Jan.L110 L2 Jan.L210 L3 Jan.L310 L410 Jan. L510 Jan. L6 Jan.L610 L7 Jan.L710 L8 Jan.L810 L9 Jan.L910 L10 Jan. 10 L11Jan. 10 L12 Jan. 10 NP1 Jan. 10 NP1 Jan. NP2 Jan. 10 NP2 Jan. MB1 Jan.MB110 MB2 Jan.MB210 MB3 Jan.MB310 MB4 Jan.MB410 MB5 Jan.MB510 WWTP no. and month WWTP no. and month sampling position: upstream upstream effluent downstream

b) 6 13.4 13 30

5 25

4 20

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1 c(Ntot)mg/L /diff 5 diff c(Ntot)mg/L / diff

0 0

-1 -5

-2 -10 L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 WWTP no. WWTP no. difference downstream – upstream Dec. 2009 Jan. 2010 Feb. 2010

Figure 5.15: Ntot contents in the effluents and receiving streams. a) Time series. WWTPs are listed by WWTP type and number. Different colours represent the different sampling positions (upstream, effluent, and downstream of the WWTPs, see legend). Three points per time series are dedicated to the sampling days in

December 2009, January 2010, and February 2010. b) Differences between the sampling points from upstream to downstream of the WWTPs at the sampling 91 days in December 2009, January 2010, and February 2010. 5. Results 92

Figure 5.16: Boxandwhiskers plots of the N tot contents upstream, in the effluents and downstream of the WWTPs, and changes from upstream to downstream for the different WWTP types (L = wastewater lagoons, MB = mechanic and biological treatment, NP = additional tertiary N and P elimination). See section 4.5.7.2 for remarks about the boxandwhiskers plots. The highest distribution can be observed upstream of the small technical WWTPs, with a median of 10.8 mg/L and a range from 4.60 mg/L to 22.4 mg/L (disregarding the outliers), and the lowest distribution upstream of the technical WWTPs with tertiary N and P elimination, with a median of 3.40 mg/L and a range from 0.92 mg/L to 41.0 mg/L. The median upstream of the wastewater lagoons accounted or 10.8 mg/L and the N tot contents ranged from 1.40 mg/L to 16.2 mg/L (Figure 5.16).

Ntot contents in the effluents ranged from 1.3 mg/L at NP1 in February to 69.7 mg/L at MB2 in January. They were usually higher than upstream of the respective WWTPs, except for L3 in December and NP1 in all three months. They showed strong variations (ca. 10 25 mg/L) at about half of the WWTPs. At the wastewater lagoons values largely increased over the months, while for the technical WWTPs no common trend is noticeable. The distribution at the small technical WWTPs was the highest, with a median of 43.9 mg/L, and a range from 13.1 mg/L to 37.0 mg/L. The distribution at the technical WWTPs with tertiary N and P elimination was the lowest, with a median of 4.75 mg/L, and showed the least variation, from 1.3 mg/L to 12.9 mg/L. The distribution at the wastewater lagoons was intermediate, with a median of 16.6 mg/L and a range from 3.70 mg/L to 40.3 mg/L.

Downstream of the WWTPs N tot contents ranged from 2.6 mg/L at L9 in February to 66.4 mg/L at MB2 in January. Disregarding MB2, the highest value was 37.7 mg/L at MB1 in February. They were largely between those upstream and in the effluents or only slightly beyond. Exceptions were L6 in December and MB2 in January and February. The medians accounted

Master thesis – Maria Redeker 5. Results 93 for 8.65 mg/L, 24.4 mg/L, and 6.65 mg/L, respectively downstream of the wastewater lagoons, the small technical WWTPs and the technical WWTPs with tertiary N and P elimination. The distribution downstream of the small WWTPs had clearly the widest range (from 5.80 mg/L to 66.4 mg/L) and that downstream of the technical WWTPs with tertiary N and P elimination the narrowest (from 5.20 mg/L to 10.0 mg/L).

In Figure 5.15b most of the values are positive, indicating increasing N tot contents from up to downstream. At the technical WWTPs they were largely higher than at the lagoons. Particularly strong increases took place at L1 in February, at L10 in January, and at MB1. The strongest increases usually occurred in February, whereas the lowest largely took place in December. The medians were similar for the three WWTP types (+1.45 mg/L, +1.80 mg/L, and +2.40 mg/L, respectively at the wastewater lagoons, the small technical WWTPs and the technical WWTPs with tertiary N and P elimination). The widest range with the highest absolute values (both positive and negative) can be observed at the small technical WWTPs, the narrowest range at the lagoons, if the outlier is not regarded.

5.1.9 Orthophosphate phosphorus

Disregarding MB2 in January and February, PO 4P contents upstream of the WWTPs ranged from below the quantification limit (at NP2 in January and L1 in February) to 0.32 mg/L at MB1 in January. At most points they decreased in course of the months, except for MB2 and

MB5 (Figure 5.17a). The highest PO 4P contents were detected upstream of the small technical WWTPs. They had a median of 0.20 mg/L, whereas those upstream of the wastewater lagoons and upstream of the technical WWTPs with tertiary N and P elimination had medians of 0.03 mg/L and 0.20 mg/L, respectively (Figure 5.18). Upstream of most wastewater lagoons and all technical WWTPs with tertiary N and P elimination the PO 4P contents were below the minimum upstream of the small technical WWTPs (0.09 mg/L).

In the effluents PO 4P contents were, in most cases considerably, higher than upstream of the WWTPs. They ranged from 0.02 mg/L at NP2 in February to 9.99 mg/L at MB1 in January. At most WWTPs they were lowest in December and highest in February, whereas the opposite situation was true for P2, MB1, MB3, and the technical WWTPs with tertiary N and P elimination.

Master thesis – Maria Redeker 5. Results

a) 6 12 1.2

5 10 1

4 8 0.8

3 6 0.6

2 4 0.4 c(PO4P) / mg/L

1 2 0.2

0 0 0 Master thesis Maria– Redeker Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 L1 Jan. 10 L1Jan. L2 Jan. 10 L2Jan. L3 Jan. 10 L3Jan. L4 Jan. 10 L4Jan. L5 Jan. 10 L5Jan. L6 Jan. 10 L6Jan. L7 Jan. 10 L7Jan. L8 Jan. 10 L8Jan. L9 Jan. 10 L9Jan. L10 Jan. L10Jan. 10 L11 Jan. L1110 Jan. L1210 Jan. NP1 Jan. 10 Jan. NP1 NP2 Jan. Jan. 10 NP2 MB1 Jan. 10 Jan. MB1 MB2 Jan. 10 Jan. MB2 MB3 Jan. 10 Jan. MB3 MB4 Jan. 10 Jan. MB4 MB5 Jan. 10 Jan. MB5 WWTP no. and month WWTP no. and month WWTP no. and month sampling position: upstream upstream effluent downstream

b) 3.5 3 4.53 5.57 0.030

3 2.5 0.025 2.5 2 0.020 2 1.5 0.015 1.5 1 0.010 diff c(PO4P)diff /mg/L 1 0.5

0.5 0 0.005

0 -0.5 0.000 L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 WWTP no. WWTP no. WWTP no. difference downstream – upstream Dec. 2009 Jan. 2010 Feb. 2010

Figure 5.17: PO 4P contents in the effluents and receiving streams. a) Time series. WWTPs are listed by WWTP type and number. Different colours represent the different sampling positions (upstream, effluent, and downstream of the WWTPs, see legend). Three points per time series are dedicated to the sampling days in December 2009, January 2010, and February 2010. b) Differences between the sampling points from upstream to downstream of the WWTPs at the sampling days in December 2009, January 2010, and February 2010. 94 5. Results 95

Figure 5.18: Boxandwhiskers plots of the PO 4P contents upstream, in the effluents and downstream of the WWTPs, and changes from upstream to downstream for the different WWTP types (L = wastewater lagoons, MB = mechanic and biological treatment, NP = additional tertiary N and P elimination). See section 4.5.7.2 for remarks about the boxandwhiskers plots. *For the purpose of clarity, two outliers at 6.34 mg/L and 7.03 mg/L are not displayed.

The highest median (6.01 mg/L) and widest range (6.85 mg/L) occurred, as upstream, at the small technical WWTPs, while the technical WWTPs with tertiary N and P elimination had the lowest median (0.16 mg/L) and the narrowest range (1.06 mg/L). The latter distribution was clearly lower than the former, and both did not overlap with the IQR of the distribution at the wastewater lagoons. Median and range at the wastewater lagoons accounted for 2.41 mg/L and 5.02 mg/L, respectively.

The PO 4P contents downstream of the WWTPs ranged from 0.013 mg/L at NP2 in February to 7.1 mg/L at MB2 in February. In all samples they were between the respective values upstream and in the effluents. In course of the months they largely increased. Also downstream of the WWTPs the highest median (0.28 mg/L) and clearly widest range (3.5 mg/L) occurred at the small technical WWTPs and the lowest median (0.03 mg/L) and narrowest range (0.06 mg/L) at the technical WWTPs with tertiary N and P elimination. The minima were rather similar at all three WWTP types (0.03 mg/L, 0.30 mg/L, and 0.01 mg/L at the lagoons, small technical WWTPs and technical WWTPs with tertiary N and P elimination) and the distributions downstream of the lagoons and small technical WWTPs were rather positively skewed.

In accordance with the high concentrations of PO 4P in the effluents compared to upstream,

PO 4P contents increased from upstream to downstream of all WWTPs (Figure 5.17b). The highest increases can be observed at MB1 (+4.53 mg/L in December, +5.57 mg/L in January), the lowest one at NP1 in February (+0.001 mg/L). At the lagoons the weakest increase

Master thesis – Maria Redeker 5. Results 96 occurred usually in December and the strongest one in February. At both technical WWTPs with tertiary N and P elimination the weakest increase can be observed in February, and for the small technical WWTPs no common pattern can be recognised. The distributions of the changes of PO 4P contents from upstream to downstream of the WWTPs have a similar pattern as the contents in the effluents and upstream, but show less variation at the small technical WWTPs; i.e. the slightest changes and lowest variability, with a median of +0.01 mg/L and a range of 0.06 mg/L, occurred at the technical WWTPs with tertiary N and P elimination, whereas the strongest changes and highest variability, with a median of +1.64 mg/L and a range of 5.00 mg/L, occurred at the small technical WWTPs.

5.1.10 Total phosphorus

Disregarding MB2 in January and February, the P tot contents upstream of the WWTPs ranged from 0.03 mg/L at L6 in February to 0.73 mg/L at MB1 in January. The values are relatively stable over the months compared to those in the effluents (Figure 5.19a). The highest median (0.35 mg/L) and the widest range (0.60 mg/L) occurred upstream of the small technical WWTPs, disregarding two outliers (at 9.87 mg/L and 7.46 mg/L), which are not represented in Figure 5.20. The technical WWTPs with tertiary N and P elimination had the lowest median (0.11 mg/L) and the narrowest range (0.14 mg/L). Distributions vary more and overlap to a greater extent than those of the PO 4P contents.

In the effluents P tot contents ranged from 0.09 mg/L at NP2 to 12.9 mg/L at MB1, both in January. In all cases they were higher than upstream, except for MB2 in January and February.

At most of the wastewater lagoons the P tot contents increased from December to February, with exception of L2 and L12, where the opposite was true. At the technical WWTPs with tertiary N and P elimination they decreased from December to February, and at the small technical

WWTPs both increases and decreases occurred. The P tot contents were highest at the small technical WWTPs and lowest at the technical WWTPs with tertiary N and P elimination, with medians of 6.63 mg/L and 0.27 mg/L, respectively. As for PO 4P contents both distributions were clearly distinct from each other. The median at the wastewater lagoons accounted for 3.11 mg/L.

Master thesis – Maria Redeker 5. Results

a) 7 14 1.2

6 12 1

5 10 0.8 4 8 0.6 3 6 0.4

c(Ptot) / mg/L c(Ptot) / 2 4

1 2 0.2

0 0 0 Master thesis Maria– Redeker Feb. 10 Feb.10 Feb. 10 Feb.10 Feb. 10 Feb. 10 Feb.10 Feb.10 Feb.10 Feb.10 Feb. 10 Feb. 10 Feb.10 Feb.10 Feb.10 Feb.10 Feb.10 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Feb.10 Feb.10 Dec.09 Dec.09 L1Jan.10 L2Jan.10 L3Jan.10 L4Jan.10 L5Jan.10 L6Jan.10 L7Jan.10 L8Jan.10 L9Jan.10 L10 Jan. 10 L11 Jan. 10 L12 Jan. 10 NP1 Jan.10 NP1 NP2 Jan.10 NP2 MB1 Jan. Jan. MB110 MB2 Jan. Jan. MB210 MB3 Jan. Jan. MB310 MB4 Jan.MB410 MB5 Jan. Jan. MB510 WWTP no. and month WWTP no. and month WWTP no. and month sampling position: upstream upstream effluent downstream

b) 4 4 7.83 6.38 0.05 3.5 3.5 0.04 3 3 0.03 2.5 2.5 2 2 0.02

1.5 1.5 0.01 1 1 diff c(Ptot)diff / mg/L 0 0.5 0.5 0 0 -0.01

-0.5 -0.5 -1.93 -0.02 L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 WWTP no. WWTP no. WWTP no. difference downstream – upstream Dec. 2009 Jan. 2010 Feb. 2010

Figure 5.19: Ptot contents in the effluents and receiving streams. a) Time series. WWTPs are listed by WWTP type and number. Different colours represent the different sampling positions (upstream, effluent, and downstream of the WWTPs, see legend). Three points per time series are dedicated to the sampling days in

December 2009, January 2010, and February 2010. b) Differences between the sampling points from upstream to downstream of the WWTPs at the sampling 97 days in December 2009, January 2010, and February 2010. 5. Results 98

Figure 5.20: Boxandwhiskers plots of the P tot contents upstream, in the effluents and downstream of the WWTPs, and changes from upstream to downstream for the different WWTP types (L = wastewater lagoons, MB = mechanic and biological treatment, NP = additional tertiary N and P elimination). See section 4.5.7.2 for remarks about the boxandwhiskers plots. *For the purpose of clarity two outliers at 7.46 mg/L and 9.87 mg/L are not displayed.

Downstream of the WWTPs the P tot contents were largely between those upstream and in the effluents of the respective WWTPs, or only slightly beyond. They ranged from 0.087 mg/L at NP2 in December to 8.56 mg/L at MB1 in January. From December to February values mostly increased. The highest P tot contents occurred downstream of the small technical WWTPs, with a median of 2.34 mg/L and a range of 8.17 mg/L. However, results agglomerated in the upper and the lower quarter of the distribution, while in between no values were measured. P tot contents downstream of the wastewater lagoons, disregarding 3 outliers, and the technical WWTPs with tertiary N and P elimination were largely distributed around the lower end of the distribution of the MB WWTPs. Their medians accounted for 0.47 mg/L and 0.14 mg/L, respectively.

The changes in P tot contents from upstream to downstream of the WWTPs are depicted in Figure 5.19b. The only reductions occurred at MB2 in February and at NP1 in January. The changes in general ranged from 1.93 mg/L at MB2 in February to +7.83 mg/L in January. At the wastewater lagoons the strongest changes between +2 mg/L and +4 mg/L occurred at L1 and L10, while at all other lagoons they were below +0.8 mg/L. At the small technical WWTPs the strongest changes exceeding +6 mg/L occurred at MB1, while at the others they were distributed relatively evenly up to 2.52 mg/L. At the technical WWTPs with tertiary N and P elimination all changes were minor than 0.05 mg/L. The medians accounted for +0.225 mg/L,

Master thesis – Maria Redeker 5. Results 99

0.84 mg/L, and 0.02 mg/L, respectively, whereas the minimal changes ranged between 0.01 mg/L and +0.05 mg/L.

5.1.11 Chloride Cl contents upstream of the WWTPs ranged from 25.5 mg/L at L3 in December to 144 mg/L at MB1 in February. In most cases they were below 50 mg/L, only at MB1 (in all three months) and at MB2 and NP2 (in January and February) they were markedly above. No clear development can be recognised over the months (Figure 5.21a). Upstream of the wastewater lagoons, small technical WWTPs and technical WWTPs with tertiary N and P elimination the Cl contents had similar minima (27.0 mg/L, 26.9 mg/L, and 34.7 mg/L) (Figure 5.22). The lowest median (32.8 mg/L) and maximum (37.7 mg/L) can be recognised upstream of the wastewater lagoons. The highest median (51.0 mg/L) and clearly highest maximum (144 mg/L) were those upstream of the small technical WWTPs, at which half of the values were in the lower quarter and the other half in the upper third of the distribution, while no values occurred in between. Upstream of the technical WWTPs with tertiary N and P elimination, the median accounted for 38.6 mg/L and the maximum for 87.5 mg/L. In the WWTP effluents Cl contents ranged from 22.0 mg/L at L6 in December to 211 mg/L at NP2 in February. At most of the WWTPs they increased from December to February, whereas at MB1 and MB2 they decreased. In most cases the Cl contents in the effluents were higher than upstream, except for L2 and L6 in December and MB1 in January and February. The medians of Cl contents in the effluents accounted for 47.9 mg/L at the wastewater lagoons, 96.0 mg/L at the small technical WWTPs, and 147 mg/L at the technical WWTPs with tertiary N and P elimination, whereas the median of the small technical WWTPs was approximately identical with the maximum of the lagoons and the minimum of the technical WWTPs with tertiary N and P elimination.

Master thesis – Maria Redeker 5. Results 100 250 90 80 200 70 60 150 50 40 100 c(Cl) / mg/L / c(Cl) c(Cl) / mg/L / c(Cl) 30 20 50 10 0 0 Master thesis Maria– Redeker Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Dec. Dec. Dec. Dec. Dec. Dec. Dec. L9Jan. L8Jan. L7Jan. L6Jan. L5Jan. L4Jan. L3Jan. L2Jan. L1Jan. L10Jan. L11Jan. L12Jan. NP1 Jan. NP1 NP2 Jan. NP2 MB1 Jan. MB1 MB2 Jan. MB2 MB3 Jan. MB3 MB4 Jan. MB4 MB5 Jan. MB5 WWTP no. and month WWTP no. and month sampling position: upstream upstream effluent downstream

60 60 85.7 96.9 106

50 50

40 40

30 30

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10 10 diff c(Cl) / / mg/L c(Cl) diff diff c(Cl) / / mg/L c(Cl) diff 0 0

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-20 -20 L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 WWTP no. WWTP no. difference downstream – upstream Dec. Jan. Feb.

Figure 5.21: Cl contents in the effluents and receiving streams. a) Time series. WWTPs are listed by WWTP type and number. Different colours represent the different sampling positions (upstream, effluent, and downstream of the WWTPs, see legend). Three points per time series are dedicated to the sampling days in

December 2009, January 2010, and February 2010. b) Differences between the sampling points from upstream to downstream of the WWTPs at the sampling 100 days in December 2009, January 2010, and February 2010. 5. Results 101

Figure 5.22: Boxandwhiskers plots of the Cl contents upstream, in the effluents and downstream of the WWTPs, and changes from upstream to downstream for the different WWTP types (L = wastewater lagoons, MB = mechanic and biological treatment, NP = additional tertiary N and P elimination). See section 4.5.7.2 for remarks about the boxandwhiskers plots

Downstream of the WWTPs Cl contents ranged from 22.7 mg/L at L11 in January to 193 mg/L at NP2 in February. In many cases they were outside the corresponding values upstream and in the effluents. Apart from L11b in January the deviations are however in the range of the measurement uncertainty. Downstream of most technical WWTPs Cl contents increased from December to February (except for MB1 and MB2), while downstream of the wastewater lagoons no general development is evident. The clearly lowest median (36.9 mg/L) and narrowest range (42.1 mg/L) can be observed downstream of lagoons, while the distributions downstream of the technical WWTPs showed much more variation (from 31.5 mg/L each to 137 mg/L downstream of the small technical WWTPs and 193 mg/L downstream of the technical WWTPs with N and P elimination) and had medians of 91.2 mg/L and 80.6 mg/L, respectively. The changes of Cl contents from upstream to downstream of the WWTPs ranged from 19.0 mg/L at MB2 in January to +106 mg/L at NP2 in February (Figure 5.21b). In about one third of the cases Cl contents decreased from upstream to downstream, while in the rest of the cases they increased. The strongest increases and reductions occurred at the technical WWTPs, while changes at the wastewater lagoons were more moderate. The most pronounced increases took place at NP2 in all three months. Accordingly, the distributions at all WWTP types spread both in the negative and positive range. The widest range of changes (from 10.7 mg/L to +106 mg/L) and the highest median (+45.9 mg/L) can be observed at the technical WWTPs with tertiary N and P elimination, whereas the values concentrate at the upper and lower 20 %

Master thesis – Maria Redeker 5. Results 102 of the range. The narrowest range (from 10.7 mg/L to +35.1 mg/L, with a median of +4.16 mg/L) can be recognised at the lagoons. The lowest median (+1.75 mg/L) was that at the small technical WWTPs, where the changes ranged from 19.0 mg/L to +52.8 mg/L.

5.1.12 Sulphate

2 SO 4 contents upstream of the WWTPs, disregarding MB2, ranged from 23.3 mg/L at L3 to 97.3 mg/L at L9, both in December (Figure 5.23a). At all three WWTP types both increasing and decreasing contents can be observed from December to February. The distributions of SO 4 contents upstream of all three WWTP types had about the same height and overlapped in their central parts (Figure 5.24). The medians accounted for 55.5 mg/L, 41.9 mg/L, and 59.3 mg/L upstream of the wastewater lagoons, small technical WWTPs and technical WWTPs with N and P elimination, and the ranges for 64.6 mg/L, 86.4 mg/L, and 33.9 mg/L, respectively.

2 In the effluents SO 4 contents ranged from 4.06 mg/L at L7 to 119 mg/L at MB2, both in

2 January. Over the months no common development can be recognised. At the lagoons the SO 4

2 contents were largely below 50 mg/L and below the corresponding SO 4 contents upstream. At the technical WWTPs all values except MB1 in February were above 50 mg/L, and they were largely higher than the corresponding values upstream. Accordingly the lowest distribution was that a the small technical WWTPs, with a median of 20.6 mg/L. The median at the technical WWTPs (73.1 mg/L) was slightly lower than that at the small technical WWTPs (80.9 mg/L), and the range was narrower (41.9 mg/L against 73.9 mg/L), but both distributions had about the same height.

2 Downstream of the WWTPs SO 4 contents ranged from 9.21 mg/L at L1 in February to 109 mg/L at MB2 in February. Similar to the Cl contents, in many cases they were not

2 between the SO 4 contents of the corresponding samples from upstream and in the effluents. Except for MB4 in January this can be explained in all cases by uncertainties of measurement. The medians downstream of the lagoons and MB WWTPs were very similar (51.7 mg/L and 51.9 mg/L, respectively). The distribution downstream of the lagoons was relatively symmetric, while that downstream of the small technical WWTPs was positively skewed. The median downstream of the technical WWTPs with tertiary N and P elimination accounted for 70.5 mg/L, whereas the actual values measured at the WWTPs concentrated near the minimum of 47.6 mg/L and the maximum of 91.5 mg/L.

Master thesis – Maria Redeker 5. Results

a) 120 140

100 120

100 80 80 60 60 40 c(SO42)mg/L / 40 c(SO42)/mg/L 20 20

0 0 Master thesis Maria– Redeker Feb. 10 Feb. 10 Feb. 10 Feb. 10 Feb.10 Feb. 10 Feb.10 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Feb.10 Feb.10 Feb. 10 Feb.10 Feb.10 Feb. 10 Feb. 10 Feb.10 Feb.10 Feb. 10 Feb. 10 Feb.10 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 Dec.09 L1Jan.10 L2Jan.10 L3Jan.10 L4Jan.10 L5Jan.10 L6Jan.10 L7Jan.10 L8Jan.10 L9Jan.10 L10 Jan. 10 L11 Jan. 10 L12 Jan. 10 NP1 Jan. 10 NP1 Jan. NP2 Jan.10 NP2 MB5 Jan. Jan. MB510 MB4 Jan.MB410 MB3 Jan. Jan. MB310 MB2 Jan.MB210 MB1 Jan. Jan. MB110 WWTP no. and month WWTP no. and month sampling position: upstream upstream effluent downstream

b) 40 60 30 50 20 40 10 30 0 20 -10 10 -20 0 diff c(SO4diff 2)/ mg/L -30 c(SO4diff 2)/ mg/L -10 -40 -20 -50 -30 -60 -40 L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 WWTP no. WWTP no. difference downstream – upstream Dec. 2009 Jan. 2010 Feb. 2010

2 Figure 5.23: SO 4 contents in the effluents and receiving streams. a) Time series. WWTPs are listed by WWTP type and number. Different colours represent the different sampling positions (upstream, effluent, and downstream of the WWTPs, see legend). Three points per time series are dedicated to the sampling days in December 2009, January 2010, and February 2010. b) Differences between the sampling points from upstream to downstream of the WWTPs at the sampling 103 days in December 2009, January 2010, and February 2010. 5. Results 104

2 Figure 5.24: Boxandwhiskers plots of the SO 4 contents upstream, in the effluents and downstream of the WWTPs, and changes from upstream to downstream for the different WWTP types (L = wastewater lagoons, MB = mechanic and biological treatment, NP = additional tertiary N and P elimination). See section 4.5.7.2 for remarks about the boxandwhiskers plots

2 Changes of SO 4 contents from up to downstream of the WWTPs (Figure 5.23b) ranged from 43.0 mg/L at L1 in February to +35.0 mg/L at MB2 in December. At the wastewater lagoons

2 SO 4 contents mainly decreased from up to downstream, while at the technical WWTPs they largely increased. The highest absolute values occurred at L1, MB2, and NP2. Over the months

2 no clear development can be observed. The lowest distribution of the changes in SO 4 contents can be recognised at the wastewater lagoons. The median was slightly negative (3.30 mg/L) and the distribution was negatively skewed. The distributions of the technical WWTPs had similar medians (+7.76 mg/L and +8.79 mg/L). They were relatively symmetric and contained only few negative values.

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5.2 Longitudinal profiles

5.2.1 Stör At the river Stör the WWTP L9 and the sampling points S6, and S7 are located in this order within a distance of about 4 km. Further downstream the points S9 and S21 are located (about 7 km respectively 20 km downstream of S7) (Figure 5.25).

Figure 5.25: Location of the sampling points S6, S7, and S9 and the WWTP L9 at the Stör

December 2009 January 2010 February 2010 3.8 3.6 3.9 1.0 1.0 1.0 0.9 0.9 0.9 0.8 0.8 0.8 0.7 0.7 0.7 0.6 0.6 0.6 0.5 0.5 0.5 0.4 0.4 0.4 c(NH4N) /mg/L c(NH4N) c(NH4N) /mg/L c(NH4N) 0.3 /mg/L c(NH4N) 0.3 0.3 0.2 0.2 0.2 0.1 0.1 0.1 0.0 0.0 0.0 S S 6 S 7 S 9 S S 6 S 7 S 9 S S 6 S 7 S 9 L9 a L9 b L9 L9 a L9 b L9 S S 21 L9 w L9 S S 21 L9 w L9 L9 a L9 b L9 L9 w L9 S 21 sampling point sampling point sampling point effluents Stör

Figure 5.26: Longitudinal profile of NH 4N contents in the river Stör and the effluent of the WWTP L9

In Figure 5.26 for NH 4N contents an increase from L9a to L9b can be observed in all three months, as already observed in section 5.1.5. Whereas the contents subsequently decrease up to the point S7, a saltation to higher values can be observed from point S7 to point S9 and, in December and January, a further increase until S21. However contents at point S21 remained

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below those at L9b. In spite of the elevated NH 4-N content at L9b in February, the value at S6 was in February at the same level as in the other months.

December 2009 January 2010 February 2010 0.52 0.60 0.59 0.10 0.10 0.10 0.09 0.09 0.09 0.08 0.08 0.08 0.07 0.07 0.07 0.06 0.06 0.06 0.05 0.05 0.05 0.04 0.04 0.04 c(PO4-P) / mg/L c(PO4-P) / mg/L c(PO4-P) 0.03 0.03 / mg/L c(PO4-P) 0.03 0.02 0.02 0.02 0.01 0.01 0.01 0.00 0.00 0.00 S S 6 S 7 S 9 S 6 S 7 S 9 S S 6 S 7 S 9 L9 a L9 b L9 a L9 b L9 L9 a L9 b L9 L9 w L9 w L9 S S 21 S 21 L9 w L9 S S 21 sampling point sampling point sampling point effluents Stör

Figure 5.27: Longitudinal profile of PO 4-P contents in the river Stör and the effluent of the WWTP L9

Also PO4-P contents (Figure 5.27) increased from L9a to L9b in all three months (cf. section 5.1.9). In January and February, they decreased continuously between the subsequent sampling points, whereas in December they fluctuated short below the value measured at L9b, and at

S21 reached a level higher than at L9b. As for NH 4-N contents, an elevated value at L9b can be observed in February compared to January and December, whereas the PO 4-P content at S6 was even slightly lower than in the other months.

December 2009 January 2010 February 2010 0.76 0.79 0.80 0.45 0.45 0.45 0.40 0.40 0.40 0.35 0.35 0.35 0.30 0.30 0.30 0.25 0.25 0.25 0.20 0.20 0.20 0.15 0.15 0.15 c(Ptot) / mg/L c(Ptot) / mg/L c(Ptot) c(Ptot) / mg/L c(Ptot) 0.10 0.10 0.10 0.05 0.05 0.05 0.00 0.00 0.00 S S 6 S 7 S 9 S 6 S 7 S 9 S S 6 S 7 S 9 L9 a L9 b L9 a L9 b L9 L9 a L9 b L9 L9 w L9 S 21 w L9 S 21 L9 w L9 S S 21 sampling point sampling point sampling point effluents Stör

Figure 5.28: Longitudinal profile of P tot contents in the river Stör and the effluent of the WWTP L9

Ptot contents as well increased from L9a to L9b (Figure 5.28), but highest P tot contents of the points sampled at the Stör were measured in December at S7 and in January at S21, while at S6 they were below the contents at L9a. In February the P tot contents at the subsequent points were between those measured at L9a and L9b.

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5.2.2 Schwale At the river Schwale the WWTP L11 is located about 4 km upstream of the entry of the ditch 1.12, which receives effluent from the WWTP MB2 about 1.2 km upstream. The point L5 is located about 1 km downstream of the entry in the river Schwale, and the points S4 and S2 are located further downstream (about 4 km and 7 km distance to the entry of the ditch) (Figure 5.29).

Figure 5.29: Location of the sampling points S2, S4, S5 and the WWTPs L11 and MB2 relative to the Schwale

December 2009 January 2010 February 2010 16.1 15.4 33.9 1.4 1.4 1.4 1.2 1.2 1.2 1.0 1.0 1.0 0.8 0.8 0.8 0.6 0.6 0.6 0.4 0.4 0.4 c(NH4-N) / mg/L c(NH4-N) c(NH4-N) / mg/L c(NH4-N) / mg/L c(NH4-N) 0.2 0.2 0.2 0.0 0.0 0.0 S S 5 S 4 S 2 S S 5 S 4 S 2 S S 5 S 4 S 2 L11 a L11 b L11 L11 a L11 b L11 a L11 b L11 L11 w L11 L11 w L11 L11 w L11 MB2 Ra MB2 Rb MB2 MB2 Ra MB2 Rb MB2 MB2 Ra MB2 Rb MB2 MB2 Rw MB2 MB2 Rw MB2 MB2 Rw MB2 sampling point sampling point sampling point effluents Schwale

Figure 5.30: Longitudinal profile of NH 4-N contents in the river Schwale, the effluent of the WWTP L11 and the entry of the ditch 1.12 transporting effluent from the WWTP MB2

NH 4-N contents increased from L11a to L11b in all three months and up to MB2Ra declined considerably, in December even to a level below the content at L11a (Figure 5.30). At MB2Rw

NH 4-N contents had already slightly declined compared to MB2b (cf. section 5.1.5). In December the value was still above that in the Schwale at MB2Ra, and accordingly MB2Rb had a slightly higher NH 4-N content than MB2Ra. The highest content in the Schwale in

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December was measured at S5. In January and February NH 4-N contents at MB2Rw were below those at MB2Ra, while the values at S5, S4, and S2 were similar or slightly above that at MB2Ra.

December 2009 January 2010 February 2010 2.80 2.93 4.85 0.30 0.30 0.30

0.25 0.25 0.25

0.20 0.20 0.20

0.15 0.15 0.15

0.10 0.10 0.10 c(PO4-P) / mg/L c(PO4-P) c(PO4-P) mg/L / c(PO4-P) 0.05 0.05 / mg/L c(PO4-P) 0.05

0.00 0.00 0.00 S S 5 S 4 S 2 S S 5 S 4 S 2 S S 5 S 4 S 2 L11 a L11 b L11 L11 a L11 b L11 L11 a L11 b L11 L11 w L11 L11 w L11 L11 w L11 MB2 Ra MB2 Rb MB2 MB2 Ra MB2 Rb MB2 MB2 Rw MB2 MB2 Ra MB2 Rb MB2 MB2 Rw MB2 MB2 Rw MB2 sampling point sampling point sampling point effluents Schwale

Figure 5.31: Longitudinal profile of PO 4-P contents in the river Schwale, the effluent of the WWTP L11 and the entry of the ditch 1.12 transporting effluent from the WWTP MB2

PO 4-P contents (Figure 5.31) showed a similar pattern as NH 4-N contents, however the values at MB2Ra were below those at L11a in all three months, and the PO 4-P content at S5 in December was only slightly higher than the one at MB2Rw. Contents at MB2Rw were reduced by 1-2 orders of magnitude compared to MB2b (cf. section 5.1.9). As the NH 4-N contents, the

PO 4-P contents were only slightly influenced by the ditch 1.12, and at the points S5, S4, and S2 they were at a similar level as at MB2Ra.

December 2009 January 2010 February 2010 3.51 3.96 5.46 0.50 0.50 0.50 0.45 0.45 0.45 0.40 0.40 0.40 0.35 0.35 0.35 0.30 0.30 0.30 0.25 0.25 0.25 0.20 0.20 0.20 0.15 0.15 0.15 c(Ptot) / mg/L c(Ptot) c(Ptot) / mg/L c(Ptot) 0.10 mg/L / c(Ptot) 0.10 0.10 0.05 0.05 0.05 0.00 0.00 0.00 S S 5 S 4 S 2 S S 5 S 4 S 2 S S 5 S 4 S 2 L11 a L11 b L11 L11 a L11 b L11 L11 a L11 b L11 L11 w L11 L11 w L11 L11 w L11 MB2 Ra MB2 Rb MB2 MB2 Ra MB2 Rb MB2 MB2 Ra MB2 Rb MB2 MB2 Rw MB2 MB2 Rw MB2 MB2 Rw MB2 sampling point sampling point sampling point effluents Schwale

Figure 5.32: Longitudinal profile of P tot contents in the river Schwale, the effluent of the WWTP L11 and the entry of the ditch 1.12 transporting effluent from the WWTP MB2

Also P tot contents increased from L11a to L11b in all three months (Figure 5.32). From L11b to

MB2a a further strong increase can be observed in January. As PO 4-P contents, also P tot contents at MB2Rw were reduced by 1-2 orders of magnitude compared to MB2b (cf. section

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5.1.10). In December the P tot contents in the Schwale were reduced slightly at the ditch 1.12. In January and February no direct influence by the ditch can be observed, as at MB2Rb the content was drastically lower respectively higher than at both MB2Ra and MB2Rb. An elevation at S5 in December can also be observed for the P tot content.

5.2.3 Buckener Au The ditch 29 transporting effluent from the WWTP L5 opens into the river Buckener Au about 800 m downstream of the sampling point S18. About 7.5 km downstream of the ditch entry the point S17 is located. In between, the WWTPs L3, L4, and L7 discharge indirectly into the Buckener Au via several pipeworks and smaller streams, which due to bad accessibility were not sampled in the scope of this thesis. Several further tributaries open into the Buckener Au in this intercept.

Figure 5.33: Location of the sampling points S17, S18 and the WWTPs L5, L7, L2 and L3 relative to the Buckener Au

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December 2009 January February 3.7 2.1 2.2 0.8 0.8 0.8 0.7 0.7 0.7 0.6 0.6 0.6 0.5 0.5 0.5 0.4 0.4 0.4 0.3 0.3 0.3 c(NH4-N) / mg/L c(NH4-N) c(NH4-N) / mg/L c(NH4-N) c(NH4-N) /mg/L c(NH4-N) 0.2 0.2 0.2 0.1 0.1 0.1 0.0 0.0 0.0 S S 18 S 17 S S 18 S 17 S 18 S 17 L5 Ra L5 Rb L5 L5 Ra L5 Rb L5 Ra L5 Rb L5 L5 Rw L5 L5 Rw L5 Rw L5 sampling point sampling point sampling point effluents Buckener Au

Figure 5.34: Longitudinal profile of NH 4-N contents at the points S18 and S17 in the river Buckener Au and the entry of the ditch 29 transporting effluent from the WWTP L5

In Figure 5.34 a slight increase of NH 4-N contents can be recognised from S18 to L5Ra in all three months, which was strongest in January. A slight increase can also be noted from L5Ra to

L5Rb. Up to S17 the NH 4-N content decreased, in December only slightly, but in January and

February to values below the ones measured at S18. The NH 4-N contents at L5Rw were reduced to ca. 20 % of those at L5w (cf. section 5.1.5).

December 2009 January 2010 February 2010 0.33 0.21 0.29 0.08 0.08 0.08 0.07 0.07 0.07 0.06 0.06 0.06 0.05 0.05 0.05 0.04 0.04 0.04 0.03 0.03 0.03 c(PO4-P) / mg/L c(PO4-P) / mg/L c(PO4-P) 0.02 0.02 /mg/L c(PO4-P) 0.02 0.01 0.01 0.01 0.00 0.00 0.00 S S 18 S 17 S 18 S 17 S S 18 S 17 L5 Ra L5 Rb L5 Ra L5 Rb L5 L5 Ra L5 Rb L5 L5 Rw L5 Rw L5 L5 Rw L5 sampling point sampling point sampling point effluents Buckener Au

Figure 5.35: Longitudinal profile of PO 4-P contents at the points S18 and S17 in the river Buckener Au and the entry of the ditch 29 transporting effluent from the WWTP L5

PO 4-P contents decreased slightly from S18 to L5Ra and increased slightly from L5Ra to L5Rb in all three months. A stronger decrease until S17 can be recognised in all three months (Figure

5.35). The PO 4-P contents at L5Rw were about one order of magnitude below those at L5w (cf. section 5.1.9).

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December 2009 January 2010 February 2010 0.45 0.75 0.54 0.30 0.30 0.30

0.25 0.25 0.25

0.20 0.20 0.20

0.15 0.15 0.15

0.10 0.10 0.10 c(Ptot) / mg/L c(Ptot) / mg/L c(Ptot) / mg/L c(Ptot) 0.05 0.05 0.05

0.00 0.00 0.00 S S 18 S 17 S 18 S 17 S 18 S 17 L5 Ra L5 Rb L5 Ra L5 Rb L5 Ra L5 Rb L5 L5 Rw L5 Rw L5 Rw L5 sampling point sampling point sampling point effluents Buckener Au

Figure 5.36: Longitudinal profile of P tot contents at the points S18 and S17 in the river Buckener Au and the entry of the ditch 29 transporting effluent from the WWTP L5

Ptot contents were nearly constant in December between S18 and L5Rb, while at S17 a higher content was measured. In January the highest content in the Buckener Au was recorded at S18, the lowest ones at L5a and L5b. In February P tot contents increased from L5Ra to L5Rb and decreased slightly from S18 to L5Ra and from L5Rb to S17, so that at S18 and S17 they were approximately identical (Figure 5.36). Also P tot contents at L5Rw were almost one order of magnitude lower than at L5w (cf. section 5.1.10).

5.2.4 Fuhlenau At the Fuhlenau the point S16 is located about 1.2 km downstream of the entry of the ditch Gliner Graben, which indirectly receives the effluent from the WWTP L1 (cf. section 4.2) (Figure 5.37).

Figure 5.37: Location of the sampling point S16 and the WWTP L1 relative to the Fuhlenau

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December 2009 January 2010 February 2010 3.5 3.5 3.5

3.0 3.0 3.0

2.5 2.5 2.5

2.0 2.0 2.0

1.5 1.5 1.5 c(NH4-N) / mg/L c(NH4-N) / mg/L c(NH4-N) c(NH4-N) / mg/L c(NH4-N) 1.0 1.0 1.0

0.5 0.5 0.5

0.0 0.0 0.0 S S 16 S 16 S S 16 L1 Ra L1 Rb L1 Ra L1 Rb L1 L1 Ra L1 Rb L1 L1 Rw L1 Rw L1 L1 Rw L1 sampling point sampling point sampling point effluents Fuhlenau

Figure 5.38: Longitudinal profile of NH 4-N contents at the entry of the Gliner Graben transporting effluent from the WWTP L1 and the point S16 in the river Fuhlenau

As Figure 5.38 shows, the NH 4-N contents increased in all three months from L1Ra to L1Rb and decreased until S16, where they were still elevated compared to L1Ra. At L1Rw they were about one order of magnitude lower than at L1b (cf. section 5.1.5).

December 2009 January 2010 February 2010 0.30 0.30 0.30

0.25 0.25 0.25

0.20 0.20 0.20

0.15 0.15 0.15

0.10 0.10 0.10 c(PO4-P) / mg/L c(PO4-P) c(PO4-P) / mg/L c(PO4-P) c(PO4-P) / mg/L c(PO4-P) 0.05 0.05 0.05

0.00 0.00 0.00 S S 16 S 16 S S 16 L1 Ra L1 Rb L1 Ra L1 Rb L1 L1 Ra L1 Rb L1 L1 Rw L1 L1 Rw L1 L1 Rw L1 sampling point sampling point sampling point effluents Fuhlenau

Figure 5.39: Longitudinal profile of PO 4-P contents at the entry of the Gliner Graben transporting effluent from the WWTP L1 and the point S16 in the river Fuhlenau

PO 4-P contents increased from L1Ra to L1Rb in all three months, although in December the

PO 4-P content at L1Rw was slightly lower than at L1Ra (Figure 5.39). In December the content at S16 was elevated compared to L1Rb, while in January and February it was slightly below. In all three months the PO 4-P content was at least slightly higher at S16 than at L1Ra.

PO 4-P contents at L1Rw were reduced compared to L1b by factors of about 20 (in December and January) respectively 10 (in February, cf. section 5.1.9).

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December 2009 January 2010 February 2010 0.70 0.70 0.70

0.60 0.60 0.60

0.50 0.50 0.50

0.40 0.40 0.40

0.30 0.30 0.30 c(Ptot) / mg/L c(Ptot) / mg/L c(Ptot) 0.20 0.20 / mg/L c(Ptot) 0.20

0.10 0.10 0.10

0.00 0.00 0.00 S S 16 S 16 S S 16 L1 Ra L1 Rb L1 Ra L1 Rb L1 L1 Ra L1 Rb L1 L1 Rw L1 Rw L1 L1 Rw L1 sampling point sampling point sampling point effluents Fuhlenau

Figure 5.40: Longitudinal profile of P tot contents at the entry of the Gliner Graben transporting effluent from the WWTP L1 and the point S16 in the river Fuhlenau

The P tot contents (Figure 5.40) decreased along the three sampling points in the Fuhlenau in

December, in spite of a higher value at L1Rw. In January and February P tot contents increased from L1Ra to L1Rb and decreased until S16, where they were slightly higher in January and slightly lower in February than at L1Ra. The P tot contents at L1Rw were almost one order of magnitude lower than those at L1b (cf. section 5.1.10).

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6 Discussion In the first part of this chapter the characteristics of the WWTP effluents are discussed and compared with the emission limits set for the single WWTPs. The second part focuses on the impacts of the sewage effluents on the receiving rivers, comparing both the different parameters and the importance of the size and contamination of the WWTPs. As a third step the impacts are regarded on a larger scale, comparing the direct vicinities of the WWTPs with selected points along the receiving rivers. The ecological status of the rivers at the sampling points is assessed by the classifications according to LAWA (1998) and RAKON (LAWAAO, 2007).

6.1 Effluents

6.1.1 Physical parameters The low water temperatures of the effluents from the WW lagoons compared to those from the technical WWTPs can be explained by the circumstance that they are more exposed to the ambient, due to the high surface/volume ratio and because most of the WW lagoons are situated on fields and surrounded by only few, if any, trees (cf. section 4.2). This makes them susceptible to temperature changes according to the ambient. An additional factor in January and February 2010 was the ice sheet, which developed in course of the sampling period on most WW lagoons (cf. section 4.3). In contrast at the small technical WWTPs, the WW does not become superficial until being discharged and is thus better insulated against ambient temperatures. In the technical WWTP NP1, the WW is exposed to the ambient in the storage basin and in the SBRs. However, detention time in the storage basin is only 4 h and in the SBRs 8 h, and the walls of the SBRs are coated by an earth wall. Slightly lower water temperatures in the effluents of the NP2 may be explained by the polishing lagoon which is passed before discharging into the Bullenbek. However, due to the detention time of about 4 5 days (Stadt Neumünster, 2010), some even lower values could have been expected. The decrease of water temperatures in the effluents can be explained by the continuing low ambient temperatures throughout the sampling period. The continuously relatively high temperatures at L9, where until the sampling series in February 2010 no ice sheet had developed on the last lagoon, may be attributed to intruding groundwater (cf. section 4.2). The low water temperatures recorded in February 2010 are well in accordance with the findings of Drebes & Grottker (1997), who found water temperatures near 1 °C in 16 icecovered naturally

Master thesis – Maria Redeker 6. Discussion 115 aerated WW lagoons of the districts Segeberg and RendsburgEckernförde, during a permanent frost period in winter 1996/1997. The pH values of the effluents were mostly in a slightly alkaline range, at which the most alkaline values occurred at L7. Only the effluents of L6 and NP1 were slightly acidic. In general, the effluents from the technical WWTPs applying tertiary N and P elimination were slightly less alkaline than those of the other WWTP types. However, the differences between the single WWTPs and between the WWTP types were not significant, and also the values of the large technical WWTPs applying tertiary N and P elimination still were in the range of those from the WW lagoons. All pH values were between 6.5 and 8.5, in which no negative impacts on the performance of the activation process are to be expected (Mudrack & Kunst, 2003) and which are set in the Austrian Ordinance concerning the general limitation of wastewater emissions into running waters and public sewers as emission limit for the discharge into running waters (AAEV, 1996). As expected, DO contents in the WWTPs were below those in the rivers and ditches, due to the high oxygen demand of the WW constituents. The oxygen contents measured in the effluent samples may rather be an effect of sampling than reflect the actual contents at the discharge, as strong turbulences in the sampling beaker caused an ingestion of air, and therewith oxygen, into the samples. A further indication are the lower DO contents recorded in the effluent samples from L9 and L10, where samples were taken from the discharge in the last lagoons, i.e. from a rather calm pool instead of a strong jet of water. At least in the WW lagoons lower DO contents are probable, as the ice sheet prevented physical and, due to the overlying snow cover, also biological oxygenation (e.g., Mudrack & Kunst, 2003). Drebes & Grottker (1997) found DO contents as low as 0 mg/L or 1 mg/L in the effluents of icecovered WW lagoons. However, the decreasing DO contents from December 2009 to February 2010 in the effluent samples from the WW lagoons reflect the development of the ice sheet in the course of this period. The relatively consistent oxygen contents at the small technical WWTPs may be due to the aeration of the WW at defined intervals, which was not affected by seasonal effects. The strong increase in DO contents at L2w is surprising, especially as the aeration did not function in January and February 2010. As also the lagoons of this WWTP were covered with ice and snow in January and February 2010, the values measured in these months appear implausibly high. At the discharge in the last lagoon of that WWTP values below 1 mg/L were recorded during that time (MarxReese, 2010). Also the other values at L2 show contradicting results, thus a sampling error is assumed: as the outlet was not too well distinguishable, water from the recipient Führbek may accidentally have been taken together with the effluent.

Master thesis – Maria Redeker 6. Discussion 116

EC is a measure of the total ion content of a sample. In the WWTP effluents EC increased from December 2009 to February 2010, as did the concentrations of most investigated ions in most of the samples (cf. the following sections). This may be due to the reduced microbial activities at lower temperatures and oxygen contents. Another reason, at least at the WW lagoons, which receive WW from combined sewer systems, can be the utilisation of road salt in January and February 2010, as the WW lagoons are connected to combined sewer systems. The lower values at the WW lagoons may, at least in December 2009 and to a lesser extent in January 2010, be due to dilution effects from precipitation, directly via the lagoon surfaces and indirectly via the sewers, while the technical WWTPs are connected to separate sewer systems. In the effluents of the technical WWTPs values above 1000 µS/cm were detected, which is markedly above the values measured at the other points in the catchment, where EC ranged between 300 µS/cm and 700 µS/cm during the sampling period (Pott, in prep.).

6.1.2 N compounds In Figures 6.1 and 6.2 the composition of the N fraction of the effluent samples is compared. In

Figure 6.1 the absolute contents of the dissolved inorganic nitrogen (DIN) compounds NH 4N,

NO 2N and NO 3N in each sample are represented as stacked columns, and for comparison of their sum with the measured N tot contents, the latter ones are represented as dots. Figure 6.2 shows the percental shares of the mentioned DIN compounds in N tot . The difference between the N tot contents and the sum of the DIN compounds represents the content in organic nitrogen

(N org ).

80

70

60

50

40 c(N) / mg/L / c(N) 30

20

10

0 Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. L9 Jan. L9 L8 Jan. L8 L7 Jan. L7 L6 Jan. L6 L5 Jan. L5 L4 Jan. L4 L3 Jan. L3 L2 Jan. L2 L1 Jan. L1 L12 Jan. L12 L11 Jan. L11 L10 Jan. L10 NP2 Jan. NP2 NP1 Jan. NP1 MB5 Jan. MB5 MB4 Jan. MB4 MB3 Jan. MB3 MB2 Jan. MB2 MB1 Jan. MB1 WWTP no. and sampling position NH4-N NO2-N NO3-N Ntot

Figure 6.1: Contents of the inorganic nitrogen compounds NH 4N, NO 2N, and NO 3N (represented as

stacked columns) and N tot in the effluents of the WWTPs

Master thesis – Maria Redeker 6. Discussion 117

120%

100%

80%

60% share in in Ntot share 40%

20%

0% Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. L9 Jan. L9 L8 Jan. L8 L7 Jan. L7 L6 Jan. L6 L5 Jan. L5 L4 Jan. L4 L3 Jan. L3 L2 Jan. L2 L1 Jan. L1 L10 Jan. L10 L11 Jan. L11 L12 Jan. L12 NP1 Jan. NP1 NP2 Jan. NP2 MB5 Jan. MB5 MB4 Jan. MB4 MB3 Jan. MB3 MB2 Jan. MB2 MB1 Jan. MB1 WWTP no. and sampling position NH4-N NO2-N NO3-N

Figure 6.2: Percental shares of the inorganic nitrogen compounds NH 4N, NO 2N, and NO 3N in N tot . Shares > 100 % result from measurement uncertainties (cf. text).

In the effluents of the wastewater lagoons the main DIN compound was NH 4N, while NO 3N occurred in very low, if any, amounts. The only lagoons where NO 3N occurred in considerable amounts were L2, L3, and L4, with shares between 11 % and 65 %. In the effluents of most technical WWTPs the main DIN compound was NO 3N, while NH 4N occurred only in low amounts. However NH 4N was the main DIN compound in the effluents of MB1 and of MB3 in February 2010, and MB1 showed the highest of all NH 4N contents with 45 mg/L. This value is especially alarming as MB1 discharges into one of the smallest recipients. NO 2N was the minor N compound in all samples, with shares in N tot below 7 %. Nevertheless the absolute content at MB2 in January 2010 accounted for nearly 5 mg/L, which is well above the guiding limits set in the EC Freshwater Fish Directive of 0.01 mg/L in salmonid and 0.03 mg/L in cyprinid waters (EC, 2006). Especially high N org contents occurred at MB2, but elevated amounts were also present at L10, L11, MB4 and MB5. The high difference between N tot and

DIN at L8 is not necessarily a sign for high N org contents, as the recorded NH 4N content was assumed not to be correct (cf. section 4.5.7.2).

In some samples the measured N tot contents were slightly below the sum of the DIN compounds, resulting in shares of DIN in N tot > 100 % . This may result from the different methods applied for their determination, which are not comparable to each other, as they analyse different traits of the respective compounds. Furthermore, and probably more important, each of the determinations of the four parameters has a certain uncertainty of measurement, which all sum up.

Master thesis – Maria Redeker 6. Discussion 118

As expected, both N tot and NH 4N contents were lowest in the effluents of the technical

WWTPs applying nitrification and denitrification steps. Also NO 3N contents were low at NP1, whereas at NP2 they were higher than at the WW lagoons with detectable NO 3N contents, but lower than in most samples from the small technical WWTPs. The observed values are in accordance with the monitoring data from the past five years, in which NO 3N contents were largely below 1.5 mg/L at NP1 and between 3 mg/L and 7 mg/L at the official discharge prior to the polishing lagoon at NP2 (UWB RendsburgEckernförde, 2009). In general, the contents of all measured N parameters (N tot , NH 4N, NO 2N, NO 3N) except NO 2N were higher at NP2 than at NP1. While the main N component in the effluent of NP2 was NO 3N, N org made up the main part of N tot in the effluent of N1. According to PehlivanogluMandlas & Sedlak (2008)

Norg is the main N component in nitrifieddenitrified WWTP effluents. It can arise from incomplete degradation of organic compounds originating from the WW, especially of those which are not readily biodegradable, or from the biological treatment processes within the WWTPs (Sattayewa et al., 2009), since microorganisms excrete organic matter relating to substrate concentrations, residence time and growth rate (Chudoba, 1985).

The high NO 3N share at NP2 indicates incomplete denitrification, although due to the ice sheet on the polishing lagoon anoxic conditions favouring denitrification may have been expected. This may be due to low water temperatures and therefore reduced microbial activity or due to a lack of organic substrate as electron donors, which are an important factor controlling the activity of denitrifiers (HallingSørensen & Jørgensen, 1993) and possibly were degraded during the treatment process. However, NO 3N contents are still low compared to those in the effluents of most small technical WWTPs.

The NO 3N contents at the WW lagoons were, if detectable, generally lower than those at the small technical WWTPs. Also Drebes & Grottker (1997) found NO 3N contents close to

0 mg/L in icecovered lagoons. Low NO 3N contents can be explained by nitrification not being a major pathway of N elimination in WW lagoons (Ferrara & Avci, 1982; Pano & Middlebrooks, 1982; Reed, 1985; Toms et al., 1975). In addition, the recorded low water temperatures and low DO contents are two further inhibitors for nitrification: several authors (cited in HallingSørensen & Jørgensen, 1993) found temperatures below 5 °C and DO contents in magnitudes around 0.5 mg/L 2 mg/L to be limiting for the growth of nitrifying bacteria. Somewhat surprising are the relatively high NO 3N contents in the effluents of L3 and L4, also compared to monitoring data from the past years (UWB RendsburgEckernförde, 2009), in spite of already low temperatures < 4 °C in December 2009.

Master thesis – Maria Redeker 6. Discussion 119

The NH 4N contents, as the main DIN compound, were higher than those of most of the investigated technical WWTPs, and compared to monitoring data from the water authorities of the districts they were in the upper range or even above (UWB RendsburgEckernförde, 2009; UWB Segeberg, 2009; UWB Steinburg, 2010). This can be attributed to the local conditions in the investigated period, as ammonia volatilisation, which is believed to be the dominant mechanism of nitrogen removal in facultative WW lagoons (Reed et al., 1995), requires warm temperatures and pH values between 10 and 12 (Reed, 1985). The other important mechanism is sedimentation of N org and subsequent accumulation of nonbiodegradable material in the sediment zone (Ferrara & Avci, 1982; Reed, 1985).

Increases from December 2009 to February 2010 in both N tot and NH 4N contents in the effluents of the WW lagoons can be explained by the decreasing dilution due to precipitation, as described above (sections 4.3, 6.1.1). Especially as no clear trend is recognisable in the share of NH 4N contents in N tot .

The low N tot and NH 4N contents at L9 may result from additional dilution by groundwater (cf. section 4.2). Decreasing N tot and NH 4N contents as well as increasing NO 3N contents recorded at L2 are more probably due to stream water included in the sample than to the actual contents in the effluent (see section 6.1.1). The NH4N contents measured at L8 are unusually low, as mentioned above. Apart from earlier monitoring data, also the lower NH 4N contents upstream and higher contents downstream of the WWTP outlet suggest higher ammonium contents in the effluent than the measured ones. Therefore an analytical error is suspected.

The on average higher N tot contents of the small technical WWTPs may be explained by more concentrated influents, as those WWTPs are connected to separate sewer systems. Relatively low NH 4N and high NO 3N contents clearly indicate the occurrence of nitrification, but only a low extent, if any, of denitrification. As for small WWTPs in the size category 1 no general requirements for N limitation exist, they are not explicitly designed for the elimination of N compounds, which therefore occurs rather as a side effect. The better nitrification can be explained on one hand by the higher temperatures as a precondition to allow for at least some microbial activity. In addition, the aeration provides aerobic conditions and a good mixing of the water. In combination with the large surface of the movingbed biofilters, this allows for an intensive contact between the nitrifying bacteria and the substrate. One of the most important factors controlling the activity of denitrifying bacteria is the availability of electron donors, i.e. of carbon sources (HallingSørensen & Jørgensen, 1993). As the considered WWTPs are primarily designed for the degradation of BOD respectively COD, potential electron donors for

Master thesis – Maria Redeker 6. Discussion 120 denitrification are possibly largely degraded. However, according to their purpose these WWTPs do not have a denitrification basin, and denitrification in secondary sedimentation tanks is undesirable, as floating sludge might develop (section 2.2.3.2). In general, strong variability can be observed in the composition of N compounds both between the single WWTPs and at MB2, MB3, and MB5 also between the months. Monitoring data from the water authority of the district RendsburgEckernförde showed also in the past five years high variation at MB1 both in NH 4N and NO 3N effluent contents, which reached for measurements in the winter months from 18 mg/L in February 2006 to 65 mg/L in February

2009, concerning NH 4N, and from 3 mg/L in February 2009 to 36 mg/L in February 2006, concerning NO 3N. As N tot is not recorded for monitoring, DIN compounds can not be expressed as shares of N tot . However, within DIN the ratios of the single compounds also showed variation: NH 4N accounted for ca. 32 % of DIN in February 2006, 78 % in January

2008 and 95 % in February 2009. The respective shares of NO 3N were ca. 67 %, 21 %, and 4 %. The latest monitoring data on hand of the WWTP MB1 from the years 2008 and 2009 showed however consistently higher NH 4N than NO 3N contents, thus the high share in NH 4 N detected in the frame of this thesis can be regarded as comparable to the usual recent pattern. Monitoring data from the municipality BokhorstWankendorf for the WWTPs MB2, MB3, MB4, and MB5 were available for the months April/May, August/September, and November 2009, as well as from May and September 2010. Data from winter were not available for N and P compounds, probably due to low temperatures which do not require the compliance with emission limits concerning N and P compounds (cf. section 4.5.7.5). Also they show considerable variability between the single WWTPs. However the pattern between NH 4N and

NO 3N was consistently the opposite than recorded in the frame of this thesis for MB2 and

MB4: they showed a higher share of NH 4N, except for the data from August 2009 (MB2) and September 2010 (MB4), respectively, whereas the samples taken at the mentioned WWTPs in the frame of this thesis had higher NO 3N contents. The monitoring data for MB3 showed consistently higher NO 3N and low NH 4N contents, so that the pattern recorded in January 2010 can be regarded as comparable to the usual data, whereas the higher share determined in

February 2010 is contradicting. Monitoring data of MB5 showed usually higher NO 3N than

NH 4N contents, with exception of May 2010. In this aspect the high ratio of NO 3N to NH 4N recorded in December 2009 and January 2010 in the frame of this thesis, but also the higher share of NH 4N in February 2010 can be regarded as usual variation. However the monitoring data include only two data sets each for one day in spring, one day in summer and one day in autumn of two years, and are thus might not necessarily be representative. Also the values

Master thesis – Maria Redeker 6. Discussion 121 recorded in the frame of this thesis reflect only records from three days, which indeed may reflect as a whole the conditions during the sampling period, but in comparison to the WW lagoons the composition of the effluents of the small technical WWTPs are much more subject to changes according to the composition of the raw WW due to the comparatively low buffer capacity. Thus, both monitoring data and results obtained in the frame of this thesis may to a certain degree, especially due to the long time intervals between the sampling days, be less representative for a certain period than those for the WW lagoons.

6.1.3 P compounds

Figures 6.3 and 6.4 show a comparison of the PO 4P and P tot contents in the samples from the

WWTP effluents. In Figure 6.3 the absolute contents of PO 4P are represented as columns, and the P tot contents are represented as dots. Figure 6.4 shows the percental shares of PO 4P in P tot .

14

12

10

8

6 c(P) / mg/L / c(P)

4

2

0 Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. L9 Jan. L9 L8 Jan. L8 L7 Jan. L7 L6 Jan. L6 L5 Jan. L5 L4 Jan. L4 L3 Jan. L3 L2 Jan. L2 L1 Jan. L1 L10 Jan. L10 L11 Jan. L11 L12 Jan. L12 NP1 Jan. NP1 NP2 Jan. NP2 MB1 Jan. MB1 MB2 Jan. MB2 MB3 Jan. MB3 MB4 Jan. MB4 WWTP no. and month Jan. MB5 PO4-P Ptot

Figure 6.3: PO 4P contents (represented as columns) and P tot contents (represented as dots) in the effluents

120%

100%

80%

60% share Ptot in 40%

20%

0% Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Feb. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. Dec. L9 Jan. L9 L8 Jan. L8 L7 Jan. L7 L6 Jan. L6 L5 Jan. L5 L4 Jan. L4 L3 Jan. L3 L2 Jan. L2 L1 Jan. L1 L12 Jan. L12 L11 Jan. L11 L10 Jan. L10 NP2 Jan. NP2 NP1 Jan. NP1 MB5 Jan. MB5 MB4 Jan. MB4 MB3 Jan. MB3 MB2 Jan. MB2 WWTP no. and month Jan. MB1 PO4-P

Figure 6.4: Shares of PO 4P in P tot in the effluents

Master thesis – Maria Redeker 6. Discussion 122

From Figure 6.3 it can be recognised that high P tot contents usually implicated high PO 4P contents.

Figure 6.4 reveals that in the effluents of all three WWTP types the share of PO 4P was largely between 60 % and 100 %, with the exception of L4 and NP2 (55 % and < 40 %, respectively). Only slight differences can be recognised between the WWTP types, in which slightly lower percentages occurred in the effluents of the WW lagoons than in those of the small technical

WWTPs. In all samples the PO 4P contents were below or equal to the respective Ptot contents.

As expected, the effluents of the large technical WWTPs applying P elimination steps had, next to some of the WW lagoons, the lowest P tot and PO 4P contents. The effluents of NP2 showed the lowest of all PO 4P and P tot contents. This can be explained by the comparably high concentrations of polyaluminium chloride added to avoid foaming in the biological stage (cf. section 4.2). The low share in PO 4P indicates well an excessive precipitation of PO 4P at NP2.

The highest P tot and PO 4P contents were found in the effluents of the small technical WWTPs. In WWTPs without explicit P elimination steps the removal of P is limited to the amount of P which settles in primary sedimentation and which is used by the microorganisms for the formation of biomass and removed with the excess sludge, which can in combination account for the elimination of up to 30 % of P (Bunch, 1977, cited in Yeoman et al., 1988).

The effluents of the WW lagoons had lower PO 4P and P tot contents than those of the small technical WWTPs. This can be attributed mainly to dilution effects from the combined sewer system, as mentioned above (section 6.1.1), and to a certain extent to the more favourable conditions of WW lagoons for settling due to the slow passage of the WW. Further potential elimination processes in WW lagoons are uptake by algae and bacteria (Houng & Gloyna, 1984). However, water temperatures were too low as to allow for microbial activity, and the light availability within the lagoon was limited by the snow cover, so that also algal growth should not have been possible.

6.1.4 Chloride and sulphate In contrast to the N and P contents, the highest Cl contents were detected in the effluents of the large technical WWTPs. This is probably due to the application of iron(III) chloride sulphate for phosphate precipitation at NP1 and of polyaluminium chloride to avoid foaming at NP2 (cf. section 4.2). As chloride is not subject to any transformation processes (Hütter, 1994) and therefore can be regarded as a conservative parameter, the low concentrations in the WW lagoons compared to

Master thesis – Maria Redeker 6. Discussion 123 the small technical WWTPs can clearly be attributed to dilution effects by rainwater in the combined sewer system. Increasing Cl contents from December 2009 to February 2010 can be explained in the WW lagoons both by the decreasing dilution from rainwater, as described above (section 6.1.1), and by the application of road salt in January and February, which may have reached the sewer via road runoff. Increasing Cl contents in the technical WWTPs cannot be explained in first place by road salt application, as they are connected to separate sewer systems and should therefore not be influenced by road runoff. At NP1 possibly it was necessary to apply higher doses of iron(III) chloride sulphate due to lower temperatures and therefore less efficient biological P elimination. In the effluents of the small technical WWTPs the Cl contents showed less variation in course of the months than at the other WWTP types, and they did not increase at all sites. Possibly their development can be attributed to usual variability. However, to ascertain this, samples should be taken more regular than once a month and values observed over a longer period.

2 The lower SO 4 concentrations observed in the WW lagoons may, as other parameters, be explained by dilution effects. However, the decreasing values from December 2009 to February 2010 contradict with the decreasing amount of precipitation which has reached the WW lagoons. Due to anaerobic conditions, they might, as in lake ecosystems, also be attributed to the

2 2 reduction of SO 4 . By dissimilatory reduction of SO 4 , hydrogen sulphide (H 2S) is formed,

2 which is partly transferred to the sediment in the form of sulphides. By assimilatory SO 4

2 reduction SO 4 is used by plants and microorganisms for the formation of S containing cell compounds, such as the amino acids cysteine and methionine (Schwoerbel & Brendelberger, 2005). The oxygen contents or redox potentials within the lagoons have not been measured in the scope of this thesis, their oxidative state therefore is not explicitly known. Due to the ice sheets on the lagoons and thus low physical aeration in January and February 2010, reductive conditions can however be assumed. As for the other variables studied, also dilution effects

2 from the combined sewer system can be assumed to have caused lower SO 4 contents in the

2 effluents of the lagoons. Since no consistent increase in SO 4 can be observed, the decreasing dilution would however at least be masked by other effects.

Master thesis – Maria Redeker 6. Discussion 124

6.2 Comparison with emission limits

In Tables 2.1 and 2.2 the emission limits of DIN and P tot for the investigated WWTPs according to their discharge permissions (LLUR, 2009) are listed together with the values measured in the scope of this thesis.

Table 6.1: DIN emission limits of the WWTPs

(LLUR, 2009) and sums of NH 4N, NO 2N and Table 6.2: Ptot emission limits of the WWTPs

NO 3N contents measured in the effluents in (LLUR, 2009) and P tot contents measured in the mg/L. Exceedances are marked in red. effluents in mg/L. Exceedances are marked in red.

WWTP emission Dec Jan Feb WWTP emission Dec Jan Feb No. limit 2009 2010 2010 No. limit 2009 2010 2010 L1 25 13.9 15.8 24.1 L1 10 3.44 3.57 4.87 L2 25 5.9 6.8 4.9 L2 10 1.28 0.85 0.47 L3 25 5.8 L3 10 0.50 L4 25 9.4 L4 10 1.87 L5 25 13.9 13.7 16.5 L5 10 2.99 3.35 4.09 L7 30 17.3 29.7 29.1 L7 10 2.76 4.49 4.64 L8 15 0.6 0.5 0.4 L8 5 5.03 ± 0.03 5.57 ± 0.05 6.1 ± 0.01 L9 15 3.8 3.6 4.0 L9 5 0.76 0.79 0.80 L10 15 0.6 29.7 ± 2.6 L10 5 4.97 5.13 ± 0.05 L11 20 16.3 15.4 34 ± 3 L11 5 3.51 3.96 5.46 ± 0.02 L12 25 14.2 13.7 14.0 L12 12 2.89 2.58 2.49 MB1 70 50.7 47.5 MB1 15 12.93 12.38 MB2 40 2.6 21.6 21.6 MB2 14 5.53 7.40 7.37 MB3 30 20.8 32 ± 3.2 MB3 8 7.11 5.90 MB4 40 32.6 MB4 10 7.53 MB5 40 22.8 23.3 13.0 MB5 10 3.44 5.01 6.14 NP1 10 0.9 0.4 0.3 NP1 2 1.08 1.12 0.44 NP2 10 6.0 6.5 8.6 NP2 0.5 0.10 0.09 0.09 Although the compliance with the emission limits is only required at temperatures > 12 °C, the Tables 6.1 and 6.2 show that, in spite of the low temperatures and resulting poor conditions for the elimination of nutrients, in most of the cases the measured contents of the respective nutrients were below the emission limits. Also the maximum NH 4N content stipulated for NP1 and NP2 was complied with (cf. section 5.1.5). However, under consideration of the measurement uncertainties two samples exceeded the emission limits for both DIN and P tot , namely L10w in January 2010 and L11w in February 2010: the permitted DIN contents of 15 mg/L respectively 20 mg/L were exceeded considerably, by nearly 100 % respectively by about 50 %; and the permitted P tot contents of 5 mg/L each were exceeded by about 2 % respectively 10 %. Two further samples (L8w in January and February 2010) exceeded their emission limit for P tot of 5 mg/L by about 10 % respectively 20 %.

In contrast to Germany, other countries set legal standards also for the emission of NH 4N and

NO 2N, without an explicit limitation to WWTPs of a certain size. The Austrian Ordinance concerning the general limitation of wastewater emissions into running waters and public

Master thesis – Maria Redeker 6. Discussion 125

sewers (AAEV, 1996) sets emission limits of 10 mg/L for NH 4N, and 1 mg/L for NO 2N. It also includes limitations for P tot (2 mg/L) and pH (6.5 – 8.5), whereas individual exceptions for single parameters are possible. The Austrian threshold for NH 4N was exceeded in about 50 % of the investigated effluent samples, and MB2w from January 2010 exceeded the Austrian threshold for NO 2N nearly 5fold. Nearly all investigated effluent samples also had P tot contents above the Austrian standard, whereas all effluent samples complied with the threshold for pH values. In comparison to these more stringent standards the limits set for the WWTPs investigated in the frame of this thesis are alarmingly tolerant, especially when considering that in spite of the immediate mixing with stream water the water quality directly at the sewage disposal point is virtually equivalent to that of the effluent. Particularly the high contents of NH 4N up to

46 mg/L and the high NO 2N content at MB2 of nearly 5 mg/L give rise to concern, due to their potential toxicity to fish and invertebrates already in concentrations which are several orders of magnitude lower (cf. section 2.1).

6.3 Impacts in the direct vicinity of the WWTPs

6.3.1 Comparison of parameters As expected, the results downstream of the WWTPs were between the respective values measured upstream and in the effluents. The distances between the upstream and downstream sampling points were relatively short, so that major processes influencing the composition of the water between the two sampling points should not have taken place. The composition of the samples taken downstream should therefore be a result of mixing of water originating from the other two points and thus have values in between.

2 Especially for NO 3N, Cl , and SO 4 , the values measured downstream were in many cases outside of the range of the values measured upstream and in the effluents. They can to a large extent be explained by the analytical uncertainties of measurement, as indicated by the error bars (Figures 5.13, 5.21, 5.23). However, the deviations of the NO 3N content in December

2 2009 and the Cl content in January 2010 downstream of L11, as well as the SO 4 contents downstream of MB4 and NP2 in January 2010 each exceed the measurement uncertainties. The sample downstream of NP2 was taken on the opposite side of a road, so some sulphate may have entered via road runoff, or from a small nearby dump site. However, as the downstream result is very similar to those from the other months and the result of the effluent sample is relatively different from the respective results in the other months, it is also possible that the

Master thesis – Maria Redeker 6. Discussion 126 result from the effluent was subject to an analytical or a sampling error. Also the sampling point downstream of the WWTP L11 is located next to a road. The low Cl content is thus surprising, as due to the application of road salt in winter it would have rather been expected to

2 increase. The low SO 4 content downstream of MB4 may be due to a dilution by the ditch 1.6, or by other possible inflows of unknown composition, for which the long distance between the upstream and the downstream sampling point allows (see section 4.2). This could also explain the downstream pH value, which is about 0.5 units higher than the pH value measured upstream, although the pH measured in the effluent sample was about 1.5 units below. Table 6.3 gives an overview of minima, maxima, and medians of the absolute values of percental deviation of the results measured in the WWTP effluents from those measured upstream. The mentioned figures are based on all samples taken in the three months from all WWTPs (missing values are listed in Table 4.5; in addition, the values measured upstream of MB2 in January and February 2010 have not been considered in Table 6.3, as they reflect the composition of the effluent rather than that of the water in the ditch 1.12 upstream of the pipe, which was frozen at that time, cf. section 4.2). Water temperatures and pH values, for which the calculation of percentages is not reasonable, as well as NO 2N contents, which were detected only in single samples, are not included.

Table 6.3: Mimima, maxima, and medians of the absolute values of percental deviation of the results measured in the WWTP effluents from the results measured upstream

2 Parameter DO EC NH 4N NO 3N N tot PO 4P P tot Cl SO 4 minimum 1 0120 2 1 1 0 1 maximum 85 172 127990 1219 1954 85885 9791 392 157 median 55 41 1192 97 137 2997 1307 59 45

The most elevated parameters in the WWTP effluents compared to the rivers upstream of the

WWTPs were obviously in the NH 4N, PO 4P, and P tot contents, for which the deviations of the effluents from upstream were one to two orders of magnitude higher than for the other parameters. These are usually the most problematic parameters of WWTP effluents. Of the mentioned parameters, the PO 4P contents showed the largest deviation. Data from Neal et al. (2005) in the Kennet/Dun subcatchments of the upper Thames Basin in England demonstrate that in the effluents of six WWTPs without tertiary P elimination processes serving between

130 and 300 PE the SRP but also the NH 4N contents were the parameters most elevated compared to the contents in the river at its upstream sampling position (8818 % and 3100 %,

2 respectively), whereas the elevations of the NO 3N, Cl , and SO 4 contents were about one

Master thesis – Maria Redeker 6. Discussion 127 order of magnitude lower (179 %, 477 %, and 145 %, respectively). These results are similar to those obtained at the sampling sites investigated in the frame of the present thesis. Table 6.4 shows the minima, maxima, and medians of the absolute values of percental deviation of the respective results measured downstream of the WWTP outlets from those measured upstream. Also these figures are based on all samples taken in the three months from all WWTPs (also in Table 6.4 the values measured upstream of MB2 in January and February 2010 have not been considered).

Table 6.4: Mimima, maxima, and medians of the absolute values of percental deviation of the results measured downstream of the WWTPs from the results measured upstream

2 Parameter DO EC NH 4N NO 3N N tot PO 4P P tot Cl SO 4 minimum 101201000 maximum 91 84 6682 1072 1000 71462 1291 247 82 median 9 3 200 16 27 462 126 15 16

The greatest impacts of the WWTPs were those on the NH 4N, PO 4P, and P tot contents of the receiving streams, the same parameters for which the effluents showed the highest deviations from the rivers and ditches upstream. The highest impact was also that on the PO 4P contents, and the impacts on NH 4N, PO 4P, and P tot contents were one to two orders of magnitude higher than those on the other parameters, which indicates a good correlation to the deviation of the contents in the effluent from the contents measured upstream. Thus, the impacts of the WWTP effluents in the catchment on the receiving streams concerning the different parameters appear to have depended to a certain extent on their deviation from the characteristics of the recipients upstream of the outlets. Neal et al. (2008b) investigated the impact of the WWTP in Marlborough on the river Kennet in England between September 2003 and October 2005. The WWTP applied a tertiary P elimination step. Percental deviations of monitoring data recorded in the effluent from those recorded at the sampling point upstream and percental deviations of the data recorded at the next sampling point 3 km downstream of the WWTP from those recorded upstream are compared in Table 6.5 for the parameters also investigated in the frame of this thesis.

Master thesis – Maria Redeker 6. Discussion 128

Table 6.5: Comparison of the percental deviation of selected parameters measured in the effluent of Marlborough WWTP from the values measured upstream with the percental deviation of the same parameters measured downstream of Marlborough WWTP from those measured upstream, based on data after Neal et al. (2008b)

2 Parameter NH 4N NO 3–N N tot Ptot Cl SO 4 deviation effluent 4933 62 90 1233 193 59 from upstream (%) deviation downstream 233 13 11 87 14 18 from upstream (%)

Also in the mentioned study the highest deviations, concerning the parameters listed in Table 6.5, of the effluent from the Kennet upstream of the WWTP can be observed for the parameters

NH 4N and PO 4P, whereas in contrast to the present study and Neal et al. (2005) the deviation was higher for NH 4N than for PO 4P. Nevertheless, the mentioned parameters were also those for which the impact of the on the stream water quality was the highest.

6.3.2 Comparison of WWTPs The dimensions of the impacts also differed between the single WWTPs. According to the box andwhiskers plots in section 5.1, the distributions of the different parameters observed in the effluents of the WWTPs are in most cases quite well distinguishable. In contrast, while the distributions of changes from upstream to downstream of the WWTPs had different maxima (or minima in the cases of negative values, respectively) and medians, the minima (respectively maxima) were similar for all WWTP types. Also the column diagrams depicting the impacts of the single WWTPs vary in part more between the single WWTPs than between the WWTP types. The magnitude of the impacts should be defined primarily by the differences of the values measured upstream and in the effluents and by the proportions of the WWTPs compared to the receiving streams. Degradation processes should, due to the low water temperatures and the relatively short distances between the upstream and downstream sampling points, not have played a major role (see section 6.3.1), and also major input sources have not been observed. The differences of the results measured upstream and in the effluents of the WWTPs are displayed graphically in the Annex E (Figures 4 11). As the assumed uncertainties of

2 measurement for the parameters NO 3N, Cl , and SO 4 (cf. section 4.5.7.1) are in most cases higher than the differences calculated from the results, these parameters will not be included in the following discussion. Also NO 2N will not be considered, as it was detected only in single

Master thesis – Maria Redeker 6. Discussion 129 samples and the values downstream were often outside the range of the corresponding samples upstream and from the effluents. Table 6.1 shows the dimensions of the WWTPs and the receiving streams. The dimensions of the streams are given in approximate discharge. Since discharge measurements of the WWTPs were not practicable, the connected PE are used as a substitute. It is important to note that the PE connected to the WWTPs do not account for possible external connections or, in case of combined sewer systems, the amount of precipitation. It should also be noted that due to the low number of measuring points per cross section also the results obtained for stream discharge are very rough approximations. Thus, both dimensions do not reflect exact values, but still can be used for an approximate comparison.

Table 6.6: C omparison of the proportions of the WWTPs, expressed in connected PE, and the receiving streams, expressed in m 3/s of discharge PE Q(river) / PE Q(river) / WWTP no. WWTP no. connected m3/s connected m3/s L1 1140 0.01* MB1 126 0 L2 224 0.02 MB2 103 *** L3 34 MB3 223 0.02 L4 342 MB4 150 *** L5 230 MB5 92 0.01 L6 409 0.05 NP1 4000** 1.44 L7 365 NP2 110816 0.2* L8 831 0.03* * discharge measured downstream of WWTP **can be considered due to the intermittent L9 394 0.17 discharge of the WWTP as four times as high L10 171 (see text) *** see text L11 211 0.01 L12 314 0.01

Concerning most of the measured parameters the large technical WWTPs with N and P elimination steps showed the lowest influence on the receiving rivers and ditches (cf. boxand whiskers plots in section 5.1). Exceptions were DO contents and EC, for which NP2 showed the highest influence, as well as N tot , for which the changes at NP2 were in a magnitude similar to those at the small technical WWTPs. In general, the influence of NP2 on the Bullenbek was mostly higher than that of NP1 on the Bünzener Au, although the differences of the respective values measured upstream and in the effluent were only for EC, NH 4N and N tot contents higher at NP2 than at NP1.

Master thesis – Maria Redeker 6. Discussion 130

NP2 is by far the largest WWTP in the upper Stör catchment and the receiving river Bullenbek is not much larger than the recipients of the other WWTPs. NP1 can be due to the intermittent discharge (all 4 hours for about 50 minutes) be considered to be slightly more than four times greater during discharge than indicated in Table 6.6, as it discharges only in slightly less than one fourth of the time. Considering this, it can still be regarded to be about one order of magnitude smaller than NP2. In addition, it discharges into the Bünzener Au, which is the largest of all recipients and thus allows for a higher dilution of the effluent. The generally low impacts of NP1 on the Bünzener Au must thus be attributed to the high dilution by the stream, as the differences of most parameters, except for NH4N, N tot , PO 4P and P tot , between upstream and in the effluent of NP1 are in an average range of those of the other WWTPs. In contrast, the water quality of the Bullenbek downstream of NP2 is strongly influenced by the composition of the effluent from the polishing lagoon or, more precisely, by the difference of the respective parameters upstream and in the effluent. The significance of the proportions of the size of the WWTP and the receiving river becomes even more obvious at NP2, as even small deviations of the effluents from the recipient upstream lead to noticeable impacts on the stream water quality, as it is the case for NH 4N (Annex E, Figure 8).

As in addition the EC as well as the DO and N tot contents in the effluent of NP2 were relatively to very high compared to the respective values in the Bullenbek upstream, the strong impacts of NP2 concerning the mentioned parameters can be explained both by a high difference between the values upstream and in the effluent and by the high proportion in size of the WWTP compared to the Bullenbek.

The small technical WWTPs showed, comparing the medians and maxima (or minima in the case of negative changes, respectively) of the distributions, greater influences on the water quality of the receiving rivers and ditches than the wastewater lagoons for all parameters except DO and NH 4N (at MB2, MB4, and MB5) contents. However, for all parameters some samples also showed only minor impacts.

For the water temperatures, EC, NH 4N (at MB1 and MB3), N tot , PO 4P, and P tot contents, larger differences between the values in the effluents and those upstream can be recognised for the small technical WWTPs than for the WW lagoons in the boxandwhiskers plots in section 5.1 and in the Figures 4b 11b in the Annex E. In contrast, for the pH values and DO contents this cannot be ascertained clearly. For those three parameters the distributions of values upstream and in the effluents were relatively similar, so that it is necessary to observe the single sites to

Master thesis – Maria Redeker 6. Discussion 131 allow for a statement. However, for most parameters the greater difference between the values in the effluents and upstream of the WWTPs played a certain role for the magnitude of the impact on the stream water quality. The size of the ditch receiving the effluent of MB2 was roughly estimated in a test determination in December 2009 to be in the same order of magnitude as the ditch receiving the effluent of MB1, or only slightly larger, and thus about one order of magnitude smaller than the ditches into which L3 and L5 discharge. For the ditch 1.6 receiving the effluent of MB4 no discharge could be determined, as the ditch was not accessible at that point. However, as this ditch receives the effluent of the WWTP MB3 about 2.5 km downstream, it should have some less discharge at the sewage disposal point of MB4, but was estimated in January 2010 not to be too much smaller at the next open point downstream. The streams receiving the effluents from the small technical WWTPs are therefore, regarding Table 6.6, on average slightly smaller at the sewage disposal points than those receiving the effluents from the WW lagoons. On the other hand, the WW lagoons have on average more PE connected, but the discharge of the small technical WWTPs was due to its intermittent nature per time unit during a discharge period higher than it would be at WWTPs of comparable size with continuous discharge. Thus it is difficult to consult the proportions between both WWTP types and the receiving streams as a predictor to distinguish their magnitude impacts on the streams in general. The WWTPs of both types will therefore be discussed separately.

Regarding the single sites at the small technical WWTPs, the greatest increases of NH 4N, N tot ,

PO 4P, and P tot contents can be observed at MB1, as well as relatively large changes in water temperatures and pH values. Also for the differences between the values upstream and in the effluent of the parameters mentioned first that site had the greatest values and still relatively high for the others. For EC and DO contents both the difference between the values measured upstream and in the effluent of MB1 and the changes from upstream to downstream of the outlet were in an average range compared to the other small technical WWTPs. MB1 discharges into the smallest stream (see discussion of MB2 below) regarding discharge, while it has an intermediate number of PE connected, compared to the other WWTPs of this type. Therefore both the magnitude of the differences between the concentrations measured upstream and in the effluent of MB1, and the high proportion of the WWTP and the receiving ditch appear to lead to the high impact of MB1 on the water quality of the ditch. As the ditch 1.12, into which MB2 discharges, was frozen under the road upstream of the outlet in January and February 2010 (see section 4.2) and therefore was fed only by the WWTP effluent during that time, only the results obtained in December 2009 will be discussed for that

Master thesis – Maria Redeker 6. Discussion 132 site. At MB2 the highest change of EC and still high changes of water temperature DO content, and N tot contents can be observed in comparison with the other small technical WWTPs. The other parameters were in an intermediate range compared to the other WWTPs of this type. For EC MB2 showed the highest difference between upstream and the effluent, and also a relatively high one for water temperature. That of DO was only in an average range and those of the other parameters rather small compared to the other WWTPs of that type. The influences of MB2 on the mentioned parameters of the ditch 1.12 therefore seem to be enhanced a bit by the proportion of the WWTP to the ditch to MB2.

MB3 showed rather high impacts for water temperature, DO and NH 4N contents in February 2010, whereas the others were comparable to those observed at the other small technical WWTPs. The differences of the parameters between upstream and in the effluent of MB3 were high for water temperatures and NH 4N, and intermediate for the other parameters. As the proportion between stream size and PE connected to the WWTP was lower than for NP1 and

NP2, the impacts on water temperature, DO and NH 4N contents in February 2010 can be attributed rather to high values in the WWTP. At the WWTPs MB4 and MB5 the influences on the receiving streams are low compared to MB1, MB2, and MB3. The differences between upstream and in the effluents were relatively high at MB4 for most parameters and at least intermediate for most parameters at MB5, compared to MB1, MB2, and MB3. The low impacts on the water quality of the receiving streams for these two WWTPs thus appear to be primarily attributed to dilution effects. However, according to Table 6.6 the proportions between the WWTPs and the receiving streams for MB4 and MB5 should be only slightly smaller than that of MB3, which showed higher impacts on the water quality of the receiving ditch. In the case of MB4 there was probably an influence by the ditch 1.6.14a which flows into the ditch 1.6 directly downstream of the upstream sampling position and could not be sampled, and possibly by further sources which may discharge into the ditch 1.6 within the long distance between the upstream and downstream sampling points.

Compared to the small technical WWTPs, at the WW lagoons slightly larger changes in DO contents were found. The impacts on NH 4N contents were between the high ones (MB1, MB4 in February 2010) and the low ones (MB2, MB3, MB5) of the small technical WWTPs. However, in the case of DO, only L1 showed a higher impact, whereas the other WW lagoons showed impacts of about the same extent as those of the small technical WWTPs.

Master thesis – Maria Redeker 6. Discussion 133

The differences of DO measured upstream and in the effluents were on average higher at the small technical WWTPs. However, they were only about 12 mg/L higher, so that this difference might be regarded as insignificant. For NH 4N contents the same pattern as for the changes from upstream to downstream can be observed: the differences at the WW lagoons were in between those of MB1 and MB3, which showed the strongest changes, and those of MB2, MB4 and MB5, which showed the weakest changes. L1 showed, compared to the other WW lagoons, rather high impacts on all investigated parameters, at which the highest on the PO 4P and P tot contents, of the receiving ditch 9.1.1. In contrast, the differences between the values measured upstream and in the effluent were similar or low compared to the other WW lagoons. Table 6.6 shows that L1 is, after NP1 and NP2, the largest WWTP in the catchment and discharges into one of the smallest streams. The high impacts observed in the ditch at L1 are therefore attributed to the high proportion of the WWTP L1 against the ditch. As it is suspected that the effluent samples of L2 taken in January and February 2010 contained partially water from the Führbek, only the results from December 2009 will be discussed here. L2 showed rather small impacts on the water quality of the Führbek. The only higher impact, but still comparable to those of L1, L7, and L8, was that on the DO content. Also the differences of the values measured upstream and in the effluent of L2 were comparatively low, except for the DO content, for which L2 showed the highest difference, compared to the other WW lagoons. The comparatively low impact of L2 on the water quality of the Führbek can therefore be ascribed to the low concentrations in the effluents, but probably also to a low dimension of the WWTP compared to the discharge of the Führbek . Also L4 showed rather low impacts on the water quality of the Grenzgraben for most parameters, except for the water temperature and NH4N contents, for which the impacts were in a medium range compared to the other WW lagoons. As well the differences between upstream and in the effluents were in a medium range for the last mentioned parameters and comparatively low for the others. In the Grenzgraben no measurement of flow velocity was possible, but it was estimated to be rather in the lower range of sizes of the investigated streams. The low impact on the Grenzgraben by L4 must thus be attributed mainly to the low differences of the single parameters between the effluent and the Grenzgraben upstream of the sewage disposal point, as due to the estimated rather high proportion between L4 and the Grenzgraben small changes in the effluent should have a higher impact than they would have on a larger recipient.

Master thesis – Maria Redeker 6. Discussion 134

The impact of L6 on the water quality of the Poyenberger Bek was comparable to the impacts of the other WW lagoons on their recipients for most parameters. Only the water temperature in December 2009 showed a slightly elevated change compared to most other WW lagoons, but there were other WWTPs at which higher changes were observed. The impacts on N tot contents in January and February 2010 were the lowest on N tot contents of all WW lagoons. The value in December 2009 was outside the range of those upstream and in the effluent. Possibly some sediment was caught with the sample. Also the differences of the values

measured upstream and in the effluent of L6 were in a medium range, except for the NO 3 contents, which showed the highest differences of the WW lagoons, and N tot contents, which showed the lowest ones in all three months. The impact of L6 on the water quality of the Poyenberger Bek thus was quite well related to the differences between the values measured upstream of L6 and in the effluent.

L7 exerted a high impact on the NH 4N content of the Steenbek and only low impacts on the pH values. For the pH values a rather high change from upstream to downstream of the outlet could be observed in January 2010, where however the value measured downstream was outside of those measured upstream and in the effluent. For the rest of the parameters the changes were in a medium range compared to the other WW lagoons. The differences of the

NH 4N contents upstream and in the effluent belonged to the highest determined at all WW lagoons. For the other parameters the differences were in the upper to medium range of all WW lagoons. The discharge of the Steenbek at the sewage disposal point could not be measured, but it is a rather small stream, but appeared to have high velocities. However, the proportion of the WWTP to the Steenbek seems to be small enough to let the impact of L7 be a bit lower than could be expected from the differences between upstream and the effluent, compared to the other WW lagoons.

L8 showed in February 2010 a strong impact on the NH4N content of the Sünderbek, however in December 2009 and January 2010 it was in a medium to lower range compared to the other WW lagoons. The impact of L8 on the other parameters was in a medium range for the parameters N tot , PO 4P, and P tot contents and rather low for the other parameters. The differences between upstream and the effluent appear to be low in the case of NH 4N, but actually cannot be ascertained, as an analytical mistake was suspected for the NH 4N contents measured in the effluent samples (section 6.1.2). High differences compared to the other WW

2 lagoons can be recognised for the water temperatures, N tot , PO 4P, P tot , and SO 4 contents and intermediate ones for the other parameters. Thus, in spite of the comparatively high proportion

Master thesis – Maria Redeker 6. Discussion 135 of the WWTP to the receiving stream, the impact of L8 on the Sünderbek is weaker than could be expected from the differences between upstream and the effluents. Compared to the impacts of the other WW lagoons on their recipients, the impacts of L9 on the Stör are small. The differences between upstream and in the effluent were in a medium range for water temperatures and DO contents and low for the other parameters, which may be, as mentioned above (section 4.2), due to dilution by groundwater. L9 discharges, as a WW lagoon of a medium size, into the largest investigated stream (Table 6.6). Low impacts on the Stör can thus be explained both by low differences between the effluent and the upstream sampling point, and by sufficient dilution of the effluent with stream water.

L10 showed high impacts on the ditch H2 in most parameters except the NH 4N contents, where only weak impacts can be observed. The impacts on the water temperature, pH value,

EC, and N tot contents were highest compared to the other WW lagoons. Also the differences of the pH values upstream and in the effluent were the highest compared to the other WW lagoons, while the differences of the other parameters were still high for the water temperature, for EC, and for N tot , PO 4P, and P tot contents. Those for DO contents in contrast were low. The high impact of L10 on most parameters in the ditch H2 are thus linked to high differences of the respective values in the effluent and the ditch upstream of the outlet. However, also the proportions between the connected PE and the size of the ditch were probably not without any significance. The flow velocity was not measured in that ditch in December 2009, but it was estimated not to be much larger than the ditch into which MB1 discharges. Therefore it is assumed that the impact of L10 on the water quality in the ditch was determined also by the proportions between the WWTP and the ditch. The impact of L11 on the water quality of the Schwale was low compared to those of the other

WW lagoons on their recipients for all parameters except DO, NH 4N, and N tot (in February 2010) contents, on which it showed still impacts of a medium extent. The differences between upstream and the effluent were in a high or medium range compared to those at the other WW lagoons. Only for EC they were in a lower range. Thus the impacts on the Schwale were relatively low compared to the differences between the Schwale upstream and the effluent of the WWTP. The proportion of PE connected to the WWTP and discharge of the Schwale at that point was similar to that at L2. Also there relatively weak impacts compared to the differences between the values upstream and in the effluent were observed. L12 showed impacts in a comparable range of those from the other WW lagoons for all parameters except the NH 4N contents, on which it had a rather high impact. Also the differences between the upstream and in the effluent were in an intermediate range. The

Master thesis – Maria Redeker 6. Discussion 136 proportion of L12 compared to the Dosenbek were comparable to that of L8 compared to the Sünderbek, where however the impact of the WWTP was rather lower than expected from the differences between upstream and the effluent, while at L12 rather the opposite appears to be true.

The magnitude of impacts of the single WWTPs on the receiving streams thus depended to different extents on the ratio of dimensions between WWTP and stream, and on the deviations of concentrations in the effluents from those in the rivers upstream of the WWTPs. Bowes et al. (2005) used monitoring data from 58 quality monitoring sites across the catchment of the river Avon in England and monitoring data from 18 WWTPs in the same catchment to estimate annual P tot loads by means of a geographical information system. Apart from P tot total oxidisable nitrogen (TON) was monitored. For four of the WWTPs there were monitoring sites in the vicinity upstream and downstream. The dimensions of the WWTPs in terms of connected PE, as well as the percental changes of P tot and TON contents from upstream to downstream of the WWTPs are summarised in Table 6.7.

Table 6.7: Percental increases of P tot and DON contents from upstream to downstream of four WWTPs in the Avon catchment compared to connected PE, based on data after Bowes et al. (2005) WWTP Redditch Leamington Harbury Lutterworth connected PE 89772 9895 4395 9771

increase P tot (%) 250 236 610 169 Increase TON (%) 97 30 33 1

It can be recognised that the impacts of the WWTPs on both P tot and TON contents are not clearly related to their dimensions, as the WWTP with the lowest amount of connected PE exerted the highest impact on P tot contents, and the same WWTP showed a similar impact on DON as one of the WWTPs of intermediate size. As the magnitudes of impact of the single WWTPs on both of the parameters are not parallel, they can also not be explained merely by the size ratio between WWTPs and receiving river, but rather also by the concentrations in the effluents. As no data were available on effluent concentrations and stream discharge, it is not possible to state to what extent both parameters contribute to the impacts. However, also in that study both appear to have played a role. A further study at Marlborough WWTP at the Kennet (Neal et al., 2000) focused on the stream water composition upstream and downstream of the WWTP prior to and subsequent to the

Master thesis – Maria Redeker 6. Discussion 137 introduction of P removal at the WWTP, both in summer 1997, and in the subsequent winter.

The changes of NO 3N, NH 4N, and PO 4P contents are shown in Table 6.8.

Table 6.8: Percental changes of NO3N, NH4N, and PO4P contents from upstream to downstream of Marlborough WWTP under baseflow conditions prior to and after introduction of P elimination and under stormflow conditions in the subsequent winter, based on data after Neal et al. (2000) prior to P elimination after introduction of P elimination subsequent winter period (summer, baseflow) (summer, baseflow) (stormflow)

NO 3N 7 16 9

NH 4N 433 500 250

PO 4P 2450 275 11

As in the data obtained from the WWTPs in the upper Stör catchment, the highest impact of

Marlborough WWTP were those on NH 4N and PO 4P contents of the river Kennet. The introduction of P elimination is reflected in a lower impact on PO 4P contents, which is well in accordance with the lower impacts observed at NP1 and NP2 on PO 4P contents of their recipients compared to the other WWTPs in the upper Stör catchment.

In summer the impacts of Marlborough WWTP on NH 4N and PO 4P contents were generally higher than in winter. It is not apparent if the WWTP was connected to a combined or a separate sewer system. In the frame of this thesis, samples were taken under extreme conditions in three winter months. The results obtained are thus not representative for the rest of the year. They rather present a “worst case” regarding that the functioning of the WWTPs is heavily impaired by the low temperatures and, in case of the WW lagoons, by anaerobic conditions due to the covering ice sheets. Thus, they are valid only for the sampling period. In summer, when temperatures are higher, biological processes proceed with a higher intensity than in winter. For the small technical WWTPs in the upper Stör catchment therefore a better performance can be expected. For the WW lagoons, apart from higher temperatures and thereby enhanced biological activity, the absence of the ice sheet is a precondition for the existence of aerobic zones. In addition, growth of phytoplankton and possibly macrophytes allows for additional nutrient uptake. Thus, also for the WW lagoons a better performance can be expected in summer. On the other hand discharge of the rivers is usually lower in summer than in winter, so that the receiving streams should be more susceptible to impacts by the effluent inputs (Howden et al., 2009). Also the WW lagoons are subject to evaporation losses of water due to their high surface/volume ratio, so that effluents should be more concentrated than in winter. Thus, in spite of better performance, also the WWTPs in the upper Stör catchment may exert higher impacts on the receiving stream in summer than in winter. A thesis

Master thesis – Maria Redeker 6. Discussion 138 currently developed on the basis of samples collected in the summer months of 2010 will follow up this issue.

6.4 Longitudinal profiles

In the investigated rivers the highest NH 4N contents were generally measured downstream of the WWTPs, where also the highest increases were detected. Further downstream the NH 4N contents decreased gradually or increased only slightly.

Decreasing NH 4N contents may be explained by dilution and possibly to some extent also by instream processes. As water temperatures were already very low in December 2009 (around 5 °C), nitrification, if at all, can not have significantly contributed to the reduction. Possible mechanisms thus are physical sorption and assimilation by algae (Newbold, 1992), whereas also the latter should have played only a minor role in winter. The high value at L9b in February 2010, which is observed also for the other parameters, is somewhat surprising, as both upstream and effluent values were similar to those in December 2009 and January 2010. Also the values measured at S6 are not markedly higher in February than in December and January. As the Stör is relatively wide at the sewage disposal point of L9 and the downstream samples were taken relatively near to the outlet in order to avoid an impact from the small channel entering from the opposite bank, the effluent may have been not yet mixed well with the water from the Stör over the entire cross section, so that both a slight change of the exact sampling position and/or another course of the current may have caused the differences in the results.

For December 2009 the strongest increase of NH 4N contents can however be observed from the point MB2Rb to the point S5 in the Schwale, which is situated only about 1 km downstream. Also the PO 4P and P tot contents were notably elevated at that point. The NH 4N content measured at that point in December 2009 has up to now been the highest NH 4N content at all detected in the samples of the subcatchment campaign (Pott, in prep.). About 200 m downstream of the point MB2 the ditch 1.11, which originates at the road 430 and drains an arable field, opens into the Schwale. This ditch may have carried some pollution. As no sample was taken from the ditch, it can however not be verified as the pollution source.

Usually, apart from sewage effluents, NH 4N in rivers originates from fields fertilized with animal manure (Thyssen, 1999). However, according to good agricultural practice the application of fertilizers on arable land is not permitted after November 1 (DüV, 2006), and as there had been rain events after November 1, elevated contents from washed out NH 4N would

Master thesis – Maria Redeker 6. Discussion 139 have been expected already in the November sample from that point, which was taken at November 18, 2009. For the WWTPs which do not discharge directly into the rivers, considerable reductions in

NH 4N contents can be observed for L1 and L5, and to a lesser extent for MB2, from the sampling points in the receiving ditches downstream of the WWTP outlets until the entries of the ditches into the rivers. The NH 4N content at MB2Rw was even below the content just upstream in the Schwale at MB2Ra in February 2010. Compared to the WWTPs L9 and L11, which discharge directly into the Stör respectively into the Schwale, their impact on the NH 4N contents of the receiving rivers is small. The exception is L1, where the NH 4N content in the Fuhlenau increases to a greater extent than in the Stör at L9. The passage of one or several ditches thus appears to be beneficial for the impact of the WWTPs on the receiving rivers in terms of NH 4N contents.

Also for PO 4P contents the highest increases along a longitudinal river profile could be observed at the WWTP outlets respectively the ditches transporting effluents. The highest concentrations in the Buckener Au were however in December 2009 and February 2010 detected at S18, the most upstream point sampled in the Buckener Au, and in the Fuhlenau in December 2009 at S16, which is further downstream from the entry of the ditch Gliner Graben transporting effluent from L1.

Thus, apart from the Fuhlenau in December 2009, PO 4P contents decreased in course of the longitudinal profiles. Neal et al. (2000) found a similar pattern, namely a marked increase in SRP from upstream to downstream of a WWTP and a slow decline downstream, as a typical trait for WWTP effluent dilution and chemical modification along a river channel (Newson, 1992; cited in Neal et al., 2000). They also found TP to be three times as high as SRP upstream of the WWTPs, while it was downstream only 25 % higher. Figures as marked as these have not been found in the streams discussed in this section, but increasing percentages of PO 4P in P tot from upstream to downstream of the WWTP outlets can also be observed at L9 and L11.

Mechanisms contributing to the reduction of PO 4P contents are, apart from dilution, the conversion into particulate and organic P via sorption onto sediments, including particulate phosphorus, uptake by biota , and coprecipitation with calcite or iron and hydroxide (several authors, reviewed by Withers & Jarvie, 2008).

As observed for NH 4N, also the PO 4P contents have been reduced from the downstream sampling positions of L1, L5, and MB2 until the entries of the receiving ditches into the

Master thesis – Maria Redeker 6. Discussion 140 respective rivers. Alike, the impacts of MB2 and L5 on the receiving rivers were smaller than those of L9 and L11, whereas L1 caused in February 2010 still a stronger increase in the

Fuhlenau than L9 in the Stör. Thus, also in terms of PO 4P pollution the passage of WWTP effluents through ditches appears to be beneficial.

Contrasting to the NH 4N and PO 4P contents, the highest P tot contents were not detected downstream of the WWTPs, but at different sampling points along the longitudinal river profiles varying from one month to another. Most striking are the points S7 and S21 in the Stör, MB2Ra and MB2Rb in the Schwale, and S17 and S18 in the Buckener Au.

The sample from MB2Ra in January 2010 was very turbid, which could explain the high P tot content compared to the other months. Also the high P tot content at MB2Rb in February 2010 could be explained by suspended sediment which may have been taken with the sample due to the turbulences present at the sampling point (cf. section 4.2).

The increases in P tot contents at the WWTPs were mostly minor than those in PO 4P. Also the

Ptot contents had been reduced from the sampling points downstream of the outlets of L1, L5, and MB2 until the entries of the ditches into the respective river.

There were also WWTPs in the vicinity of the investigated rivers which were not explicitly sampled along their discharge route into the rivers. The Sünderbek, which opens into the Stör between the points S6 and S7, receives effluent from the WWTP L8 about 1 km upstream of its entry. The NH4N, PO 4P and P tot contents downstream of L8 were about one order of magnitude higher than the contents at S6. However, only the P tot content showed an increase from S6 until S7, so that the impact of the WWTP L8 on the water quality of the river Stör can be regarded as insignificant in the investigated period regarding NH 4N and PO 4P contents. Between the points L5Rb and S17 in the Buckener Au the WWTPs L3, L4, and L7 discharge into the Buckener Au via several smaller streams and pipeworks. Nevertheless, for NH 4N and

PO 4P strong reductions could be observed between L5Rb and S17 in the sampling period, which may be explained by several further small tributaries opening into the Buckener Au in this reach. An influence of the mentioned WWTPs on the contents measured in the Buckener Au, as assumed by Fr ckiewicz (2010) in the summer months of 2009, can thus not be affirmed for the present sampling period in winter.

Master thesis – Maria Redeker 6. Discussion 141

As the measurement of discharge from the WWTPs was not practicable within the frame of this thesis, only concentrations, but not loads could be considered. Concentrations are the important dimension for the assessment of water quality (Jarvie et al., 2006), so that a comparison of the impacts of WWTPs with pollution from other sources is possible in terms of water quality. A comparison in terms of absolute amounts of nutrient inputs, i.e. of loads, has however to be forgone in the present thesis. Due to the short distances between the sampling points upstream and downstream of the WWTPs, which account for few meters or tens of meters, and the longer distances between the other sampling points, which account for up to 13 km, the changes occurring at the sewage disposal points can be detected more exactly than those occurring in between the other sampling points, since the latter ones may be mitigated or masked by other tributaries or diffuse inputs. As between the different sampling sites a number of tributaries open into the investigated streams, it is possible that high local concentrations at other parts along the streams are masked by the influence of the tributaries, but also that effects of the single tributaries cancel each other out. To set the impacts of WWTPs in relation with impacts of other sources, which may have been overlooked due to the long distances between the points investigated in this thesis, a denser series of sampling points along the streams would be required. It would be advisable to install sampling points at least at major tributaries or tributaries with expected pollution in a manner as realised by Bieger (2008). To consider also instream processes and impacts from diffuse sources, it would be recommendable to establish points also at shorter distances, at least where higher inputs from diffuse sources can be expected. This might be of greater importance in summer, when biological activity is higher and instream processes proceed with a higher intensity and when also diffuse inputs can be expected to play a more inportant role.

6.5 Water quality assessment To estimate the impact of the WWTPs on the ecology of the receiving streams, this chapter is dedicated to the assignment of the results measured at the sampling points upstream and downstream of the WWTPs to water quality classes according to LAWA (1998) and the comparison with the background (BG) and benchmark (BM) values according to RAKON (LAWAAO, 2007).

Master thesis – Maria Redeker 6. Discussion 142

6.5.1 Dissolved oxygen The Tables 6.9 and 6.10 show the classification of the average DO contents of the three sampling months upstream and downstream of the WWTPs according to LAWA and RAKON.

Table 6.9: Classification of average dissolved oxygen contents upstream and downstream of the WWTPs according to LAWA (1998)

L1 L2 L3 L4 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 up II III III III III III II II IIIIV III IIIII III III III III III III III stream down III III III III III III II II III III IIIII II III III III III III II stream

Table 6.10: Classification of average dissolved oxygen contents upstream and downstream of the WWTPs according to RAKON (LAWAAO, 2007)

L1 L2 L3 L4 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 up BM BG BG BG BG BG BM BG BG BG BG BG BG BG BG stream down BG BG BG BG BG BM BG BM BM BG BG BG BG BM stream According to LAWA, both upstream and downstream of the WWTPs most sampling points achieved, in terms of DO contents, the target water quality class II (moderately polluted) or better. Except for L10a and L12a, which can be described as very heavily contaminated (class IIIIV) respectively critically polluted (class IIIII) based on the DO content, all sampling points upstream of the WWTPs achieved the target class II or better. Most of the points could be described as lightly polluted (class III). Downstream of the WWTPs the assignment to water quality classes showed a similar pattern as upstream. Deteriorations in water quality from upstream to downstream can be observed at the WWTPs L1, MB1, and NP2, where they increased from classes II to III, III to II, and III to II, respectively. An improvement can be observed at L10, from very heavily contaminated (class IIIIV) upstream to heavily contaminated (class III) downstream. For the other WWTPs no effect can be established. According to RAKON, the majority of samples from upstream and downstream of the WWTPs accomplished at least the benchmark values, which indicate the transition from a good to a moderate status. Upstream of the WWTPs at most sampling points dissolved oxygen contents were on average above the background values, except upstream of L1 and L9, where they complied only with the benchmark values, and upstream of L8, L10, and L12, where the benchmark was not achieved. Also downstream of the WWTPs at most sampling points the oxygen contents were on average above the background values. Downstream of L9, MB1, MB2, and NP2 the oxygen contents accomplished the benchmark values, and downstream of L1, L8, L10, and L12 none

Master thesis – Maria Redeker 6. Discussion 143 of the thresholds was achieved. An average deterioration can thus be observed from upstream to downstream of three WWTPs, at which only at L1 a transition from good to moderate status occurred.

6.5.2 pH values Table 6.11 shows the classification of the average pH values of the three sampling months recorded at the sampling points upstream and downstream of the WWTPs according to RAKON. For the pH values only benchmark values have been established.

Table 6.11: Classification of average pH values upstream and downstream of the WWTPs according to RAKON (LAWAAO, 2007)

L1 L2 L3 L4 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 up BM BM BM BM BM BM BM BM BM BM BM BM BM BM BM BM BM BM stream down BM BM BM BM BM BM BM BM BM BM BM BM BM BM BM BM BM stream Nearly all points, both upstream and downstream of the WWTPs, complied on average with the benchmark, except MB4b, which was however sampled only in January 2010. Regarding the single months, also L7a in December 2009 and L6b in January 2010 had pH values outside the benchmark values. However, the pH values at L6b and MB4b in January 2010 were outside the respective values recorded upstream and in the effluents and thus might not reflect an effect of the WWTPs.

6.5.3 Ammonium nitrogen

Tables 6.12 and 6.13 show the classification of the average NH 4N contents of the samples from the three sampling months from upstream and downstream of the WWTPs according to LAWA and RAKON.

Table 6.12: Classification of average NH 4N contents upstream and downstream of the WWTPs according to LAWA (1998)

L1 L2 L3 L4 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 up IV IIIII IIIII III II III IIIIV II III III IIIII III I IIIII II IIIII IIIII II stream down IV III III IIIIV IIIIV IV IV IIIII IIIII III IV IV IIIII IV IIIII III IIIII III stream

Table 6.13: Classification of average NH 4N contents upstream and downstream of the WWTPs according to RAKON (LAWAAO, 2007)

L1 L2 L3 L4 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 up BM BM BM BM BM BG BM BM stream down stream

Master thesis – Maria Redeker 6. Discussion 144

According to the classification after LAWA, all water quality classes from I to IV occurred upstream of the WWTPs. Eight out of 18 sampling points can be classified on average as unpolluted (class I, point MB2a), lightly polluted (class III, point L4a, L10a, L11a) or moderately polluted (class II, points L6a, L9a, MB4a, NP2a) and thus achieved the target class II or better. Most of the other sampling points fall in class IIIII (critically polluted), two points (L7a, MB1a) were heavily contaminated (class III) and each one point was very heavily (L8a, class IIIIV) respectively excessively contaminated (L1, class IV) in terms of NH 4N contents. Downstream of the WWTPs only NP1a in December 2009 can be classified as moderately polluted with NH 4N (cf. Annex F, Table 20). None of the downstream sampling points achieved on average the target class II. Downstream of five WWTPs (L1, L7, L8, L12, MB1) the receiving streams were excessively contaminated (class IV) in all three sampling months regarding NH 4N. Also MB3b was excessively contaminated in February 2010. Downstream of the other WWTPs the NH 4N contents can be considered as critical pollution, heavy contamination or very heavy contamination (classes IIIII, III, and IIIIV, respectively). Thus, from upstream to downstream of the WWTPs a general deterioration by one to four categories can be observed.

According to the RAKON classification only MB2a had an average NH 4N content below the background level, but only one suitable sample from December 2009 was available from that point. Also L11a achieved NH 4N contents below the background level in January and February 2010 (cf. Annex F, Table 20). Seven points upstream of the WWTPs (L4a, L6a, L9, L10, L11, MB4, NP2) achieved on average the benchmark, whereas the others had higher

NH 4N contents and thus missed the target category “good status”. Downstream of the WWTPs all samples except NP1b in December 2009 exceeded the benchmark for NH 4N contents and thus also missed the target. The State Agency for Agriculture, Environment and Rural Areas (Landesamt für Landwirtschaft, Umwelt und ländliche Räume, LLUR) of SchleswigHolstein is carrying out in collaboration with the water authorities of the districts on behalf of the Ministry of Agriculture, the Environment and Rural Areas (Ministerium für Landwirtschaft, Umwelt und ländliche Räume, MLUR) a project to identify in the course of the WFD the significance of water pollution by WWTPs (MLUR, 2009). The first step was a calculationbased assessment from annual averages of monitoring data. Although the compliance with the benchmark levels was assessed to be uncertain at the wastewater disposal points of ca. 70 % of the WWTPs (MLUR, 2009), for the upper Stör catchment no conspicuous results were found (Janson, 2009). The

Master thesis – Maria Redeker 6. Discussion 145 results of the present thesis, under the given extreme conditions of the sampling period in the winter of 2009/2010, thus are in contrast with the findings from the mentioned study.

6.5.4 Nitrite nitrogen

The classification of the average NO 2N contents of the samples taken upstream and downstream of the WWTPs according to LAWA is shown in Table 6.14.

Table 6.14: Classification of average NO 2N contents upstream and downstream of the WWTPs according to LAWA (1998)

L1 L2 L3 L4 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 up IIIII II III I III I II I III I I I I stream down IIIIIIIII III I IIIII IV III I III I II stream Most samples, from both upstream and downstream of the WWTPs, were unpolluted to very lightly polluted with NO 2N (class I). Upstream of the WWTPs, L9a and L11a could be considered as lightly polluted (class III) and MB3a as moderately polluted (class II), each in February 2010 (cf. Annex F, Table 21). These values resulted in an average light pollution (class III) at the respective sampling points each. The only sample which did not achieve the target class II was MB1a in December 2009, which was heavily contaminated (class III) in terms of NO 2N contents (cf. Annex F, Table 21). However, on average also that point was only moderately polluted (class II) with NO 2N. Downstream of the WWTPs the pattern was similar, but deteriorations can be observed for MB1 in December 2009 and February 2010, where the water quality changed from class III respectively I upstream to class IIIIV respectively IIIII downstream, at MB5 in February 2010 (upstream class I, downstream class III) and at NP2 in December 2009 (upstream class I, downstream class IIIII), resulting in average deterioration by one category at MB1 and MB5 each, and by two categories at NP2. At MB2, where the upstream conditions from January and February 2010 are unknown and the water downstream is virtually equivalent to the WWTP effluent, excessive (class IV) respectively very heavy (class IIIIV) contamination can be recognised downstream in the mentioned months. An improvement can be recognised for L9 in February 2010, where water quality changed from lightly polluted upstream to unpolluted to very lightly polluted downstream. That effect was reflected in the average classification at that point. Thus, also downstream of the WWTPs all points except MB1b achieved the good status.

Master thesis – Maria Redeker 6. Discussion 146

6.5.5 Nitrate nitrogen

The water quality assessment of the average NO 3N contents at the sampling points upstream and downstream of the WWTPs according to the classification after LAWA is summarized in Table 6.15.

Table 6.15: Classification of average NO 3N contents upstream and downstream of the WWTPs according to LAWA (1998)

L1 L2 L3 L4 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 up I IIIII III IIIIV IIIIV III I II I IIIIV II III IV III IIIIV III IIIII I stream down I IIIII III III IIIIV III I II I III II III IIIIV III III III IIIII III stream All water quality classes occurred at the sampling points upstream of the WWTPs. From December 2009 to February 2010 improvements can be observed at L9a (from class IIIII to class II), L11a (IIIIV to III), L12a (IIIII to I), MB5a (IIIIV to IIIII), and NP1a (III to IIIII) (cf. Annex F, Table 22).

Downstream of the WWTPs the water quality in terms of NO 3N contents was in general similar as upstream. The values can be assigned to the same classes or one category better. Only at NP2 the downstream water quality changed from unpolluted or very lightly polluted upstream to heavily contaminated at the sampling point downstream, which means a difference of four categories. In general, also downstream of the WWTPs slight improvements of water quality can be recognised from December 2009 to February 2010 in terms of NO 3N contents (cf. Annex F, Table 22).

6.5.6 Total nitrogen

Table 6.16 summarizes the classification of the average N tot contents from the three sampling series at the sampling points upstream and downstream of the WWTPs according to the classification of LAWA.

Table 6.16: Classification of average N tot contents upstream and downstream of the WWTPs according to LAWA (1998)

L1 L2 L3 L4 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 up III IIIII III III IIIIV III II II III III II III IIIIV III III III III III stream down IIIIV IIIII III III IIIIV III IIIII II IIIIV IIIIV IIIII IV IV IIIIV IIIIV III III III stream

The average N tot contents at the sampling points upstream of the WWTPs were classified as lightly polluted (class III) to very heavily contaminated (class IIIIV). A moderate pollution (class II) or better was achieved upstream of five WWTPs (L8, L9, L10, L12, and NP2), whereas most of the other sampling points upstream of the WWTPs were heavily contaminated

Master thesis – Maria Redeker 6. Discussion 147

(class III) with N tot . Exceptions were L2a (class IIIII) as well as L6a and MB2a (class IIIIV). From December 2009 to February 2010 the classification remained constant or showed a slight improvement by one or two categories (cf. Annex F, Table 23). Downstream of the WWTPs only L9b achieved on average a moderate pollution (class II), whereas MB1b and MB2b were excessively contaminated with N tot . The other downstream sampling points were on average critically polluted (class IIIII) to very heavily contaminated

(class IIIIV). From December 2009 to February 2010 the water quality in terms of N tot remained in the same classes, deteriorated by one class or improved by one or two categories. On average, at about half of the WWTPs no effect on water quality can be observed, whereas the water quality at L10 and NP2 deteriorated by four respectively three categories. At the other WWTPs a deterioration by one or two categories can be recognised.

6.5.7 Orthophosphate phosphorus

Tables 6.17 and 6.18 show the classification of the average PO 4P contents measured upstream and downstream of the WWTPs, based on the arithmetic means of the three sampling series, according to LAWA and RAKON.

Table 6.17: Classification of average PO 4P contents upstream and downstream of the WWTPs according to LAWA (1998)

L1 L2 L3 L4 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 up III III III I III II II I IIIII II II III II III II III III I stream down IV IIIII IIIII III IIIII IIIIV III II IV III IIIIV IV IV IV III IIIIV II III stream

Table 6.18: Classification of average PO 4P contents upstream and downstream of the WWTPs according to RAKON (LAWAAO, 2007)

L1 L2 L3 L4 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 up BM BM BG BM BM BG BM BM BM BG stream down BM BMBM stream Regarding the classification according to LAWA, upstream of the WWTPs the water quality ranged between unpolluted to very lightly polluted (class I) and heavily contaminated (class III). Most of the sampling points achieved class II (moderately contaminated) or better, whereas at five points the target was missed. They were critically (L10) or heavily contaminated (L3a, MB1a, MB3a, MB5a), respectively, with PO 4P. In contrast downstream of the WWTPs only three points achieved a good status, namely L9b, NP1b (class II each) and NP2b (class III). Five sampling points (L1b, L10b, MB1b, MB2b,

MB3b) were excessively contaminated (class IV) with PO 4P, while the rest was classified as

Master thesis – Maria Redeker 6. Discussion 148 critically polluted (class IIIII) to very heavily contaminated (class IIIIV). Thus, in most cases a deterioration by one (MB5, NP1, NP2) to five (L1) categories occurred from upstream to downstream of the WWTPs. Only at L3 an improvement from class III to class IIIII can be observed. According to the RAKON classification at slightly more than half of the upstream sampling points the PO 4P contents were on average below the benchmark value and thus reached a good status. At three points they were below the background levels (L4a, L9a, NP2a). Downstream of the WWTPs only L9b, NP1b and NP2b had PO 4P contents below the benchmark, while none of the downstream sampling points achieved the background level. All other points had higher PO 4P contents and thus missed the good status.

6.5.8 Total phosphorus

The Tables 6.19 and 6.20 show the classification of the average P tot contents at the sampling points upstream and downstream of the WWTPs according to LAWA and RAKON.

Table 6.19: Classification of average P tot contents upstream and downstream of the WWTPs according to LAWA (1998)

L1 L2 L3 L4 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 up III II III I III IIIII III II IIIII II II III II III II IIIII IIIII III stream down IV IIIII IIIII III IIIII IIIIV IIIIV IIIII IV IIIII IIIIV IV IV IV III III IIIII II stream

Table 6.20: Classification of average P tot contents upstream and downstream of the WWTPs according to RAKON (LAWAAO, 2007)

L1 L2 L3 L4 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 up BM BG BM BM BM BM stream down BM stream According to the LAWA classification, upstream of the WWTPs only one sampling point was unpolluted to very lightly polluted (class I) and only two points were lightly contaminated

(class III) with P tot . However six points were classified as moderately contaminated (class II), so that still half of the points achieved a good status. The other points were either critically polluted (class IIIII) or heavily contaminated (class III) with P tot .

Downstream of the WWTPs only one point achieved a good status in terms of P tot (NP2b, class II). The same five points (L1b, L10b, MB1b, MB2b, MB3b) were excessively contaminated

(class IV) with P tot as with PO 4P. The other points were classified as critically polluted (class IIIII) to very heavily contaminated (class IIIIV), of which the majority fell in class IIIII. A deterioration of one to four categories can be observed from upstream to downstream of most

Master thesis – Maria Redeker 6. Discussion 149

WWTPs. The P tot content at NP1b fell in the same class as the one at NP1a, and from L3a to L3b an improvement from heavily contaminated (III) to critically polluted (IIIII) occurred.

According to RAKON, upstream of the WWTPs six points had a P tot content below the benchmark, whereas only one point (L4b) had a P tot content below the background value.

Downstream of the WWTPs all sampling points except NP2b had on average P tot contents above the benchmark.

6.5.9 Chloride In Tables 6.21 and 6.22 the classification of the average Cl contents over the three sampling months at the sampling points upstream and downstream of the WWTPs according to LAWA and RAKON is summarised.

Table 6.21: Classification of average P tot contents upstream and downstream of the WWTPs according to LAWA (1998)

L1 L2 L3 L4 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 up III III III III III III III III III III III IIIII III III III III III II stream down III III III III III III III III II III III IIIII IIIII III III II III IIIII stream

Table 6.22: Classification of average P tot contents upstream and downstream of the WWTPs according to RAKON (LAWAAO, 2007)

L1 L2 L3 L4 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 up BG BG BG BG BG BG BG BG BG BG BG BM BG BG BG BG BG BM stream down BG BG BG BG BG BG BG BG BM BG BG BM BM BG BG BM BG BM stream According to the LAWA classification nearly all sampling points upstream of the WWTPs can be regarded as lightly polluted (class III) with Cl. Only one point (NP2a) was moderately (class II) and one point (MB1) critically polluted (class IIIII). Thus, only the latter one missed the target. Also downstream of the WWTPs most of the sampling points had Cl contents which are classified as lightly polluted. Three points (L10b, MB2b, MB5b) showed a moderate and two points (MB1b, NP2b) showed a critical pollution. Thus, at four points a deterioration of water quality in terms of Cl can be observed from upstream to downstream of the WWTPs, however also downstream only at three points the Cl contents exceeded a moderate pollution (class II). According to the RAKON concept nearly all sampling points upstream of the WWTPs had Cl contents below the background value. Two exceptions were MB1a and NP2a, which however complied with the benchmark. Downstream of the WWTPs, apart from the mentioned sites (MB1b, NP2b) also L10b, MB2b, and MB5b complied only with the benchmark, whereas the

Master thesis – Maria Redeker 6. Discussion 150 rest of the points had Cl contents below the background level. Thus, a change from a very good to a good status occurred from upstream to downstream of three WWTPs. All sampling points thus achieved at least a good status in terms of Cl .

6.5.10 Sulphate

2 Table 6.23 shows the classification of the average SO 4 contents from the three sampling months upstream and downstream of the WWTPs according to LAWA.

Table 6.23: Classification of average P tot contents upstream and downstream of the WWTPs according to LAWA (1998)

L1 L2 L3 L4 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 up II III I III III III II II II II II III II III II III II II stream down I III III III III III II II III II II III IIIII II III III II II stream

2 Except for the point MB2b, both upstream and downstream of all WWTPs the SO 4 contents can be classified as moderately polluted (class II) or better, at which most points were moderately (class II) or lightly (class III) polluted. The sampling points upstream of L3 and downstream of L1 can be described as unpolluted to very lightly polluted (class I). Improvements from upstream to downstream can be observed at L1, L3, L10, and MB4, while

2 at the other sites the water quality in terms of SO4 deteriorated from upstream to downstream or remained in the same class. However, as mentioned, all sampling points except MB2b achieved on average a good status.

2 It should be kept in mind that in many cases the downstream SO 4 contents downstream of the samples were outside the range of the respective contents upstream and in the WWTP effluents and thus might not be the result of the WWTP impact on the stream water quality.

6.5.11 Average water quality over three months The Tables 6.24 and 6.25 summarise the classification according to LAWA and RAKON of the average results at all sampling points in the rivers and ditches upstream and downstream of the WWTPs over the three sampling months by the investigated parameters. They give information on the average water quality in the investigated period within the rivers and ditches. The changes from upstream to downstream reflect the impacts of the WWTP effluents on the quality of stream water and thus on the ecological conditions, i.e. the conditions for the existence of biota, at the respective points.

Master thesis – Maria Redeker 6. Discussion 151

They do not reflect a representative pattern for the upper Stör catchment, but they demonstrate the ecological conditions and their spatial changes at the selected sampling sites during the period of investigation.

Table 6.24: Water quality classification of the investigated parameters according to LAWA (1998) based on the overall arithmetic means of the sampling points upstream and downstream of the WWTPs in the three sampling months

2 DO pH NH 4N NO 2N NO 3N N tot PO 4P P tot Cl SO 4 up III * III I III III II IIIII III II stream down III * IV III III IIIIV IV IV II II stream * no classes defined

Table 6.25: Water quality classification of the investigated parameters according to RAKON (LAWA AO, 2007) based on the overall arithmetic means of the sampling points upstream and downstream of the WWTPs in the three sampling months

2 DO pH NH 4N NO 2N NO 3N N tot PO 4P P tot Cl SO 4 up BG BM * * * BG * stream down BG BM * * * BM * stream * no thresholds defined

2 Regarding the parameters DO contents, pH values, NO2N, Cl , and SO 4 contents, the target class II or better according to the LAWA classification, or the good or very good status according to the RAKON classification, respectively, were achieved both upstream and downstream of the WWTPs. Thus, the target water quality was not threatened by the WWTP effluents in terms of these parameters during the period of investigation.

Regarding the NO 3N contents, the conditions both upstream downstream of the WWTPs can be described as heavily contaminated (class III) and were thus notably worse than in case of the parameters mentioned before. As in most cases the NO 3N contents in the effluents were below those at the upstream sampling points (cf. section 5.1.7) and the downstream values were in part assigned to a better water quality class than the values measured upstream (cf. section 6.5.5), the poor downstream conditions can be mainly attributed to the upstream contamination in the rivers, whereas the WWTPs showed on average no effect on the water quality in terms of NO 3N.

The most problematic parameters downstream of the WWTPs were NH 4N, N tot , PO 4P, and P tot contents, which were on overall average classified as excessive contamination (class IV) or very heavy contamination (class IIIIV) in the case of N tot , respectively, according to LAWA.

According to RAKON, NH 4N, PO 4P and P tot contents were assigned to the moderate status, whereas for N tot contents no background or benchmark levels are defined.

Master thesis – Maria Redeker 6. Discussion 152

Regarding the parameters NH 4N and N tot , already upstream of the WWTPs the overall average contents complied, according to LAWA, with a heavy contamination (class III) and according to RAKON (in the case of NH 4N) with a moderate status. According to the LAWA classification, the conditions downstream deteriorated further to very heavy contamination

(class IIIIV) in the case of N tot and excessive contamination (class IV) in the case of NH 4N. According to RAKON a further deterioration can not be indicated, as the upstream value was already assigned to the worst category. Thus the high contents downstream of the WWTPs were in part also due to high “background” contents upstream of the WWTPs, which however were deteriorated further by impact of the effluents.

Pieterse et al. (2003) concluded from investigations of N tot and P tot in the Dommel catchment in the Netherlands that diffuse sources can cause already problematic nutrient contents in small streams, which however by effluents from point sources are further elevated. This also applies to the observations gained for N tot and especially NH 4N, but also to P tot (see below) in the frame of this thesis. As mentioned above, ammonium can under favourable conditions be converted to ammonia, which is toxic to fish. The Council Directive 78/659/EEC on the quality of fresh waters needing protection or improvement in order to support fish life (EC, 1978) thus sets a mandatory limit of 0.025 mg/L of ammonia in salmonid and cyprinid waters.

In contrast to the N compounds, the average PO 4P content upstream of the WWTPs complied, according to LAWA, with the target class II. The average P tot content exceeded the target, but still could be described as “critically polluted” (class IIIII). However, according to the RAKON classification both values exceeded the target and can be assigned only to a moderate status. For both parameters the average downstream contents complied with an excessive contamination (class IV). In the case of the P compounds the poor downstream conditions can therefore be even more clearly attributed to the WWTPs than in the case of the N compounds.

Studies in the Kennet in England showed that if PO 4P contents in the effluents of a municipal WWTP were largely below even 1 mg/L, an improved biological health of the river could not be achieved (Neal et al., 2008b).

Master thesis – Maria Redeker 7. Conclusions and outlook 153

7 Conclusions and outlook The aim of this thesis was to investigate the impacts of the wastewater treatment plants (WWTPs) in the upper Stör catchment on the water quality of their receiving rivers and ditches. For this purpose the composition of the WWTP effluents was compared with the conditions in the receiving rivers and ditches. Sampling was realised in two campaigns in the months December 2009, January 2010 and February 2010. The first campaign, which is also part of a doctoral thesis currently being developed (Pott, in prep.), aimed at analysing the water quality of the subcatchments of the upper Stör catchment. The second campaign, which represents the main part of work of this thesis, aimed at assessing the water quality of the rivers in the direct vicinity of the WWTPs. For this purpose samples were taken from the effluents and from the receiving rivers and ditches upstream and downstream of the WWTPs. All samples were analysed for water temperatures, pH values, DO contents, EC, as well as for the nutrients NH 4N, NO 2N, NO 3N,

2 Ntot , PO 4P, P tot , and for Cl and SO 4 . 19 of the 23 municipal WWTPs in the catchment were sampled, the two largest of which are technical WWTPs with elimination steps for P and N. Five smaller technical WWTPs apply mechanical purification and movingbed biofiltration, whereas the other WWTPs consist of naturally aerated wastewater lagoons. The sampling period coincided with three extreme winter months, which provided conditions which are not representative for the rest of the year and affected the performance of the WWTPs in different ways: the main impact on all WWTPs were the low ambient temperatures, resulting in low water temperatures which reduce biological activity. On the WW lagoons an ice sheet developed after the first sampling series and caused anoxic conditions in the WW, as physical aeration was interrupted and due to the snow cover on the ice sheet also the biological aeration was impaired by reduced irradiation. Another difference between the WW lagoons and the technical WWTPs was the sewer systems, as the sampled WW lagoons are connected to combined sewer systems, whereas the sampled technical WWTPs are connected to separate sewer systems.

Comparison of the effluents of the different types of WWTPs showed that effluents of the two largest WWTPs had due to their treatment mechanisms generally low nutrient contents, but were very rich in chloride, which was attributed to the application of chemical precipitants. The effluents from the WW lagoons had generally lower contents in all investigated parameters

Master thesis – Maria Redeker 7. Conclusions and outlook 154

except NH 4N than those from the small technical WWTPs, with mostly increasing values from December 2009. Both could be a consequence of (decreasing) dilution with rainwater from the combined sewer systems. The highest concentrations of nearly all parameters were detected at the small technical WWTPs. For most parameters the distributions of the effluent concentrations were quite well distinguishable. This pattern was however not reflected in the changes from upstream to downstream of the WWTPs, but rather superposed by the dimensions of the single WWTPs and their receiving streams as well as by the upstream pollutions of the rivers.

Observing the NH 4N, PO 4P, and P tot concentrations at selected points along the longitudinal river profiles revealed highest increases in NH 4N and PO 4P from upstream to downstream of the WWTPs, followed by gradual decrease. This indicates that these parameters are determined mainly by the WWTPs, which in turn exert a higher impact on these than on the other parameters. Due to the low water temperatures microbial degradation processes were assumed to have been negligible during the sampling period, so that the reductions in the mentioned parameters were concluded to occur mainly via dilution and sorption processes. It was also observed that the passage of the effluents through one or more ditches prior to discharging into a river can markedly reduce their impact on the river. In contrast to NH 4N and PO 4P, the highest concentrations of P tot , which originates usually from diffuse inputs, occurred at various points along the rivers other than the sewage disposal points. Thus, a qualitative influence on these parameters by the WWTPs can be recognised, but the long distances between the sampling points do not allow for a quantitative comparison of high concentrations with those possibly arising from other sources.

Assigning the values measured in the recipients upstream and downstream of the WWTPs to the classification system after LAWA (1998) as well as comparing them with the background and benchmark values according to RAKON (LAWAAO, 2007) revealed in general low adverse effects of the effluents on the stream water quality in terms of pH values, DO, NO 2N,

2 NO 3N, Cl , and SO 4 contents. They were all in a range which complies with the target class II according to LAWA, respectively with the good status according to RAKON. In contrast,

NH 4N, N tot , PO 4P, and P tot were the parameters of highest concern. They caused excessive, respectively (in the case of N tot ) very high, contamination. Also for NO 2N three samples downstream of the WWTPs showed critical pollution (class IIIII) and very heavy contamination (class IIIIV), respectively. This means an extreme change in water quality in the case of PO 4P and P tot contents, which were upstream classified as moderate (class II)

Master thesis – Maria Redeker 7. Conclusions and outlook 155

respectively critical (class IIIII) pollution. In terms of NH 4N and N tot the rivers showed already upstream pollution which could be described as heavy contamination (class III), and according to RAKON none of the four parameters complied with the good status upstream of the WWTPs. However, in spite of the high contents upstream, also for the NH 4N and N tot contents further deterioration was observed from upstream to downstream of the WWTPs.

Although nearly all WWTPs complied with their N tot and P tot emission limits, they exerted considerable impact on the water quality of the recipients during the sampling period, the ecological consequences of which may be immense. They include the conversion of ammonium to ammonia, which is toxic to fish and for which the EC Freshwater Fish Directive sets a mandatory limit of 0.025 mg/L. In addition, especially P involves the risk of eutrophication from enhanced primary production, leading to a shift from more sensitive specialist to generalist species, as well as algal blooms, oxygen depletion and eventually the extinction of communities. Although high nutrient concentrations emerging at the sewage disposal points in the rivers may be diluted within certain distances downstream of the WWTPs, they can be lethal to the river biota and do strongly affect the integrity of the ecosystem. Thus, in the upper Stör catchment there is a clear need to reduce N and P emissions from the effluents of the investigated WWTPs.

Especially in terms of phosphorus a reduction of inputs from WWTPs could help to improve the ecological status of the recipients under the given conditions. An option for the small technical WWTPs, which can well be applied with low temperatures, would be P precipitation (ATV, 1985). In terms of nitrogen, the design of the small technical WWTPs allows for an adjustment to nitrificationdenitrification processes with reasonable technical and financial effort (Porath, 2010c, 2011), which is strongly recommended in face of the high nitrogen contents detected. A possible solution for the further treatment of the effluents from the WW lagoons might be interconnected trickling filters or biological contactors (ATV, 1985). However, under low temperature conditions as those during the sampling period, an improved biological degradation is improbable. Also nitrification by combination with soil filters installed downstream of the last lagoon, as suggested by Kayser (2003), is improbable to result in significant reductions of N contents in winter. However, if an appropriate substrate is applied, phosphate and ammonium contents can be reduced by sorption to iron and aluminium oxides, respectively to clay minerals (Lorch, 1997). An option for both WWTP types would be the sorption of phosphates by means of iron filters (Rolf, 2002).

Master thesis – Maria Redeker 7. Conclusions and outlook 156

In general the application of WWTPs with tertiary N and P elimination steps is most recommendable, based on the presented results. However, the techniques applied in larger WWTPs are affordable only for larger municipalities, due to disproportionally increasing investment costs for smaller WWTPs and as expenses for monitoring and control facilities are largely independent of the size of a plant (Rolf, 2002). For a larger WWTP to serve several smaller municipalities long sewer systems would have to be installed, which would also mean a high financial burden, as the investment costs for the sewer systems in SchleswigHolstein are markedly higher than the construction costs of the WWTPs themselves (MLUR, 2005). Considering the results obtained for the WW lagoons and small technical WWTPs in the frame of this thesis, the small technical WWTPs should be preferred to the WW lagoons, in spite of higher N tot and P tot concentrations in the effluents, as the low concentrations in the effluents of the lagoons appear to have been rather a result of dilution than of better performance, and as the small technical WWTPs appear to offer potential for application of more efficient methods for N and P removal. In any case it appears recommendable for the construction of a new WWTP not to choose a site where it discharges directly into a (small) river, but where the effluent can pass one or several ditches before entering into the next river, which reduces the nutrient concentrations reaching the river.

Future investigation should include not only the measurement of concentrations, but also the determination of loads in order to determine the absolute contribution of the WWTPs to the amount of nutrients transported in the upper Stör catchment. In order to evaluate the performance of the different types of WWTPs influent and effluent loads of nutrients should be determined. To allow for a better comparison of the impacts exerted on the river water quality by the WWTPs with those exerted by diffuse sources, tributaries or other sources, further sampling points, at least at major or suspicious tributaries or upstream and downstream of reaches suspected to contribute higher inputs, should be established. A denser sequence of sampling points would also be valuable to observe dilution and/or degradation processes. This would give clarity on the mechanisms of nutrient reduction, but also allow for estimation of the distances required for the system to recover from high nutrient inputs. The sampling period of this thesis exhibited extreme conditions which are not representative for the rest of the year. To cover a wider variation of seasonal characteristics and thus gain more comprehensive information, it is necessary to consider also other times of the year.

Master thesis – Maria Redeker 7. Conclusions and outlook 157

Currently a second thesis is being developed, which is based on a sampling series from the summer months in 2010 (Honsel, in prep.). However, as the usual conditions in Schleswig Holstein are in between those two extremes, investigation should be extended to the more moderate months in spring and autumn.

Master thesis – Maria Redeker . References 158

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Personal communication: Eberhard (2010a,b): personal interviews, January 14, April 30, 2010, Gemeindewerke Aukrug. Haustein (2011): personal interview, January 6, 2010, LLUR, Flintbek. Janson (2009): personal interview, October 22, 2009, LLUR, Flintbek. MarxReese (2010): personal interview, October 4, 2010, WWTPs in Mörel, Tappendorf and Grauel. Nass (2009, 2010a,b, 2011): personal interviews, December 18, 2009, June 5, 2010, October 4, 2010, January 7, 2011, water authority district Segeberg. Porath (2010a,b,c, 2011): personal interviews, June 16, October 6, November 26, 2010, January 14, 2011, company ROTOX Klärtechnik, Burg/Dithmarschen. Rieper (2009): personal interview, November 2009, WWTP Negenharrie.

Master thesis – Maria Redeker Annex I

Annex

Annex A: Databases Annex B: Thematic maps Annex C: Reagents Annex D: Results Annex E: Comparison of results between effluents, upstream and downstream of the WWTPs Annex F: Water quality in the single months

Masterarbeit Maria Redeker Annex II

A. Databases

Table 1: Overview of databases Administrative districts, Shapes: Landesvermessungsamt natural zones Kreise, Naturräume, SchleswigHolstein of SchleswigHolstein Siedlungsflächen (2005) Bodenformenkarte, Ecology Center, Soils 1 : 100,000 Finnern University of Kiel Land use Corine Landcover EEA 250 m raster BG13 River network Basisgewässernetz (Bearbeitungsgebiet 13) Landesvermessungsamt Topographic map TK 25 SchleswigHolstein 1 : 25,000 (2003) stations Neumünster, monthly (mean), Meteorological data DWD Padenstedt daily (mean) Information about technical data, LLUR WWTPs emission limits water authorities of the districts Rendsburg districts Rendsburg Monitoring data of Eckernförde, Segeberg, Eckernförde, Segeberg, WWTPs Steinburg, Plön Steinburg, municipality BokhorstWankendorf

Masterarbeit Maria Redeker Annex III

B. Thematic maps

Masterarbeit Maria Redeker 5. Results Master thesis Maria– Redeker

running waters arable land forest grasslang urban area wetland Figure 1: Land use in the upper Stör catchment (EEA 2006, Corine Landcover) IV 5. Results Master thesis Maria– Redeker

Figure 2: Soil distribution in the upper Stör catchment (nomenclature according to AdhocArbeitsgruppe Boden, 2005) (Ecology Centre Kiel) V 5. Results Master thesis Maria– Redeker VI Figure 3: River network in the upper Stör catchment (Basisgewässernetz, BG13) Annex VII

C. Reagents

Reagents used for determination of ammonium nitrogen contents nitroprusside dihydrate / sodium salicylate solution: 0.1 g sodium nitroprusside dihydrate 8.5 g sodium salicylate dissolved in 50 mL distilled water oxidising solution: 50 mL citric acid solution 12.5 mL dichloroisocyanuric acid solution citric acid solution: 100 g trisodium citrate dihydrate 10 g sodium hydroxide dissolved in 500 mL distilled water dichloroisocyanuric acid solution: 0.29 g dichloroisocyanuric acid sodium salt dihydrate dissolved in 50 mL distilled water

Reagents used for determination of orthophosphate phosphorus contents ammonium heptamolybdate / antimony potassium tartrate solution: 13 g ammonium heptamolybdate tetrahydrate dissolved in 100 mL distilled water 300 mL sulphuric acid (50 % v/v) 0.35 g antimony potassium tartrate hemihydrate dissolved in 100 mL distilled water

Reagents used for determination of total phosphorus contents oxidising solution: 350 mL 1 N NaOH 50 g potassium peroxodisulphate 30 g boric acid dissolved in 1000 mL distilled water

Masterarbeit Maria Redeker Annex VIII

D. Results

Results displayed in the time series:

Table 2: Water temperatures recorded in scope of the WWTP campaign T / °C T / °C sampling sampling point Dec. 2009 Jan. 2010 Feb. 2010point Dec. 2009 Jan. 2010 Feb. 2010 L1a 2.8 4.3 2.4 L11a 5.8 6.5 5.6 L1w 1.5 2 1 L11w 2.5 0.8 0.2 L1b 2.1 2.5 1.4 L11b 5.9 6.6 5.7 L2a 4 1.3 1 L12a 4.4 5.9 6.4 L2w 3.3 1.2 1 L12w 2.2 2.1 2.9 L2b 3.9 1.4 1.1 L12b 4.2 5 5.8 L3a 6.6 MB1a 2.3 2.9 1.3 L3a1 5.4 MB1w 7.2 5.4 L3w 3.4 MB1b 4.7 4.9 2 L3b 5 MB2a 1.7 5.5 2.6 L4a 6.7 MB2w 9.6 7.5 5.9 L4w 4.2 MB2b 4.2 6.4 5.6 L4b 6.2 MB3a 0.1 0.2 L5a MB3w 8.9 8.1 L5w 3.5 2.4 1 MB3b 1.1 3.5 L5b MB4a 0.2 L6a 4.2 4.2 4.1 MB4w 8.4 L6w 1.8 1.6 0.7 MB4b 1.7 L6b 2.9 4.5 4.1 MB5a 2.8 0.1 0.3 L7a 6.2 4.3 4.2 MB5w 8.9 7.8 7.5 L7w 3.9 1.4 0.6 MB5b 2.9 0.1 1 L7b 6.3 3.7 3.6 NP1a 5.1 1.9 1.7 L8a 5.3 5.7 5.3 NP1w 10.2 6.8 6.1 L8w 1.5 0.8 0.3 NP1b 5.1 1.8 1.7 L8b 5 5.4 4.8 NP2a 5.7 4.3 3.4 L9a 6.6 6.6 5.8 NP2w 5.5 4.4 3.8 L9w 3.7 4.3 4.2 NP2b 6.9 3.6 3.7 L9b 6 6.2 6.2 L10a 6.7 L10w 1.6 1 L10b 1.8

Masterarbeit Maria Redeker Annex IX

Table 3: pH values recorded in scope of the WWTP campaign pH pH sampling sampling point Dec. 2009 Jan. 2010 Feb. 2010point Dec. 2009 Jan. 2010 Feb. 2010 L1a 6.98 7.02 7.1 L11a 7.48 7.85 7.94 L1w 7.38 7.23 7.2 L11w 7.21 7.48 7.25 L1b 7.22 7.28 7.15 L11b 7.46 7.71 7.83 L2a 7.29 6.85 7.73 L12a 7.17 7.17 7.27 L2w 7.3 7.14 7.57 L12w 7.45 7.2 7.16 L2b 7.54 6.75 7.59 L12b 7.21 7.31 7.19 L3a 6.63 MB1a 7.29 6.8 7.24 L3a1 7.4 MB1w 7.61 7.57 L3w 7.32 MB1b 7.57 7.5 7.43 L3b 7.48 MB2a 7.89 7.78 7.42 L4a 7.1 MB2w 7.53 7.68 7.42 L4w 7.21 MB2b 7.69 7.75 7.32 L4b 7.05 MB3a 7.86 7.87 L5a MB3w 7.12 7.31 L5w 7.46 7.36 7.31 MB3b 7.67 7.54 L5b MB4a 8.41 L6a 7.03 6.56 7.02 MB4w 6.95 L6w 6.94 6.73 6.9 MB4b 8.79 L6b 7.07 6.4 6.98 MB5a 7.39 7.43 7.58 L7a 7.14 8.46 7.28 MB5w 7.2 7.29 7.33 L7w 7.9 8 7.1 MB5b 7.45 7.56 7.57 L7b 7.11 7.77 7.19 NP1a 7.21 7.34 7.48 L8a 7.31 7.33 7.41 NP1w 6.68 7.23 6.8 L8w 7.55 7.5 7.18 NP1b 7.1 7.59 7.46 L8b 7.31 7.36 7.34 NP2a 7.37 7.45 7 L9a 7.59 7.6 7.59 NP2w 7.15 7.36 6.96 L9w 7.46 7.53 7.43 NP2b 7.23 7.42 7.02 L9b 7.62 7.63 7.56 L10a 6.54 L10w 7.47 7.42 L10b 7.34

Masterarbeit Maria Redeker Annex X

Table 4: Dissolved oxygen contents recorded in scope of the WWTP campaign

c(O 2) / mg/LO c(O 2) / mg/LO sampling sampling point Dec. 2009 Jan. 2010 Feb. 2010point Dec. 2009 Jan. 2010 Feb. 2010 L1a 7.63 7.88 7.73 L11a 8.28 8.88 14.67 L1w 5.25 3.78 3.99 L11w 3.89 3.93 4.17 L1b 5.93 4.53 4.43 L11b 7.5 7.59 13.25 L2a 15.64 11.74 13.72 L12a 6.3 5.02 6.02 L2w 4.13 7.52 12.76 L12w 3.82 1.92 1.79 L2b 13.6 11.27 13.41 L12b 5.92 4.52 4.58 L3a 10.01 MB1a 6.2 10.32 L3a1 12.59 MB1w 4.97 5 L3w 6.68 MB1b 5.47 9.25 L3b 13.98 MB2a 12.81 7.62 8.58 L4a 11.74 MB2w 6.5 6.71 8.69 L4w 10.5 MB2b 10.87 7.21 7.6 L4b 12.15 MB3a 9.93 12.07 L5a MB3w 4.45 4.57 L5w 8.31 6.23 5.82 MB3b 9.26 9.8 L5b MB4a 14.06 L6a 11.13 10.09 11.63 MB4w 4.35 L6w 4.1 2.98 2.56 MB4b 12.75 L6b 10.91 10.62 11.25 MB5a 10.87 9.23 12.54 L7a 4.23 11.83 11.79 MB5w 4.52 4.41 4.61 L7w 2.34 3.7 3.86 MB5b 10.79 9.41 12.05 L7b 4.11 10.18 9.96 NP1a 13.1 10.37 11.31 L8a 7.23 5.2 7.98 NP1w 4.91 3.91 3.88 L8w 6.38 4.03 4.03 NP1b 13.3 10.29 11.13 L8b 7.07 5.15 6.37 NP2a 13.28 9.37 10.39 L9a 7.66 6.88 8.17 NP2w 7.67 4.09 4.71 L9w 1.82 1.03 2.05 NP2b 10.18 6.59 6.75 L9b 7.37 6.48 9.63 L10a 2.54 L10w 0.51 0.53 L10b 4.84

Masterarbeit Maria Redeker Annex XI

Table 5: EC recorded in scope of the WWTP campaign EC / µS/cm EC / µS/cm sampling sampling point Dec. 2009 Jan. 2010 Feb. 2010point Dec. 2009 Jan. 2010 Feb. 2010 L1a 595 598 603 L11a 563 537 528 L1w 402 480 725 L11w 477 594 843 L1b 459 511 710 L11b 552 542 538 L2a 399 406 405 L12a 666 748 738 L2w 298 489 454 L12w 669 793 1044 L2b 388 416 436 L12b 668 756 796 L3a 516 MB1a 719 693 825 L3a1 476 MB1w 1276 1202 L3w 385 MB1b 943 1003 897 L3b 465 MB2a 579 1564 1404 L4a 406 MB2w 1577 1562 1401 L4w 421 MB2b 903 1564 1398 L4b 416 MB3a 652 583 L5a MB3w 1020 1164 L5w 418 399 522 MB3b 710 824 L5b MB4a 634 L6a 385 402 407 MB4w 1221 L6w 335 588 837 MB4b 689 L6b 386 387 429 MB5a 642 603 576 L7a 473 464 MB5w 1030 1190 1263 L7w 792 788 MB5b 661 617 743 L7b 522 517 NP1a 444 487 491 L8a 655 660 652 NP1w 745 848 1026 L8w 612 648 832 NP1b 446 493 499 L8b 650 655 666 NP2a 499 597 676 L9a 516 518 508 NP2w 994 1144 1341 L9w 519 556 557 NP2b 879 1068 1246 L9b 515 520 515 L10a 347 L10w 752 811 L10b 577

Masterarbeit Maria Redeker Annex XII

Table 6: NH 4N contents recorded in scope of the WWTP campaign

c (NH 4N) / mg/L c (NH 4N) / mg/L Dec. 2009 Jan. 2010 Feb. 2010 Dec. 2009 Jan. 2010 Feb. 2010 x s x s x s x s x s x s L1a 10.52 0.07 11.21 0.03 11.59 0.04 L11a 0.17 0.00 0.04 0.00 0.03 0.00 L1w 13.88 0.02 15.69 0.10 24.13 0.11 L11w 16.09 0.32 15.35 0.02 33.89 0.35 L1b 11.82 0.26 14.84 0.07 23.57 0.10 L11b 0.74 0.00 0.70 0.00 1.05 0.00 L2a 0.17 0.00 0.42 0.00 0.52 0.02 L12a 0.42 0.00 0.36 0.00 0.44 0.00 L2w 4.86 0.00 3.94 0.01 2.13 0.00 L12w 13.79 0.46 13.67 0.02 13.97 0.21 L2b 0.40 0.01 1.04 0.00 1.41 0.00 L12b 3.10 0.02 3.20 0.01 2.94 0.01 L3a 0.56 0.00 MB1a 1.31 0.01 1.59 0.00 0.60 0.00 L3a1 0.30 0.01 MB1w 45.76 0.66 45.35 0.15 L3w 1.39 0.00 MB1b 22.68 0.23 27.95 0.95 11.60 0.03 L3b 0.74 0.02 MB2a 0.01 0.00 0.29 0.00 0.49 0.01 L4a 0.07 0.00 MB2w 0.15 0.00 0.25 0.00 0.55 0.00 L4w 6.94 0.02 MB2b 0.82 0.00 0.30 0.01 0.54 0.00 L4b 1.37 0.00 MB3a 0.32 0.00 0.82 0.00 L5a MB3w 4.21 0.03 30.38 0.36 L5w 13.27 1.08 13.13 0.26 15.78 0.22 MB3b 0.90 0.00 14.16 0.05 L5b MB4a 0.28 0.00 L6a 0.13 0.00 0.10 0.00 0.11 0.00 MB4w 5.07 0.01 0.00 0.00 L6w 7.85 0.05 13.70 0.27 18.50 1.38 MB4b 0.45 0.00 L6b 0.47 0.00 2.01 0.01 1.16 0.03 MB5a 0.36 0.00 0.46 0.00 0.85 0.00 L7a 1.75 0.02 0.19 0.00 0.11 0.00 MB5w 0.03 0.00 0.29 0.00 7.39 0.02 L7w 17.11 0.02 29.50 0.12 28.94 0.25 MB5b 0.34 0.00 0.64 0.01 1.27 0.04 L7b 3.26 0.00 4.26 0.01 4.96 0.06 NP1a 0.29 0.00 0.39 0.00 0.44 0.00 L8a 1.76 0.00 2.01 0.01 2.25 0.02 NP1w 0.04 0.00 0.05 0.00 0.16 0.00 L8w 0.64 0.00 0.55 0.00 0.40 0.00 NP1b 0.26 0.00 0.38 0.00 0.43 0.01 L8b 2.47 0.00 3.25 0.01 6.36 0.00 NP2a 0.21 0.00 0.29 0.00 0.30 0.00 L9a 0.20 0.00 0.15 0.01 0.16 0.00 NP2w 0.82 0.00 1.04 0.01 1.43 0.01 L9w 3.81 0.00 3.61 0.01 3.94 0.01 NP2b 0.67 0.00 0.91 0.00 1.33 0.01 L9b 0.41 0.00 0.35 0.01 0.80 0.01 L10a 0.08 0.00 L10w 12.98 0.05 29.73 0.41 L10b 0.57 0.00

Masterarbeit Maria Redeker Annex XIII

Table 7: NO 2N contents recorded in scope of the WWTP campaign

c (NO 2N) / mg/L c (NO 2N) / mg/L sampling sampling point Dec. 2009 Jan. 2010 Feb. 2010point Dec. 2009 Jan. 2010 Feb. 2010 L1a 0 0 0 L11a 0 0 0.04 L1w 0 0 0 L11w 0 0 0 L1b 0 0 0 L11b 0 0 0.04 L2a 0 0 0 L12a 0 0 0 L2w 0.22 0 0 L12w 0 0 0 L2b 0 0 0 L12b 0 0 0 L3a 0 MB1a 0.21 0 0 L3a1 0 MB1w 0 0.31 L3w 0.17 MB1b 0.46 0 0.11 L3b 0 MB2a 0 4.41 0.63 L4a 0 MB2w 0 4.7 0.5 L4w 0 MB2b 0 3.81 0.68 L4b 0 MB3a 0 0.06 L5a MB3w 0.33 0.08 L5w 0 0 0 MB3b 0 0.08 L5b MB4a 0 L6a 0 0 0 MB4w 0.42 L6w 0 0 0 MB4b 0 L6b 0 0 0 MB5a 0 0 0 L7a 0 0 0 MB5w 0.05 0.52 0.42 L7w 0 0 0 MB5b 0 0 0.04 L7b 0 0 0 NP1a 0 0 0 L8a 0 0 0 NP1w 0 0 0 L8w 0 0 0 NP1b 0 0 0 L8b 0 0 0 NP2a 0 0 0 L9a 0 0 0.04 NP2w 0.16 0 0 L9w 0 0 0 NP2b 0.15 0 0 L9b 0 0 0 L10a 0 L10w 0 0 L10b 0

Masterarbeit Maria Redeker Annex XIV

Table 8: NO 3N contents recorded in scope of the WWTP campaign

c (NO 3N) / mg/L c (No 3N) / mg/L Dec. 2009 Jan. 2010 Feb. 2010 Dec. 2009 Jan. 2010 Feb. 2010 x s x s x s x s x s x s L1a 1.47 0.13 0.86 0.08 0.29 0.03 L11a 11.05 0.97 11.28 0.99 9.88 0.87 L1w 0.03 0.00 0.07 0.01 0.02 0.00 L11w 0.23 0.02 0.00 0.00 0.15 0.01 L1b 0.46 0.04 0.26 0.02 0.04 0.00 L11b 13.73 1.21 7.18 0.63 8.67 0.76 L2a 4.55 0.40 3.52 0.31 2.81 0.25 L12a 3.79 0.33 1.57 0.14 0.82 0.07 L2w 0.86 0.08 2.90 0.26 2.80 0.25 L12w 0.45 0.04 0.03 0.00 0.03 0.00 L2b 4.09 0.36 3.72 0.33 3.16 0.28 L12b 3.03 0.27 1.03 0.09 0.73 0.06 L3a 6.95 0.61 MB1a 7.74 0.68 8.42 0.74 7.16 0.63 L3a1 5.35 0.47 MB1w 4.90 0.43 1.83 0.16 L3w 4.28 0.38 MB1b 5.81 0.51 5.68 0.50 7.81 0.69 L3b 5.38 0.47 MB2a 21.65 1.91 15.68 1.38 17.94 1.58 L4a 10.10 0.89 MB2w 2.43 0.21 16.65 1.46 20.58 1.81 L4w 2.50 0.22 MB2b 17.18 1.51 13.20 1.16 18.79 1.65 L4b 8.06 0.71 MB3a 9.81 0.86 6.44 0.57 L5a MB3w 16.22 1.43 1.57 0.14 L5w 0.60 0.05 0.57 0.05 0.75 0.07 MB3b 11.10 0.98 4.52 0.40 L5b MB4a 10.63 0.94 L6a 11.83 1.04 12.63 1.11 12.31 1.08 MB4w 27.14 2.39 0.00 0.00 L6w 0.22 0.02 0.03 0.00 0.30 0.03 MB4b 9.29 0.82 L6b 13.23 1.16 14.14 1.24 10.78 0.95 MB5a 13.04 1.15 4.51 0.40 3.62 0.32 L7a 5.68 0.50 7.62 0.67 7.13 0.63 MB5w 22.73 2.00 22.45 1.98 5.22 0.46 L7w 0.18 0.02 0.22 0.02 0.11 0.01 MB5b 12.11 1.07 4.79 0.42 3.31 0.29 L7b 6.33 0.56 7.97 0.70 6.23 0.55 NP1a 6.43 0.57 4.43 0.39 3.84 0.34 L8a 0.58 0.05 0.31 0.03 0.07 0.01 NP1w 0.84 0.07 0.32 0.03 0.15 0.01 L8w 0.00 0.00 0.00 0.00 0.03 0.00 NP1b 5.13 0.45 4.35 0.38 4.03 0.35 L8b 0.86 0.08 0.23 0.02 0.06 0.01 NP2a 0.95 0.08 0.59 0.05 0.54 0.05 L9a 2.95 0.26 2.30 0.20 1.97 0.17 NP2w 5.06 0.45 5.51 0.48 7.17 0.63 L9w 0.00 0.00 0.00 0.00 0.03 0.00 NP2b 4.21 0.37 5.90 0.52 6.37 0.56 L9b 2.34 0.21 1.85 0.16 1.62 0.14 L10a 0.06 0.01 L10w 0.00 0.00 0.00 0.00 L10b 0.53 0.05

Masterarbeit Maria Redeker Annex XV

Table 9: Ntot contents recorded in scope of the WWTP campaign

c (N tot ) / mg/L c (N tot ) / mg/L sampling sampling point Dec. 2009 Jan. 2010 Feb. 2010point Dec. 2009 Jan. 2010 Feb. 2010 L1a 13.1 11.1 11.4 L11a 12.5 10.1 9.7 L1w 18.5 17.6 27.1 L11w 19.7 28.2 36.4 L1b 17 14.4 24.8 L11b 11.5 10.7 13.9 L2a 5.5 4.3 3 L12a 4.3 2.3 1.4 L2w 7.5 6.8 5.1 L12w 12.7 13.3 14.5 L2b 5.7 4.6 4.9 L12b 5.7 4.2 3.8 L3a 9.4 MB1a 10 10.8 10.4 L3a1 7.1 MB1w 55.6 66.9 L3w 6.6 MB1b 34.8 37.7 L3b 7.4 MB2a 22.4 73.1 56 L4a 10 MB2w 53.1 69.7 57.3 L4w 11.2 MB2b 32.1 66.4 54.3 L4b 9.1 MB3a 12.7 8.5 L5a MB3w 28 33.5 L5w 14.9 14.6 18.4 MB3b 14.4 16.6 L5b MB4a 10 L6a 12.2 16.2 14.2 MB4w 46.5 L6w 11.9 16.6 17.9 MB4b 13 L6b 14.6 16.2 14.3 MB5a 10.8 6.1 4.6 L7a 9.1 9.4 9.1 MB5w 34.6 32.5 13.1 L7w 19.4 27.6 29.8 MB5b 12.7 6.5 5.8 L7b 10 11.8 11.8 NP1a 6.8 6.3 5.1 L8a 2.8 2.7 2.9 NP1w 1.9 1.5 1.3 L8w 15.4 31.6 40.3 NP1b 6.9 6.3 5.2 L8b 3.6 4.2 7.3 NP2a 1.7 1.4 0.92 L9a 3.6 2.8 2.6 NP2w 7.6 10.2 12.9 L9w 3.7 4.8 5 NP2b 6.4 9 10 L9b 3.4 2.8 2.6 L10a 1.3 L10w 26.7 37.2 L10b 14.3

Masterarbeit Maria Redeker Annex XVI

Table 10: PO 4P contents recorded in scope of the WWTP campaign

c (PO 4P) / mg/L c (PO 4P) / mg/L Dec. 2009 Jan. 2010 Feb. 2010 Dec. 2009 Jan. 2010 Feb. 2010 x s x s x s x s x s x s L1a 0.051 0.002 0.033 0.001 0.004 0.000 L11a 0.109 0.001 0.100 0.001 0.074 0.000 L1w 2.354 0.028 2.494 0.015 3.703 0.005 L11w 2.797 0.026 2.929 0.009 4.851 0.005 L1b 1.500 0.010 1.706 0.004 3.082 0.000 L11b 0.196 0.001 0.189 0.001 0.255 0.000 L2a 0.035 0.001 0.026 0.001 0.017 0.000 L12a 0.064 0.002 0.037 0.001 0.034 0.001 L2w 0.944 0.017 0.567 0.000 0.320 0.001 L12w 2.245 0.000 2.120 0.006 2.259 0.021 L2b 0.075 0.000 0.117 0.001 0.213 0.001 L12b 0.490 0.004 0.463 0.005 0.396 0.001 L3a 0.274 0.001 MB1a 0.180 0.000 0.324 0.001 0.115 0.001 L3a1 0.063 0.002 MB1w 9.989 0.194 9.284 0.071 L3w 0.393 0.001 MB1b 4.711 0.007 5.894 0.124 1.644 0.006 L3b 0.183 0.003 MB2a 0.090 0.000 6.340 0.012 7.031 0.023 L4a 0.018 0.001 MB2w 4.648 0.021 6.954 0.142 7.105 0.018 L4w 1.027 0.001 MB2b 1.537 0.004 6.404 0.086 7.099 0.072 L4b 0.222 0.001 MB3a 0.205 0.004 0.255 0.000 L5a MB3w 6.040 0.011 5.338 0.005 L5w 2.413 0.007 2.316 0.011 2.657 0.004 MB3b 1.216 0.009 2.324 0.021 L5b MB4a 0.059 0.002 L6a 0.028 0.000 0.025 0.001 0.017 0.001 MB4w 7.093 0.005 0.000 0.000 L6w 1.143 0.027 2.121 0.004 2.626 0.006 MB4b 0.315 0.000 L6b 0.088 0.001 0.302 0.000 0.157 0.000 MB5a 0.173 0.000 0.252 0.001 0.192 0.002 L7a 0.232 0.001 0.031 0.002 0.021 0.000 MB5w 3.137 0.004 4.357 0.043 5.983 0.016 L7w 2.447 0.012 3.788 0.014 4.307 0.002 MB5b 0.307 0.001 0.301 0.002 0.701 0.001 L7b 0.420 0.002 0.520 0.001 0.645 0.002 NP1a 0.059 0.000 0.031 0.000 0.024 0.000 L8a 0.094 0.000 0.108 0.001 0.056 0.000 NP1w 1.079 0.006 0.963 0.000 0.276 0.004 L8w 4.035 0.025 4.382 0.005 5.339 0.007 NP1b 0.066 0.001 0.041 0.001 0.025 0.001 L8b 0.210 0.000 0.293 0.002 0.546 0.011 NP2a 0.007 0.000 0.003 0.000 0.005 0.000 L9a 0.019 0.000 0.023 0.003 0.008 0.000 NP2w 0.038 0.000 0.022 0.000 0.019 0.000 L9w 0.523 0.006 0.601 0.006 0.594 0.000 NP2b 0.029 0.000 0.024 0.000 0.013 0.000 L9b 0.038 0.001 0.033 0.001 0.081 0.001 L10a 0.171 0.028 L10w 4.115 0.048 4.473 0.033 L10b 2.062 0.013

Masterarbeit Maria Redeker Annex XVII

Table 11: Ptot contents recorded in scope of the WWTP campaign

c (P tot ) / mg/L c (P tot ) / mg/L Dec. 2009 Jan. 2010 Feb. 2010 Dec. 2009 Jan. 2010 Feb. 2010 x s x s x s x s x s x s L1a 0.450 0.003 0.371 0.000 0.601 0.001 L11a 0.117 0.007 0.212 0.005 0.094 0.001 L1w 3.442 0.021 3.567 0.070 4.868 0.025 L11w 3.514 0.006 3.957 0.073 5.462 0.019 L1b 2.559 0.011 2.751 0.001 4.582 0.028 L11b 0.247 0.005 0.244 0.002 0.283 0.000 L2a 0.118 0.000 0.095 0.000 0.058 0.001 L12a 0.123 0.005 0.152 0.023 0.095 0.004 L2w 1.284 0.007 0.847 0.031 0.467 0.031 L12w 2.892 0.000 2.576 0.049 2.494 0.002 L2b 0.168 0.004 0.211 0.018 0.287 0.001 L12b 0.811 0.034 0.671 0.001 0.570 0.000 L3a 0.336 0.000 MB1a 0.399 0.012 0.729 0.000 0.520 0.016 L3a1 0.143 0.004 MB1w 12.93 0.003 12.38 0.191 L3w 0.503 0.005 MB1b xx xx 8.556 0.282 6.901 0.024 L3b 0.284 0.000 MB2a 0.130 0.001 7.463 0.000 9.866 0.362 L4a 0.038 0.002 MB2w 5.526 0.037 7.397 0.084 7.367 0.014 L4w 1.866 0.014 MB2b 1.815 0.048 7.546 0.120 7.938 0.207 L4b 0.429 0.001 MB3a 0.270 0.001 0.343 0.000 L5a MB3w 7.113 0.022 5.896 0.015 L5w 2.994 0.165 3.346 0.089 4.086 0.028 MB3b 1.409 0.024 2.863 0.121 L5b MB4a 0.096 0.002 L6a 0.068 0.001 0.089 0.001 0.031 0.000 MB4w 7.527 0.044 0.000 0.000 L6w 1.917 0.000 2.718 0.023 3.111 0.069 MB4b 0.365 0.002 L6b 0.158 0.003 0.412 0.000 0.196 0.002 MB5a 0.248 0.002 0.351 0.006 0.228 0.001 L7a 0.409 0.003 0.081 0.002 0.065 0.002 MB5w 3.438 0.067 5.005 0.044 6.142 0.028 L7w 2.760 0.006 4.486 0.086 4.642 0.009 MB5b 0.388 0.002 0.396 0.000 0.759 0.001 L7b 0.625 0.004 0.745 0.002 0.848 0.001 NP1a 0.182 0.000 0.188 0.004 0.145 0.003 L8a 0.375 0.001 0.352 0.001 0.549 0.003 NP1w 1.077 0.012 1.117 0.002 0.436 0.004 L8w 5.031 0.030 5.568 0.052 6.095 0.009 NP1b 0.195 0.008 0.179 0.000 0.167 0.000 L8b 0.523 0.000 0.714 0.003 1.053 0.013 NP2a 0.052 0.002 0.073 0.000 0.067 0.002 L9a 0.111 0.001 0.117 0.001 0.087 0.000 NP2w 0.095 0.001 0.089 0.000 0.092 0.002 L9w 0.757 0.004 0.788 0.003 0.800 0.000 NP2b 0.087 0.001 0.089 0.000 0.107 0.001 L9b 0.140 0.007 0.133 0.004 0.184 0.008 L10a 0.293 0.001 L10w 4.970 0.034 5.126 0.049 L10b 2.567 0.044

Masterarbeit Maria Redeker Annex XVIII

Tabelle 12: Cl contents recorded in scope of the WWTP campaign c (Cl ) / mg/L c (Cl ) / mg/L Dec. 2009 Jan. 2010 Feb. 2010 Dec. 2009 Jan. 2010 Feb. 2010 x s x s x s x s x s x s L1a 29.0 3.1 34.1 3.6 29.7 3.1 L11a 32.4 3.4 33.4 3.5 27.0 2.9 L1w 30.4 3.2 47.9 5.1 68.3 7.2 L11w 42.6 4.5 49.8 5.3 75.7 8.0 L1b 27.6 2.9 56.3 6.0 64.8 6.9 L11b 41.5 4.4 22.7 2.4 28.9 3.1 L2a 29.4 3.1 36.6 3.9 29.9 3.2 L12a 34.5 3.7 33.3 3.5 28.8 3.0 L2w 22.9 2.4 52.9 5.6 40.5 4.3 L12w 56.6 6.0 60.0 6.4 94.9 10.1 L2b 26.6 2.8 41.8 4.4 40.8 4.3 L12b 42.9 4.6 35.1 3.7 45.2 4.8 L3a 40.0 MB1a 105.8 11.2 114.9 12.2 144.0 15.3 L3a1 25.5 MB1w 0.0 98.0 10.4 84.2 8.9 L3w 32.1 MB1b 91.2 9.7 129.0 13.7 136.8 14.5 L3b 30.0 MB2a 41.0 4.3 130.7 13.9 129.6 13.7 L4a 30.8 MB2w 145.3 15.4 138.9 14.7 129.4 13.7 L4w 32.8 MB2b 93.7 9.9 111.7 11.8 128.3 13.6 L4b 30.7 MB3a 0.0 26.9 2.8 29.9 3.2 L5a MB3w 0.0 83.9 8.9 93.9 10.0 L5w 26.6 2.8 34.9 3.7 47.7 5.1 MB3b 0.0 38.3 4.1 54.2 5.7 L5b MB4a 27.0 2.9 L6a 27.8 2.9 28.5 3.0 37.7 4.0 MB4w 0.0 105.4 11.2 0.0 0.0 L6w 21.9 2.3 55.4 5.9 96.2 10.2 MB4b 26.2 2.8 L6b 32.1 3.4 40.2 4.3 38.6 4.1 MB5a 51.0 5.4 29.8 3.2 33.9 3.6 L7a 37.0 3.9 37.0 3.9 35.4 3.8 MB5w 68.4 7.3 89.0 9.4 112.2 11.9 L7w 47.2 5.0 64.1 6.8 62.2 6.6 MB5b 43.7 4.6 31.5 3.3 79.8 8.5 L7b 43.0 4.6 51.3 5.4 41.2 4.4 NP1a 42.1 4.5 35.0 3.7 34.7 3.7 L8a 31.2 3.3 35.8 3.8 33.9 3.6 NP1w 90.3 9.6 123.4 13.1 170.4 18.1 L8w 48.0 5.1 46.6 4.9 59.1 6.3 NP1b 31.5 3.3 38.1 4.0 40.6 4.3 L8b 35.2 3.7 35.0 3.7 33.7 3.6 NP2a 34.7 3.7 67.6 7.2 87.5 9.3 L9a 34.3 3.6 31.2 3.3 29.5 3.1 NP2w 132.4 14.0 161.0 17.1 210.6 22.3 L9w 35.5 3.8 40.5 4.3 42.0 4.5 NP2b 120.5 12.8 164.5 17.4 193.4 20.5 L9b 29.2 3.1 26.1 2.8 31.9 3.4 L10a 45.4 L10w 60.9 53.3 5.7 L10b 50.5

Masterarbeit Maria Redeker Annex XIX

2 Tabelle 13: SO 4 contents recorded in scope of the WWTP campaign

2 2 c (SO 4 ) / mg/L c (SO 4 ) / mg/L Dec. 2009 Jan. 2010 Feb. 2010 Dec. 2009 Jan. 2010 Feb. 2010 x s x s x s x s x s x s L1a 53.9 6.1 56.3 6.4 52.2 6.0 L11a 70.1 8.0 73.3 8.4 62.4 7.1 L1w 11.4 1.3 5.7 0.6 5.1 0.6 L11w 22.7 2.6 21.4 2.4 25.1 2.9 L1b 22.8 2.6 23.8 2.7 9.2 1.0 L11b 81.5 9.3 50.3 5.7 57.8 6.6 L2a 36.0 4.1 43.7 5.0 39.3 4.5 L12a 66.1 7.5 67.0 7.6 54.6 6.2 L2w 18.5 2.1 44.0 5.0 42.7 4.9 L12w 39.1 4.5 44.3 5.1 35.2 4.0 L2b 32.9 3.8 49.1 5.6 48.1 5.5 L12b 62.6 7.1 53.6 6.1 59.6 6.8 L3a 23.3 2.7 MB1a 31.7 3.6 39.5 4.5 27.4 3.1 L3a1 27.0 3.1 MB1w 78.5 8.9 44.9 5.1 L3w 29.3 3.3 MB1b 41.2 4.7 50.8 5.8 42.8 4.9 L3b 27.2 3.1 MB2a 57.3 6.5 113.8 13.0 109.2 12.5 L4a 48.5 5.5 MB2w 115.0 13.1 118.8 13.5 110.1 12.5 L4w 34.1 3.9 MB2b 92.4 10.5 99.1 11.3 109.2 12.5 L4b 41.4 4.7 MB3a 47.3 5.4 41.9 4.8 L5a MB3w 65.5 7.5 83.4 9.5 L5w 8.1 0.9 9.0 1.0 7.8 0.9 MB3b 51.8 5.9 56.2 6.4 L5b MB4a 55.1 6.3 L6a 32.6 3.7 33.7 3.8 34.7 4.0 MB4w 65.1 7.4 0.0 0.0 L6w 5.7 0.6 5.7 0.6 20.6 2.3 MB4b 42.5 4.8 L6b 37.2 4.2 39.0 4.4 30.0 3.4 MB5a 76.4 8.7 37.7 4.3 33.5 3.8 L7a 39.1 4.5 48.8 5.6 47.2 5.4 MB5w 59.1 6.7 75.8 8.6 86.2 9.8 L7w 25.0 2.8 4.1 0.5 15.1 1.7 MB5b 60.9 6.9 39.4 4.5 41.2 4.7 L7b 47.3 5.4 53.1 6.1 44.8 5.1 NP1a 58.2 6.6 51.1 5.8 45.0 5.1 L8a 82.2 9.4 88.4 10.1 70.6 8.1 NP1w 56.5 6.4 69.2 7.9 68.6 7.8 L8w 30.7 3.5 16.4 1.9 6.4 0.7 NP1b 47.6 5.4 52.3 6.0 51.6 5.9 L8b 92.0 10.5 82.0 9.3 57.3 6.5 NP2a 60.3 6.9 78.9 9.0 75.4 8.6 L9a 97.3 11.1 92.6 10.6 81.2 9.3 NP2w 98.4 11.2 77.0 8.8 92.5 10.5 L9w 64.0 7.3 59.0 6.7 57.4 6.5 NP2b 91.5 10.4 89.8 10.2 88.7 10.1 L9b 81.7 9.3 74.3 8.5 78.3 8.9 L10a 52.2 6.0 L10w 39.6 4.5 5.7 0.7 L10b 37.6 4.3

Masterarbeit Maria Redeker Annex XX

Results displayed in the time series:

Table 14: NH 4N contents recorded in scope of the subcatchment campaign and at the entries of ditches transporting effluent in scope of the WWTP campaign

c(NH 4N) / mg/L Dec. 2009 Jan. 2010 Feb. 2010 sampling point x s x s x s S2 0.26 0.001 0.18 0.000 0.27 0.001 S4 0.46 0.002 0.24 0.001 0.39 0.003 S5 1.27 0.003 0.20 0.000 0.30 0.001 S6 0.24 0.001 0.24 0.002 0.24 0.003 S7 0.17 0.000 0.19 0.000 0.23 0.001 S9 0.26 0.000 0.30 0.000 0.41 0.001 S16 0.52 0.005 0.59 0.004 0.70 0.000 S17 0.32 0.001 0.44 0.006 0.58 0.005 S18 0.30 0.000 0.47 0.003 0.64 0.005 S21 0.28 0.001 0.32 0.003 0.37 0.001 L1Ra 0.36 0.000 0.35 0.002 0.34 0.007 L1Rw 1.52 0.004 2.11 0.006 3.17 0.007 L1Rb 0.65 0.001 0.89 0.015 0.83 0.004 L5Ra 0.32 0.000 0.56 0.005 0.66 0.003 L5Rw 3.72 0.011 2.12 0.001 2.22 0.007 L5Rb 0.34 0.000 0.60 0.000 0.70 0.004 MB2Ra 0.10 0.003 0.19 0.006 0.32 0.005 MB2Rw 0.55 0.013 0.17 0.000 0.15 0.000 MB2Rb 0.16 0.001 0.08 0.000 0.29 0.003

Masterarbeit Maria Redeker Annex XXI

Tabelle 15: PO 4P contents recorded in scope of the subcatchment campaign and at the entries of ditches transporting effluent in scope of the WWTP campaign

c(PO 4P) / mg/L Dec. 2009 Jan. 2010 Feb. 2010 sampling point x s x s x s S2 0.04 0.000 0.02 0.001 0.02 0.001 S4 0.06 0.001 0.03 0.006 0.03 0.001 S5 0.09 0.000 0.03 0.000 0.01 0.000 S6 0.03 0.000 0.03 0.001 0.03 0.000 S7 0.03 0.000 0.03 0.000 0.02 0.000 S9 0.03 0.000 0.03 0.000 0.02 0.000 S16 0.08 0.001 0.05 0.000 0.1 0.000 S17 0.04 0.000 0.02 0.000 0.03 0.001 S18 0.05 0.000 0.05 0.001 0.07 0.001 S21 0.04 0.000 0.02 0.000 0.02 0.000 L1Ra 0.06 0.002 0.05 0.000 0.04 0.000 L1Rw 0.05 0.001 0.09 0.000 0.26 0.001 L1Rb 0.07 0.002 0.06 0.001 0.11 0.001 L5Ra 0.05 0.000 0.05 0.001 0.06 0.002 L5Rw 0.33 0.001 0.21 0.000 0.29 0.000 L5Rb 0.05 0.001 0.05 0.001 0.07 0.000 MB2Ra 0.02 0.000 0.03 0.002 0.01 0.000 MB2Rw 0.09 0.001 0.01 0.000 0.03 0.000 MB2Rb 0.02 0.000 0.02 0.000 0.02 0.000

Masterarbeit Maria Redeker Annex XXII

Table 16: Ptot contents recorded in scope of the subcatchment campaign and at the entries of ditches transporting effluent in scope of the WWTP campaign

c(P tot ) / mg/L Dec. 2009 Jan. 2010 Feb. 2010 sampling point x s x s x s S2 0.19 0.000 0.14 0.001 0.19 0.002 S4 0.21 0.001 0.13 0.001 0.15 0.002 S5 0.32 0.001 0.16 0.001 0.17 0.004 S6 0.11 0.002 0.10 0.001 0.12 0.000 S7 0.22 0.001 0.18 0.000 0.18 0.000 S9 0.15 0.001 0.16 0.001 0.19 0.000 S16 0.19 0.001 0.22 0.002 0.23 0.002 S17 0.22 0.002 0.19 0.006 0.14 0.001 S18 0.13 0.001 0.26 0.000 0.13 0.001 S21 0.17 0.003 0.40 0.001 0.18 0.002 L1Ra 0.23 0.003 0.19 0.013 0.24 0.007 L1Rw 0.3 0.000 0.44 0.005 0.61 0.006 L1Rb 0.21 0.002 0.36 0.009 0.32 0.012 L5Ra 0.14 0.003 0.15 0.002 0.12 0.001 L5Rw 0.45 0.008 0.75 0.017 0.54 0.001 L5Rb 0.14 0.001 0.16 0.011 0.15 0.005 MB2Ra 0.13 0.006 0.47 0.012 0.24 0.019 MB2Rw 0.13 0.006 0.4 0.009 0.13 0.009 MB2Rb 0.13 0.007 0.1 0.005 0.37 0.019

Calculation of discharge:

Table 17: Measurement techniques and calculation of discharge of the rivers and ditches receiving WWTP effluents based on the data obtained in February 2010 Position technique river width / m A / m 2 v / m/s Q / m 3/s L1b 1 point 0.65 0.05 0.13 0.01 L2a 2 points 1 0.1 0.22 0.02 L6a 2 points 1.1 0.14 0.36 0.05 L8b 1 point 1.5 0.2 0.14 0.03 L9a profile 5.7 1.29 0.13 0.17 L11b float 1 0.05 0.16 0.01 L12a 1 point 0.8 0.04 0.24 0.01 MB1b float 0.4 0.01 0.04 0 MB3a profile 1.45 0.09 0.21 0.02 MB5a 1 point 0.9 0.09 0.1 0.01 NP1b profile 7.7 4.17 0.35 1.44 NP2b 2 points 2.9 0.58 0.34 0.2

Masterarbeit Maria Redeker Annex XXIII

E. Comparison of results between effluents, upstream and downstream of the WWTPs

Masterarbeit Maria Redeker 5. Results

a) 1 5

0 4

-1 3

-2 2 diff Tdiff °C / diff Tdiff /°C -3 1

-4 0 Master thesis Maria– Redeker

-5 -1 L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 WWTP no. WWTP no. difference downstream – upstream Dec. 2009 Jan. 2010 Feb. 2010

b) 1 10

0 8 -1 6 -2 4 -3 2 diff Tdiff °C / diff Tdiff /°C -4 0 -5

-6 -2

-7 -4 L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 WWTP no. WWTP no. difference effluent – upstream Dec. 2009 Jan. 2010 Feb. 2010 XXIV Figure 4: Differences of water temperatures between a) the sampling points upstream and downstream of the WWTPs and b) the effluents and the downstream sampling positions at the sampling days in December, January, and February 5. Results

a) 1 1

0.8 0.8

0.6 0.6

0.4 0.4

0.2 0.2 diff pH diff diff pH diff 0 0

-0.2 -0.2 -0.69 Master thesis Maria– Redeker -0.4 -0.4 L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 WWTP no. WWTP no. difference downstream – upstream Dec. 2009 Jan. 2010 Feb. 2010

b) 1.2 1 1 0.5 0.8 0.6 0 0.4 0.2 -0.5 0 diff pH diff diff pH diff -1 -0.2 -0.4 -1.5 -0.6 -0.8 -2 L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 WWT P no. WWTP no. difference effluent – upstream Dec. 2009 Jan. 2010 Feb. 2010

Figure 5: Differences of pH values between a) the sampling points upstream and downstream of the WWTPs and b) the effluents and the downstream sampling XXV positions at the sampling days in December, January, and February 5. Results

a) 4 4

3 3

2 2

1 1

0 0

-1 mg/L c(O2) diff / diff mg/L c(O2) diff / -1

-2 -2

-3 -3

Master thesis Maria– Redeker -4 -4 L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 WWTP no. WWTP no. difference downstream – upstream Dec. 2009 Jan. 2010 Feb. 2010

b) 2 2

0 0

-2 -2

-4 -4

-6 -6 diff mg/L c(O2) diff / diff mg/L c(O2) diff / -8 -8

-10 -10

-12 -12 L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 WWTP no. WWTP no. difference effluent – upstream Dec. 2009 Jan. 2010 Feb. 2010

Figure 6: Differences of dissolved oxygen contents between a) the sampling points upstream and downstream of the WWTPs and b) the effluents and the XXV I downstream sampling positions at the sampling days in December, January, and February 5. Results

a) 400 600

300 500

400 200 300 100 200 diff EC / S/cm EC/ diff diff EC / S/cm EC/ diff 0 100

-100 0

-200 -100 L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2

Master thesis Maria– Redeker WWTP no. WWTP no. difference downstream – upstream Dec. 2009 Jan. 2010 Feb. 2010

b) 500 1500

400 1000 300

200 500 100 0 0 S/cm EC/ diff diff EC / S/cm EC/ diff

-100 -500 -200

-300 -1000 L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 WWTP no. WWTP no. difference effluent – upstream Dec. 2009 Jan. 2010 Feb. 2010 Figure 7: Differences of electric conductivities between a) the sampling points upstream and downstream of the WWTPs and b) the effluents and the downstream sampling positions at the sampling days in December, January, and February XXVII 5. Results

a) 5 12.0 30 1.2 4.5 25 1 4 3.5 0.8 20 3 0.6 2.5 15 0.4 2 10 diff c(NH4N) / mg/L / c(NH4N) diff 1.5 0.2 1 5 0 0.5

Master thesis Maria– Redeker 0 0 -0.2 L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 MB1 MB3 MB2 MB4 MB5 NP1 NP2 WWTP no. WWTP no. WWTP no. difference downstream – upstream Dec. 2009 Jan. 2010 Feb. 2010

b) 40 50 7 35 6 40 30 5 25 30 4 20 20 3 15 2 10 10 diff c(NH4N) / mg/L / c(NH4N) diff 5 1 0 0 0

-5 -10 -1 L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 MB1 MB3 MB2 MB4 MB5 NP1 NP2 WWTP no. WWTP no. WWTP no. difference effluent – upstream Dec. 2009 Jan. 2010 Feb. 2010 XXVIII

Figure 8: Differences of NH 4N contents between a) the sampling points upstream and downstream of the WWTPs and b) the effluents and the downstream sampling positions at the sampling days in December, January, and February 5. Results

a) 6 13.4 13 30

5 25

4 20

3 15

2 10

1 mg/L / c(Ntot)diff

diff c(Ntot) / mg/L / c(Ntot) diff 5

0 0

-1 -5

-2 -10 L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 Master thesis Maria– Redeker WWTP no. WWTP no. difference downstream – upstream Dec. 2009 Jan. 2010 Feb. 2010

b) 40 70 35 60 30 50 25 40 20 30 15 20 diff c(Ntot) / mg/L / c(Ntot) diff diff c(Ntot) / mg/L / c(Ntot) diff 10 10 5 0 0 -10 -5 -20 L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 WWTP no. WWTP no. difference effluent – upstream Dec. 2009 Jan. 2010 Feb. 2010

Figure 9: Differences of N tot contents between a) the sampling points upstream and downstream of the WWTPs and b) the effluents and the downstream sampling positions at the sampling days in December, January, and February XXIX 5. Results

a) 3.5 3 4.53 5.57 0.030

3 2.5 0.025 2.5 2 0.020 2 1.5 0.015 1.5 1 0.010 diff c(PO4P)diff mg/L / 1 0.5

0.5 0 0.005

Master thesis Maria– Redeker 0 -0.5 0.000 L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 WWTP no. WWTP no. WWTP no. difference downstream – upstream Dec. 2009 Jan. 2010 Feb. 2010

b) 6 12 1.2

10 5 1.0 8 4 0.8 6 3 0.6 4 2 0.4 diff c(PO4P)diff /mg/L 2

1 0 0.2

0 -2 0.0 L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 WWTP no. WWTP no. WWTP no. difference effluent – upstream Dec. 2009 Jan. 2010 Feb. 2010

Figure 10: Differences of PO 4P contents between a) the sampling points upstream and downstream of the WWTPs and b) the effluents and the downstream XXX sampling positions at the sampling days in December, January, and February 5. Results

a) 4 4 7.83 6.38 0.05 3.5 3.5 0.04 3 3 0.03 2.5 2.5 2 2 0.02

1.5 1.5 0.01 1 1 diff c(Ptot) / mg/L c(Ptot) / diff 0 0.5 0.5 0 0 -0.01 -1.93 Master thesis Maria– Redeker -0.5 -0.5 -0.02 L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 WWTP no. WWTP no. WWTP no. difference downstream – upstream Dec. 2009 Jan. 2010 Feb. 2010

b) 6 14 1 12 0.9 5 10 0.8 4 8 0.7 0.6 6 3 0.5 4 0.4 2 2 diff c(Ptot) / mg/L c(Ptot) / diff 0.3 0 1 0.2 -2 0.1 0 -4 0 L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 MB1 MB2 MB3 MB4 MB5 NP1 NP2 WWTP no. WWTP no. WWTP no. difference effluent – upstream Dec. 2009 Jan. 2010 Feb. 2010 XXX I Figure 11: Differences of P tot contents between a) the sampling points upstream and downstream of the WWTPs and b) the effluents and the downstream sampling positions at the sampling days in December, January, and February Annex XXXII

F. Water quality in the single months

Table 18: Classification of dissolved oxygen contents recorded upstream and downstream of the WWTPs in the single sampling months according to a) LAWA (1998) and b) RAKON (LAWAAO, 2007) a) upstream downstream b) upstream downstream

Dec Jan Feb Dec Jan Feb Dec Jan Feb Dec Jan Feb 2009 2010 2010 2009 2010 2010 2009 2010 2010 2009 2010 2010 L1 II II II IIIII III III L1 BM BM BM L2 III III III III III III L2 BG BG BG BG BG BG L3 III III L3 BG BG L4 III III L4 BG BG L6 III III III III III III L6 BG BG BG BG BG BG L7 III III III III III III L7 BG BG BG BG L8 II IIIII II II IIIII II L8 BM BM BM L9 II II III II II III L9 BM BM BM BG L10 IIIIV III L10 L11 III III III II II III L11 BM BM BG BM BM BG L12 II IIIII II IIIII III III L12 BM BM MB1 II III IIIII III MB1 BM BG BG MB2 III III II II MB2 BG BG BM BM MB3 III III III III MB3 BG BG BG BG MB4 III III MB4 BG BG MB5 III III III III III III MB5 BG BG BG BG BG BG NP1 III III III III III III NP1 BG BG BG BG BG BG NP2 III III III III II II NP2 BG BG BG BG

Table 19: Classification of pH values recorded upstream and downstream of the WWTPs in the single sampling months according to RAKON (LAWAAO, 2007)

upstream downstream Dec Jan Feb Dec Jan Feb 2009 2010 2010 2009 2010 2010 L1 BM BM BM BM BM BM L2 BM BM BM BM BM BM L3 BM BM L4 BM BM L6 BM BM BM BM BM L7 BM BM BM BM BM L8 BM BM BM BM BM BM L9 BM BM BM BM BM BM L10 BM BM L11 BM BM BM BM BM BM L12 BM BM BM BM BM BM MB1 BM BM BM BM BM BM MB2 BM BM BM BM MB3 BM BM BM BM MB4 BM MB5 BM BM BM BM BM BM NP1 BM BM BM BM BM BM NP2 BM BM BM BM BM BM

Masterarbeit Maria Redeker Annex XXXIII

Table 20: Classification of NH 4N contents recorded upstream and downstream of the WWTPs in the single sampling months according to LAWA (1998) and RAKON (LAWAAO, 2007)

a) upstream downstream b) upstream downstream Dec Jan Feb Dec Jan Feb Dec Jan Feb Dec Jan Feb 2009 2010 2010 2009 2010 2010 2009 2010 2010 2009 2010 2010 L1 IV IV IV IV IV IV L1 L2 II IIIII IIIII IIIII III IIIIV L2 BM L3 IIIII III L3 L4 III IIIIV L4 BM L6 II II II IIIII IIIIV III L6 BM BM BM L7 IIIIV II II IV IV IV L7 BM BM L8 IIIIV IIIIV IIIIV IV IV IV L8 L9 II II II IIIII IIIII III L9 BM BM BM L10 III IIIII L10 BM L11 II I I III III III L11 BM BG BG L12 IIIII IIIII IIIII IV IV IV L12 MB1 IIIIV IIIIV III IV IV IV MB1 MB2 I III IIIII IIIII MB2 BG MB3 IIIII III III IV MB3 MB4 II IIIII MB4 BM MB5 IIIII IIIII III IIIII III IIIIV MB5 NP1 II IIIII IIIII II IIIII IIIII NP1 BM BM NP2 II II II III III IIIIV NP2 BM BM BM

Table 21: Classification of NO 2N contents recorded Table 22: Classification of NO 3N contents recorded upstream and downstream of the WWTPs in the single upstream and downstream of the WWTPs in the single sampling months according to LAWA (1998) sampling months according to LAWA (1998)

upstream downstream upstream downstream Dec Jan Feb Dec Jan Feb Dec Jan Feb Dec Jan Feb 2009 2010 2010 2009 2010 2010 2009 2010 2010 2009 2010 2010 L1 I I I I I I L1 III I I I I I L2 I I I I I I L2 IIIII IIIII IIIII IIIII IIIII IIIII L3 I I L3 III III L4 I I L4 IIIIV III L6 I I I I I I L6 IIIIV IIIIV IIIIV IIIIV IIIIV IIIIV L7 I I I I I I L7 III III III III III III L8 I I I I I I L8 I I I I I I L9 I I III I I I L9 IIIII II II II II II L10 I I L10 I I L11 I I III I I III L11 IIIIV IIIIV III IIIIV III III L12 I I I I I I L12 IIIII II I IIIII III I MB1 III I I IIIIV I IIIII MB1 III III III III III III MB2 I I IV IIIIV MB2 IV IIIIV IIIIV IIIIV MB3 I II I II MB3 III III IIIIV IIIII MB4 I I MB4 IIIIV III MB5 I I I I I III MB5 IIIIV IIIII IIIII IIIIV IIIII IIIII NP1 I I I I I I NP1 III IIIII IIIII III IIIII IIIII NP2 I I I IIIII I I NP2 I I I IIIII III III

Masterarbeit Maria Redeker Annex XXXIV

Table 23: Classification of N tot contents recorded upstream and downstream of the WWTPs in the single sampling months according to LAWA (1998)

upstream downstream Dec Jan Feb Dec Jan Feb 2009 2010 2010 2009 2010 2010 L1 IIIIV III III IIIIV IIIIV IV L2 IIIII IIIII II IIIII IIIII IIIII L3 III III L4 III III L6 IIIIV IIIIV IIIIV IIIIV IIIIV IIIIV L7 III III III III III III L8 II II II IIIII IIIII III L9 IIIII II II IIIII II II L10 III IIIIV L11 IIIIV III III III III IIIIV L12 IIIII II III IIIII IIIII IIIII MB1 III III III IV IV MB2 IIIIV IV IV IV MB3 IIIIV III IIIIV IIIIV MB4 III IIIIV MB5 III III IIIII IIIIV III IIIII NP1 III III IIIII III III IIIII NP2 II III I III III III

Table 24: Classification of PO 4P contents recorded upstream and downstream of the WWTPs in the single sampling months according to a) LAWA (1998) and b) RAKON (LAWAAO, 2007)

a) upstream downstream b) upstream downstream Dec Jan Feb Dec Jan Feb Dec Jan Feb Dec Jan Feb 2009 2010 2010 2009 2010 2010 2009 2010 2010 2009 2010 2010 L1 II III I IV IV IV L1 BM BM BG L2 III III I II IIIII III L2 BM BM BG BM L3 III IIIII L3 L4 I III L4 BG L6 III III I II III IIIII L6 BM BM BG L7 III III III IIIIV IIIIV IIIIV L7 BM BM L8 II IIIII II III III IIIIV L8 BM L9 I III I III III II L9 BG BM BG BM BM L10 IIIII IV L10 L11 IIIII II II IIIII IIIII III L11 L12 II III III IIIIV IIIIV III L12 BM BM BM MB1 IIIII III IIIII IV IV IV MB1 MB2 II IV IV IV MB2 MB3 III III IV IV MB3 MB4 II III MB4 BM MB5 IIIII III IIIII III III IIIIV MB5 NP1 II III III II II III NP1 BM BM BM BM BM BM NP2 I I I III III I NP2 BG BG BG BM BM BG

Masterarbeit Maria Redeker Annex XXXV

Table 25: Classification of P tot contents recorded upstream and downstream of the WWTPs in the single sampling months according to a) LAWA (1998) and b) RAKON (LAWAAO, 2007)

a) upstream downstream b) upstream downstream Dec Jan Feb Dec Jan Feb Dec Jan Feb Dec Jan Feb 2009 2010 2010 2009 2010 2010 2009 2010 2010 2009 2010 2010 L1 III III IIIIV IV IV IV L1 L2 II II III IIIII IIIII IIIII L2 BM BM BM L3 III IIIII L3 L4 I III L4 BG L6 III II I IIIII III IIIII L6 BM BM BG L7 III II III IIIIV IIIIV IIIIV L7 BM BM L8 III III III III IIIIV IIIIV L8 L9 II II II II II IIIII L9 BM L10 IIIII IV L10 L11 II IIIII II IIIII IIIII IIIII L11 BM L12 II IIIII II IIIIV IIIIV III L12 BM BM MB1 III IIIIV III IV IV MB1 MB2 II IV IV IV MB2 MB3 IIIII III IV IV MB3 MB4 II III MB4 BM MB5 IIIII III IIIII III III IIIIV MB5 NP1 IIIII IIIII II IIIII IIIII IIIII NP1 NP2 III III III II II II NP2 BM BM BM BM BM

Table 26: Classification of Cl contents recorded upstream and downstream of the WWTPs in the single sampling months according to a) LAWA (1998) and b) RAKON (LAWAAO, 2007)

a) upstream downstream b) upstream downstream Dec Jan Feb Dec Jan Feb Dec Jan Feb Dec Jan Feb 2009 2010 2010 2009 2010 2010 2009 2010 2010 2009 2010 2010 L1 III III III III II II L1 BG BG BG BG BM BM L2 III III III III III III L2 BG BG BG BG BG BG L3 III III L3 BG BG L4 III III L4 BG BG L6 III III III III III III L6 BG BG BG BG BG BG L7 III III III III II III L7 BG BG BG BG BM BG L8 III III III III III III L8 BG BG BG BG BG BG L9 III III III III III III L9 BG BG BG BG BG BG L10 III II L10 BG BM L11 III III III III I III L11 BG BG BG BG BG BG L12 III III III III III III L12 BG BG BG BG BG BG MB1 IIIII IIIII IIIII II IIIII IIIII MB1 BM BM BM BM BM BM MB2 III II IIIII IIIII MB2 BG BM BM BM MB3 III III III II MB3 BG BG BG BM MB4 III III MB4 BG BG MB5 II III III III III II MB5 BM BG BG BG BG BM NP1 III III III III III III NP1 BG BG BG BG BG BG NP2 III II II IIIII IIIII IIIII NP2 BG BM BM BM BM BM

Masterarbeit Maria Redeker Annex XXXVI

2 Table 27: Classification of SO 4 contents recorded upstream and downstream of the WWTPs in the single sampling months according to LAWA (1998)

upstream downstream Dec Jan Feb Dec Jan Feb 2009 2010 2010 2009 2010 2010 L1 II II II I I I L2 III III III III III III L3 I III L4 III III L6 III III III III III III L7 III III III III II III L8 II II II II II II L9 II II II II II II L10 II III L11 II II II II II II L12 II II II II II II MB1 III III III III II III MB2 II II II IIIII MB3 III III II II MB4 II III MB5 II III III II III III NP1 II II III III II II NP2 II II II II II II

Masterarbeit Maria Redeker Erklärung

Ich versichere, dass ich die vorliegende Arbeit “Impacts of wastewater treatment plants on the stream water quality in the upper Stör catchmnent” selbständig verfasst und keine anderen als die angegebenen Quellen und Hilfsmittel verwendet habe.