Norwegian Institute for Water Research REPORT Main Office Regional Office, Sørlandet Regional Office, Østlandet Regional Office, Vestlandet Akvaplan-NIVA A/S P.O. Box 173, Kjelsås Televeien 3 Sandvikaveien 41 Nordnesboder 5 N-0411 Oslo N-4879 Grimstad N-2312 Ottestad N-5008 Bergen N-9005 Tromsø Norway Norway Norway Norway Norway Phone (47) 22 18 51 00 Phone (47) 37 29 50 55 Phone (47) 62 57 64 00 Phone (47) 55 30 22 50 Phone (47) 77 68 52 80 Telefax (47) 22 18 52 00 Telefax (47) 37 04 45 13 Telefax (47) 62 57 66 53 Telefax (47) 55 30 22 51 Telefax (47) 77 68 05 09 Internet: www.niva.no Title Serial No. Date Implementation of the Urban Waste Water Treatment Directive in 4466-2001 10.05.2002 Norway- An Evaluation of the Norwegian Approach regarding Wastewater Report No. Sub-No. Pages Price Treatment 21195 70 Author(s) Topic group Distribution Torsten Källqvist Wastewater Technology Jarle Molvær Eivind Oug Geographical area Printed Dag Berge Norway NIVA Torulv Tjomsland Svein Stene Johansen Client(s) Client ref. Norwegian Pollution Control Authority 3001181 Abstract This report discusses the effects and benefits of full implementation of the Urban Waste Water Treatment Directive in Norway. The Norwegian policy for wastewater treatment has targeted phosphorus removal as the primary measure to reduce adverse ef- fects of discharge of wastewater to freshwater and marine recipients. Chemical precipitation is therefore used at more than 70% of the wastewater treatment plants. This technique is very efficient in reducing the phosphorus concentration and in addition gives a high reduction of suspended solids, micropollutants and bacteria. The removal of organic matter is, however, not always sufficient to fulfil the requirements in the Directive. The high amount of available fresh water, and the high sensitivity of fresh water systems to incresed phosphorus loading implies that the primary load of organic matter from wastewater is less important than the organic matter produced in the surface waters on the basis of nutrients from the wastewater (secondary organic load). For wastewater dicharged to marine waters the situation is more diverse due to the large variation in receiving water conditions. The most sensitive marine recipients are the fjords with restricted exchange of deep water. Like in lakes, the secondary organic load caused by primary production may contribute far more than the primary load to the oxygen depletion of the deep water. Therefore nutrient removal is required as the primary measure also for wastewater discharged to marine waters. 4 keywords, Norwegian 4 keywords, English 1. Kommunalt avløpsvann 1. Urban Wastewater 2. Renseanlegg 2. Treatment plants 3. Organisk stoff 3. Organic matter 4. Næringssalter 4. Nutrients Torsten Källqvist Torsten Källqvist Kari Nygaard Project manager Research manager Head of research department ISBN 82-577-4113-2 Versjon: 08.07.02 11:45 Implementation of the Urban Waste Water Treatment Directive in Norway An Evaluation of the Norwegian Approach regarding Wastewater Treatment. Versjon: 08.07.02 11:45 NIVA 4466-2001 Preface In 2001, the Norwegian Pollution Authority commissioned the Norwe- gian Institute for Water Research (NIVA) to perform an evaluation of the environmental benefits of implementation of the Urban Waste Water Treatment Directive in Norway. The section in this report on the history of wastewater treatment in Norway has been compiled by Svein Stene Johansen, The sections on the evaluation of effects of wastewater on freshwater recipients and the description of water quality status in lakes and rivers have been made by Dag Berge, Torulv Tjomsland and Torsten Källqvist. A similar analysis of the marine environment has been made by Jarle Molvær and Eivind Oug. Oslo, 10.5.2002 Torsten Källqvist Project leader NIVA 4466-2001 Contents Summary 6 1. Background 8 2. Population density and distribution 8 3. Environment and water resources 10 3.1 Geology, climate and hydrology 10 3.2 Coastal zone 11 4. Eutrophication status 14 4.1 Fresh water 14 4.2 Marine waters 17 5. Wastewater management in Norway - Historical account 21 6. Development of wastewater facilities 22 7. Treatment efficiency related to wastewater treatment methods 27 8. Effects of urban wastewater in rivers, lakes and marine waters 28 8.1 Method 28 8.2 Rivers and running waters 28 8.3 Lakes 29 8.4 Coastal waters and fjords 34 9. Examples on effects on water quality of implementation of the Norwegian policy for wastewater management 38 9.1 Rivers and lakes 38 9.1.1 Glomma River. 38 9.1.2 Lake Gjersjøen 40 9.1.3 Lake Mjøsa 42 9.1.4 Lake Tyrifjord and Lake Øyeren 43 9.1.5 Discussion 44 9.2 Fjords and coastal waters 46 9.2.1 Outfalls to coastal waters 46 9.2.2 Outfalls to open fjords 50 9.2.3 Fjords with shallow sills and restricted water exchange 52 9.2.4 Discussion and recommendation 61 NIVA 4466-2001 10. References 63 Appendix A. 67 Appendix B. Overview for marine outfalls 68 NIVA 4466-2001 Summary The wastewater treatment policy in Norway has been tailored to meet local and regional environ- mental quality objectives. Due to the large quantity of runoff and scattered population, only 0.7 % of the available freshwater resources are utilised as municipal or industrial water supply, and the load of wastewater into receiving waters is generally very low. This means that the oxygen demand resulting from degradation of the organic matter from urban wastewater is low, compared with the oxygen pool in the receiving waters. Consequently, oxygen depletion in rivers due to discharges of urban wastewa- ter has not been a problem in Norwegian freshwaters to date. Eutrophication, on the other hand, repre- sents a significant problem in many watercourses, and particularly in lakes. In these systems, phospho- rus is the primary limiting element for production of algae. The organic biomass that can be produced from the content of phosphorus in wastewater may be fifteen times higher than the amount of organic matter in the wastewater. The oxygen demand caused by this secondary organic load is mainly ex- pressed in the deep layers of lakes, which are the most vulnerable environments in terms of oxygen depletion. Since eutrophication and the secondary organic load arising from this process, have been identified as more crucial for the water quality than the organic load from urban wastewater, the treatment technol- ogy in Norway has mainly been focused on phosphorus removal. The phosphorus removal is per- formed by installation of chemical precipitation at treatment plants serving about 60 % of the popula- tion. In the most nutrient sensitive areas, where additional nitrogen removal is required, the chemical treatment is combined with biological treatment. A recent survey of plants with mechanical/chemical treatment showed average removals of approximately 60% for BOD5 and COD. The average effluent concentration of organic matter, measured as BOD5, was 38 mg/l. There were, however, large varia- tions between the plants and it was estimated that about 38% of the plants fulfil the requirement for BOD removal in the Directive. On the other hand, the P-removal at chemical treatment plants nor- mally exceeds 90%, which is well above the Directive's requirement for effluents to sensitive areas (>80 % removal). During the last twenty years, environmental monitoring has demonstrated that the policy to focus on P-removal has been successful in rivers and lakes severely affected by pollution from urban wastewa- ter before the implementation of modern treatment. A reduction in the density of plankton algae and increased transparency of the surface waters have been observed in lakes where urban wastewater rep- resents a significant part of the P-load. The removal of organic matter that is achieved by the chemical treatment is sufficient to avoid significant heterotrophic growth in the rivers and streams where urban wastewater is discharged. The treatment of wastewater discharged into coastal waters is adapted to the local recipient conditions, as well as to the need for regional reductions of pollutant loading. In some fjords where the bottom topography prevents continuous exchange of the deep water, periodic oxygen depletion may occur even without any anthropogenic input of pollutants. Organic matter from wastewater or from stimu- lated algal production has the effect of increasing the extension in time and space of anoxic water masses under the said conditions. Like in lakes, the secondary organic load arising from production of algae greatly exceeds the primary load from urban wastewater. Therefore, removal of nutrients has been the primary measure to reduce algal growth in the surface layers of marine recipients and to re- duce oxygen problems in deeper layers of these recipients. The role of phosphorus and nitrogen as limiting factors for primary production in marine waters may vary in time and space, but P-removal is considered as an effective measure to reduce local eutrophication. 6 NIVA 4466-2001 Based on a scientific evaluation, we see no need for a change in the Norwegian recipient-orientated strategy for the purpose of complying with the Urban Waste Water Treatment Directive. A number of recipient studies are in the final phase (such as those dealing with the main outfalls of wastewater to nutrient sensitive area in the outer Oslofjord - and the Trondheimsfjord) or are being planned (such as the new Arendal outfall to coastal waters and the four outfalls to the fjord area around Bergen). The Mandal outfall of wastewater (mechanical treatment) to the sensitive area is being considered for up- grading to chemical precipitation. The outfalls with no treatment or fairly coarse mechanical treat- ment in northern Norway are also under consideration for upgrading. A further evaluation of the need for upgrading the treatment of these and other wastewater outfalls should be performed whenever deemed appropriate.