Osberstown WWTP Preliminary Report Vol 1 Rev F

Kildare County Council

Comhairle Chondae Chill Dara

UPPER LIFFEY VALLEY REGIONAL SEWERAGE SCHEME

EXTENSION TO OSBERSTOWN WASTEWATER TREATMENT PLANT - STAGE 3

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PRELIMINARY REPORT VOLUME 1

WASTEWATER TREATMENT PLANT

March 2002

James J. Lynch B.E., C.Eng. County Engineer

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DOCUMENT CONTROL SHEET

Client Kildare County Council

Project Title Upper Liffey Valley Regional Sewerage Scheme

Extension to Osberstown Waste/Water Treatment Plant - Stage 3 Document Title Preliminary Report - Volume 1 – Wastewater Treatment Plant

Document No. MCOS/207-501-001/Rp0010

DCS TOC Text List of Tables List of Figures No. of Appendices

This Document Comprises 1 i-ii 123 - - A, B, C

pgs App.1 – App. 22

For inspection purposes only. Revision Status Author(s)Consent of copyright owner Reviewed required for anyBy other use. Approved By Issue Date

F Final John Bennett Ciaran O’Keeffe 5th March 2002 Ciaran Hughes Jerry Grant Ole Dalgaard Ciaran O’Keeffe Jerry Grant

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TABLE OF CONTENTS

1. EXECUTIVE SUMMARY...... 1

1.1. Introduction and Project Brief 1 1.2. Receiving water study 1 1.3. Load assessment and categorisation 2 1.4. Wastewater Treatment Plant Assessment 2 1.5. Polluter Pays 3 1.6. Planning, construction, and procurement 4 1.7. Summary Recommendations 4

2. INTRODUCTION AND PROJECT BRIEF ...... 5

2.1. Scope and brief of the project 7 2.2. Current WWTP 8 2.3. Environmental Impact Statement 8 2.4. Sewage treatment options 8

3. RECEIVING WATER STUDY ...... 10

3.1. General Description of Liffey Catchment 10 3.2. Terms of Brief 14 3.3. Water quality standards 15 3.4. Existing water quality and effluent discharge at Osberstown 20 3.5. River Liffey flows at Osberstown 28 3.6. Assimilative capacity 30 For inspection purposes only. 4. LOAD ASSESSMENT AND CATEGORISATIONConsent of copyright owner required ...... for any other use. 35

4.1. Sources of data 35 4.2. Current connection to Osberstown and sectoral loads 36 4.3. Future load projections 41 4.4. Summary 47

5. ASSESSMENT OF WASTEWATER TREATMENT PLANT ...... 48

5.1. Evaluation of loads 49 5.2. Evaluation of Present WWTP 52 5.3. Evaluation of WWTP unit operation and need for extension 59 5.4. Sludge treatment 64 5.5. Area available for future extension 68 5.6. Extension options and descriptions 69 5.7. Plant configuration options 80 5.8. Option 1 - New SBR process line and mesophilic digester 81 5.9. Option 2 - Conventional Activated sludge process and mesophilic digester 89

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5.10. Option 3 - New Biofilter system and mesophilic digester 95 5.11. Option 4 - New SBR process line and thermophilic digester 101 5.12. Summary and recommendation 107

6. POLLUTER PAYS ...... 108

6.1. Introduction 108 6.2. loads 108 6.3. Marginal Costs 109 6.4. Operation and maintenance costs 111 6.5. Implementing the Polluter Pays principle 112 6.6. Summary Conclusions and recommendations 114

7. PLANNING, CONSTRUCTION, AND PROCUREMENT...... 115

7.1. Planning and construction 115 7.2. Procurement 117 7.3. Conclusion 119

8. CONCLUSIONS AND RECOMMENDATIONS ...... 120

8.1. Summary Conclusions 120 8.2. Summary Recommendations 123

Appendices

Appendix A Water quality standards Appendix B Detailed report on large industrial/commercial monitoring in the Osberstown catchment For inspection purposes only. Appendix C Polluter pays calculationsConsent of copyright owner required for any other use.

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1. EXECUTIVE SUMMARY

1.1. INTRODUCTION AND PROJECT BRIEF Osberstown Wastewater Treatment Plant (WWTP) serves the towns and villages of Naas, Newbridge, Kilcullen, Clane, Sallins, Prosperous, Kill, Johnstown, Walshestown, and parts of Athgarvan and Caragh, in County Kildare. Sewage is transferred to the plant via a network of gravity sewers, pumping stations and rising mains. The plant is located approximately 1 km north-west of Naas adjoining the M7, with the River Liffey a short distance to the west of the site.

M.C. O’Sullivan & Co. Ltd in association with COWI of Denmark were appointed to prepare, on behalf of Kildare County Council, a feasibility study and justification for an extension of Osberstown Wastewater Treatment Works, Co. Kildare.

The objective of the study is to establish the drainage network and treatment requirements to provide for continued sustainable development of the Mid-Kildare area while at the same time satisfying the water quality objectives for the River Liffey arising from national and EU Regulations and Policy. The study addresses three main areas:

• Receiving Waters Study; an assessment of the baseline water quality status of the river Liffey with a view to establishing the assimilative capacity of the river to accept treated wastewater to a BATNEEC standard from an extended plant at Osberstown

• Drainage Catchment Study; involving detailed surveys to establish an understanding of current loads (residential/industrial) to the treatment plant; an assessment of development pressures within the catchment in order to predict future loads to the treatment plant; detailed contract surveys, modelling and analysis of the current drainage network and recommendations on required upgrading of the network to deal with existing hydraulic/structural shortcomings and with increased loadings from future development.

• Wastewater Treatment Works Study; an assessment of the available capacity in the newly expanded works at Osberstown, andFor inspection it's flexibility purposes only. for process upgrading and extension. Consent of copyright owner required for any other use. The boom in the Irish economy and the continuing expansion of the Dublin area is resulting in major development pressure in surrounding counties, most particularly in County Kildare.

The option of extending the current treatment plant at Osberstown is considered to be the most practical and cost effective solution to the sewage treatment needs of The Upper Liffey Valley to the year 2021, due mainly to the configuration of the catchment sewerage system and the remaining available area on the site.

1.2. RECEIVING WATER STUDY A receiving water study was carried out for the River Liffey with a view towards establishing the required effluent standards necessary to meet the water quality objectives for the river. Cognesence was taken of all relevant water quality standards and objectives, including the Framework Directive, the Phosphorus Regulations, the Salmonid Regulations, the Urban Wastewater Treatment Directive, and the Liffey Water Quality Management Plan.

It was found that the river upstream of Osberstown is unpolluted, with both physico-chemical and biological characteristics supportive of this status. With regard to achieving the objectives of the Phosphorus Regulations downstream of the effluent discharge, the target quality index for 2007 at Castlekeely Ford is Q4 – unpolluted status. The current water quality in the Liffey downstream of the plant shows nutrient levels that are either within set standard limits or consistent with the values in the

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Liffey upstream of the plant, except for MRP and ammonia values. The main assimilative capacity restriction of the Liffey at Osberstown is thus in terms of phosphorus capacity.

The current (Stage 2) WWTP is unlikely to meet the phosphorus targets for the Liffey at current phosphorus treatment levels and effluent standards. This plant was designed before the advent of stricter water quality standards - principally the Framework Directive and Phosphorus Regulations – and cannot therefore be expected to be consistent with target effluent treatment requirements for 2007.

The assimilative capacity of the Liffey at Osberstown would safely allow an upgraded WWTP plant with a maximum capacity of 130,000 population equivalent (PE), under the two main conditions that stormwater misconnection is minimised, and that a median concentration effluent standard for TP of 0.35 mg/l is adopted. The upgraded plant requires state of the art treatment based on “P” removal assisted by chemical treatment to meet the best practicable standard. Reference plants for this standard have been identified in Denmark, characterised by expert process monitoring and management.

1.3. LOAD ASSESSMENT AND CATEGORISATION The current loads and estimates of future loads to the Osberstown Wastewater Treatment Plant were analysed. and categorised into domestic, commercial, and industrial contributions. The analysis of sectoral loads concludes that there is current connection of 45,500 residential population, 15,000 PE large industrial-commercial, and 7,500 PE commercial connection. The total load to the plant for the mid-2000 to mid-2001 period was 60,500 PE. The capacity of the current plant is 80,000 PE.

There are significant extraneous inputs to the sewer system, most likely from storm misconnection and groundwater infiltration. A programme of extraneous flow reduction in the sewer system is essential and fundamental to ensuring that the full capacity of both the current and an upgraded plant can be realised. Failure to achieve this element will compromise the capacity of the current plant to below the 80,000 PE design figure, and the proposed upgraded plant to well below the 130,000 PE target.

The current plant is projected to reach capacity between 2003 and 2005. The proposed flow reduction programme should be implemented to ensure that the full capacity of this Stage II plant can be achieved, otherwise the timescale to reach capacity will certainly be closer to 2003. The proposed upgraded plant (Stage III) is projected to reach capacity in 2018 at the earliest. Again, this is provisional on the proposed flow reduction programme. For inspection purposes only. Consent of copyright owner required for any other use. The timescales for development in the Upper Liffey Valley catchment presented in this text are based on both the “Strategic Planning Guidelines” and building capacity. The projected growth to 2021 is in the range 112,000 PE to 135,000 PE. The range presented represents a reasonable low and high envelope. It may be noted that the building capacity in the catchment is subject to a fair degree of uncertainty given the multitude of driving forces behind this aspect.

1.4. WASTEWATER TREATMENT PLANT ASSESSMENT The current plant was assessed in detail in regard to the treatment standards and capacity of existing units. It was concluded that the existing plant does not have any available capacity beyond the design 80,000 PE. It is recommended that the entire treatment plant should be extended to treat the increasing load to a future load of 130,000 PE. Assuming the present CASS biological treatment units fulfil the process guarantee, the extension of the biological treatment can be achieved by building a parallel line to the existing CASS tanks. The additional phosphorous removal should be performed in a subsequent polishing step.

Commonly used treatment technologies were described and assessed, and four realistic options for the extension of the plant were investigated from both technical and economical viewpoints. Four design options are presented as applicable to the extension under a probable ‘design-build’ or ‘design- build-operate’ procurement process:

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Option 1 - New SBR process line and mesophilic digester Option 2 - Conventional Activated sludge process and mesophilic digester Option 3 - New Biofilter system Option 4 - New SBR process line and thermophilic digester

The design options are based on the following extension of capacity and upgraded treatment:

Existing mechanical treatment Extension of primary clarifiers New biological treatment line New conventional sand filter system with contact filtration Extension of sludge digester capacity

A Public Private Procurement Process (PPP) is recommended. This format should optimise value for money through whole-life cost minimisation and best management of operational risk. The estimated capital costs (including sludge treatment extension) are in the range IR£12m to IR£16m (€15m to €20m). The estimated operation and maintenance cost (including sludge treatment extension) is IR£0.8m per year (€1m).

It is concluded that there are no limiting conditions for the extension of the plant to a capacity of 130,000 PE at the current site using BATNEEC technologies.

1.5. POLLUTER PAYS A ‘Polluter Pays’ assessment was prepared as a framework for Kildare County Council to recover costs of improving and expanding drainage and wastewater treatment facilities at Osberstown. It has been prepared in accordance with circulars L/16/00 and L/4/00 from the Department of the Environment & Local Government (DoELG). In accordance with this policy, an assessment has been made of the portion of capital costs that the commercial/industrial sector should pay towards the Extension to Osberstown WWTP – Stage 3, together with the sectoral split for the overall operation and maintenance costs of the extended plant.

Eighty-eight percent (88%) of the capital costs of the proposed extension are attributable to domestic sewage treatment – estimated at €11.28m (subject to the uncertainties of a probable design-build or design-build-operate contract process). Twelve percent (12%) of the capital costs of the proposed extension are attributable to industrial and commercial sewage treatment – estimated at €1.53m. The For inspection purposes only. sectoral split is set to change significantlyConsent of copyright from owner the required current for any other situation use. of 75%/25% domestic/non- domestic to 61%/39% for the extended plant. The capital costs and marginal costs should be reassessed on acceptance of a final design and tender.

Sixty-one percent (61%) of the operation and maintenance costs of the extended plant are attributable to domestic sewage treatment – estimated at €1.37m. Thirty-nine percent (39%) of the operation and maintenance costs of the extended plant are attributable to industrial and commercial sewage treatment – estimated at €0.87m.

The operation and maintenance costs for industrial and commercial sewage treatment should continue to be recovered by the council from this sector under the ‘polluter pays principle’. The current council programme of monitoring medium to large industry and commercial has significant advantages in both cost recovery and effluent minimisation at source. This should be continued and expanded as appropriate to cater for future development. Small industry and commercial is not practical to monitor individually, and should be charged for sewage treatment on a standard charge basis until such time as other methods are available (such as in relation to water usage).

The capital costs of the proposed extension attributable to the industrial and commercial sectors should be recovered from both new development and existing concerns over an appropriate period. This is justified on the basis that the extension of the works is needed not only for additional capacity, but for improved treatment under recent regulations and directives, and must also allow for future strategic provision for such development types.

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1.6. PLANNING, CONSTRUCTION, AND PROCUREMENT The various issues in regard to planning, construction, and procurement were assessed. Statutory process, the requirements of the Environmental Impact Assessment, technical investigations, construction impacts, and stakeholder issues were addressed.

In regard to procurement, a ‘Design-Build’ (DB) or ‘Design-Build-Operate’ (DBO) contract is possible. A DBO should have a long operating period (20 years), and is likely to provide optimum risk transfer. There are advantages and disadvantages of DB versus DBO. The advantage of a DBO contract normally lies in the transfer of risk from design through to operation, with a high degree of efficiency inherent in the competitive nature of the contract, together with the transfer of operational risk associated with process selection, design, and construction standards. Incorporation of capital replacement funding on a competitive basis is also a major benefit of DBO as practised in Ireland.

A design-build contract provides for a high level of innovation and cost competitiveness in design and construction, but can be a source of increased risk in operation. Against this, the particular circumstance in Kildare where the council has trained and experienced personnel capable of operating this type of plant provides an advantage in the DB contract. The council’s personnel costs are low, and DBO will inherently provide for some degree of the risk as an increased cost for operation.

The ultimate choice of procurement route would be based on the outcome of a PPP Assessment Report prepared in accordance with the DoELG Guidance Document “Public Private Partnerships in the Water Services Sector – Technical Note No. 2”. Key inputs to this report would be:

• Initial output specification based on this Preliminary Report and the project EIS • Preliminary risk assessment taking a systematic view of operational risk in particular • Value for money assessment based on market indicators and risk transfer benefits • Legal viability and stakeholder considerations, including other related contract arrangements.

1.7. SUMMARY RECOMMENDATIONS An extended and upgraded wastewater treatment plant should be developed at Osberstown to a total capacity of 130,000 PE, to cater for the sewage treatment needs of the Upper Liffey Valley area for the period to 2021. The extension should be procured under a ‘design-build’ or ‘design-build-operate’ contract, depending on the tender costs (whole life assessment). The extended plant should be in place no later than 2005. For inspection purposes only. Consent of copyright owner required for any other use. A programme of extraneous flow reduction in the sewer system is essential and fundamental to ensuring that the full capacity of both the current and an upgraded plant can be realised. Failure to achieve this element will compromise the capacity of the current plant to below the 80,000 PE design figure, and the proposed upgraded plant to well below the 130,000 PE target. Without this programme, the current plant is likely to reach capacity by 2003.

There are several viable options for extension and upgrading of the plant. A high degree of phosphorus removal is needed to ensure consistency with the 2007 Phosphorus Regulations water quality targets, and therefore the extended plant will require a filtration system for phosphorus removal together with chemical dosing.

Given the tight timescale, both the plant extension and flow reduction programme should be adopted urgently.

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2. INTRODUCTION AND PROJECT BRIEF

Osberstown Wastewater treatment Plant (WWTP) serves the towns and villages of Naas, Newbridge, Kilcullen, Clane, Sallins, Prosperous, Kill, Johnstown, Walshestown, and parts of Athgarvan and Caragh, in County Kildare. Sewage is transferred to the plant via a network of gravity sewers, pumping stations and rising mains. The plant is located approximately 1 km north-west of Naas adjoining the M7, with the River Liffey a short distance to the west of the site. A project area schematic and site location map are shown in Figures 2.1 and 2.2. The site is shown in the photo below, with the river Liffey visible at the top of the photo.

Figure 2.1 Osberstown Sewer System

River Liffey

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River Liffey

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Figure 2.2 Osberstown location map

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Current Osberstown plant (during construction), with river Liffey visible at the top of the photo

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The current plant incorporates modern treatment facilities, including primary treatment, secondary treatment utilising CASS process, and a high degree of nitrogen and phosphorus removal. The treatment process utilises activated sludge, and incorporates sludge digestion and dewatering. Further treatment, processing, and utilisation options for this final sludge are currently being prepared as a separate project. The current plant has a design capacity of 80,000 population equivalent (PE). A high quality effluent is discharged to the River Liffey via a diffuser system in the river bed.

2.1. SCOPE AND BRIEF OF THE PROJECT M.C. O’Sullivan & Co. Ltd in association with COWI of Denmark were appointed to prepare, on behalf of Kildare County Council, a feasibility study and justification for an extension of Osberstown Wastewater Treatment Works, Co. Kildare.

The objective of the study is to establish the drainage network and treatment requirements to provide for continued sustainable development of the Mid-Kildare area while at the same time satisfying the water quality objectives for the River Liffey arising from national and EU Regulations and Policy. The study is thus addressed in three stages:

Stage 1: Receiving Waters Study; an assessment of the baseline water quality status of the river Liffey, using existing available data, with a view to establishing the assimilative capacity of the river to accept treated wastewater to a BATNEEC standard from an extended plant at Osberstown

Stage 2: Drainage Catchment Study; involving detailed surveys to establish an understanding of current loads (residential/industrial) to the treatment plant; an assessment of development pressures within the catchment in order to predict future loads to the treatment plant; detailed contract surveys, modelling and analysis of the current drainage network and recommendations on required upgrading of the network to deal with existing hydraulic/structural shortcomings and with increased loadings from future development.

Stage 3: Wastewater Treatment Works Study; an assessment of the available capacity in the newly expanded works at Osberstown, having regard to the design parameters of the plant, it's flexibility for load variations in terms of organic loading, nutrients and hydraulics, and it's flexibility for process upgrading and extension.

The boom in the Irish economy and the continuing expansion of the Dublin area is resulting in major For inspection purposes only. development pressure in surroundingConsent counties, of copyright most owner requiredparticularly for any other in use.County Kildare. The development of the national road network, availability of high quality train services and zoning of land for industrial and commercial development to provide sustainable employment for new populations in the county, will give rise to a significantly increased demand for sewerage facilities over the coming 20 years. This development is consistent with the Strategic Planning Guidelines for the Greater Dublin region, which envisage significant growth in the towns of Naas and Newbridge.

The feasibility studies into the extension of the Osberstown Treatment Works includes the following:

• Studies of the River Liffey as a receiving water, focusing on its sensitivity and limited effluent capacity, particularly in the middle and lower reaches, and having regard to its hydrological resources and existing water quality conditions. These studies take account of the implications of the Phosphorus Regulations and future water quality objectives in the context of the European Water Framework Directive and the effects of improved management of diffuse pollution and the need to provide for other pressures apart from the Osberstown discharge.

• Consideration of the available capacity in the newly expanded works at Osberstown having regard to the design parameters of the plant, its flexibility for load variations in terms of organic loading, nutrients and hydraulics, flexibility for process upgrading and extension

• Determination of appropriate effluent standards for the Osberstown discharge to the River Liffey in terms of organic and nutrient levels for the likely design year load conditions

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having regard to an overall management framework for the river system and the achievable standards using proven technologies

• Consideration of the options to treat the increased loads to the future standards by extension of the Osberstown Wastewater Treatment Plant under appropriate contractual arrangements (e.g. DB). This will have to consider the interaction with the existing plant design criteria, performance and operational regime

• Stabilisation treatment and disposal of sludge consistent with the sludge management plan for County Kildare, currently under development

2.2. CURRENT WWTP The current plant was (substantially) completed mid-2000 although commissioning was not completed until late this year. The wastewater treatment stream consists of an inlet works, screens, de-gritting, primary clarifiers (sedimentation and sludge removal), CASS (cyclic activated sludge system) process secondary treatment incorporating nitrogen and phosphorus removal, chemical phosphorus removal using precipitation, and outlet works including a river-bed diffuser.

There are stormwater facilities at various stages of the woks including capacity overflows to twin stormtanks coming online for storm flows over 2.5 times dry weather flow (dwf). Storm flows exceeding the capacity of the stormtanks are discharged to the outlet works via screens. All other storm flows are recirculated to the inlet screens to begin treatment.

Primary sludge from the primary clarifiers, surplus activated sludge from the CASS tanks, and external sludge from other minor treatment facilities are mixed in homogenisation tanks and thickened in mechanical thickeners before it is pumped to digesters for anaerobic stabilisation. Gas from the digestion is collected and used for power and heat production. Digested sludge is dewatered in belt filter presses to approx. 20% dry solids and subsequently land-spread outside the county.

2.3. ENVIRONMENTAL IMPACT STATEMENT An EIS is to be submitted to An Bord Pleanala in early 2002. The EIS sets out the impacts and mitigation measures under the normal headings: water quality, socio-economics, landscape and visual impact, flora and fauna (land and aquatic), noise and vibration, air quality, archaeology, and interaction of impacts. The proposed extension For inspection of purposes the plantonly. would occur entirely within the existing Consent of copyright owner required for any other use. site, and discharge effluent to the river Liffey via the current diffuser system.

2.4. SEWAGE TREATMENT OPTIONS Several options for the location or transfer of sewage from the Upper Liffey Valley area were considered, including:

1. Upgrade/extension of the existing Osberstown plant

2. Siting a new plant in the Upper Liffey Valley area

3. Transfer of sewage to Leixlip and upgrade/extension of the plant

4. Transfer of sewage to the Ringsend system in Dublin

The first option was considered to be the most practical and cost effective solution at the outset because of the configuration of the catchment sewerage system and the remaining available area on the site, and so was examined in detail, beginning with a receiving water study. This examined the ability of the River Liffey to accept treated wastewater whilst ensuring that this was consistent with water quality objectives for the river. The results are detailed in the next section.

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It was not necessary to consider the remaining three options in detail. Either a new plant or an extension to Leixlip would require additional sewerage infrastructure, a new site would be more complicated and time-consuming to locate and approve than utilising an existing site, and the Leixlip plant site is small and difficult to develop further. The transfer of sewage to Ringsend is considered a difficult option due to the pressures on both the plant and sewerage system.

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3. RECEIVING WATER STUDY

The water quality information presented here is derived from the project report “Receiving Water Study” (December 2000). The only significant change from this report is the inclusion of the year 2000 biological water quality ratings that were not available at the time of writing of the original report.

3.1. GENERAL DESCRIPTION OF LIFFEY CATCHMENT The River Liffey rises near the Sally Gap in Co. Wicklow and the upper catchment drains a high mountainous area in west Wicklow. The catchment area extends as far as Islandbridge (freshwater limit) encompassing an area of approximately 1185 km2. The upper Liffey and Kings River catchments were impounded by a dam at Poulaphuca in the 1940’s to form the major reservoir (the Blessington Lakes/Poulaphuca reservoir) that now services hydroelectric generation by the E.S.B. and major water abstraction by Dublin Corporation for the Dublin region. Figure 3.1 shows the general land-use and river systems in the catchment.

The upper catchment has an area of approximately 314 km2, with an average rainfall of almost 1,400mm in an area of granite geology and relatively little development. Forestry and moderate intensity agriculture are the main catchment activities in the upland areas, with peat- covered uplands generally uncultivated. The main tributaries to the reservoir are the Kings and Brittas Rivers.

The dam at Poulaphuca is capable of passing up to 80 m3/s when generating at full capacity. The Golden Falls reservoir is a smaller balancing reservoir downstream, which limits the maximum discharge (apart For inspection purposes only. 3 Consent of copyright owner requiredfrom for any other overflow use. spills), to 30 m /s, with a continuous compensation flow release of 1.5 m3/s. No overflow spills have been recorded at the dam. The major town in the upper catchment is Blessington, the effluent from which is treated and discharged downstream of Poulaphuca to Golden Falls reservoir.

At present, Poulaphuca reservoir supports daily abstractions in the order of 240 million litres per day and Dublin Corporation has permission to abstract up to 320 million litres per day for the Dublin region. The reservoirs are managed by the E.S.B. who are responsible for balancing abstraction, power generation, fishery and other interests. The reservoir also supports significant boating and other amenity activities.

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Figure 3.1 Land-use and rivers in the Liffey Catchment

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Downstream of Golden Falls, the River Liffey flows in a westerly direction to Kilcullen and then northwesterly through the Curragh to Newbridge. After Newbridge it turns northeasterly past Naas to Celbridge and Leixlip and thereafter flows in a generally easterly direction to Islandbridge, from where it is tidal through Dublin, discharging to Dublin Bay.

The river is impounded again at Leixlip, where the storage volume is small the E.S.B. manage a hydropower station at this site also. Since the 1960s, Leixlip has been developed as a substantial source of water abstraction, notably for north Kildare, Fingal and the northern environs of Dublin City. At present, the abstraction rate at Leixlip is in the order of 140 million litres per day and a maximum figure of 175 million litres/day can be achieved. ESBI model studies demonstrate that these abstractions are sustainable from the Liffey provided managed releases in addition to compensation flow (1.5 m3/s) are provided for some 20% of the time (one day in five) from Pollaphuca storage. Power generation is limited water levels above a defined threshold level.

Between Golden Falls and Kilcullen, the natural channel flow is effectively regulated by the impoundment discharge, with base flows equivalent to the compensation release. In summertime, following fishery representations, the E.S.B. discharge freshets in order to improve water quality and fishery conditions. In future, as abstraction rates at Leixlip are increased, more sustained releases will be provided in the middle reach to satisfy abstraction and Leixlip compensation flows (2.5 m3/s). Notable tributaries in this section include the Lemonstown and Kilcullen streams that flow northward to join the main channel near Kilcullen. The Lemonstown and Kilcullen streams drain a predominately agricultural area composed mainly of pasture and silage land-uses. The middle Liffey catchment between Golden Falls and Leixlip comprises a flat, fertile plain with deep glacial deposits overlying limestone rock generally. The area has substantial groundwater storage (Curragh Aquifer) with significant exchange between groundwater and river flows. It has relatively low run-off response to rainfall due to the gravel aquifers in central Kildare.

For inspection purposes only. The towns of Newbridge and NaasConsent are fast of copyright growing owner centres required for of any population other use. and industry and are served by a modern municipal wastewater treatment plant at Osberstown. This plant is currently being upgraded, and has been largely operational since July this year, at a population equivalent (PE) of 60,000. The design capacity of the works will reach 80,000 PE upon full completion. Prior to the upgrade, overloading and large shock loads to the plant resulted in a frequently poor effluent, and consequently poor water quality in the Liffey downstream of the plant.

Two of the notable tributaries in this area are the Awillyinish and Naas streams. The Awillyinish Stream drains the area west of and including Caragh village, a mainly agricultural area, whilst the Naas Stream drains both agricultural land and parts of Naas town.

The Morrell/Painestown tributary system originates in the foothills of the Dublin and Wicklow Mountains and flows westward to join the main Liffey channel east of Naas. This system flows through moderately intensive agricultural areas with significant urban centres.

At Leixlip, the Liffey is joined by the Ryewater, a major tributary that drains the areas around Kilcock and Maynooth. The towns of Celbridge and Leixlip on the main Liffey River, together with Kilcock and Maynooth, are all major urban centres that have experienced major expansion in recent years and are strong growth centres. They are also significant centres of industry, with the large Intel and Hewlett Packard electronics industries located in the catchment. The M4 motorway runs generally parallel to the Ryewater and provides a high capacity transport link from these towns to Dublin City Centre.

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The regional sewerage scheme at Leixlip was recently upgraded to cater for the sewerage needs of the region, and the new plant was commissioned in 2000. The new plant incorporates Nitrogen and Phosphorus removal.

The Ryewater is characterised by significant pollution pressures exacerbated by a very low dry weather base flow and a high level of run-off response to rainfall. A river with these characteristics is also vulnerable to the impacts of catchment urbanisation on run-off and pollution load. The Ryewater has been regarded as an important fisheries nursery, for which it currently appears less than satisfactory.

Downstream of Leixlip, the significant tributaries are the Camac and Griffeen rivers in South Dublin. These are essentially urban streams, with environmental pressures due to pollution in surface run-off and loss of base flow due to urbanisation. Available monitoring data confirms them as moderately polluted and unsatisfactory for salmonids. These environmental pressures are being considered in the development of future drainage strategies in the Saggart/Newcastle, Clondalkin and Lucan catchments.

3.1.1. Review of Key Catchment Characteristics Available water quality data demonstrates the presence of elevated concentrations of phosphorus in the middle and lower Liffey river systems. This can render these rivers prone to eutrophication and poor water quality. There is a general correlation between ecological and fisheries conditions and the levels of phosphorus in Irish rivers, although this can be disputed as it does not always hold true for local conditions. The relationship correlates the levels of phosphorus in the river to the biological quality index, and if possible data on fish catches, fish counts and anecdotal evidence regarding fish numbers as well as visual indicators in the rivers. Available water quality data for the Liffey is summarised in the following sections.

3.1.2. Geological Context In general, the bedrock throughout Ireland is overlaid by a complex mixture of glacial deposits comprising clays, clay/sand/gravel mixtures, cleaner sand/gravels and including a covering of peat particularly in central areas of the country. These conditions give rise to highly variable and relatively unpredictable subsoil conditions, with varying groundwater flow characteristics.

The underlying bedrock is similarly complex For inspection and is purposes illustrated only. in geological mapping provided by the Geological Survey of Ireland. The Consenttypical of bedrockcopyright owner classification required for any otherin the use. catchment is as follows:

Three main geological units can be distinguished:

• The south-eastern part of the catchment, in the Wicklow Mountains, is underlain by Wicklow Granite • To the west of the granite lie Ordovician greywackes and slates • The lower part of the catchment is underlain by Lower Carboniferous limestones, mainly the shaly limestones of the Calp Formation

In the south and southwest of the catchment especially in the Curragh and in the Blessington area, extensive gravel deposits, often several tens of metres in thickness, overlay the bedrock.

These geological conditions impact on water characteristics to some extent. The upper Liffey waters are relatively soft and have low alkalinity consistent with granite bedrock, whereas in the lower Liffey at Leixlip, the water is characterised by high alkalinity and carbonate hardness due to the limestone bedrock.

3.1.3. Rainfall and Run-off Run-off characteristics of a catchment are influenced by rainfall intensity and volume, catchment slope and channel slope. In the case of the Liffey the upper catchment in the Wicklow Mountains has annual

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3.2. TERMS OF BRIEF Under the terms of the brief, an assessment of the baseline water quality status of the River Liffey is to be carried out. This assessment is based on existing available data with the objective of establishing the assimilative capacity of the river to accept treated wastewater to a BATNEEC standard from an expanded plant at Osberstown. The primary objective is good ecological quality in accordance with the EU framework directive. The assessment will also consider previous EU directives and National Regulations which take account of the primary beneficial use and associated water quality objectives and standards for the river, in particular the Phosphorus Regulations SI 258 (1998).

The assessment is considered on a catchment basis taking consideration of inputs to the river upstream of Osberstown, both point source inputs and diffuse inputs. The available data from the relevant local authorities (Kildare County Council, Fingal County Council, Dublin Corporation) is used in this report as well as findings from the Three Rivers Project, on which M.C. O’Sullivan & Co. Ltd are consultants. M.C. O’Sullivan & Co. Ltd wish to acknowledge the cooperation of Fingal Co. Co. and Dublin Corporation Central Laboratory in supplying water quality data for the Liffey in the vicinity of Osberstown.

For inspection purposes only. Consent of copyright owner required for any other use.

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3.3. WATER QUALITY STANDARDS Effluent standards are set by considering all relevant standards, regulations, and legislation, principally in regard to protection of water quality and beneficial uses of the receiving water. The main change since the current plant was designed in 1995 is the enactment of the 1998 Phosphorus Regulations, setting interim targets for water quality to be achieved by 2007, and the adoption of the Water Framework Directive, discussed below. Cognisance was also taken of the draft Liffey Water Quality Management Plan that was fundamental to the 1995 plant EIS.

3.3.1. Overview of Legislative Standards Table 3.1 is a schedule of European and National Legislation relevant to the control and monitoring of water quality in the Liffey catchment.

Table 3.1 Legislative Framework for Catchment Water Quality Ref. Title/Scope Status/Implications COM (97) 49 Final Amended proposal for a Council Directive Establishing a (Framework Directive) Framework for Community Action in the Field of Water Policy. Local Government (Water Pollution) Act, 1977, Primary Legislation Amendment Act, 1990 Various Local Government (Water Pollution) Regulations 1978 to Statutory 1996 S.I. 258, 1998 Local Government (Water Pollution) Act 1977 (Water 10 Year Interim Quality Standards for Phosphorus) Regulations Standards S.I. 257, 1998 Local Government (Water Pollution) Act 1977 (Nutrient Management Planning Consultation) Regulations S.I. 85, 1994 Environmental Protection Agency (Licensing) IPC Licensing Regulations, 1994 The Fisheries Act 1959-1997

75/440/EEC & S.I. Council Directive concerning the Quality Required of Surface Water 294, 1989 Surface Water Intended for the Abstraction of Drinking Standards (Surface Water in Member States Water Directive) 79/869/EEC & Council Directive For concerning inspection purposes the only. Methods of Monitoring Consent of copyright owner required for any other use. S.I. 294, 1989 Measurement and Frequency of Sampling and Analysis Requirements of Surface Water Intended for Abstraction of Drinking Water 78/659/EEC & Council Directive on the Quality of Freshwater Needing Salmonid Standards S.I. 293, 1988 Protection in Order to Support Fish Life and Associated (also cyprinid) (Fish Regulations Directive) 91/271/EEC & Council Directive on Urban Waste Water Treatment Specified Treatment S.I. 419, 1994 Directive and Environmental Protection Agency Act, Standards (UWWT 1992 (Urban Waste Water Treatment) Regulations Directive) 91/676/EEC Council Directive on Protection of Water Against Nitrates Directive Pollution Caused by Nitrates from Agricultural Sources 76/160/EEC & Council Directive concerning the Quality of Bathing Bathing Waters S.I. 84, 1988 Waters and Associated Regulations Directive S.I. 99, 1989 S.I. 155, 1992 S.I. 230, 1996 76/464/EEC Council Directive on Pollution Caused by Certain Dangerous Dangerous Substances Discharged into the Aquatic Substances Directive Environment of the Community 91/271/EEC & S.I. EU Directive on the use of sewage sludge in agriculture 419, 1994

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3.3.2. The Framework Directive The Council Directive “Establishing a Framework for Community Action in the Field of Water Policy” contains a general outline and technical specification for definition, classification and monitoring of ecological and chemical status of surface waters, and quantitative and chemical status of groundwater.

The classification of ecological status of surface waters would be based on indicators chosen from the main biological groupings within an eco-system; aquatic flora, macro-invertebrate, fauna and fish fauna. Taken together with hydromorphological and physico-chemical parameters, the ecological status of the river, lake, estuary or coastal water would be defined. Water quality impacts, therefore, could be assessed based on the concept of departure from the conditions for an identical water body that is relatively unimpaired (i.e. against reference conditions).

This approach differs from the previous Directives relating to water quality that focused on the protection of beneficial uses with reliance on corresponding physical and chemical standards. The aim of the framework directive is to establish ecological quality as the basic measure of water quality status.

The Directive envisages the following normative definitions of ecological surface water status: -

• High Status; where hydromorphological characteristics are subject to minimal anthropogenic alterations and chemical conditions are close to background concentrations for naturally occurring substances, so that the biology present will conform to the conditions set in the Directive for biological parameters; a species composition and abundance corresponding totally, or almost totally, to the type specific conditions,

• Good Status; the key to the definition of good status is the identification of the point of sustainability; while the water body may be subject to anthropogenic input, only slight changes in species composition and abundance compared to type specific conditions should result, indicating that the modifications are sustainable. For hydromorphological parameters (physical changes to the channel etc), the issue is whether the biological community that exists is very close to the type-specific community, in other words the biology is relatively undisturbed. Physico-chemical parameters are set to provide an independent basis for establishing compliance with the “no-effect” concentration values,

• Moderate status; for biological parameters, this involves the concept of a moderate deviation For inspection purposes only. from the type-specific characteristics.Consent of copyright Definitions owner required forof any hydromorphology other use. and physico-chemical parameters are phrased in terms of their support of the biological community.

The essence of the Framework Directive is of an approach to water quality that focuses on good ecological conditions consistent with a healthy eco-system. The Directive is now in force, and has been used as a guiding instrument for the approach to the Three Rivers Catchment Management & Monitoring Systems and thus is incorporated into the Receiving Water Study for the Liffey at Osberstown.

3.3.3. Water Pollution Control The Local Government (Water Pollution) Acts, 1977 and 1990, are the primary legislation which empower Local Authorities to control pollution by means of a system of licensing of effluents, monitoring and the serving of Statutory Notice on persons suspected of causing pollution. Under this legislation, trade effluents are controlled by means of:

Section 4 Licences, where effluents are discharged to surface waters, set down the maximum loads and concentrations, monitoring requirements and other parameters for the discharge

Section 16 Notices provide similar criteria for discharges to municipal sewers

The Environmental Protection Agency (Licensing) Regulations 1994, provided for the issue of integrated pollution control (IPC) licences by EPA in respect of certain scheduled industries. This

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The fisheries Acts 1959 to 1997 and byelaws, made there-under together with the Local Government (Water Pollution) Acts 1977 and 1990, are the legislation which empower Fisheries Board to control Water Pollution.

3.3.4. Phosphorus Regulations The Local Government (Water Pollution) Act, 1977 (Water Quality Standards for Phosphorus) Regulations, 1998, has set new standards for rivers having regard to:

• Biological Quality Rating; a rating of water quality for any part of a river based principally on the composition of macro-invertebrate communities/faunal groups present and their general sensitivity to organic pollution, as used by the Environmental Protection Agency and described in the First Schedule of the Regulations (consistent with the Framework Directive ecological indicators)

• Median Concentration for Molybdate–Reactive Phosphate (MRP); sets limiting median concentrations applicable to the corresponding target biological water quality rating as determined by the Environmental Protection Agency

The Regulations have set out interim statutory standards for rivers and lakes to be complied with by end of 2007, as set out in Third Schedule of Regulations (Table 3.2 of this report). Target quality ratings and tropic status are based on monitoring carried out by the EPA during the period 1995-1997, or subsequent monitoring if no monitoring was carried out during those years.

Where water quality is satisfactory at present (Q rating of 5, 4-5 and 4), the objective is conservation and maintenance of that rating. Where the waters are slightly, moderately or seriously polluted, the objective is an improvement in the Q rating as shown in Table 3.2 of this report. Corresponding with the target Q rating, annual median levels of MRP expressed as µg P/l are defined. The maximum allowable median MRP value corresponding with a minimum Q rating of 3 (moderately polluted) is 70µg P/l, with 50µg P/l corresponding with Q3-4, and 30µg P/l corresponding with Q4.

For inspection purposes only. Table 3.2 - Interim Statutory QualityConsent of Standardscopyright owner required For Phosphorusfor any other use. in Rivers. Based on Local Government (Water Pollution) Act, 1977 (Water Quality Standards for Phosphorus) Regulations, 1998; after the EPA (Lucey et al, 1999).

Current Status Target Status Either/or Existing Q-value Category Median orthophosphate Minimum Q-value 1 concentration 2 (ugP/l) 5 Unpolluted 15 5 4-5 Unpolluted 20 4-5 4 Unpolluted 30 4

3-4 Slightly polluted 30 4

3 moderately polluted 50 3-4 2-3 moderately polluted 70 3

2 seriously polluted 70 3

1 Biological Quality Ratings (Q-value) as assessed by EPA staff during National River Monitoring Programmes

2 Molybdate-Reactive Phosphate (MRP). Median concentration to be determined from a minimum of ten samples taken at intervals of four weeks or longer in any twelve consecutive month period. Where the requisite number of

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For lakes, standards are based on existing and target trophic status and corresponding annual average concentrations of Total P expressed in µg P/l. As for rivers, the objective is for improvement in water quality of eutrophic and hypertrophic waters by reduction in nutrient load.

3.3.5. Water Quality Standards relating to Specific Uses Standards corresponding with water uses are those relating to: -

• Surface waters used for abstraction for drinking water,

• Fisheries Directive – standards for salmonid waters, whether designated or defined as a quality objective,

• Bathing water standards for designated bathing areas.

While standards have been set in order to implement directives established in the late 1970s, these standards, in general, would not necessary be suitable for maintaining "good ecological status" in surface waters but only to protect waters for that use covered by the Directive. However, prior to the advent of the Phosphorus Regulations (1998), these were the only water quality standards available for protecting surface waters.

Raw water for abstraction Appendix A (Table A1) provides a summary of quality standards required for 3 categories of raw water intended for abstraction for drinking water. For example, where normal coagulation/sedimentation and filtration treatment is provided, river waters are required to comply with Category A2 standards. For Category A2 waters, the standards show limit values for a wide range of parameters including physico-chemical, microbiological, metals and organic contaminants.

Of particular interest in relation to ecological quality of surface waters are the standards set for nitrates, BOD, ammonium, suspended solids and standards for pesticides.

Fisheries directive The Fisheries Directive "On the quality of For freshwaters inspection purposes needing only. protection or improvement in order to Consent of copyright owner required for any other use. support fish life" sets out mandatory and guideline values for 14 different parameters that are of particular significance to fish life. The implementation of this Directive should, therefore, protect a major biological element of riverine ecology. The standards set out in the directive, however, relate only to waters, which has been designated under this directive by National Government. In Ireland, only a limited number of freshwaters have been designated as salmonid waters and none have been designated as cyprinid waters. Designated areas in the three rivers include the main channel of the River Boyne and the Aherlow River in the Suir catchment. However, in the water quality management plans previously developed for the three river catchments, the objective of compliance with salmonid water quality conditions is affirmed. Moreover, this is consistent with the biological quality rating objectives in the Phosphorus Regulations in that waters sustaining a Q4 rating are considered to be suitable for sustaining a salmonid population.

The standard set for salmonid waters (National Regulations implementing the Directive) are summarised in Appendix A (Table A2) and include guideline limits in the Directive. Key standards in relation to water quality for salmonids are those for pH, temperature, dissolved oxygen, BOD, nitrites, non-ionised and total ammonia.

3.3.6. Urban Wastewater Treatment Regulations The Urban Wastewater Treatment Regulations, 2001 (S.I. 254 of 2001) specifies effluent requirements relating to size of the plant for discharges to specified sensitive areas, with further requirements in regard to compliance date. In this case, the proposed and existing plant capacity of 130,000 PE,

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3.3.7. Liffey Water Quality Management Plan and other standards The Liffey WQMP sets down recommended standards to achieve protection of two main uses; water abstraction and salmonid fisheries. The objectives of the plan are thus considered in the standards considered in the above sections.

There are no designated bathing waters in the Liffey Catchment. However, sections of the Liffey main channel are used for bathing and water contact recreation. In these areas, it would be desirable that these waters comply with the microbiological standards stated in the Bathing Waters Regulations.

3.3.8. Summary of water quality standards The objective of good ecological quality in the Framework Directive is assumed to be catered for by compliance with the standards in the Phosphorus Regulations (Q-index and MRP). The EPA has defined a set of physico-chemical threshold values that are also useful guideline values for assessing the level of impairment of water quality (Table A3, Appendix A). At the same time, the standards in the various beneficial use Regulations encompassed in the Liffey WQMP must be satisfied. In general, the standard of Q4 or better would ensure that the waters would be suitable for most beneficial uses.

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3.4. EXISTING WATER QUALITY AND EFFLUENT DISCHARGE AT OSBERSTOWN This section presents the biological and physico-chemical water quality characteristics of the Liffey in the area upstream and downstream of the Osberstown discharge, in relation to the effluent characteristics from the wastewater treatment plant (WWTP).

The EPA has carried out biological monitoring of the River Liffey in 1995/6 and 1998. In 1999 and 2000 biological monitoring was carried out on behalf of the Three Rivers Project by Conservation Services Ltd. at selected sites throughout the catchment. Physico-chemical water quality data has been analysed for the years 1998-2000 for a number of monitoring stations upstream and downstream of the outfall at Osberstown. The water quality data used was provided by Dublin Corporation Central Laboratory on behalf of Fingal County Council, and also by the Three Rivers Project.

The monitoring stations in the vicinity of the outfall are shown in Figure 3.2. The stations considered are (upstream and downstream of the effluent discharge);

• Upstream sites: Victoria Bridge (Liffey main channel), Awillyinish (Caragh) Stream (tributary), FCC Upstream (Liffey)

• Downstream sites: Castlekeely Ford (Liffey), Naas Stream (tributary), Leinster Aquaduct (Liffey), and Millicent Bridge (Liffey).

Figure 3.2 Water quality monitoring stations in the vicinity of the WWTP discharge

Millicent Br.

For inspection purposes only. Consent of copyright owner required for any other use. Leinster Aquaduct

Castlekeely Ford

Awillyinish Naas Stream

FCC Upstream

Victoria Br.

Key: Three Rivers Project monitoring site Fingal monitoring site Pre-summer 2000 WWTP pipe-outfall Post-summer 2000 WWTP diffuser-discharge

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3.4.1. Osberstown WWTP and effluent discharge The old treatment plant had become chronically overloaded, and was having a serious impact on the Liffey. The new works began discharging in July 2000, with processes gradually coming on-stream, and thus the nature of the effluent has changed significantly through the period analysed.

Table 3.3 overleaf shows a summary of the effluent characteristics for 1998 to 2000. Figure 3.3 graphs the effluent phosphorus (MRP) and ammonia concentrations during 2000. The new plant effluent load is a fraction of the loads from the old works. The phosphorus removal process was largely functioning to the discharge limit for TP of 0.9 mg/l, with median and maximum values from mid-September to October of 0.64 mg/l and 1.1 mg/l, respectively. The MRP discharge during this period had a median concentration of 0.33 mg/l, and a maximum of 0.98 mg/l.

Figure 3.3 Osberstown WWTP effluent during 2000 50 10 40 Ammonia 8 MRP 30 6 20 4 10 2 mg/l MRP mg/l ammonia 0 0 12-Jan- 22-Jan- 10-Mar- 11-Aug- 19-Aug- 27-Aug- 12-Sep- 20-Sep- 28-Sep- 10-Jul-00 18-Jul-00 26-Jul-00 3-Aug-00 4-Sep-00 16/6/00** date

Table 3.4 shows the design standards for the current plant. The plant has a design capacity of 80,000 PE and a design dry weather flow (dwf) of 20,000 m3/d. The plant is currently operating at an estimated 60,000 to 65,000 PE at dwf.

For inspection purposes only. 3.4.2. Approach to analysingConsent the of copyright impact owner of requiredthe WWTP for any other on use. the Liffey

Effluent from the old plant had a serious impact on Liffey water quality, and is discussed briefly in the next section. Given the significant changes in the effluent characteristics from the old to the current plant, and the more extensive river water quality dataset available for 2000, this analysis will concentrate on year 2000 data. The main water quality standards used are the EPA1 limits (detailed in Appendix A, Table A3) and the Salmonid Regulations (Appendix A, Table A2).

These standards are the most restrictive in terms of limits, and are consistent with preserving good ecological status in the river, and hence would protect all other interests and uses (to the limit of current monitoring). The standards for Bathing Waters are used for assessing faecal coliforms limits.

1 Threshold limits used by the EPA in assessing impaired water quality in Irish rivers

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Table 3.3 Summary Effluent data for Osberstown Wastewater Treatment Plant

Year BOD5 COD SS TKN NH3-N NO3-N NO2-N Total P PO43- Flow Loading Plant Perform -ance mg/l N mg/l N mg/l N mg/l N mg/l P mg/l P m3/day kg % BOD/day 1998 Median 43 158 76 27.9 27.28 1.76 0.03 7.10 7.31 15140 666 87 Maximum 134 344 177 39.2 57.00 3.53 0.12 23.60 15.62 21780 2049 97 Minimum 17 62 39 14.0 11.90 0.54 0.01 0.10 2.71 10790 265 57 1999 Median 43 147 81 27.4 29.05 0.23 0.03 4.90 5.67 14950 691 84 Maximum 117 351 166 35.0 40.20 1.42 0.09 8.90 11.28 22790 1849 97 Minimum 11 70 31 13.0 6.00 0.02 0.03 3.10 3.42 12180 169 47 2000 Median 26 117 64 27.0 20.70 0.11 0.15 5.75 5.74 15750 429 89 Old Plant Maximum 76 201 143 56.0 46.70 4.07 0.61 7.40 7.53 21380 968 100 Minimum 1 8 1 4.0 0.20 0.02 0.03 1.70 2.93 5920 12 63 2000 Median 5 23 7 4.0 0.10 4.29 0.61 2.40 1.96 13420 62 98 New Plant Maximum 77 167 684 98.0 3.60 7.46 0.92 15.00 9.13 21601 1280 100 Minimum 1 8 1 1.0 0.00 0.16 0.15 0.36 0.33 6535 13 59

Table 3.4 Current WWTP design specification for effluent For inspection purposes only. Parameter DWF BOD COD SS TP TNConsent Oxidisedof copyright owner N requiredKjeldahl for any otherN use. unit m3/d mg/l mg/l mg/l mg/l mg/l mg/l mg/l limit 20000 15 125 35 0.9 25 20.05 4.95

Notes: “DWF” = dry weather flow

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3.4.3. Biological water quality in the Liffey in the vicinity of Osberstown Table 3.5 below shows the biological assessment Q-rating for the various sites.

Table 3.5 Biological Q-rating at the monitoring sites Site Q-rating 95/96 Q-rating 1998 Q-rating 1999 Q-rating 2000 Victoria Bridge 4 4 3-4 4 Awillyinish Stream - - 3 3 Castlekeely Ford 3-4 2 2-3 3-4 Naas Stream - - 3 3 Millicent Bridge 3-4 3 - -

Key: [Q5, Q4-5, Q4] = unpolluted, [Q3-4] = slightly polluted, [Q3, Q2-3] = moderately polluted, [less than or equal to Q2] = seriously polluted

The Q-values show that Victoria Bridge is currently classed as unpolluted (upstream of the Osberstown discharge), but this quality declines to slightly polluted at Castlekeely Ford (downstream of the Osberstown discharge). The rating at Castlekeely Ford has been improving over the last three years from seriously polluted during 1998 to moderately polluted in 1999, and the current slight pollution rating. Millicent Bridge (further downstream) was classed as moderately polluted during 1998. Both of the sites downstream of the Osberstown discharge have shown significant decline in water quality from the 95/96 survey to 1998 and 1999 values. The two tributaries Awillyinish and Naas streams both show moderately polluted ratings during 1999 and 2000 due to diffuse pollution sources and known discharges.

3.4.4. Physico-chemical water quality of the Liffey in the vicinity of Osberstown Fingal County Council monitoring data at “FCC Upstream” and Leinster Aquaduct are assessed for the period January 1998-July 2000. Grab samples were taken at varying frequency from daily to weekly. For the period mid-July to November 1999 there are no results available for the site at Leinster Aquaduct. The samples were analysed for Biochemical Oxygen Demand (BOD), Molybate Reactive Phosphorus (MRP), Ammonia, Total Oxidised Nitrogen (TON), Suspended Solids, Dissolved Oxygen (DO % saturation), Faecal coliforms, Nitrite and Nitrate.

Data was available from January to September For inspection 2000purposes foronly. the five Three Rivers Project sites. Grab Consent of copyright owner required for any other use. samples were generally taken weekly. The following parameters were analysed: DO (% saturation), MRP, Ammonia and TON. It should be noted that BOD is not measured as part of the Three Rivers Project, as it is a nutrient focussed project with a primary interest in eutrophication.

Table 3.6 presents statistical characteristics of the water quality at the sites in relation to water quality standards. Figures 3.4-3.5 graph the parameters MRP and ammonia during 2000 for the sites.

Upstream of the WWTP, the Liffey main channel shows characteristics of an unpolluted water, consistent with the biological Q-rating results. All parameters except nitrite are within median standard limits, and values are also generally within maximum standard limits. Nitrite limits set in the Salmonid Regulations were exceeded during 1998 and 1999 at FCC Upstream, and were exceeded five times during 2000. However, nitrite levels higher than the specified standard are common in Irish rivers, and are not necessarily an indication of poor water quality.

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Table 3.6 Summary water quality analysis results Site Criteria BOD Nitrate Nitrite Ammonia MRP TON DO % sat SS F.Coli Victoria Bridge Median 2000 1.414 0.010 0.014 0.010 1.43 96.2 (Three Rivers) No. of samples 2000 0 29 29 29 29 29 27 0 0 No. samples > max limit 2000 0 1 0 0 0 0 Awillyinish Stream Median 2000 2.109 0.059 0.339 0.144 2.20 76 (Three Rivers) No. of samples 2000 0 28 28 28 28 28 27 0 0 No. samples > max limit 2000 0 28 16 13 0 11 FCC Upstream Median 1998 2.0 1.558 0.027 0.050 0.028 1.63 89.0 10.0 1120 (Fingal Co. Co.) Median 1999 2.0 1.387 0.018 0.040 0.020 1.40 93.0 10.0 795 Median 2000 1.570 0.013 0.030 0.010 1.60 91.0 10.0 510 No. of samples 2000 0 21 21 22 22 22 21 15 26 No. samples > max limit 2000 0 5 1 1 0 1 0 4 Castlekeely Ford Median 2000 1.617 0.016 0.152 0.125 1.64 94.9 (Three Rivers) No. of samples 2000 0 28 28 28 28 28 26 0 0 No. samples > max limit 2000 0 17 13 8 0 0 Naas Stream Median 2000 2.888 0.018 0.066 0.047 2.91 91 (Three Rivers) No. of samples 2000 0 29 29 29 29 29 26 0 0 No. samples > max limit 2000 0 19 1 0 0 1 Leinster Aquaduct Median 1998 3.0 1.642 0.040 0.264 0.129 1.72 10.0 6550 (Fingal Co. Co.) Median 1999 2.0 1.790 0.032 0.140 1.85 10.0 8800 Median 2000 1.750 0.038 0.125 1.84 10.0 3100 No. of samples 2000 0 25 25 0 24 25 0 14 24 For inspection purposes only. No. samples > max limit 2000 Consent of copyright0 owner required24 for any other use. 8 0 2 16 Millicent Bridge Median 2000 1.665 0.023 0.038 0.111 1.68 99.5 (Three Rivers) No. of samples 2000 0 29 29 29 29 29 27 0 0 No. samples > max limit 2000 0 22 6 10 0 0

Median Limit 3 0.1 0.03 5.65 70>A<130 25 Maximum Limit 5 0.015 0.3 0.15 5.65 2000

Notes: overleaf

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Notes (for Table 3.6) 1. Sites have a varying number of samples from month to month and in each year 2. Data in 2000 spans either January to July (FCC sites) or January to September (Three Rivers Project sites) 3. The maximum limits for BOD and Nitrite are taken from "Standards for Salmonid Waters", S.I. No. 293 of 1998 (Appendix A, Table A2). Conformance to standard is defined by maximum allowable concentration at either 95 or 100 percentiles (depending on sample frequency). 4. The median BOD limit is also taken from the above reference, but considers that the (therein stated) E.U. Guidance limit can be used as an indicative median. 5. Parameters [Nitrate, Nitrite, Ammonia, TON] are in mg/l of N, [MRP] is in mg/l of P 6. “SS” = suspended solids, “F.Coli” = faecal coliforms (No. per 100ml) 7. BOD values could not be detected when less than 2 mg/l, hence the actual median values would likely be less than shown above 8. The "No. samples > max limit 2000" for DO refers to values below the 70% saturation standard limit 9. Values exceeding prescribed limits are shown in bold

The tributary Awillyinish Stream (or Caragh Stream) shows water quality characteristics indicative of moderate to serious pollution. The ammonia load from this stream would appear likely to be the cause of the increase in ammonia levels at the FCC Upstream site on the Liffey, just before the WWTP (the ammonia levels double in the Liffey after the Awillyinish enters).

The parameters nitrate, TON, DO, and SS are all within standard limits (where available), and do not change significantly from upstream to downstream of the WWTP. BOD was not measured during 2000 due to the difficulties in measuring BOD values below 2.0 mg/l. A value of less than 2.0 mg/l is also consistent with the decreasing trend evident from the previous years. Thus both 1999 and 2000 median values for BOD at Leinster Aquaduct of 2.0 mg/l are within standard limits. There is little difference between nitrite values upstream and downstream of the plant, although it must be pointed out that the median value increases from slightly below to slightly above standard limits. It is also noteworthy that nitrite values increase significantly from Castlekeely Ford to Leinster Aquaduct, most likely due to the conversion of ammonia to nitrite over this stretch of river.

The faecal coliform count increases significantly from upstream to downstream of the plant. The Bathing Waters standard maximum limit was exceeded in two thirds of samples taken downstream of the plant (at Leinster Aquaduct) during 2000, although it must be recognised that whilst the waters in this area are used for bathing and water-contact sports, they are not designated bathing waters. This is not surprising for normal wastewater treatment without disinfection.

For inspection purposes only. The evaluation of water quality monitoringConsent of copyrightresults owner will requiredconcentrate for any other on use. MRP and ammonia as the critical parameters. The median MRP value for the period upstream of the plant discharge (FCC Upstream) is 0.01 mg/l, increasing to 0.125 mg/l downstream of the plant discharge (Castlekeely Ford). The median ammonia value for the period is 0.03 mg/l upstream, and 0.152 mg/l downstream of the plant discharge.

These downstream values are indicative of polluted waters, consistent with the biological Q-rating results. However, the effluent characteristics changed significantly from July onwards in 2000, with lower MRP and ammonia discharge levels.

Figures 3.4 and 3.5 shows the water quality values for MRP and ammonia upstream and downstream of the plant discharge for the period January 2000 to October 2000. This clearly shows the dramatic decrease in ammonia discharge during the period July 2000 onwards. The MRP values for Castlekeely Ford decrease significantly during the last three samples from mid-September to Early October 2000, suggesting a possible effect of the lower effluent load evident if Figure 3.3, combined with increased flow in the river (post summer low flows).

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Figure 3.4 MRP levels upstream and downstream of Osberstown Victoria Bridge FCC Upstream 0.5 0.4 Castlekeely Ford 0.3 new plant

mg/l 0.2 0.1 0 31-Dec- 19-Feb- 09-Apr-00 29-May- 18-Jul-00 06-Sep- 26-Oct-00 99 00 00 00 month

Figure 3.5 Ammonia levels upstream and downstream of Osberstown Victoria Bridge FCC upstream 2 Castlekeely Ford 1.5

1 mg/l new plant 0.5 0 06-Dec- 25-Jan- 15-Mar- 04-May- 23-Jun- 12-Aug- 01-Oct- 20-Nov- 99 00 00 00 00 00 00 00 month For inspection purposes only. Consent of copyright owner required for any other use.

However, it is difficult to comment with confidence on the effects of the current effluent loads on river water quality, due to the relatively long period needed to establish verifiable change in water quality (at least one year), and the fact that the plant was not commissioned until October 2001, before which the plant was not fully functional.

3.4.5. Point source and diffuse water quality impacts on the Liffey upstream of Osberstown In assessing the water quality or assimilative capacity of the river it must be considered that a certain portion of the assimilative capacity of the river Liffey is utilised by other sources upstream of Osberstown, both point source contributors and diffuse source contributors. However, given that Liffey waters upstream of Osberstown are unpolluted, with low MRP levels at 0.01 mg/l median, it is not considered feasible to reduce this concentration below this already low value.

Nonetheless, cognisance must be taken of catchment management in this area, as any increase in nutrient load would effectively decrease assimilative capacity. Some typical point source pollutant loads to a watercourse in these areas could include other wastewater treatment plants, foul sewer overflows, stormwater discharges from urban catchments (particularly “first foul flush discharges”). Diffuse sources of pollution could include agriculture, commercial forestry and rural dwellings, which generally discharge to septic tanks. Any additional pressures from these sources would have to be

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The Awillyinish catchment should be carefully monitored, as current nutrient levels are already high. There is development pressure in the Caragh area, which could lead to increased pressures on the stream. However, the recent changeover from the old WWTP at Caragh to a new pumping station would be expected to have a positive effect on water quality into the future.

3.4.6. Conclusions on the water quality of the Liffey in the vicinity of Osberstown The Liffey upstream of Osberstown is unpolluted, with both physico-chemical and biological characteristics supportive of this status.

With regard to achieving the objectives of the Phosphorus Regulations downstream of the effluent discharge, the target quality index for 2007 at Castlekeely Ford is Q4 (from Q3-4 during 1995/96). The current water quality in the Liffey downstream of the plant shows nutrient levels that are either within limits or consistent with the values in the Liffey upstream of the plant, except for MRP and ammonia values. The decrease in effluent ammonia values post-July this year has lead to a significant decrease in river ammonia levels, to apparently acceptable values. The decrease in MRP effluent loads may also result in a decrease in river MRP levels, but there is no conclusive evidence of this to-date.

The effects of the current plant on river water quality can only be assessed when combined with the assimilative capacity analysis in the next section of this report, in order to allow meaningful conclusions.

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3.5. RIVER LIFFEY FLOWS AT OSBERSTOWN There is very scant flow data available for the Middle Liffey catchment area. Kildare County Council have no flow-measuring device in the vicinity of Osberstown, and the recently installed site at Millicent Bridge has an inadequate period of flows. As part of the Three Rivers Project, Kildare County Council have undertaken major upgrading of the hydrometric network on the Liffey catchment. This work has included the construction of ‘flat-V’ type weirs at monitoring stations at strategic locations on tributaries in the catchment.

However, there is still no good quality hydrometric station in the vicinity of Osberstown on the main river, as the high cost involved was outside the budget of the Three Rivers Project. Significantly, there is also currently no long-standing hydrometric station with a good rating between Golden Falls and Leixlip. Therefore, the estimation of flows at Osberstown will use the available information in ESBI’s “River Liffey Water Supply Model Study”2, and the Liffey Water Quality Management Plan3 (WQMP). Reference is also made to the analysis carried out as part of the design of the current (Stage 2) plant4. It was an urgent recommendation of the original “Receiving Water Study” report that the necessary budget for a high quality flow measurement station be approved, for immediate implementation. This has been taken up by the council, and the station is due to be installed in early 2002.

Baseflows in the middle Liffey are effectively determined by the releases at Golden Falls dam. The minimum (compensation) flow released at Golden Falls is 1.5m3/s. The ESB generator at Golden Falls releases a fixed flow of 30m3/s during generation. The generation duration is approximately 7-8 hours at a time with an interval of 5-6 hours between runs, to prevent sudden flooding downstream. In the summer, the normal discharge of 1.5m3/s is occasionally supplemented by short high flow discharges or freshets. These are usually released by ESB in liaison with the Marine Institute and Eastern Region Fisheries Board and are designed to protect fishery conditions in the river.

In the Middle Liffey, there is a significant interaction between river flows and storage in the Curragh aquifer. This is evident from the chemical characteristics of the water with greatly increased hardness and alkalinity compared to the water at Poulaphuca. The Middle Liffey catchment is relatively flat and shows a slow response to rainfall. The area is covered by deep sand and glacial deposits, with bedrock as low as 75m below the surface in some locations.

Flow measurements in response to rainfall have indicated a varied hydrological response. For example, in 1986 during the Hurricane Charlie storm, the percentage runoff was estimated at just 15%, with the balance going into recharge. Other significant events have recorded much higher runoff parameters. Nevertheless, significant flooding For inspection can purposes occur only. in the middle catchment area, notably Consent of copyright owner required for any other use. 3 between Straffan and Celbridge, where bank full capacity is estimated at 40m /s. The influence of the Curragh Aquifer on the hydrological response of the Liffey is not fully understood.

3.5.1. Determining flows at Osberstown Table 3.7 overleaf presents data derived from the ESBI report. The average annual inflow and percentile flow figures are net of abstractions, with the net flows being after abstractions. The flows at Osberstown were derived from the Pollaphuca inflow/outflow data, proportioned by area only. The net 70-percentiles at Pollaphuca and Osberstown are lower than the compensation flow of 1.5 m3/s, and therefore would not actually occur (the flows would be supplemented using storage). It is not possible to estimate the 95-percentile flows from the ESBI data.

2 River Liffey Water Supply Model Study, July 1996, ESB International. 3 Draft Water Quality Management Plan – The Liffey Catchment, May 1993 Update (ERU), An Foras Forbartha. 4 Osberstown Waste Water Treatment Works. Preliminary Report and Estimate. Volume 1 September 1995. John B. Barry and Partners Limited, Dublin.

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Table 3.7 Flows and abstractions in the Liffey (from ESBI data) Net Pollaphuca Net middle catchment Gross Osberstown catchment (to Leixlip) catchment Area (km2) 309 534 580 Average annual inflow 8.8 5.7 11.7 (m3/s) 50-percentile (m3/s) 5.0 4.2 7.1 70-percentile (m3/s) 3.0 2.0 4.0 Abstractions (m3/s) 2.8* 1.62** 2.8 Net AA flow (m3/s) 6.0 8.9 Net 50-percentile (m3/s) 2.2 4.3 Net 70-percentile (m3/s) 0.2 1.2 Compensation (m3/s) 1.5 1.5 *240 Ml per day ** 140 Ml per day

Data from the WQMP at Newbridge and Clane hydrometric stations imply flows at Osberstown of 4.7, 3.3, and 2.2 m3/s for the 50-percentile, 70-percentile, and 95-percentile flows, respectively (including compensation flows). Analysis in the Stage 2 EIS report indicates a 95-percentile flow of 2.42 m3/s (also derived from WQMP data). These figures suggest that the low flows in the middle catchment are very small when compensation flow is excluded. The derived ESBI data for low flows at Osberstown are theoretical with respect to inflows and ignore the impoundment effect, as flows at and below the 70-percentile are less than the known compensation flow of 1.5 m3/s.

The abstraction licenses at Pollaphuca and Leixlip allow for a further 80 Ml and 35 Ml, respectively, over current abstraction rates. Given the expansion in demand for water in the Dublin region, it is foreseeable that low flows in the middle Liffey will continue to be dominated by the compensation flow discharged at Pollaphuca. The ESBI report outlines that abstractions at these license limits would necessitate special discharges from Pollaphuca to augment Leixlip inflows (on average every five days), and would place restrictions on power generation at Pollaphuca. It is thus concluded that dry- season discharges (other than compensation flow) will be further restricted and cannot be included in any assessment of low flows. Nevertheless, the higher Leixlip abstraction will have the effect of increasing low flows, through planned releases. Given the WQMP data and the Leixlip abstraction effect, the 95-percentile flow is assumed to be 2.42 m3/s (some 10% over the minimum derived value).

3.5.2. Flows at Osberstown - Conclusions For inspection purposes only. Consent of copyright owner required for any other use. The figures adopted for the purpose of this study are the average of the ESBI and WQMP flows for the 50-percentile, and the figures derived from WQMP values for the 70-percentile and 95-percentile flows, as follows:

50-percentile flow: 4.5 m3/s 70-percentile flow: 3.7 m3/s 95-percentile flow: 2.4 m3/s

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3.6. ASSIMILATIVE CAPACITY

3.6.1. Approach The assimilative capacity of the Liffey at Osberstown is considered for the parameters BOD, MRP, ammonia, suspended solids (SS) and TON. The applicable standards are the EPA maximum limits and Salmonid Regulations 95% conformance limit. There are no standard limits for nitrate, and nitrite values indicate very little difference between upstream and downstream values, rendering it difficult to recommend effluent nitrite limits. Daytime DO levels are considered a poor indication of river ecological status. Compliance with the parameters listed above is considered a better target than daytime DO compliance.

3.6.2. Assimilative capacity of the Liffey at Osberstown The baseline conditions in regard to water quality are those conditions were set-out the previous sections. Table 3.8 below shows the current assimilative capacity of the Liffey, calculated by defined standards and targets. Two scenarios with respect to assimilative capacity are considered. The first scenario is where a median target standard is applicable, and is calculated using median flows (50- percentile). The second scenario occurs at the low flow 95-percentile in the river, where effluent loads must not cause exceedence of the assimilative capacity of the river as calculated using the upper-end standard limits (EPA maximum limits and Salmonid Regulations 95% conformance limit). In this case, analysis of influent flows indicate that high effluent flow values (in excess of 80-percentile), which only tend to occur during rainfall events, are extremely unlikely to occur simultaneously with the low flow 95-percentile in the river. Together, the probability that a low flow 95-percentile in the river occurs at the same time as an 80-percentile effluent flow is estimated at 1%.

Conformance to a standard (limit) is thus taken as follows:

1. Median effluent value [parameter] at 50-percentile flow must not exceed the median target standard (e.g. EPA standards), and must not exceed the Salmonid Regulations 95% compliance limit.

2. 80-percentile effluent value [parameter] at 95-percentile flow must not exceed the maximum target standard (e.g. EPA standards), and must not exceed the Salmonid Regulations 95% compliance limit. For inspection purposes only. Consent of copyright owner required for any other use. The formulae used are thus:

[parameter] Assimilative capacity – at Median (kg/d) = (Smed - Cus) x 50-percentile flow

[parameter] Assimilative capacity – at maximum (kg/d) = (Smax - Cus) x 95-percentile flow where: Smed = median limit standard for that parameter (concentration) Smax = maximum limit standard for that parameter (concentration) Cus = concentration upstream of effluent discharge

Table 3.8 Assimilative capacity of the Liffey at Osberstown

BOD MRP Ammonia SS TON Scenario (kg/d) (kg/d) (kg/d) (kg/d) (kg/d) Median load limit 390 7.8 27 5830 1575

Maximum load 620 29.0 56 3100 1165

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3.6.3. Impact of the current WWTP Table 3.9 shows a comparison of assimilative capacity against the design effluent loads from the WWTP at the current 60,000 PE, and at the design 80,000 PE. The effluent loads are generally below assimilative capacity for both 60,000 and 80,000 PE loads, with the exception of phosphorus, which is significantly in excess of the assimilative capacity at both PE loads. It must be noted, however, that current loads are significantly below the effluent design limits. The median MRP effluent concentration was 0.33 mg/l during the process functioning period in September/October this year, which would equate to approximately 77% of the available assimilative capacity. The daily MRP load was less than the assimilative capacity for 60% of the time. The condition where the plant discharges into low flow in the Liffey (95-percentile) is within limits for MRP.

It is therefore concluded that the current plant will only be consistent with the water quality objectives for the Liffey if median MRP effluent discharge loads remain significantly below the allowable design limits. The current plant at 80,000 PE would have to achieve a median MRP effluent concentration of approximately 0.39 mg/l to be within the assimilative capacity of the Liffey.

Table 3.9 Assimilative capacity versus WWTP load

BOD MRP Ammonia SS TON Scenario (kg/d) (kg/d) (kg/d) (kg/d) (kg/d) Median load limit 390 7.8 27 5830 1575

Maximum load 620 29.0 56 3100 1165

Current Plant 60k PE – at DWF 225 11.3 1.5* 525 301

Current Plant 60k PE – at 80% flow 295 14.8 11.8* 689 404

Current Plant 80k PE – at DWF 300 15.2 2.0* 700 401

Current Plant 80k PE – at 80% flow 402 20.1 16.1* 937 549 Notes: 1. The upstream BOD for median and maximum is assumed to be 2.0 mg/l For inspection purposes only. 2. All other upstream values are Consentbased of on copyright year 2000owner required water forquality any other data use.

3. The load from the current plant at dwf (dry weather flow) is calculated at the design specification standard (concentration) for that parameter, or for MRP at 84% of the specified standard for TP (based on the observed effluent MRP/TP relationship)

4. “80%” refers to the 80-percentile flow at the current plant of 17,644 m3/d at 60k PE, estimated 26,800 m3/d at 80k PE

5. * ammonia is not a design effluent standard for the current plant, current plant (June to Oct 2000) has a median value of 0.1 mg/l and a normal maximum of 0.6 mg/l

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3.6.4. Scope for increasing the WWTP load Table 3.10 shows the capacity remaining in terms of PE under current treatment standards, and for the conditions specified in the accompanying notes. The critical (limiting) parameter is phosphorus. Under the current effluent standard for phosphorus, there is no scope to increase the WWTP load.

Table 3.10 Capacity remaining for current treatment standards BOD MRP Ammonia SS TON Scenario (PE) (PE) (PE) (PE) (PE) Capacity remaining above 80k PE – dwf flow/load, current treatment 32k 0 n/r n/r n/r standard Capacity remaining above 80k PE – 80% flow/load, current treatment 59k 30k n/r 250k 123k standard

Notes: 1. “n/r” denotes not relevant, where capacity is very large

2. Capacity remaining (PE) is based on new connections at 170 l/PE/d dwf, existing connections have an existing dwf of 227 l/PE/d, all new connections are assumed to be restricted to a maximum flow of 225 l/PE/d, all existing and new PE assumed to be treated to the same effluent concentrations as the current design standards

Any increase in PE load to the WWTP would have to meet one of the following criteria:

1. A decrease in effluent standard limits for phosphorus, and the setting of both median and 95- percentile limits for TP and BOD.

2. Influent TP and MRP load reduction – urban phosphorus reduction strategies

3. A combination of both the above.

For inspection purposes only. It may also be noted that the currentConsent treatment of copyright ownerstandards required for would any other limit use. capacity to 112,000 PE under BOD load conditions. However, it must again be considered that the median effluent load is much less than that calculated at the design effluent standard limit.

State of the art effluent standards State of the art BATNEEC technology can currently achieve TP effluent concentrations of 0.3 mg/l and 0.4 mg/l at median and maximum levels, respectively. This technology would allow an estimated maximum of 134,000 PE. This would be consistent with a very high level of performance of biological treatment, assisted by filtration and chemical treatment for “P” removal.

Recommended phosphorus effluent standards and design PE It is recommended that a more conservative effluent standard for phosphorus is adopted for an upgraded plant at Osberstown, of 0.35 mg/l and 0.9 mg/l TP at median and 95 percentile maximum. These TP values are consistent with achieving target standards for MRP based on the observed average relationship where MRP equals 84% of TP. These effluent standards allow an increased factor of safety, and correspond to a plant capacity of 130,000 PE.

Influent TP and MRP load reduction The phosphorus load to the plant could be reduced by implementing urban phosphorus reduction strategies. A single effective strategy could be to prohibit the sale and use of detergents containing phosphates. It is presently unclear what reduction in load is achievable using this strategy.

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It is concluded that the assimilated capacity of the Liffey is restricted by the limiting phosphorus concentrations in the river, and that the maximum safe capacity of an upgraded WWTP plant is 130,000 PE under the recommended limits for phosphorus discharge, based on the best practical treatment capability that may be anticipated.

3.6.5. Recommended parameters for effluent standards The adoption of design standard limits for median load as well as the normal 95-percentile load is recommended. It is important that river water quality is protected both by limiting the median level of a nutrient or other substance, which protects the overall ecological health of the river, and by limiting the maximum level of a nutrient or other substance, a breach of which could cause a pollution incident (e.g. BOD or ammonia).

It is thus recommended that the effluent concentration limits detailed in Table 3.11 are adopted in the design of a new treatment plant, to the outline specifications detailed in this section. The recommendations either use the assimilative capacity basis, or the design limits for the current plant, whichever is the lesser. These are general recommendations covering concentration only, and must be specified in more detail to set actual effluent standards for a new plant (depending on agreed DWF/storm flows and conditions).

Table 3.11 Recommended parameters for effluent standards (concentrations)

Current Phase II Plant Median limit 95-percentile limit Parameter 95-percentile limit Mg/l Mg/l (Mg/l) BOD 10 15 15 COD - 125 125 TP 0.35 0.9 0.9 Ammonia 0.9 1.5 none SS - 35 35 TON - 20 20.05 TN - For inspection purposes only.25 25 Consent of copyright owner required for any other use.

Kjeldahl N - 5 4.95

An additional parameter that should be considered is faecal coliforms, particularly to protect the major water abstraction at Leixlip. There is no data available on faecal coliforms in the current plant effluent. It is recommended that this effluent parameter be measured, and consideration given to appropriate measures to ensure that this parameter falls within acceptable standards. This would also protect the amenity value of this stretch of river. Measurement of background levels is recommended for further assessment of this parameter.

3.6.6. Assimilative capacity conclusions The main assimilative capacity restriction of the Liffey at Osberstown is in terms of phosphorus capacity.

The current WWTP at 60,000 PE and 80,000 PE loads will only comply with the water quality standards set down for the Liffey, including the Phosphorus Regulations targets for 2007 (unpolluted status), if the effluent characteristics remain at the current MRP median of 0.33 mg/l, or at least at a median of 0.39 mg/l.

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The assimilative capacity of the Liffey at Osberstown would safely allow an upgraded WWTP plant with a maximum capacity of 130,000 PE, under the two main conditions that stormwater misconnection is minimised, and that a median concentration effluent standard for TP of 0.35 mg/l is adopted.

This requires state of the art treatment based on “P” removal assisted by chemical treatment to meet the best practicable standard. Reference plants for this standard have been identified in Denmark, characterised by expert process monitoring and management.

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4. LOAD ASSESSMENT AND CATEGORISATION

This report outlines the current loads and estimates of future loads to the Osberstown Wastewater Treatment Plant (WWTP). The loads are categorised into domestic, commercial, and industrial contributions.

The current plant has a capacity of 80,000 population equivalent (PE). The Receiving Water Study report (December 2000) prepared for this project recommended a maximum capacity of 130,000 PE for an upgraded plant.

This report presents:

• the existing loads to the plant - domestic, commercial and industrial • existing population estimates • imminent connection loads • proposed connection (i.e. existing population centres) • zoned future development (industrial and residential) • planning permissions (PP) due for connection • potential connection of existing development (where proximal to sewers or new development) • potential large connections from un-zoned development • estimates of new connection timescales

4.1. SOURCES OF DATA The five main sources of data used in this report are:

1. Influent data supplied by Kildare County Council (KCC) and Earth-Tec from the Osberstown WWTP 2. KCC development plans; Naas (1999), Newbridge (1996), Sallins (1996), Kilcullen (1996), Athgarvan (1996), Clane (draft 2000), Kill (draft 2000) 3. KCC report “Osberstown Treatment Plant – Projected Loading from Housing”, M. Tinsley, 26th June 2000. For inspection purposes only. Consent of copyright owner required for any other use. 4. “Housing Statistics Bulletin, September Quarter 2000”. Department of the Environment and Local Government. 5. An Post / OSI Geodirectory for County Kildare 6. Industrial monitoring survey carried out by City Analysts Ltd. between December 2000 and January 2001 for this project. 7. “Wastewater Collection/Disposal – The Curragh”. Feasibility Report. Nicholas O’Dwyer for Kildare County Council. September 1999.

Item no. 3 above was used to ascertain residential loads from planning permissions. Item no.5, the Geodirectory, provided the location coordinates and use of every building in Kildare (status September 1999).

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4.2. CURRENT CONNECTION TO OSBERSTOWN AND SECTORAL LOADS

4.2.1. Urban centres and population connected to osberstown, and imminent connection of existing population The urban centres of Naas, Newbridge, Clane, Sallins, Kill, Kilcullen, Johnstown, Prosperous, and Walshestown are currently connected to Osberstown.

Athgarvan and Caragh are partially connected and complete connection is due within the coming months. The area encompassing Maddenstown, Brownstown, Cut Bush, Suncroft, and the Curragh Camp are part of a proposed sewerage scheme involving several options including the transfer of the sewage to Osberstown (according to the Feasibility Report, Section 1.1, item No.7).

The method used to define current populations in the urban centres connected to Osberstown consisted of defining a ‘sewered boundary’ for each urban centre, and then analysing the number of residential units Kilcullen Pumping Station – Commissioned in 2000 falling within that boundary (as at September 1999). Table 4.1 shows the existing and imminent connection to Osberstown. Taking an occupancy rate of 3.25 persons per unit (see Section 4.3.1), there were approximately 43,000 domestic PE connected to Osberstown in September 1999 (Prosperous and Athgarvan were not connected). Additional connection and development during late 1999 and 2000 would give estimated average of 45,500 residential population during 2000.

Table 4.1: Domestic Population and Commercial PE based on House Counts Area Residential Population Commercial Units Units For inspection purposes only. 17,914 Naas Consent of copyright owner5512 required for any other use. 589 Newbridge 4590 14,918 492 Clane 1301 4,228 122 Sallins 737 2,395 24 Kill 533 1,732 18 Kilcullen 497 1,615 66 Johnstown 46 150 1 Prosperous 426 1,385 31 Walshestown 31 101 0 Athgarvan* 60 195 5

Proposed/imminent connection Athgarvan* 67 218 0 Caragh 43 140 4 Curragh Camp 4,500

Totals 14268 50871 1384 Total currently connected 13733 44632 1348 Notes: * approximately half of Athgarvan is currently connected ** Greater Curragh Area includes Maddenstown, Brownstown, Cut Bush, and Suncroft

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The total existing, imminent, and proposed connection to Osberstown is just under 51,000 residential population, with an additional 1,400 commercial units.

4.2.2. Current large commercial and industrial loads All major industry and large commercial business discharging to sewer in the catchment were monitored during December 2000 and January 2001. The survey was carried out in co-operation with the Environment section of Kildare County Council, who have been implementing the ‘polluters pays principle’ over recent years, using similar monitoring surveys. Automatic flow proportional samplers were used to monitor 18 major businesses and 5 industrial estates in the Catchment. The sampling was carried out for seven days on each of the industrial estates and for a range of 2-7 days for the other industries depending on their size. The parameters BOD, COD, pH, ammonia, total phosphorus (TP), ortho-phosphorus, total kjeldahl nitrogen (TKN), and suspended solids (SS) were analysed. Table 4.2 summarises the results of the survey. A detailed report with analysis and results is contained in Appendix B.

Table 4.2 indicates the average, maximum, and minimum BOD PE from the survey. The 7-day average for the survey was 14,670 PE, when figures are adjusted for the opening regime of the industries. The average flow of 2,660 m3/d (181 litres per PE) indicates lower flows and higher concentrations from these industrial areas when compared to residential figures in the catchment (see Section 4.2.4). The weekday average load is 17,164 PE, and the weekend load is 7,779 PE.

1.1. Table 4.2 Summary industrial loads Industry PE (from BOD) 7-day average Minimum Maximum QK Foods 3,703 11,911 5,984 Maudlins Industrial Estate 1,125 7,854 4,984 Monread Industrial Estate 787 4,421 2,505 Green Isle Foods 928 2,425 1,777 Clongowes Wood College 733 2,607 1,681 Newbridge Industrial Estate 289 4,017 1,503 Newbridge Foods 0 1,625 859 Wyeth Medica 443 1,512 840 For inspection purposes only. Newbridge BusinessConsent Park of copyright owner required23 for any other2,121 use. 836

Monread Lodge 676 851 764 Naas Industrial Estate 34 969 629 Donnelly Mirrors1 142 1,184 568 Mc Carthy Meats 166 1,020 482 Poldy Foods 160 627 358 Clane Cleaners Ltd 19 478 176 Crogeen 44 269 126 Ambassador Hotel 4 200 96 Clane Hospital 42 53 47 Ashbourne Meats 23 73 43 Champion Spark Plugs 4 76 27 Newbridge Cutlery 1 2 2 Schloetter 0 0 0

Totals2 4,384 26,371 14,670 Notes: 1. Donnely Mirrors is in the process of but not currently connected 2. The totals shown are not straight sums down the column, but allow for the industries that were both monitored individually and within industrial estates 3. Calculation of PE from BOD results taken at 60g BOD per PE

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Individually, QK Foods is the single largest contributor (5984 PE), with Clongowes Wood College (1681 PE) and Green Isle foods (1777 PE) the two next largest. Together, these three businesses contribute more than 50% of the large industrial load, with QK Foods alone contributing almost one third.

There is variation in the PE load according to which parameter is considered, e.g. Appendix A shows average PE loads of [5984, 3357, 6904, 2889] for QK Foods for the parameters [BOD, COD, TP, TKN]. Overall, the COD load of 11,531 PE, the TP load of 10,333 PE, and the TKN load of 8,881 PE are all appreciably less than the PE BOD load (calculated at 150, 2.5, 11, and 60 g/head/day, respectively).

A significant element of the survey results concerns the maximum loads monitored from each of the industries. On average, the maximum load is approximately twice the average load from any particular industry. The theoretical ‘shock’ load from all these industries is over 26,000 PE. Although this coincidence is unlikely to result in a full extra 12,000 PE, it would nonetheless partially account for the significant variation in influent loads to the plant discussed in Section 4.2.4. Also notable is that minimum loads account for less than one third of the average load. The estimated range of load is from less than 5,000 PE to more than 26,000 PE.

4.2.3. Small commercial loads When categorising and apportioning sectoral loads, small commercial contributions are logistically unsuitable for direct monitoring and normally too widely dispersed for group monitoring. Thus a more indirect approach using residential water usage compared to influent flow can normally be used to estimate the small commercial load. However, in this case the high extraneous flows to the plant render it impossible to estimate the commercial contribution. This will be further investigated and analysed following the flow survey (in progress). In the interim, a figure of 15-20% of the residential PE BOD load will be adopted, giving 7000 to 9000 small commercial PE.

4.2.4. Influent monitoring Table 4.3 below shows summary influent load characteristics for 1998-2000, and the period July 2001 to June 2001 for the new Stage II plant. It is notable that whilst average flows are increasing, corresponding to development and new connection of urban centres such as Walshestown and Kilcullen, BOD loadings are decreasing significantly. This may be partly due to changes in industrial discharges following the introduction of charges For inspection on purposes industry only. post-1998. Consent of copyright owner required for any other use.

Table 4.3: Influent flow and load Average Maximum Flow BOD Load PE Flow BOD Load PE m3/d kg/d m3/d kg/d 1998 15,566 5,456 90,925 21,780 15,984 266,399

1999 15,534 4,927 82,109 22,790 14,096 234,937

2000 18,030 3,661 58,169 48,111 9,547 141,281

July00 – June01 18,195 3,231 51,449 48,111 9,547 129,853

Note: “PE” = population equivalent

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Table 4.4 shows the large variations in daily loads during the period July 2000 to June 2001. Eighty percent (80%) of daily loads are below 70,000 PE, and the 95-percentile load was 93,000 PE during the period. The maximum weekly-averaged load or ‘peak-week’ was 98,600 PE.

Table 4.4 Variation in daily loads during July 2000 to June 2001

Category (PE) Percentage < 30,000 19% 30,000 – 50,000 36% 50,000 – 70,000 25% 70,000 – 90,000 14% > 90,000 6%

The daily and yearly flow and loads are therefore highly variable. The plant is operating at approximately 51,500 PE based on BOD load, but the average flow figure of 18,000 m3/d is far higher than that expected in the Stage II design for the equivalent population. The expected flow figure was 20,000 m3/d for the plant at full 80,000 PE capacity. It is concluded that the capacity of the plant will be reached well before 80,000 PE due to excessive influent flows.

The average flow figures are equivalent to 300 litres-per-head-per-day, and cannot be accounted for by industrial flows, and thus would indicate significant extraneous inputs such as storm misconnection and groundwater infiltration. The highly variable flows and loads will present some difficulty in plant design and operation.

4.2.5. Analysis of all loads The influent average load of 51,500 PE over the past year does not tally with the sum of residential and industry PE loads of 60,500 PE.

The weekday and weekend results were compared along with the industry survey results as summarised in Table 4.5.

For inspection purposes only. Table 4.5 Variation in weekdayConsent of and copyright weekend owner required loads for any during other use. July 2000 to April 2001 Domestic- Category Parameter Total Load Industry Load Commercial Av. BOD kg/d 3,212 1,030 2,182 Weekday Av. Flow m3/d 18,927 6,246 12,681 Av. PE 53,528 17,164 36,364 Av. BOD kg/d 3,141 467 2,674 Weekend Av. Flow m3/d 17,582 1,565 16,017 Av. PE 52,342 7,779 44,564 Av. BOD kg/d 3,185 880 2,305 Overall Av. Flow m3/d 18,542 2,412 16,130 Av. PE 53,084* 14,670 38,414 * Note that the average PE of 53,000 over the 10-month period analysed is somewhat higher than the full year average of 51,500

The industry PE is some 17,000 PE during weekdays, but less than 8,000 PE during weekends. The overall load to the plant is similar on weekdays and weekends, with an additional 500 PE on weekdays and a 700 PE reduction on weekends when compared to the average. This implies a ‘dormitory town’ phenomenon. This is the effect of weekday commuting to and from Dublin (and other centres), resulting in a reduction in the effective residential population of the Osberstown catchment equivalent to 10,500 PE. At weekends, there is a reduction in industrial PE to less than 8,000.

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The residential population reduction during weekdays combined with the industrial reduction at weekends results in a reduced average PE of 51,500.

There is also some evidence to suggest that the accepted figures of 60g BOD per head of population may be too high in this instance. Recent studies in mainland Europe have indicated residential population figures in the range 45-55g BOD per head of population. This would have implications both in terms of flow and load. A sewered residential population would still result in a certain volume of flow irrespective of a reduced load. Commercial premises have a certain water usage by the same residential population (e.g. toilet facilities), and a certain additional water usage (e.g. washings), which together with extraneous inputs in the sewer network result in a foul flow. The combination of a reduced residential load at full residential flows together with additional commercial flows could contribute to the relatively dilute foul influent measured at the treatment plant (together with extraneous inputs in the sewer network). In terms of figures, 45,500 residential population at 50g/head is equivalent to only 38,000 PE. Therefore, the potential total load of 60,500 PE would comprise 38,000 residential PE and 15,000 industrial PE, leaving an outstanding figure of 7,500 PE as commercial load. This figure is close to the 7000 to 9000 PE commercial figure estimated in Section 4.2.3.

4.2.6. Summary

• The average PE connected to the Osberstown WWTP over the period July 2000 to June 2001 is approximately 51,500.

• This comprised 45,500 population and commercial connection, and 15,000 large industrial/commercial, totalling 60,500 potential PE.

• The commercial component of the load can only be indirectly estimated due to the unfeasibility of direct measurement, and is thus estimated in the range 7,500 – 9,000 PE.

• The loads to the plant have been apportioned to allow implementation of the ‘polluter pays principle’ with a view towards both the operational costs of the Stage II and proposed Stage III plants and marginal capital costs of the Stage III plant.

• There is evidence to indicate that the ‘dormitory town’ phenomenon accounts for a significantly For inspection purposes only. reduced influent load duringConsent weekdays, of copyright equivalent owner required forto any23% other of use. the residential population.

• The difference between the calculated connection of 60,500 PE and the influent load measured of 51,500 PE is explained by the reduced weekday residential load and the reduced weekend industrial load.

• The flow and load to the WWTP varies considerably, with 20% of current loads above 70,000 PE, a 95-percentile load of 1.8 times the average load, and a maximum load of 2.5 times the average load. This will present some difficulties in design of an upgraded plant.

• The large industrial/commercial component of load accounts for a degree of the variation in flow and load at the plant.

• There are significant extraneous inputs to the sewer system, most likely from storm misconnection and groundwater infiltration.

• The current high influent flows will effectively limit the capacity of the current plant to below the 80,000 PE design figure, unless a programme of extraneous flow reduction in the sewer system is undertaken.

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4.3. FUTURE LOAD PROJECTIONS Table 4.7 overleaf is a summary of existing population, industrial and future development loads for the urban centres that are either currently connected to or likely to be connected to Osberstown (as considered at the time of writing).

The urban centres considered in this report are expected to comprise the vast majority of urban growth that is likely to be connected to Osberstown, and these urban centres coincide with the major transport corridors of the N7/M7 and N9/M9.

4.3.1. Occupancy rates, commercial loads, and future development densities Table 4.6 below shows the residential occupancy rates presented in the “Strategic Planning Guidelines for the Greater Dublin Area” (1999) for Kildare (hereafter referred to as “SPG”).

Table 4.6: Occupancy Rates in Kildare

Year Occupancy Rate (Persons Per House) 1991 3.71 1996 3.46 2001 3.25 2006 3.00 2011 2.73

For inspection purposes only. Consent of copyright owner required for any other use. Therefore the occupancy rate adopted in this report for existing residential units is 3.25 persons per house.

New residential development is assumed to connect at the occupancy rates shown in the above table. The timescale for connection is analysed in more detail in the following sections, but an occupancy rate of 2.7 has been adopted for the purposes of Table 3.6. A medium density of 27.5 units/Ha has been adopted for residential development. A standard figure of 53 PE/Ha has been adopted for light industrial development load. This could vary significantly according to actual industry type.

4.3.2. Imminent, proposed and particular connection loads This section covers the individual urban area and large individual developments in the catchment. The normal zoned and Planning Permissions (PP) connection is analysed in the following sections.

As outlined, the remainder of Athgarvan is to be connected in the coming months (218 PE). Caragh, the Curragh camp, and the Greater Curragh area are also proposed near-future connections (6201 PE). Of the large industrial developments in the catchment, the only likely large completion is Millennium Park in Naas (approximately 4,500 PE) over the coming 2 years, with the majority of industry uptake likely to be spread over the period 2001-2005.

The total estimated load from these imminent and proposed urban centres, and particular connection loads, is 10,712 PE. This does not include any existing significant industrial loads.

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Table 4.7 Existing and future population and development connecting to Osberstown WWTP Existing populations Existing Proximal Existing population New Development Industrial Zoned Loads Existing Population Existing Existing Population Existing Zoned Units Residential Population Residential Zoned Industrial Industrial Non-zoned Area residences Density population residences Density population Residential1 Density Units PP Density Population Industrial Density Population developments persons per persons per persons per house PE house Ha units/Ha units house Ha PE per Ha PE PE

Naas 5512 3.25 17914 8881 217 3.25 705 109 27.5 2998 953 2.7 8093 331 53 17543 Newbridge 4590 3.25 14918 3482 140 3.25 455 84 27.5 2310 1852 2.7 6237 50 53 2650 8500 Clane 1301 3.25 4228 2211 213 3.25 692 42 27.5 1155 355 2.7 3119 15 53 795 Sallins 737 3.25 2395 46 3.25 150 62.5 27.5 1719 438 2.7 4641 Kill 533 3.25 1732 96 36 3.25 117 34 27.5 935 163 2.7 2525 36 53 1908 1288 Kilcullen 497 3.25 1615 6 3.25 20 50 27.5 1375 813 2.7 3713 16 53 848 2 Johnstown 46 3.25 150 Naas 26 27.5 715 249 2.7 1931 12879 Prosperous 426 3.25 1385 92 3.25 299 30 27.5 825 95 2.7 2228

3 Walshestown 31 3.25 101 Newbridge 26 27.5 715 40 2.7 1931 6 Athgarvan 60 3.25 195 Subtotals 13733 44632 14670 750 2438 463.5 12746 4958 34415 448 23744 22667 Imminent Connections

6 Athgarvan 67 3.25 218 87 3.25 283 21 27.5 578 70 2.7 1559 Subtotals 67 218 87 283 21 578 70 1559 Proposed Connections

5 Caragh 43 3.25 140 400 400 2.7 1080

Greater Curragh 4,5 Area 425 3.25 1381 For inspection purposes only. Consent of copyright owner required for any other use.

Curragh Camp 4500 462 3.25 1500 Subtotals 468 6021 862 400 2580

Subtotals 14268 50871 14670 837 2720 485 14185 5428 38554 23744 22667

Total PE 153226

Notes: 1. Zoned new residential land as per 1996 development plan, less land already built on by September 1999 2. Johnstown non-connected existing residences are included in the Naas figure 3. Walshestown non-connected existing residences are included in the Newbridge figure 4. The "Greater Curragh Area" refers to the areas of Maddenstown, Brownstown, Cut Bush, and Suncroft 5. The units shown as zoned residential in Carragh are PP units, and units at the Curragh Camp are estimated, with both added to this column to give an correct total residential units

6. approximately half of Athgarvan is currently connected 7. The column "PP" (Planning Permissions) is a subset of the "Zoned Residential Units" figure 8. "Proximal Existing Population" referes to units close to the existing or proposed sewer systems that could be considered for connection

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4.3.3. Building capacity and timescale for development House completions in Kildare during the period 1996-1999 (inclusive) were 8,923 according to SPG data (2231 p.a.). This rate increased through the period, with a 1999 value of 2,419, and a three- quarters 2000 figure of 1,723, with an estimated total for the year of 2,500.

Approximately one third of the residential housing in Kildare County is presently connected to Osberstown WWTP. The estimated residential building resource that is likely to be devoted to this area of Kildare is approximately 40%, or 1000 units p.a. It is assumed that the Kildare County rate of 2500 or above can be maintained to 2006, and that slower growth will see a reduction in completions beyond this date.

There were 5,245 PP’s granted by June 2000. These would be expected to develop before 2006 (875 p.a.). There is an estimated zoning and PP total of 15,113 units of residential development. The timescale for development based on building capacity and completions is therefore 14 years at the above rate (year 2014).

The uptake of zoned industrial land is likely to be variable. Certain zoned and intended PP applications are discussed further in the following section. Other than these exceptions, industrial zoned land is assumed to develop over the same time-span as outlined above for residential development.

4.3.4. Future household and population estimates for Kildare county The SPG report details several scenarios for population growth in the greater Dublin area for the period 1996-2011. The SPG report presents figures for overall growth in Kildare, as well as three main strategic options summarised as follows:

1. Containment: confines a larger proportion of growth to an area close to existing built up Dublin (not including the Osberstown catchment) 2. Dublin and the North-East: considers a bias towards development in this area (again not including the Osberstown catchment) 3. Western Satellite Towns: considers the complete development of employment and services as well as residence in this area, particularly including the greater Naas-Newbridge-Kilcullen area. For inspection purposes only. The summary household and populationConsent of copyright data forowner these required optionsfor any other asuse. derived from the SPG data for

Kildare, are shown in Table 4.8.

Table 4.8 SPG future households and population estimates for Kildare

Scenario Households % Persons Population population increase per increase household 1996 recorded 39,041 - 3.46 134,992 - SPG 2001 44,079 13% 3.25 143,000 6% SPG 2006 50,223 29% 3.00 151,000 12% SPG 2011 57,741 48% 2.73 158,000 17%

Containment 2011 58,000 49% 2.60 151,000 12% Dublin & NE 2011 56,000 43% 2.60 147,000 9% Western Satellites 65,000 66% 2.60 169,000 26% 2011

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It may be noted that these figures are based on a natural increase plus high levels of in-migration to the greater Dublin area. The table clearly shows the concept of households increasing at a far greater rate than population, due to a reduction in pph. The total number of households by 2011 is estimated between 56,000 and 65,000 (1200 to 2000 units p.a.). To date, the SPG Review (April 2000) and anecdotal evidence suggests that the development of the greater Dublin area is spread through these three areas, with accelerated growth during the 1998-2006 period. The SPG review states that the 2011 population figures could be reached by 2006. The latest Kildare register of electors would indicate a population of approximately 150,000 to 157,000. This is based on 110,201 electors representing 70% to 75% of the population (1991 and 1996 proportions were 68% and 69%, respectively). The number of completions for the period 1996 to 2001 was approximately 11,000 houses. This would give a 2001 household figure of 50,000. The estimated population would therefore be 150,000 to 162,500 (at 3.00 to 3.25 pph). The current Kildare population adopted for this report is taken as 155,000 (50,000 households at 3.1 pph)

It is assumed that relatively rapid growth continues over the period to 2006, with a fall-off to 2011 and beyond. Given that current house completions are at least 2500 p.a., it is envisaged that this rate will average at least 2000 units p.a. to 2006, giving 60,000 households, but at a lesser pph of 2.73. The resultant 2006 population would be 164,000. The rate of house completion and population growth would then slow, with an estimated 67,500 households and 176,000 population (at 2.6 pph) by 2011. The period 2011-2021 are assumed to follow the decreasing growth rate, with interim figures estimated for 2016 of 72,500 households at 2.5 pph, giving 181,000 population, and 2021 figures of 77,500 households at 2.4 pph, giving 186,000 population.

The adopted figures are summarised in Table 4.9.

Table 4.9 Revised future households and population estimates for Kildare

Year Households % Persons per Population population increase household increase SPG 2001 50,000 - 3.1 155,000 - SPG 2006 60,000 20% 2.73 164,000 6% SPG 2011 67,500 35% 2.6 176,000 14% SPG 2016 72,500 45% 2.5 181,000 17% SPG 2021 77,500 55% 2.4 186,000 20%

For inspection purposes only. These figures for Kildare as a wholeConsent will of copyrightbe used owner as required a context for any other in use. which development connected to

Osberstown will be estimated.

4.3.5. Non-connected existing population and non-zoned developments Table 4.7 outlines over 2,700 non-connected population. This refers to population that is proximal to either the existing network or zoned area in the Osberstown catchment. The methodology used was simplified, taking in areas with relatively high densities of houses that are located alongside or proximal to existing or zoned areas. Whether this population is actually connected or not will depend on the policy adopted. Should this type of connection be allowed, then the timescale would be expected to coincide with the overall development in the catchment discussed in the previous section.

Table 4.7 also outlines almost 23,000 PE of potential development that is not currently zoned or has PP. These are potential developments that are known to the council, but PP has not yet been sought. The timescale for connection (if any) would be at least the period outlined in Section 4.3.6, if not longer.

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4.3.6. Osberstown zoned/PP development and timescale Table 4.7 lists 14,185 zoned residential units, of which 5428 have PP. The PP development would be expected to be built before 2006 (at 1100 units p.a.). The remaining zoned units would be spread over at least the period to 2014 (according to completion rates). It may be noted that this is a relatively long period for development, particularly as the development plans relate to 1996-2000, and would normally be expected to function over a 5-7 year period.

Industrial development would be assumed to follow in tandem with residential growth (or vice-versa), with an estimated 23,744 PE zoned. Millennium Park with an estimated 4500 PE would be expected to have developed fully before 2006. The remainder of the development is assumed to be spread over 14 years, at 1,400 PE p.a., although again it is notable that the actual PE and rate of development is likely to be highly variable.

4.3.7. Summary of population loads for the period to 2021 and timescale to reach the capacity of the current and upgraded WWTP Given the maximum capacity at the current plant is 80,000 PE and the current connected load is 60,500 PE, there remains a theoretical 19,500 PE of available capacity. Table 3.7 shows total current, zoned, and potential future connections to Osberstown of over 150,000 PE, of which 113,169 is current, zoned, or PP. The proposed capacity at Osberstown for an upgraded plant is 130,000 PE.

Imminent, proposed, and particular connections are estimated at 11,500 PE (including allowances for industry and commercial), over the next five years. There is no evidence to suggest accelerated connection.

Two scenarios are presented for timescale of development in the Osberstown catchment. The first is based on the future development and population estimates for Kildare presented in Section 4.3.4. The second scenario predicts much higher growth, assuming that development proceeds at just in excess of the current building completion rate until 2006, completing all current PP’s during that period, It is then assumed that there is a fall-off back to growth based on Kildare household and population estimates.

Table 4.10 summarises the estimated residential and industrial populations or PE connected to Osberstown for the period 2001 to 2021. Figure 3.1 overleaf graphs the total PE connected to Osberstown during this period. These figures For inspection do not purposes include only. any ‘non-connected existing population’ or non-zoned development. Consent of copyright owner required for any other use.

Table 4.10 Projected Osberstown loads for the period 2001 to 2021 Year 2001 2006 2011 2016 2021 Households - low 14483 24866 27974 30044 32118 Households - high 14983 26650 29981 32200 34421 Persons per house - low 3.10 2.73 2.60 2.50 2.40 Population - low 44897 67884 72733 75111 77082 Population - high 46447 72754 77951 80499 82611 Population PE - low 37414 56570 60611 62592 64235 Population PE - high 38706 60628 64959 67082 68842 Commercial - low 7483 11314 12122 12519 12847 Commercial - high 7741 12126 12992 13417 13769 Industrial - low 14670 19670 24670 29670 34670 Industrial - high 14670 24170 33670 43170 52670

Total PE - low 59567 87554 97403 104781 111752 Total PE - high 61117 96924 111621 123669 135281

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Figure 4.1 Projected Osberstown loads for the period 2001 - 2021

140000 130000 Total PE - low 120000 Total PE - high 110000 100000

PE 90000 80000 70000 60000 50000 2001 2006 2011 2016 2021 year

Therefore, the current (80,000 PE) plant is likely reach capacity between 2003 and 2005. This will also be affected by the high influent flows discussed in Section 4 of this report. A programme of extraneous flow reduction in the sewer system should be implemented to ensure that the full capacity of the Stage II plant can be achieved, otherwise the timescale to reach capacity will certainly be closer to 2003.

The proposed upgraded plant (130,000 PE) is estimated to reach capacity in 2018 at the earliest. Again, this assumed that a programme of extraneous flow reduction in the sewer system is implemented to ensure efficient use of the proposed plant.

It must be noted that there is a significant difference between the high and low estimates, due particularly to the range of growth to 2006. This is related to the amount of proposed connection of existing population and the amount of PPFor inspection likely purposes to be only. completed over the period, but also to the Consent of copyright owner required for any other use. difference in SPG derived population growth, versus the building capacity in the catchment. The highest SPG estimate for Kildare has an average of little over 1700 households p.a. to 2011. The building industry is capable of completing in excess of 2500 units p.a., with some estimates bringing this figure closer to 3000 units p.a. by 2002. This has particular implications for the rate of development in high growth areas such as the Osberstown catchment.

It may also be noted that it is assumed that the current load to the plant is approximately 60,000 PE, and not the measured average influent load of 51,500 PE. The current and possible future effect of the ‘dormitory town’ phenomenon discussed in Section 4.2.5, which could result in a reduced load, is ignored due to the adverse effect of high influent flows on plant operation. Therefore it is considered conservative to assume that both current and future loads will exhibit a degree of both ‘dormitory town’ and high flows effects, and that these will effectively cancel each other out, even allowing for the proposed programme of flow reductions.

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4.4. SUMMARY

1. There is a current average influent load of 51,500 PE, out of a total of 60,500 PE connected to the plant. The difference in these actual and potential figures is explained by the weekday commuting of residential population to Dublin and other work-centres, and significant variation in the industrial weekday-weekend load.

2. There is significant variation in the daily loads connected to the plant, with approximately 20% of daily loads below 30,000 PE, and 20% of daily loads above 70,000 PE. The 95-percentile and maximum loads during the past year were 1.8 and 2.5 times the average load, respectively. The design of a future extension to the WWTP will have to allow for these variations.

3. The analysis of sectoral loads concludes that there is current connection of 45,500 residential population, equivalent to approximately 38,000 PE (at 50g BOD per head), 15,000 PE large industrial-commercial, and 7,500 PE commercial connection.

4. There are significant extraneous inputs to the sewer system, most likely from storm misconnection and groundwater infiltration. A programme of extraneous flow reduction in the sewer system is essential and fundamental to ensuring that the full capacity of both the current and an upgraded plant can be realised. Failure to achieve this element will compromise the capacity of the current plant to below the 80,000 PE design figure, and the proposed upgraded plant to well below the 130,000 PE target.

5. The current plant is projected to reach capacity between 2003 and 2005. The proposed flow reduction programme should be implemented to ensure that the full capacity of this Stage II plant can be achieved, otherwise the timescale to reach capacity will certainly be closer to 2003.

6. The proposed upgraded plant (Stage III) is projected to reach capacity in 2018 at the earliest. Again, this is provisional on the proposed flow reduction programme.

7. The timescales for development in the Upper Liffey Valley catchment presented in this text are based on both the “Strategic Planning Guidelines” and building capacity. The projected growth to 2021 is in the range 112,000 PE to 135,000 PE. The range presented represents a For inspection purposes only. reasonable low and high envelope.Consent of copyright It may owner be required noted for that any other the use. building capacity in the catchment is subject to a fair degree of uncertainty given the multitude of driving forces behind this aspect.

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5. ASSESSMENT OF WASTEWATER TREATMENT PLANT

The Osberstown Wastewater Treatment Works was first developed in the 1970s in conjunction with a regional drainage scheme serving the towns of Naas, Newbridge, Sallins, Clane, Kill and Johnstown in mid Kildare. A biofilter and conventional aeration treatment works was constructed at Osberstown with a capacity of 40,000 population equivalents (PE).

By the early 1990s, this plant had become significantly overloaded, with flows and loads indicating a population equivalent of approximately 50,000, and adverse impacts were identified in the River Liffey in terms of organic pollution and nutrient enrichment. Combined with elevated background levels of nutrients, this has given rise to water quality problems in the river affecting a variety of beneficial uses including fisheries and the major water works abstraction at Leixlip operated by Fingal County Council.

A new plant at Osberstown expands the current capacity to 80,000 PE and also achieves a higher quality effluent discharge. Nitrogen and phosphorous reduction measures are included in the new plant. The commissioning of this upgraded treatment plant was completed in October 2001.

The ‘Load Assessment and Categorisation’ section (4) carried out as part of this project presents an assessment of the future load to the plant due to large regional development and the connection of more catchment areas to the Osberstown WWTP during Phase 2 construction treatment plant. This study For inspection purposes only. Consent of copyright owner required for any other use. suggests that the capacity of the upgraded treatment plant may be reached as early as year 2003.

This section evaluates the options for extending the capacity to 130,000 PE including an upgrading to allow for more extensive phosphorous removal, as proposed in the “Receiving Water Study”. The extension will allow for continued growth in County Kildare for an expected period of more than 15 years.

In this section of this study the proper design load and effluent requirements for an extended WWTP are established. The operation of the present wastewater treatment plant is evaluated the to establish the expected capacity and to find possibilities for optimisation of units to increase the existing capacity. The relevant wastewater and sludge treatment technologies for the extension of the wastewater treatment plant are presented. Furthermore, four different options for extending the treatment plant are presented including design, costs and implications for the existing site. Finally, the conclusion and a recommendation for the future strategy are presented.

The commissioning of the existing wastewater treatment plant had not been finalised at the time of writing of this section (August 2001) and as the future extension of the plant is expected to be procured under the PPP model the evaluation of capacity and calculations of this report shall be regarded as subject to some uncertainty.

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EPA Export 26-07-2013:00:24:08 Osberstown WWTP Preliminary Report Vol 1 Rev F Upper Liffey Valley Sewerage Scheme Preliminary Report – Volume 1 Extension to Osberstown WWTP - Stage 3

5.1. EVALUATION OF LOADS

5.1.1. Measurements July 2000 to June 2001 Based on daily measurements the monthly average flow and concentration have been calculated and are presented in Table 5.1

Table 5.1 Composition of influent - monthly averages July 2000-June 2001 Composition of Influent 2000-2001 m3/day 85% mg/l mg/l mg/l mg/l mg/l mg/l mg/l

Flow Percenti BOD COD SS Total N NH3 Total P PO4-P le jul-00 11,953 12,504 323 723 210 44 43 13.3 8.5 aug-00 12,913 14,177 235 503 233 36 34 5.5 5.5 sep-00 14,856 17,995 257 494 307 37 31 5.7 5.2 oct-00 18,519 22,179 155 367 199 41 28 4.3 5.2 nov-00 25,303 30,653 188 397 240 30 20 3.6 3.9 dec-00 24,616 30,284 121 337 210 28 22 3.6 3.6 jan-01 19,066 21,234 126 267 234 24 24 5.1 4.2 feb-01 19,888 22,026 104 248 227 24 26 6.3 4.6 mar-01 16,923 17,592 128 281 205 30 27 8.0 5.2 apr-01 18,405 21,906 145 324 180 31 24 7.9 4.7 may-01 17,142 18,335 219 379 320 36 32 9.6 5.8 jun-01 16,275 18,878 281 443 316 32 31 8.9 5.2

Average 17,988 20,647 190 397 240 33 29 6.8 5.1 For inspection purposes only. Consent of copyright owner required for any other use. Notes: (1) Measurements of concentrations have been disregarded on days when the influent flow was higher than 24,000 m3/d (until 06-12-2000) or on days with return of storm water to screens. Please refer to section 5.2.2.

(2) For several months the PO4-P-concentration is higher than the total-P concentration. The reason for this is unclear, but it is probably due to analysing errors.

The flow figures above are an average of all days and the 85% percentile shows the percentile for each month. The 85% percentile for all recordings is approx. 23,000 m3/day. A point to note about the flow measurements is that they are made before the grit chamber and the stormwater overflow outtake. This means that on days of heavy rain a part of the stormwater might be included twice, i.e. both as incoming flow and as return flow from the stormwater tanks.

Influent measurements of pollutants are made after the screen and therefore before the outtake for storm water and after the return of storm water. Please refer to section 5.2.2 regarding the appropriateness of the present flow-measuring regime. The concentrations in Table 5.1 are calculated as simple averages of recordings each month.

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5.1.2. Loads July 2000 to June 2001 The influent loads to the wastewater treatment plant for the period July 2000 to June 2001 are presented in Table 5.2.

Table 5.2 Pollution load - monthly averages (July 2000 to June 2001) Loads

2000-2001 Flow BOD COD SS Total N NH3 Total P PO4 kg/day kg/day kg/day kg/day kg/day kg/day kg/day jul-00 11,953 3,925 8,753 2,563 520 519 161 102 aug-00 12,913 3,117 6,693 3,108 476 454 73 76 sep-00 14,856 3,796 7,272 4,422 531 446 82 77 oct-00 18,519 2,827 6,941 3,661 738 508 77 96 nov-00 25,303 4,639 9,696 5,645 737 474 85 93 dec-00 24,616 3,254 7,924 4,885 659 516 85 89 jan-01 19,066 2,308 5,002 4,298 466 453 96 80 feb-01 19,888 2,075 4,866 4,529 477 515 124 92 mar-01 16,923 2,202 4,764 3,475 506 460 135 91 apr-01 18,405 2,563 5,071 3,295 568 442 146 86 may-01 17,142 3,730 6,431 5,423 612 540 163 99 jun-01 16,275 4,530 7,089 5,149 505 495 142 81

Calculations Average 17,988 3,247 6,709 4,204 566 485 114 89 St. dev. 884 1,594 983 98 34 34 9 For inspection purposes only. Consent of copyright owner required for any other use. St. dev. % 27 24 23 17 7 30 10

p.e. Av. 54,117

Per P.e. 0.33 0.060 (1) 0.124 0.078 0.010 0.002 Ratio to BOD 1 0.48 0.77 5.7 28 Notes: (1) Actual measurements of BOD-loads per person equivalents for instance conducted by the Danish EPA have shown that typically values are 45-55 g BOD/person/day. This means that the actual numbers of persons connected to the system typically are higher than calculated from the standard value of 60 g BOD/p.e./day.

Average monthly loads have been calculated by finding the daily load using the recordings of flow and concentration for each day and thereafter finding the average load of the month.

It can be seen that the average flow (including rain) per p.e. is rather high – 0.33 m3/day compared to a normal of less than 0.2. The sewerage system is primarily a separate system, and the relatively low concentrations of pollutants could indicate infiltration of ground water or misconnections.

Actions toward a lowering of the hydraulic loads are being proposed as part of this project, and therefore the hydraulic load for the future Stage 3 is not expected to increase as much as the pollutants load.

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5.1.3. Design load compared to actual load Actual loads and design loads are compared in Table 5.3.

Table 5.3 Comparison of actual and design load Influent

Load Design load Concentrations Actual Present Phase 2 Phase 3 Actual Design Total Total Total Average Average kg/day kg/day kg/day mg/l mg/l BOD 3,247 4,800 7,800 190 240 COD 6,709 13,060 21,223 397 653

SS 4,204 6,080 9,880 240 304 Kjeldahl N 566 960 1,560 33 48 Total-P 114 208 338 6.8 10

Load (PE) 54,117 80,000 130,000

The column Phase 3 presents the loads at the proposed 130,000 PE.

The completed wastewater treatment plant, currently undergoing commissioning, has been designed to fulfil the requirements of Phase 2. However, it can be seen that for the load parameters listed above the monthly averages have not reached the design load (Phase 2).

5.1.4. Hydraulic design load compared to actual The flow measurements indicate an average flow of 17,988 m3/day. The highest monthly flow of 25,300 m3/d occurred in November 2000, with a 95-percentile calculated at 39,200 m3/day or 1,630 m3/h.

For inspection purposes only. The hydraulic design load from theConsent tender of copyrightis presented owner required in Table for any other5.4 use.below. The column “Phase 3” has been calculated based on a load of 130,000 PE, with DWF calculated presuming all further connection is limited to 170 litres-per-head-per-day (l/h/d) and a maximum flow of 225 l/h/d. PWWF is calculated as 2.5 times DWF using the same criteria as for Phase 1 and 2.

Table 5.4 Hydraulic design load Hydraulic design load

Present Phase 2 Phase 3

Flow, DWF m3/day 20,000 28,500

Flow, PWWF, day m3/hour 3,700 6,013

Flow, PWWF (treatment) (1) m3/hour 2,083 3,385 Notes: (1) Flows in excess of these figures will be directed to the storm water tanks. Evaluation and recommendation of the total size of storm water tanks will be described in the foul/combined sewer network study report.

The average influent flow has been high and is close to the design DWF for Phase 2 and higher in the months of November and December. With a present average flow of approx. 18,000 m3/day the hydraulic load has reached or is close to the design hydraulic load of 20,000 m3/day.

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5.2. EVALUATION OF PRESENT WWTP

5.2.1. Overview of WWTP The units of the existing wastewater treatment plant are illustrated on the process diagram overleaf and the individual units are listed in Table 5.5 below.

Table 5.5 Unit Processes Wastewater treatment facilities Sludge treatment facilities

Inlet pumping station Collection and homogenisation tanks Screens and screenings classifier Drum thickeners Grit chambers and grit classifier Storage/loading tank before digesters Primary clarifiers Digesters Intermediate pumping station and distribution Gas storage tank chamber Gas Engines (CHPs) Sequencing batch reactors (CASS tanks) Gas/oil boilers Blowers Digested sludge storage tanks Return sludge pumps Belt filter presses Chemical dosing and storage Storm water overflow system Storm water tanks Storm return pumps

Key figures for wastewater treatment facilities are presented in Table 5.6 and for sludge treatment facilities in Table 5.7.

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Existing process diagram for CASS process Screens (2) Grit- Primary clarifier (2) Distribution CASS Basins (4) chambers (2) Zone 1 Zone 2 Zone 3

Inlet Outlet to river Liffey

Screenings- Grit classifier (1) Air Classifier (1) Reject Biological return sludge/Recirculation

Storm water reject Primary Floating sludge Biological excess sludge Storm tank (2) sludge Overflow Homogenisation tank (2)

Imported sludge Polymer Drumthickener (2) Digester (2) Degasifier (2) Beltfilter press (2) Sludge transport

Polymer Biogas

Reject water Heat exchanger (2)

For inspection purposes only. Reject water Consent of copyright owner required for any other use. Symbols Gas engine - CHP (2) Flowmeter Boiler (2) Pump Gas storage (1)

Blower

Osberstown Wastewater treatment plant, Ireland P-053577-A

COWI A/S Process diagram Parallelvej 15 Existing process DK-2800 Lyngby Eng. Check Date Doc STCODA 03-05-01 See footer

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Table 5.6 Dimension and capacities - Wastewater Treatment Inlet pumping station Pumps Nos. 4 Capacity, total m3/h 3,700 Screens Units Nos. 2 Bar spacing mm 6 Capacity, total m3/h 7,402 Screenings classifier Units Nos. 1 Grit chambers Units Nos. 2 Volume, total m3 52 Retention time, min min 3 Grit classifier Units Nos. 1 Primary clarifiers Units Nos. 2 Diameter, each m 24 Volume, total m3 3,620 Intermediate pumping station Pumps Nos. 3 Capacity, total m3/h 2,083 CASS tanks Units Nos. 4 Volume, max m3 20,000 F/M-ratio (Present load) kg BOD/kg SS*day 0.04 Blowers For inspection purposes only. Consent of copyright owner required for any other use. Units Nos. 7 Capacity, total N m3/h N/A Return sludge pumps Pumps Nos. 4 Capacity, total m3/h N/A Chemical storage Units Nos. 1 Volume, total m3 36 Chemical dosing pumps Pumps Nos. 4 Capacity, per pump m3/h 2.5 Storm water tanks Units Nos. 2 Diameter m 28 Height m 2 Volume, total m3 2,463

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Table 5.7 Dimension and capacities - Sludge Treatment Collection and homogenisation tanks Units Nos. 2 Volume, total m3 520 Drum thickeners Units Nos. 2 Capacity, total kg DS/hour 2,220 Dry solids after dewatering %DS 6.8 Polymer consumption kg/tDS 2.6 Loading tank Units Nos. 1 Volume m3 2.5 Sludge digesters Units Nos. 2 Volume, total m3 2,634 Gas storage tank Units Nos. 1 Storage volume, max. m3 500 CHP Units Nos. 2 Capacity per unit, elec. output kW 84 Capacity per unit, water output kW 120 Boilers Units Nos. 2 Capacity, per unit kW 160 Digested sludge storage Units Nos. 2 Volume, total m3 1,840 For inspection purposes only. Belt filter presses Consent of copyright owner required for any other use.

Units Nos. 2 Capacity, total kg DS/hour 1,110 Dry solids after dewatering %DS 20 Polymer consumption kg/tDS 6.4

In the following sections the individual units are briefly described and their present operation is evaluated.

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5.2.2. Influent Measurement at the treatment plant The current monitoring system combined with the variations in flow and load at the wastewater treatment plant has given some difficulties in assessing the influent characteristics. The system of sampling and flow metering at the wastewater treatment plant has been reviewed and options for improvement are planned. A short description of possible optimisations is presented below.

Influent measuring At present it is not possible to establish a direct measurement of the influent flows to the treatment plant as the measurement is performed after the return of storm water.

In the ‘Load Assessment and Categorisation’ report it was decided to disregard some monitoring results due to problems of influent measurements, namely:

• Until the 6th December 2000 the pollutant concentration of the influent could not be measured for flows higher than 24,000 m3/d and in the analyses of the influent loads it was decided to disregard measurements on those days.

• On days with return of storm water the sampling results are not valid as they contain a mixture of influent and storm return. Therefore it was decided to disregard measurements on those days.

The present location of the influent measurement can give important information of the actual loading of the subsequent treatment units. There are plans to monitor the influent in the vicinity of the inlet pumping station, thereby establishing a better determination of the influent flow to the wastewater treatment plant. Measurements should be made proportional to flow.

Effluent measuring In a wastewater treatment plant based on SBR technology special attention should be given to the effluent measuring, as the flows are uneven in time.

At present the effluent measuring is established based on 1 litre samples taken each hour and mixed prior to analysis. This corresponds with the SBR process in which one of the four tanks has controlled discharge for each hour, and has the advantage of allowing investigation of tank effluent characteristics (and thus performance) if required. However, if the correct effluent concentrations and loading are to be established this system should be changed to ensure that concentrations occurring For inspection purposes only. during time of high flow are weighted.Consent of Incopyright the owner current required system for any other concentrations use. measured during low influent flows (e.g. at night time) are averaged with high flows during mid-day. Therefore, the measuring should either be changed to flow proportional or the outlet flow should be adequately logged. No measuring is currently performed in the outlet, however it could be calculated indirectly based on information from the level meters in the CASS tanks or a flow meter on the common outlet pipe could be installed.

5.2.3. Evaluation of overall performance A previous study has evaluated the performance of the present wastewater treatment plant in relation to the influent wastewater characteristics and the possibility for inhibition. The investigation gave some possible reasons for the difficulties in performance of the treatment plant.

To supplement that investigation an evaluation of the overall performance of the present plant is presented hereunder and guidelines to future optimisation for the fulfilment of the process guarantee are given. It should be noticed that the treatment efficiency has been highly variable during the commissioning period to date (July 2000 to June 2001). In order to have a more reliable evaluation it should be performed following a running-in period, as the WWTP has not as yet been working optimally. Treatment efficiency for the test period July 2000 – March 2001 is shown in Figure 5.1.

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Table 5.8 Evaluation of present capacity of existing treatment plant

Hydraulic load Flow, av. month 17,988 m3/day Flow, max day 32,880 m3/day Flow, max hour 2,055 m3/hour

Present operation of plant Influent Effluent Requirements Average 95-perc.* Phase 2 kg/day mg/l mg/l reduction mg/l mg/l BOD 3,247 190 8 96% 20 15* COD 6,709 397 27 93% 45 125 SS 4,204 240 53 78% 217 35* Total N 566 33 11 67% 19 25 Total-P 114 6.8 3 56% 7 0.9* Load 54,117 p.e. * 95% Percentile for measurements from October (Following running-in).

Treatment efficiencies

100%

90%

80%

70% For inspection purposes only. Consent of copyright owner required for any other use.

60%

50%

40% BOD COD 30% SS Total N 20% NH3 Total P 10% PO4(-3)

0% Jul-00 Aug-00 Sep-00 Oct-00 Nov-00 Dec-00 Jan-01 Feb-01 Mar-01 Month

Figure 5.1 Treatment efficiencies from July 00 to March 01

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5.2.4. Evaluation of possible spare capacity It is assumed that after final commissioning and optimisation of the existing wastewater treatment plant, the plant will be able to fulfil the requirements stated in the process guarantee. In Table 5.9 below it is evaluated if the treatment plant could be expected to have a higher capacity than assumed in the process guarantee, for evaluation of the need for extension.

Table 5.9 Evaluation of spare capacity of existing treatment plant Design Load 1) Influent Unit Present load Spare Phase 2 Flow m3/day 20,000 17,988 10% 2,012 BOD kg/day 4,800 3,247 32% 1,553 COD kg/day 13,060 6,709 49% 6,351 SS kg/day 6,080 4,204 31% 1,876 Total N kg/day 960 566 41% 394 Total-P kg/day 208 114 45% 94 Load (PE) p.e. 80,000 54,117 32% 25,883 1) Theoretical spare capacity when compared to the actual lower load measured July-March.

With regards to the influent flows the wastewater treatment plant is very close to its capacity, whereas it can be seen from the above table that the WWTP should at present have a spare capacity for organic pollution (actual load compared to design load) of approx. 32%. As outlined, the ability of the treatment plant to fulfil the process requirements remains yet to be proven, and even at this low loading there have been difficulties in fulfilling the effluent requirements. Taking the present capacity of the plant into consideration, it is expected that the requirements for Phase 2 will be fulfilled eventually. It should not, however, be expected that the treatment plant will have any spare capacity beyond the requirements for Phase 2 following commissioning. This means that with the present relatively low pollution concentrations, the capacity will be defined by the hydraulic load as the limiting parameter with a DWF of 20,000 m3/d, but only a pollution load of approximately 65,000 PE.

For inspection purposes only. 5.2.5. Need for extension Consent of copyright owner required for any other use.

Based on the evaluation in the previous sections the following main conclusions can be made:

1. Commissioning of the existing treatment plant must be completed with a proof of fulfilment of the process guarantee.

2. Following the commissioning additional possibilities for optimisation of the treatment plant can be evaluated.

3. The entire treatment plant shall be extended to treat the increasing hydraulic load increasing from the present DWF capacity of 20,000 m3/d to 28,500 m3/d. Depending on the change of concentration of pollutants in the raw wastewater, this will mean an increase from 65,000 PE to a future of 130,000 PE.

4. To full-fill the stricter treatment requirements for phosphorous as required in the Phosphorus Regulation, 1998, the existing treatment plant and the extension shall be upgraded.

5. Assuming the present CASS biological treatment units fulfil the process guarantee, the extension of the biological treatment can be achieved by building a parallel line to the existing CASS tanks. The additional phosphorous removal should be performed in a subsequent polishing step. The design of the new parallel line can be based on the load as stated in Table 5.10. The need for extension of the existing units of primary treatment for which the main design parameter is the hydraulic load, is evaluated in the next section.

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Table 5.10 Design load for treatment plant in parallel to CASS Phase 2 Phase 3 Total Total Extension* m3/d m3/d m3/d DWF 20,000 28,500 8,500 kg/day kg/day kg/day BOD 4,800 7,800 3,000 COD 13,060 21,223 8,163 SS 6,080 9,880 3,800 Kjeldahl N 960 1,560 600 Total-P 208 338 130 Load (PE) 80,000 130,000 50,000 *Design load for new treatment plant in parallel to existing CASS

The load to the new treatment plant depends on the present influent concentration increasing to the design concentration – by means of: changes in the sewer network, by reducing household water consumption or by reducing infiltration to the sewer system. In the event that these changes cannot be effectively achieved, the upgrading of the plant should consider an increase in hydraulic design load.

5.3. EVALUATION OF WWTP UNIT OPERATION AND NEED FOR EXTENSION

5.3.1. Inlet Pumping Station Evaluation of Present Situation The full peak wet weather flow is currently being pumped to the screens. The inlet pumping is functioning satisfactorily. Arguments could be made that a measurement at the inlet pumping station of load parameters (prior to the mixing with returned storm water) would make overall evaluation of the efficiency of the treatment plant easier.

For inspection purposes only. Options for extension Consent of copyright owner required for any other use. The requirements for extension of pumping is assessed below:

Present Situation Phase 3 Situation 3 3 m /h m /h Inlet pumping station 3,700 6,000 Intermediate pumping station 2,083 2,083

During the design of the existing plant under the DB contract it was decided for economical reasons to construct the CASS tanks at ground level to avoid constructing beneath the ground water level. This has resulted in a large loss of head at several locations at the plant. In the extension of the plant it is not considered necessary to include a new intermediate pumping station (subject to detailed design). This means that a considerable amount of energy can be saved.

5.3.2. Screens Evaluation of Present Situation The bar spacing of the two installed screens is 6 mm and according to information from the operators the screens are operating well except from minor details regarding the removal of screenings. The Screens of 3-20 mm are normal and the size primarily depends on the sensitivity of the subsequent units and equipment.

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Options for extension The design capacity of the current installed screens was made based on a requirement of full capacity during PWWF even if one screen was out of operation.

In the consultants opinion the above requirement, for the extension of the plant, could be modified to a requirement of treating the PDWF if one screen is out of operation and the full capacity only when both screens are operating. This design will then require the inlet pumps to reduce pumping if one screen is out of operation and the full capacity of one screen is reached. In this exceptional case the excess storm water flow will flow by the emergency overflow channel in the inlet pumping station to the storm water overflow tanks – as they would have after the grit chambers in all circumstances.

Present Phase 3

Situation Situation Nos. 2 2 Size 6 mm 6 mm Capacity 7,402 m3/h 7,402 m3/h

One screen in operation has a capacity of approx. 3,700 m3/hour, which should be compared to an average hydraulic load to the extended plant of approx. 1,200 m3/hour, a peak dry weather flow of approx. 2,400 m3/hour and a peak wet weather flow of approx. 6,000 m3/hour.

5.3.3. Grit Chambers Evaluation of Present Situation Wastewater gravitates through the grit chamber. After the grit chamber the flow is divided: Up to approx. 2,000 m3/h gravitates through a flow meter and then to the primary clarifiers, excess flow is directed to the storm water tanks.

An efficient removal of grit from the raw wastewater prevents settling of grit in subsequent treatment steps (activated sludge tanks, digesters etc.) and reduces the wear of mechanical equipment. Various designs of grit removal exist, the better units ensure efficient removal of grit with little organic matter content.

The grit chambers are of the Vortex type, Forwhich inspection provide purposes a only. simple degritting of the raw wastewater, with no possibility of adjusting the efficiencyConsent ofof copyright the unit. owner requiredThe operation for any other use. of the grit chamber is considered satisfactory. However, there are no measurements of the grit content of the primary sludge. It is recommended that such an evaluation be made to ensure problems of grit settling in the digesters does not arise at a later stage.

Options for extension The requirements for extension of piping and grit chambers is assessed below:

Present Situation Phase 3 Situation Before grit chamber 3,700 m3/h 6,013 m3/h After grit chamber 2,083 m3/h 3,385 m3/h Nos. of chambers 2 3 Volume (each) 52 m3 52 m3

5.3.4. Primary clarifiers Evaluation of Present Situation Organic matter in the form of suspended solids may be removed prior to the biological treatment of the raw wastewater. The advantages of removing the solids prior to biological treatment include a reduction of energy consumption, the option for energy recovery in the digester, and a reduction of the

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The existing primary clarifiers seem to be operating well and the efficiencies as shown in Table 5.11 below are within the range which the consultant would normally expect for this type of treatment plant.

Grease is usually removed from the raw wastewater for hygienic reasons and to reduce the risk of poor settleability of the subsequent treatment step. A grease chamber performs the typical removal of grease, but grease together with floating sludge may also, as in Osberstown WWTP, be removed from a primary clarifier.

In the absence of a grease chamber the pre-dewatering of the floating sludge prior to pumping to the digesters may, in the consultants experience, result in problems of clogging of the filter cloth at the pre-dewaterer or other places, which has actually been experienced at the existing plant. The best solution for this problem will, of course, be to establish grease chambers. If no major problems occur, it can also be solved by mixing of grease taken from the surface of the primary clarifiers and hot sludge from the digesters before it is pumped directly to the digesters.

Table 5.11 Evaluation of primary sedimentation Present operation of plant

Influent After Primary Flow, av. month 17,988 m3/day Flow, max day 32,880 m3/day Flow, max hour 2,055 m3/hour kg/day mg/l kg/day mg/l Efficiency BOD 3,075 164.2 2,002 115.6 35% COD 8,598 459.1 5,512 295.0 36% SS 3,999 213.6 1,675 87.1 58%

Total N 525 28.0 For inspection 540 purposes 29.2 only. -3% Consent of copyright owner required for any other use. Total-P 148 7.9 95 5.3 36%

Options for extension The requirements for extension of the primary clarifiers is assessed below:

Primary clarifiers Present Situation Phase 3 Situation Nos. 2 3 Diameter 24 m 24 m Height 4 m 4 m Capacity PWWF 2,083 m3/h 3,385 m3/h

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5.3.5. CASS tanks General description of CASS process The CASS process has several references world-wide, and includes some advantages in the design compared to normal SBR processes. However some features of the process could cause the treatment to be less than optimal and these are discussed hereunder.

The process of the CASS tanks is not a conventional SBR tank as it includes a recirculation flow to a selector plug-flow compartment.

The influent wastewater is mixed with return sludge flow (RAS = 0.2 *Qinlet) and led through a plug-flow tank section with no aeration. This tank section, designated Zone 1, is meant to work as a selector/bio-P tank and thereby improve the settleability of the sludge and improve the biological phosphorus removal.

The mixed liquid flows from Zone 1 to the next tank compartment, designated “Zone 2”, where aeration and settling takes place. From Zone 2 the liquid flows to the actual SBR tank compartment, designated “Zone 3”, where sequences of “aeration”, “settling”, “draw”, and “idle” are carried out. Return of activated sludge from "Zone 3" to "Zone 1" is performed during all cycles of the CASS tank operation.

No mechanical mixers are installed in the tanks in the CASS system.

Brief evaluation of CASS process at Osberstown WWTP From the overall performance as described in Section 5.2.3 it can be seen that the present CASS system does not seem to be working well, as the suspended solids and the phosphorous concentration in the effluent is too high.

The high concentration of suspended solids may be due to poor sludge settleability and/or due to poor operation of the decanter system. High concentration of phosphorous has occurred in spite of periods with high dosing of precipitant and it is understood that the contractor has concluded that the biological phosphorous removal has not been working at all. Possible reasons for the lack of a biological phosphorous removal can be found in the following section. Furthermore a high concentration of suspended solids will normally give a raised phosphorous content in the effluent.

Phosphorous removal For inspection purposes only. In the CASS system some features,Consent asof copyright described owner required below, for any seem other use. to have adverse effects on the selection of phosphorous accumulating bacteria and thereby reduce the efficiency of biological phosphorous removal. When the biological phosphorous removal is not working properly it is necessary to dose more chemicals and thereby increase the running costs of the plant.

Conventional design of the anaerobic tank includes a mix of return activated sludge and influent wastewater to a MLSS concentration close to the one in the process tank. Conventional RAS flow is 0.5-1.5*Qinlet compared to 0.2*Qinlet in the CASS and in conventional activated sludge treatment plants the sludge concentration is approximately 10 kg/m3 in RAS compared to approximately 3.5 kg/m3 in the CASS system. This results in relatively low MLSS concentration in Zone 1.

The volume of the anaerobic tank in conventional wastewater treatment plants provides an approximate hydraulic retention time of 1.5 hours during average inlet flow, whereas CASS is designed for only 0.7 hours.

In conventional design for biological P removal the oxygen concentration in the RAS is relatively low due to the retention in the clarifier. Furthermore an additional pre-denitrification tank is often installed to eliminate nitrate in the RAS. In the CASS system sludge is returned during aeration cycles and the sludge therefore contains high concentration of oxygen and nitrate. The biological phosphorous removal depend on anaerobic conditions with high amounts of easy degradable organic matter and the presence of nitrate or oxygen in the inlet to the Zone 1 tank will therefore reduce the effectiveness of biological P removal.

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Nitrogen removal The present requirements for nitrogen removal are not very strict and sufficient nitrogen removal can be performed almost entirely through the removal of surplus sludge.

The nitrification process appears to be appropriately designed, but if more strict requirements for total nitrogen are to be met in the future, optimisation of the denitrification process may be required.

The demand for easily degradable organic matter during anoxic conditions for optimal denitrification does not seem to be satisfied as the aerobic period prior to denitrification will consume most of the easily degradable organic matter in the influent to Zone 2. Furthermore the lack of mixers does not provide the best conditions for the biomass to be exposed to the influent organic matter or the nitrate.

Proposed changes to the CASS system The following changes can improve the performance of the CASS system:

• At present inlet flow and RAS are mixed in the beginning of the Zone 1, which means that the oxygen and nitrate in the RAS will use some of the readily available organic matter that should be used for biological phosphorus removal. It would be a benefit that return sludge is provided with some retention time before mixing with raw wastewater to reduce the oxygen and nitrate content of the return sludge. This could be accomplished by changing the position of influent raw wastewater to the second section of Zone 1, but this will on the other hand reduce the contact time between RAS and influent in the “anaerobic zone”.

• The oxygen content of the raw wastewater is removed by ensuring that no “splashing” of water occurs before the grit chambers, after the primary clarifiers, at the mixing well after the primary clarifiers, and at the intermediate pumping station.

• Return sludge pumping is increased.

• The operation of the decanter is optimised.

• Mixers could be installed in Zone 2 and 3, allowing for separation of mixing and aeration requirements. This could help the process performance for both biological phosphorus removal and nitrification/denitrification as more optimal conditions can be achieved in the different cycles of the CASS operation.

• If increased nitrogen removal should For inspection be purposes required only. cycles of aeration and non-aeration with Consent of copyright owner required for any other use. mixing could be implemented.

• The contractor is presently optimising the wastewater treatment plant and several of the above changes may be implemented as part of this optimisation.

Options for extension of secondary treatment The requirements for extension of the secondary treatment process units is assessed hereunder and key figures for three different suggested options are provided:

Present SBR system Present Situation Nos. (CASS or SBR) 4 Anaerobic volume 1,100 m3 SBR Volume 20,000 m3 Total volume 21,100 m3

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Options for extension – Key figures

Extension Phase 3 Situation SBR process Nos. (CASS or SBR) 2 Anaerobic volume 700 m3 SBR Volume 9,400 m3 Total volume 10,100 m3

Extension Phase 3 Situation Conventional system Anaerobic volume 530 m3 New process tank volume 8,300 m3 Nos. new process tank 1 New final clarifier volume 3,400 m3 Nos. new final clarifier 2 Total volume 10,830 m3

Extension Phase 3 Situation Biofilter system New filter media volume 1,350 m3 Nos. biofilters cells 6 Total volume 1,350 m3

For inspection purposes only. 5.4. SLUDGE TREATMENTConsent of copyright owner required for any other use.

5.4.1. Description Primary sludge from the primary clarifiers, surplus activated sludge from the CASS tanks, and external sludge from other minor treatment facilities are mixed in homogenisation tanks and thickened in mechanical thickeners before it is pumped to digesters for anaerobic stabilisation. Gas from the digestion is collected and used for power and heat production. Digested sludge is dewatered in belt filter presses to approx. 20 %DS and subsequently transported to agricultural land.

The sludge treatment configuration is conventional and well suited for the actual sludge production.

5.4.2. Sludge Quantities The loads given in Table 5.12 below have been used for sludge design considerations and calculations. The future loads are compared to the actual load.

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Table 5.12 Sludge Quantities (average) Design values Design values Parameter Unit Actual values (80,000 PE) (130,000 PE) *) Primary sludge - Dry solids, average kg SS/day 2,940 2,605 4,233 - DS content % 1.5-2.0 3.0 3.0 - Amount, average m3/day 168 87 141 Biological sludge - Dry solids, average kg SS/day 1,875 4,147 6,739 - DS content % 0.5-1.0 1.25 1.25 - Amount, average m3/day 250 332 539 External sludge - Dry solids, average kg SS/day 325 1,250 1,250 - DS content % 2.0-3.0 1.76 1.76 - Amount, average m3/day 13 71 71 Total - Dry solids, average kg SS/day 5,140 8,002 12,222 - DS content % 1.2 1.63 1.63 - Amount, average m3/day 431 490 751 After sludge thickening - Dry solids, average kg SS/day n/a 8,002 12,222 - DS content % 6.8 6.0** 6.0 - Amount, average m3/day 91 133 204 After digestion - Dry solids, average kg SS/day 2,100 5,600 8,560 - DS content % 2.8 4.2 4.2 - Amount, average m3/day 75 133 204 After dewatering - Dry solids, average kg SS/day 2,100 5,600 8,560 - DS content % 20.4 20 20 - Amount, average m3/day 10.3 28 43 *) For primary and surplus activated sludge a proportional growth in sludge production from 80,000 to 130,000 PE is assumed. External sludge amount is not increased. **) 30% DS-reduction in the digesters is assumed. For inspection purposes only. Consent of copyright owner required for any other use.

5.4.3. Collection and homogenisation tanks Evaluation of Present Situation Primary sludge from the primary clarifiers, surplus activated sludge from the CASS tanks, and external sludge is pumped to the two collection and homogenisation tanks, which also act as buffer tanks for the drum thickeners.

Options for extension The capacity and retention times of the collection and homogenisation tanks are shown in the table below at present and future loads.

Present Situation Phase 3 Situation Nos. 2 2 Volume, total 520 m3 520 m3 Retention time approx. 1.2 days 0.7 days

The collection and homogenisation tanks are evaluated to have sufficient capacities for the future extension of the plant to 130,000 PE.

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5.4.4. Drum thickeners Evaluation of Present Situation Homogenised sludge is thickened from approx. 1.2 to 6.8 %DS in two Alfa Laval drum thickeners before digestion.

The drum thickeners have a total capacity of approx. 2200 kg DS/hour.

The polymer consumption for the drum thickeners is approx. 2.6 kg/tons DS, which is in line with normal operation practice.

Options for extension The drum thickeners have a total capacity of approx. 2,200 kgDS/hour giving a necessary operation time of 3.6 hours per day for the 80,000 PE design load. If sludge production is increased to approx. 12,200 kg DS/day corresponding to 130,000 PE, the necessary operation time will be approx. 5.6 hours per day. Therefore it is assessed that it will not be necessary to extend the capacity of the drum thickeners.

5.4.5. Sludge digesters Evaluation of Present Situation The thickened sludge (approx. 6 %DS) is pumped to sludge digesters for anaerobic digestion. The digesters are operated with mesophilic conditions, i.e. with a temperature of approx. 33-35 °C.

The gas from the digesters is collected in a gas storage tank. Gas is utilised for power production in two CHP units and/or in two gas boilers. If the gas production is not sufficient for heating of the digesters, the boilers can utilise oil as external fuel.

The digesters are designed for a retention time of 20 days at 80,000 PE load, which is according to normal design practice.

The digesters are not insulated, which gives a relatively high heat loss. Heating is provided through two spiral sludge/water heat exchangers. Mixing is provided through a gas diffuser system, which has advantages of relatively low power consumption and that no running parts are installed inside the digesters, but disadvantages of relatively poor mixing efficiency and risk of corrosion problems in the gas compressor. For inspection purposes only. Consent of copyright owner required for any other use. Options for extension The digesters are designed for a retention time of 20 days at 80,000 PE load. If the sludge production is increased to approx. 12,200 kg DS/day corresponding to 130,000 PE and the same digester technology is used, it will be necessary to extend the digester volume by approx. 1,450 m3 or one extra digester with approx. the same capacity as the existing digesters.

Present Situation Phase 3 Situation Nos. 2 3 Volume, total 2,634 m3 4,100 m3 Retention time 29 days 20 days

5.4.6. Gas storage tank Evaluation of Present Situation Gas from the two digesters is collected and stored in a gas storage tank. Gas is utilised for heat production in 2 boilers and excess gas production is used for power/heat production in 2 CHP units.

The capacity of the gas storage tanks is relatively low compared to normal design practice. Therefore it will be necessary to extend the storage capacity during extension of the plant.

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Options for extension The capacity and retention times at present and future loads of the gas storage tank is shown in the following table.

Design Phase 3 Present Situation 80,000 p.e. Situation Nos. 2 2 3 Storage volume, max. 500 m3 500 m3 1000 m3 Gas Production * approx. 2,400 m3/day 3,200 m3/day 4,900 m3/day Retention time 5.0 hours 3.8 hours 5.0 hours *) A specific gas production of 400 l/kg DS is assumed.

5.4.7. Digested sludge storage Evaluation of Present Situation Digested sludge (approx. 4.2 %DS) is transferred from the sludge digesters to two storage and degasification tanks.

Options for extension The capacity and retention times at present and future loads of the digested sludge storage tanks are shown in the table below.

Present Design Phase 3

Situation 80,000 p.e. Situation Nos. 2 2 2 Volume, total 1,840 m3 1,840 m3 1,840 m3 Retention time 25 days 14 days 9 days

The retention time in the sludge storage tanks is not essential for the overall operation of the treatment plant. It is assessed that capacity of the tanks For inspection is sufficient purposes only. even when the sludge production increases Consent of copyright owner required for any other use. to approx. 12,200 kgDS/day corresponding to 130,000 PE.

5.4.8. Sludge dewatering Evaluation of Present Situation Digested sludge is dewatered in two belt filter presses. Dewatered sludge is transferred to containers for final disposal. Reject water from the filter presses is returned to the CASS tanks.

A dewatering degree of 20%DS with polymer consumption at 6.4 kg/tDS is satisfactory.

Options for extension With a sludge production of 5,600 kg DS/day at 80,000 PE the necessary daily operation hours for the filter presses is approx. 5 hours. If sludge production is increased to approx. 8,560 kg DS/day corresponding to 130,000 PE, the necessary operation time will be approx. 8 hours per day. This would not allow adequate down-time for startup/stop and maintenance. Therefore it is recommended that one additional belt filter press be installed. This could be located either within the existing building with some alterations to the building and polymer units, or in a new building close to the existing units.

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Present Design Phase 3

Situation 80,000 p.e. Situation Nos. 2 2 3 Capacity, total 1,100 kg DS/hour 1,100 kg DS/hour 1,650 kg DS/hour Sludge production 2,115 kg DS/day 5,600 kg DS/day 8,560 kg DS/day Operation time approx. 2 h/day 5 h/day 5 h/day

5.4.9. Hydraulics and piping of existing WWTP From the hydraulic profile of the treatment plant it appears that there are several places where there is large reduction in hydraulic head. As stated earlier, some of these locations involve splashing of wastewater, which creates problems from a process point of view. The hydraulics of the section from the inlet works to the secondary treatment units will need particular attention in the detailed design of the extension to the wastewater treatment plant.

5.5. AREA AVAILABLE FOR FUTURE EXTENSION As it can be seen on the site plan, the following areas can be utilised for the extension of the wastewater treatment plant:

• To the north-east an area of approximately 200 m times 45 m ~ 0.9 ha.

• To the north – just east of the entrance road an area of 35 m * 45 m ~ 0.16 ha.

1. To the west an area of 50 m * 60 m ~ 0.3 ha.

An area to the south-east along the motor-way could also be available, but this area is disregarded due to restrictions regarding distance to the motor-way and the expected future placement of a sludge treatment facility.

For inspection purposes only. Consent of copyright owner required for any other use.

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5.6. EXTENSION OPTIONS AND DESCRIPTIONS

The objective of this chapter is describe and assess realistic scenarios for a future extension of the wastewater treatment plant at Osberstown.

The different options for wastewater and sludge treatment technologies that could be used in the extension of the plant are assessed, and combined to form four different technical plant configuration options.

5.6.1. Conditions for plant extension There are no limiting conditions for the extension of the plant to a capacity of 130,000 p.e. at the current site using BATNEEC technologies.

5.6.2. Mechanical treatment Different options for mechanical treatment are not described in this report, as the existing mechanical treatment facilities are commonly used at modern wastewater treatment plants and are generally regarded to be satisfactory.

The capacities of some of the mechanical treatment facilities will, however, have to be extended when the load to the plant is increased. The necessary extension of the mechanical treatment facilities is described for each extension option.

5.6.3. Secondary treatment Biological removal of organic matter The organic matter is biologically converted into energy, new biomass and CO2 by the metabolism of the biomass (e.g. activated sludge). The degradation of organic matter is performed in a process tank with either activated sludge or fixed film processes. In order to keep a constant sludge amount in the tanks without exceeding the effluent criteria, the produced surplus sludge must be removed from the biological treatment units to dewatering or a digester.

Nitrogen removal Removal of nitrogen is besides the removal For inspection of produced purposes only. sludge performed by biological nitrification Consent of copyright owner required for any other use. and denitrification.

Figure 5.2 presents schematically the three main processes for nitrogen removal. These are hydrolysis or ammonification, nitrification and denitrification.

Nitrogen in raw wastewater is present mainly in the form of ammonia and organically-bound nitrogen. The breakdown of organic matter, called hydrolysis or ammonification, releases the organic nitrogen in the form of ammonia, which is highly water-soluble.

Nitrifying bacteria in the presence of oxygen convert ammonia to nitrate by a process known as nitrification. Denitrification is a process whereby bacteria utilises nitrate as their oxidising agent and release nitrogen gas to the atmosphere.

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Figure 5.2 Nitrogen removal processes

Nitrification Nitrification is the process in which ammonia nitrogen is oxidised into nitrite and subsequently into nitrate. Two factors critical to nitrification are sludge age and oxygen supply. Additionally, certain physical or chemical conditions may inhibit the process.

Nitrification requires a large supply of oxygen. Demand is approximately 4.3kg of oxygen per kg of nitrate produced. Oxygen concentration in the biological reactor should be 1.0-2.0 mg/l for optimal nitrification.

Temperature, pH and certain chemical constituents of wastewater can interfere with the rate of the nitrification process.

Denitrification In the absence of free oxygen (anoxic conditions), bacteria utilise nitrate as their energy source during the decomposition of organic matter. This is called denitrification, where nitrate is consumed and nitrogen gas is produced. For inspection purposes only. Consent of copyright owner required for any other use.

The denitrification process functions properly when the following conditions are fulfilled:

• nitrate must be available (nitrification must first be achieved) • sufficient easy degradable organic carbon source must be available • anoxic conditions must prevail

The carbon to nitrogen-rate (expressed as BOD5/total-N) should be at least 4 for wastewater coming into the denitrification process. A ratio lower than this may reduce the denitrification efficiency, since cell processes require carbon.

Raw wastewater can usually serve as the carbon source, but its variations in assimitable carbon may lead to an insufficient rate of denitrification. Furthermore the primary clarification may remove too much of the easy degradable organic matter.

5.6.4. Phosphorous Removal Biological Phosphorous Removal The biological phosphorous removal is ensured by providing the best growth conditions to a special kind of bacteria. These bacteria store relatively large amounts of phosphorous and the sludge removal will therefore contain more phosphorous. The bacteria are able to absorb organic matter in

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The bacteria gets energy for absorbing the organic matter by releasing phosphorous, which is stored in the bacteria in energy depots (long chains of phosphorous). Therefore high concentrations of phosphorous can be measured in the anaerobic tank. The absorbed organic matter cannot be digested by the bacteria in the anaerobic tank. When the bacteria are in an environment with oxygen or nitrate – the aerobic/anoxic tanks - they start to digest the absorbed organic matter and start to build up their energy depots by taking up phosphorus again from the water. When the sludge is then separated from the cleaned water in the clarifiers it therefore contains large amounts of phosphorous. The biological removal of phosphorus is accomplished by taking the phosphorous rich biological surplus sludge out of the plant.

An important consideration in the implementation of biological phosphorus removal is that the surplus sludge treatment should be prepared for this process. The surplus sludge will, under the anaerobic conditions in the thickeners, release some of the phosphorus again. Phosphorous is released when easily degradable carbon is present in water without oxygen and nitrate. Hence, it is important to minimise anaerobic storing periods.

When the necessary anaerobic volume and easy degradable organic matter are present, biological P- removal can be responsible for the phosphorous removal required at a plant. However, it can be necessary to supplement with a minor amount of precipitation chemicals to fulfil the effluent standards.

Chemical Phosphorous removal Chemical phosphorous removal involves a reaction between the phosphorous contents of wastewater in form of ortho-phosphates, and a chemical precipitant e.g. ferric chloride (FeCl3) or ferric sulphate (Fe2(SO4)3). The result is formation of phosphorous containing particles, which can be removed with the biological surplus sludge following sedimentation in the clarifiers.

The precipitation chemical is pumped either to the inlet (simultaneous precipitation) and/or to the outlet part of the process tank (post precipitation).

5.6.5. Process options for secondary treatment The biological removal of organic matter and nutrients can be accomplished by a very large variety of designs. The designs could be broadly categorised in three types of treatment plants: For inspection purposes only. • Conventional extended aerationConsent activated of copyright sludge owner requiredprocess for any with other secondary use. clarification

• Activated sludge process with build-in clarification (SBR) • Fixed film processes

The three types of processes are briefly described in the sections hereunder. The conventional activated sludge process is by far the most common process for treatment both with and without biological nutrient removal. The SBR has, until recently, primarily been used for small treatment plants with no nutrient removal. The fixed film processes have historically been widely used based on stationary filter medium. Recently new innovations of fixed film based on movable filter medium have proved competitive, especially on sites with limited available area. Other types do exist, but are not considered relevant for this project.

Conventional activated sludge process Wastewater either with or without primary treatment is led to the activated sludge tank where biological decomposition of organic matter and nutrient removal takes place by means of micro-organisms (activated sludge) suspended in the water of the process tank. The activated sludge from the process tank is discharged into the secondary clarifiers. In the clarifier suspended sludge and treated wastewater are separated by sedimentation. Part of the suspended sludge is recirculated to the process tanks and part is taken out as surplus sludge.

To accomplish biological phosphorous removal, the first tanks to which sludge is recirculated should have anaerobic conditions, and subsequent tanks should have aerobic conditions.

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Biological nitrogen removal is accomplished by having alternating conditions of aerobic conditions and anoxic conditions, preferably with inlet flow during anoxic conditions. The alternation can be achieved by recirculation of wastewater as described below, or by having aeration equipment turned off for part of the time.

In the following section the recirculation process is presented and evaluated as a part of the conventional activated sludge processes.

Recirculation process for nutrient removal

The recirculation process is a process designed to ensure a stable nitrogen removal at low energy costs and at low BOD5/N ratios.

The recirculation process is the most common process configuration for nitrogen removal worldwide. The standard configuration provides an anaerobic zone followed by an anoxic zone before the aerated zone. The raw water flows into this anaerobic zone and is mixed with return sludge. In the anaerobic and the anoxic zones the activated sludge is mixed, but not aerated.

Return sludge from the clarifier is pumped back into the anaerobic zone. To achieve a low nitrate concentration in the treated effluent, additional recirculation of mixed liquor from the downstream end of the aeration tank to the anoxic zone is necessary.

This treatment consists of two process volumes with mixed liquor recirculation. Aeration is provided in the aerobic process volume. Denitrification is accomplished primarily in the anoxic tank and nitrification in the aerobic tank .

Anae- Anoxic Aerobic robic Tank Tank Tank

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Recirculation

Figure 5.3 Process diagram – Recirculation

In the process tanks the decomposition of organic matter and nitrification require considerable amounts of oxygen and it is important that the activated sludge is fully suspended during the processing period. In order to obtain maximum operation stability and to keep power consumption low, both mixing and aeration equipment is installed in the aeration zone. Oxygen is provided in the form of compressed air. The blowers are automatically controlled by on line metering of the actual oxygen concentration in the process tanks. The suspension of activated sludge is provided by continuously running slowly rotating propeller mixers.

The biological processes continuously create new micro-organisms (activated sludge) and therefore an equivalent amount of sludge shall be removed from the system as biological surplus sludge. Due to the biological phosphorous removal the biological surplus sludge will contain high amounts of phosphorous.

In the clarifier, treated wastewater is drawn from the surface via overflow weirs and settled sludge is concentrated in the bottom hoppers. Floating sludge formed in the clarifier is retained in the clarifier and scraped off to a collector for floating sludge.

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The concentrated sludge is returned to the process tanks in order to secure a sufficient amount of activated sludge in the process tanks and biological surplus sludge is pumped to sludge treatment. The return sludge pumping is controlled in correspondence with the influent flow.

The main advantages for conventional activated sludge process technology are: • Inexpensive • Simple to operate • Good biological N and P removal capacity

The main disadvantage for conventional activated sludge process technology is:

• Large area requirements

This option may prove to be the optimal for the extension of Osberstown, if the focus is mainly on hydraulic, running costs, and economic considerations. This will, however, also depend on the operating personnel who will be accustomed to operating a different process.

Sequencing Batch Reactor As an alternative to the traditional activated sludge plant with separate process tanks and secondary clarifiers a plant based on the SBR-process, as in the present CASS process, is an obvious option for the extension.

The SBR process (Sequencing Batch Reactors) is a fill-and-draw, variable reactor volume technology, developed as one of the first treatment plant types based on the activated sludge concept. Shortly after the initial studies, the emphasis switched to continuous flow "conventional" activated sludge. Further developments with SBR technology were not pursued because of limitations of equipment and engineering experience.

Recent innovations in aeration systems, monitoring and control systems, level meters etc. have revitalised interest in SBR technology, which has led to construction of several wastewater treatment plants based on this technology. The plants have mainly been built in the U.S.A, whereas the number of plants in Europe is moderate.

The SBR consists of a self-contained treatment system incorporating equalisation, aeration, and clarification within one-basin and if necessary anaerobic and anoxic reactions. Intermittently fed SBRs consist of the following basic steps: For inspection purposes only. Consent of copyright owner required for any other use.

1. Fill In the filling stage it is possible to start the aeration and/or mixing of MLSS. 2. React The react stage may comprise mixing or aeration, or both, depending of the effluent standards, for instance the needs for denitrification 3. Settle Liquid-solid separation occurs during the settle phase, similar to the operation of a conventional final clarifier. 4. Draw Clarified effluent is decanted in the draw phase. 5. Idle Only used in multibasin applications. Redraw of excess sludge will typically be performed during the idle phase.

The design of the CASS system includes two additional zones – one plugflow selector and one zone (zone 2) working in parallel to the SBR zone (zone 3). In the plugflow zone the raw wastewater is mixed with a recirculation stream from the zone 3 to improve sludge characteristics and provide biological phosphorous removal. Another special feature of the CASS system is the lack of mixing during the anoxic periods. Please refer to Section 5.3.5 for a more detailed description and evaluation.

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The normal design for nutrient removal in a SBR system includes the filling stage with mixing and no aeration to provide a period of time for biological P-removal. This constitutes the typical characteristic of SBR systems working in time rather than space. In the react step the system will be aerated, and if denitrification is needed the react step will be operating with intermittent aeration and no aeration/mixing to provide alternating conditions of aerobic and anoxic conditions. Additional carbon may be provided during anoxic conditions to ensure sufficient easily degradable organic carbon.

The SBR process has some advantages compared to continuous flow systems. For instance, the SBR process is more tolerant to peak flows as the wastewater is always led to an equalisation tank. Furthermore, return sludge or recycling systems is normally not necessary and total quiescence during clarification occurs. On the other hand, the SBR process is somewhat more sophisticated and difficult to operate and control due to the intermittent operation. Furthermore, aeration equipment must be larger since process air must be supplied over a shorter period.

The main advantages for SBR technology compared to activated sludge are:

• Low area requirement • Tolerant to peak flows

The main disadvantages of SBR compared to activated sludge include:

• Difficulties of biological nutrient removal • More expensive • May require additional carbon for denitrification

With the operational experience at Osberstown already in place, this option has an additional advantage at this specific wastewater treatment plant in comparison to other systems.

Fixed Film Process Fixed film technology are characterised by bacteria (activated sludge) being attached to a solid surface in shape of a biofilm. The basic biological processes that take place in fixed film process are identical to the processes in a plant based on suspended activated sludge.

Particulate is removed from the raw wastewater in primary clarifiers in order to reduce the risk of clogging of the subsequent fixed film reactors. Biological decomposition of organic matter and nutrient removal takes place in the reactors by means of micro- organisms (activated sludge) attached to the filter media. Dead micro-organisms loosen For from inspection the purposes filter media.only. Torn off material is separated from the Consent of copyright owner required for any other use. treated wastewater by means of filtration or sedimentation and removed as surplus sludge.

Biological nitrogen removal is accomplished by alternating aerobic and anoxic conditions and with inlet during anoxic conditions, so called pre-denitrification, or by aerobic compartments followed by anoxic compartments, post-denitrification.

The alternation for pre-denitrification can be achieved by recirculation of wastewater as described earlier. The removal of organic matter in the primary clarifiers can mean that the amount of organic matter available for denitrification may be insufficient. In this case, the denitrification process must be supplied with additional organic matter e.g. acetic acid, molasses or alcohol.

In case of post-denitrification, most of the organic matter will decompose in the aerobic compartment and the subsequent denitrification must be based exclusively on addition of external organic matter. Oxidation of excess organic matter is then required.

Nitrogen removal will normally be performed in a pre-denitrification process, i.e. a nitrifying filter after the denitrifying filter and recirculation of the nitrified water. Hence it has been decided to present and evaluate this process as a representative of the fixed film process.

Biological phosphorus removal, except what is obtained from ordinary cell growth, is not consistent with the fixed film principle. Consequently phosphorus removal shall be carried out by means of chemical precipitation.

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Design of fixed film reactors The design of biofilters depends on effluent standards, type of filter, type and specific surface area of filter medium, temperature etc.

None of the submerged filter types have gained such common practical use to allow actual recommendations in respect of loading. Research has confirmed the critical influence of particle size in optimising performance but have shown size effects to impact less on BOD removal than on nitrification. For media size about 3.5 mm, design loading for nitrification has been stated at 0.8 kg N/m3/day at 10 °C in design calculation presented in Denmark. The comparable loading rate for denitrification was 0.9 kg N/m3/day.

5.6.6. Secondary treatment recommendations All three options for secondary treatment (Conventional, SBR and Biofilter) are investigated in further detail as they all could prove relevant, depending on the wishes of the client – or possible DB contractors.

5.6.7. Tertiary treatment In order to fulfil the future effluent standards for phosphorus, it will be necessary to include tertiary treatment facilities. The most reliable tertiary treatment includes filtration possibly combined with additional chemical dosing before the filter units, i.e. contact filtration.

In principle a filtration operation is divided in two phases, i.e. a filtration phase, where the wastewater is led through the filter units, and a cleaning or regeneration phase, commonly called backwashing. While the filtration phase is essentially the same for all filter systems, the cleaning phase is quite different depending on whether it is a conventional filter, where the filtration and cleaning phase is separated in time, or a continuous filter system, where the filtration and cleaning phases occur simultaneously.

Conventional filtration Most conventional filters are designed as downflow filters either as mono-medium, i.e. typically sand filters, and dual-medium filters, typically anthracite coal as a top layer followed by a sand layer.

A conventional sand filter consists of the units:

For inspection purposes only. • Feeding pumps Consent of copyright owner required for any other use. • Sand filter divided in a number of cells • Level transmitters • Storage tank for backwash water • Blower for air flushing • Pumps for backwash • Balancing tank for spent backwash water

Typical filter media specifications are:

• Top layer: 500mm of anthracite coal, 1.6mm-2.5mm. • Filter sand: 300mm quartzite sand, 0.8mm-1.2mm • Filter bed: 200mm quartzite sand, 2.5mm-8.0mm o 300mm gravel, 8.0mm - 35.0mm

Operation of the filter is fully automated. Backwash cycles are initiated by high level indication in a filter cell.

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Continuous sand filter systems Two types of continuous filter systems are commonly used: Travelling-bridge filter and up-flow filter.

Travelling-bridge filter In the travelling-bridge filter, the incoming wastewater floods the filter bed, flows through the medium by gravity, and exists to the clearwell via effluent ports located under each cell. During the backwash cycle, the carriage and the attached backwash hood move slowly over the filter bed, consecutively isolating and backwashing each cell. The backwash pump, located in the clearwell, draws filtered wastewater from the effluent chamber and pumps it through the effluent port of each cell, forcing water to flow up through the cell and backwashing the filter medium of the cell. The wastewater pump located above the hood draws water with suspended matter collected under the hood and transfers it to a backwash water trough, from where it is led back to the grit chamber. During the backwash cycle, wastewater is filtered continuously through the cells that are not being backwashed.

Upflow filter In the upflow filter, the liquid to be filtered flows upward through the filter bed. At the same time the sand bed, moving in the counter-current direction, is being cleaned continuously. An airlift is used to pump the sand from the bottom of the filter up through a central pipe to a washer unit at the top of the filter. The sand washes the sand with a small amount of clean filtrate. In the sand washer, the accumulated material removed from the sand is removed over a weir.

Design parameters Continuous filter systems are in principle designed with the same necessary surface hydraulic load at peak flow as conventional sand filters. As no cells (or only a very small part as for the travelling-bridge filter) are taken out of operation for backwash, the extra capacity that is necessary for conventional filters is not necessary for continuous filter systems.

Another advantage of continuous filters is that neither backwash tanks nor a buffer tank for backwash water is needed for these filters.

The main disadvantages are that these systems are prefabricated units, with a limited number of suppliers, and that the continuous filter systems are a little more complicated to operate.

Contact filtration If it is necessary to obtain a very low effluent concentration of phosphorus, i.e. typically <0.3 mgP/l, it For inspection purposes only. might be necessary to make a postConsent treatment of copyright of theowner wastewater required for any otherin a use. contact filter.

In principle, a contact filter is a filter where the precipitant is added to the influent. Hereby a major part of the remaining dissolved phosphate is bound in particles that are caught in the filter. Furthermore colloids which did not settle in the biological/chemical plant are removed. In order to prevent the running time of the filter from being too short, it is an advantage to use a dual-media filter (for example). Continuous filters are also used successfully for contact filtration.

The precipitation and flocculation mechanisms in a contact filter fully correspond to those in other precipitation processes. Ferric salts are often used as the precipitant.

5.6.8. Tertiary treatment recommendations Effluent values below 0.3 mg total-phosphorus per litre are achievable for some well-designed and well-operated wastewater treatment plants based on biological/chemical treatment followed by sand filtration. However, to be sure to fulfil the effluent standards, it is recommended to install facilities for contact filtration, i.e. chemical dosing equipment, coagulation and flocculation chamber etc.

When the biological plant is fully optimised it might be possible – at least for some periods - to fulfil the effluent standards without adding additional precipitation chemicals before the sand filter units.

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5.6.9. Sludge treatment As the existing plant includes anaerobic digestion of sludge and gas utilisation with energy recovery, it is reasonable that the future sludge treatment also will be based on existing or similar technologies.

The final decision of sludge treatment should, however, be co-ordinated and take into account the requirements for the future further sludge treatment facilities to be located at Osberstown WWTP.

Sludge digestion Thickened primary and surplus activated sludge are pumped to digesters for anaerobic stabilisation. In the anaerobic digestion process, the organic material in mixtures of primary settled and biological sludges is converted biologically to a variety of end products including methane and carbon dioxide. The process is carried out in an airtight reactor. Sludge, introduced continuously or intermittently, is retained in the reactor for varying periods of time. The stabilised sludge, withdrawn from the reactor, is reduced in organic and pathogen content and is non-putrescible.

Mesophilic digestion The most common anaerobic process used for the treatment of sludge is a mesophilic fully mixed digester where the sludge is heated to approx. 35 °C. The main parameter for anaerobic sludge digestion is the hydraulic retention time, with typical design figures of 20-25 days.

Sludge has traditionally been stabilised with the main objective of minimising the risk of odours. In addition a substantial reduction in sludge solids is achieved during the stabilisation process and gas is produced which can be used for heating and/or electricity production.

In order to accelerate the solids reduction during stabilisation, the use of modified and new stabilisation methods is increasing:

Thermophilic digestion Thermophilic anaerobic digestion involves stabilisation at about 55o C, and increases to some extent the decomposition of sludge and increases gas production. The main benefits of thermophilic digestion are a shorter necessary hydraulic retention time (i.e. approx. 10 days) and a higher degree of sludge disinfection. Disadvantages include higher energy consumption for heating, and the digested sludge has a high content of colloids that negatively affects the dewatering properties of the sludge. For inspection purposes only. Consent of copyright owner required for any other use. In order to regain some of the energy used for heating of the sludge at thermophilic digesters, sludge/sludge heat exchangers are often installed, but can give operational problems.

Thermal hydrolysis Thermal hydrolysis in combination with anaerobic digestion further accelerates the decomposition of organic matter in the sludge to more easily degradable substances, thereby increasing gas production and reducing solids content in the subsequent digestion step. The thermal hydrolysis process is operated in a pressure vessel at about 50 bar and a temperature of 200o C.

A comparison of the above stabilisation processes is shown in the table below.

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Process parameters of various stabilisation methods. Figures given for 1 t dry solids of raw sludge.

Sludge volume Method after Advantages Disadvantages centrifugation

Mesophilic 2.8 m3 - well known and stable - poor hygienic effect anaerobic digestion process – good dewatering characteristics Thermophilic 2.8 m3 - considerable destruction - may negatively effect anaerobic digestion of pathogens dewatering characteristics – increased gas – may create odour nuisance production – special care to be taken against corrosion problems Thermal hydrolysis 1.1 m3 - total destruction of - high investment costs + digestion pathogens – odours must be addressed – improved dewatering – complicated process characteristics

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Sludge dewatering For mechanical sludge dewatering three different methods are the most commonly used: centrifuges, belt filter press and plate filter press. In the table below, obtainable dry solids contents for stabilised combined primary and surplus activated sludge from the different methods are presented. The main advantages and disadvantages are also listed.

Comparison of different sludge dewatering methods DS content Dewatering with polymer Advantages Disadvantages Method addition

Centrifuges 20 - 25% Clean appearance, minimal Scroll wear potentially a high odour problems, fast start up maintenance problem and shut down capabilities Skilled maintenance personnel Easy to install required Relatively low capital cost to Moderately high suspended capacity ratio solids in filtrate Low floor area required for Relatively high energy equipment requirements

Belt filter press 20 - 25% Relatively low energy Sensitive to incoming sludge requirements feed characteristics Relatively low capital and Automatic operation generally operating costs not advised Less complex mechanically and High flush water consumption easier to maintain

Plate filter press 30 - 35% Highest cake solids Batch operation concentration High capital costs Low suspended solids in filtrate For inspection purposes only. Labour-intensive Consent of copyright owner required for any other use. Large floor area required for equipment Skilled maintenance personnel required

5.6.10. Sludge treatment recommendations It is recommended that the future sludge treatment is based on anaerobic digestion, as digesters and gas utilisation facilities already exist. For sludge digestion both mesophilic and thermophilic digestion are realistic alternatives for the future extension of the plant. Mesophilic digestion will demand construction of one new digester, whereas thermophilic digestion will demand extension of the heat exchanger system with installation of a sludge/ sludge heat exchanger. It is recommended to leave both options open for the PPP procurement process.

Thermal hydrolysis of sludge before digestion is also a realistic option, but it is recommended that such a solution is investigated in connection with the future sludge treatment facilities to be installed at Osberstown WWTP.

In general the final decision of sludge treatment should be co-ordinated and take into account the requirements for the future further sludge treatment facilities to be located at Osberstown WWTP.

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5.7. PLANT CONFIGURATION OPTIONS In this section the different options for treating the wastewater and sludge as described are put together to form four suggested options for the extension and upgrading to Phase 3. The options have been selected based on the advantages/disadvantages of the different unit operation steps, based on having both high-end and low-end options, and finally based on local conditions.

Option 1 - New SBR process line and mesophilic digester • Existing mechanical treatment. • Extension of primary clarifiers. • New biological treatment line based on SBR/CASS technology in parallel to existing CASS system • New conventional sand filter system with contact filtration • Extension of digester capacity for mesophilic digestion of all sludge.

Option 2 - Conventional Activated sludge process and mesophilic digester • Existing mechanical treatment • Extension of primary clarifiers • New biological treatment line based on conventional activated sludge technology in parallel to existing CASS system • New conventional sand filter system with contact filtration • Extension of digester capacity for mesophilic digestion of all sludge 2.

Option 3 - New Biofilter system • Existing mechanical treatment and primary clarifiers • Extension of primary clarifiers • New biological treatment line based on biofilter technology in parallel to existing CASS system For inspection purposes only. • New conventional sand filterConsent system of copyright with owner contact required filtration for any other use.

• Extension of digester capacity for mesophilic digestion of all sludge

Option 4 - New SBR process line and thermophilic digester • Existing mechanical treatment and primary clarifiers • New biological treatment line based on SBR/CASS technology in parallel to existing CASS system • New conventional sand filter system with contact filtration • Thermophilic digestion of all sludge

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5.8. OPTION 1 - NEW SBR PROCESS LINE AND MESOPHILIC DIGESTER

5.8.1. Plant description This option is in principle an extension of the existing plant using the same processes at the plant by upgrading all units to the new load. To accomplish the more strict requirements for phosphorous in the effluent, a sand filter with contact filtration is installed for tertiary treatment.

The units of the wastewater treatment plant are illustrated on the process diagram on the following pages and the units are briefly described hereunder to give an impression of the extent of the upgrading.

5.8.2. Inlet works and mechanical treatment In all options the inlet works, screens and grit chambers must be extended. It is assumed that the extension will be implemented as described in Section 5.3.1. The extension therefore involves new pumps and piping, and a new grit chamber.

For all four options one additional primary clarifier is included to comply with the new hydraulic load of the system.

5.8.3. Secondary treatment This option includes construction of two new SBR-tanks (CASS system or similar). Distribution between the existing and the new SBR-tanks will take place in a new distribution chamber. The capacity of the existing blower system must be extended. There would be an advantage in building one complete line in parallel to the existing at the north-east part of the plant area.

5.8.4. Tertiary treatment As stated in Section 5.6.8, it will be necessary to install a sandfilter system with contact filtration if the effluent standard for phosphorus is to be fulfilled.

Therefore, conventional or continuous sand filter system including contact filtration is included in all For inspection purposes only. alternatives. As there are no majorConsent differences of copyright in owner cost required estimates for any other for use. conventional and continuous sand filter system, and therefore conventional systems are assumed for all plant configuration options hereafter. The final choice of sand filter system will depend on the PPP procurement process.

5.8.5. Sludge treatment In this option, mesophilic digestion is chosen, which means that construction of one additional sludge digester is necessary. (Option 3 is basically the same option but with thermophilic digestion). Sludge hydrolysis is not considered relevant for this project.

For sludge dewatering the upgrading of the existing systems only is evaluated – meaning drum filter for pre-dewatering and belt filter-press for final dewatering.

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5.8.6. Wastewater treatment facilities

Present New Total

no. units no. units no. units Inlet pumps 4 2 6 Screens (and Screenings classifier) 2 + (1) 0 2+(1) Grit chambers (and Grit classifier) 2 1 3 Primary clarifiers 2 1 3 Intermediate pumping station 1 + (1) 0 + (1) 1 + (2) (and distribution chamber) CASS tanks 4 2 6 Storm water tanks 2 0 2 Figure in brackets indicate backup/storm systems

5.8.7. Sludge treatment facilities

Present Total New units no. units units Collection and homogenisation tanks 2 0 2 Drum thickeners 2 0 2 Loading tank for digesters 1 0 1 Digesters 2 1 3 Gas storage tank 1 0 1 CHPs 2 0 2 Gas/oil boilers 2 0 2 Digested sludge storage tanks 2 0 2 Belt filter presses 2 1 3

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5.8.8. Investment cost estimate In Table 5.13 an estimate for the investment cost for Option 1 is given. The calculation of the investment costs based on a DB (design and build) contract.

Table 5.13 Preliminary estimate of Investment costs for option 1 Present New units for option 1 Unit Size/nos. Price (IR£) Inlet pumping – Upgrading 4*1,200 m3/h 2*1,200 m3/h 180,000 Grit chambers 2*52 m3 1*52 m3 30,000 Primary clarifiers 2*1,810 m3 1*1,810 m3 310,000 SBR tanks 4*5,050 m3 2*5,050 m3 2,600,000 Sandfilters incl. contact filtration equipment - 6*125 m² 4,000,000 Blowers incl. building 13,200 Nm3/h 7,800 Nm3/h 190,000 Digesters incl. associated equipment 2*1,320 m3 1*1,320 m3 730,000 Belt filter press 2*550 kg/h 1*550 kg/h 300,000 Piping - - incl. SCADA – upgrading - - 300,000 Ground works, landscaping, pavement, etc. 5% 420,000 Total 9,060,000

Design, supervision and commissioning 12.5% 1,133,000 Contingency 20% 1,812,000

Grand Total, excl. VAT 12,005,000

Prices include all investment costs related to engineering, equipment, civil work and installation as part of a DB contract.

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5.8.9. Operations costs An estimate for the operation and maintenance costs for the extended wastewater treatment plant is given in Table 5.14 below. The estimate includes the extra O&M cost related to the extension.

Table 5.14 O&M cost estimate – Option 1

Type Units Nos. IR£/unit IR£/year Electricity kWh/year 1,310,000 0.06 79,000 Precipitation chemicals tons/year 370 120 44,500 Polymers kg/year 9,300 5 46,500 tons/year Sludge transport and disposal 5,200 60 312,000 (20% DS) Staff persons/year 2 25,000 50,000 Miscellaneous % 10 - 53,000 % Maintenance 2.5 - 219,000 (of investment cost) Total 804,000 Notes: In the calculation for power consumption it is assumed that approx. 30% of the total power consumption can be covered by the CPHs.

The precipitation chemicals include both chemical precipitations in the biological treatment unit as support to the biological phosphorus removal and chemical dosing for contact filtration.

Polymer consumption is both for the mechanical thickeners and for final dewatering.

The O&M cost estimate corresponds approximately to IR£0.26 per m3 of treated wastewater.

5.8.10. Evaluation of Option 1 The main advantage of Option 1 is the use of process technology similar to the existing plant, which means that the operation personnel can use the experience gained from the operation of the existing plant. For inspection purposes only. Consent of copyright owner required for any other use. A disadvantage is that the present plant, at least to date, has shown performance difficulties especially in relation to biological phosphorus removal and retaining suspended solids. When more strict effluent standards are introduced, the performance of the biological stage is very important in fulfilling these standards.

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Proposed Osberstown plant showing Option 1: new primary, CASS units, and tertiary sand filters (no landscaping shown)

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Figure 5.4 Process diagram – Option 1

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Figure 5.5 Process diagram – Option 1

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Figure 5.6 Layout plan – Option 1

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5.9. OPTION 2 - CONVENTIONAL ACTIVATED SLUDGE PROCESS AND MESOPHILIC DIGESTER

5.9.1. Plant description In this option a conventional extended aeration activated sludge process is constructed in parallel to the existing CASS units. Other treatment units are similar to Option 1.

The units of the wastewater treatment plant are illustrated on the process diagram on the following page and the units are briefly described hereunder to give an impression of the extent of the upgrading.

5.9.2. Inlet works and mechanical treatment As Option 1.

5.9.3. Secondary treatment This option includes construction of a conventional activated sludge tank. Distribution between the existing CASS tanks and the new conventional activated sludge tank will take place in a new distribution chamber.

5.9.4. Tertiary treatment As Option 1.

5.9.5. Sludge treatment As Option 1.

5.9.6. Wastewater treatment facilities

Present New Total

no. units no. units no. units Inlet pumps 4 2 6 For inspection purposes only. Screens (and Screenings classifier)Consent of copyright 2 +owner (1) required for any 0 other use. 2+(1)

Grit chambers (and Grit classifier) 2 1 3 Primary clarifiers 2 1 3 Intermediate pumping station 1 + (1) 0 + (1) 1 + (2) (and distribution chamber) CASS tanks 4 2 6 Activated sludge tanks 0 1 1 Secondary clarifiers 0 2 2 Return sludge pumping station 0 1 1 Storm water tanks 2 0 2 Figure in brackets indicate backup/storm systems

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5.9.7. Sludge treatment facilities

Present Total New units no. units units Collection and homogenisation tanks 2 0 2 Drum thickeners 2 0 2 Loading tank for digesters 1 0 1 Digesters 2 1 3 Gas storage tank 1 0 1 CHPs 2 0 2 Gas/oil boilers 2 0 2 Digested sludge storage tanks 2 0 2 Belt filter presses 2 1 3

5.9.8. Investment cost estimate The calculation of the investment costs for Option 2, based on a DB (design and build) contract, is summarised in Table 5.15 below:

Table 5.15 Preliminary estimate of Investment costs for Option 2 Present New units for option 2 Unit Size/nos. Price (IR£) Inlet pumping – Upgrading 4*1,200 m3/h 2*1,200 m3/h 180,000 Grit chambers 2*52 m3 1*52 m3 30,000 Primary clarifiers 2*1,810 m3 1*1,810 m3 310,000

Activated sludge tank For inspection purposes only.- 1*8,300 m3 1,940,000 Consent of copyright owner required for any other use. Secondary clarifiers - 2*1,700 m3 600,000 Return sludge pumping station - - 65,000 Sandfilters incl. contact filtration equipment - 6*125 m² 4,000,000 Digesters incl. associated equipment 2*1,320 m3 1*1,320 m3 730,000 Belt filter press 2*550 kg/h 1*550 kg/h 300,000 Piping - - incl. SCADA - upgrading - - 300,000 Ground works, landscaping, pavement, etc. 5% 410,00 Total 8,865,000

Design, supervision and commissioning 12.5% 1,108,000 Contingency 20% 1,773,000

Grand Total, excl. VAT 11,746,000

Prices include all investment costs related to engineering, equipment, civil work and installation as part of a DB contract.

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5.9.9. Operations costs An estimate for the operation and maintenance costs for extended wastewater treatment plant is given in Table 5.16 below. The estimate includes the extra O&M cost related to the extension.

Table 5.16 O&M cost estimate – Option 2 Type Units Nos. IR£/unit IR£/year Electricity kWh/year 1,110,000 0.06 66,500 Precipitation chemicals tons/year 300 120 36,000 Polymers kg/year 8,900 5 44,500 tons/year Sludge transport and disposal 4,900 60 294,000 (20% DS) Staff persons/year 2 25,000 50,000 Miscellaneous % 10 - 49,000 % Maintenance 2.5 - 215,000 (of investment cost) Total 755,000

Notes: Compared to Option 1 the power consumption is estimated to be approx. 15% lower due to more continuous and effective aeration and mixing of the process tanks.

The biological phosphorus removal is assessed to be more efficient for the conventional activated sludge process compared to the SBR/CASS process, whereas the precipitation chemical consumption is lower than for Option 1.

Polymer consumption and expenses for sludge transport and disposal are slightly lower than Option 1 due to less chemical sludge production.

The O&M cost estimate corresponds to approximately. IR£0.24 per m3 of treated wastewater.

5.9.10. Evaluation of Option 2

Option 2 with a conventional activated For sludge inspection processpurposes only. has advantages in terms of slightly less investment and O&M costs. It is furthermoreConsent of copyright considered owner required that for any the other treatment use. performance is better, due to the continuous operation of the process tanks and secondary clarifiers, which makes the operation control simpler. A well operating SBR system can, however, obtain similar treatment results as for a conventional system.

The main disadvantages of Option 2 is that it will include two different process configurations at the plant, which is an inconvenience for the daily operation.

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Figure 5.7 Process diagram – Option 2

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Figure 5.8 Process diagram – Option 2

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Figure 5.9 Layout plan – Option 2

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5.10. OPTION 3 - NEW BIOFILTER SYSTEM AND MESOPHILIC DIGESTER

5.10.1. Plant description In this option a new biological line based on submerged biofilm technology is constructed in parallel to the existing CASS units. Other treatment units are similar to Option 1. The main advantage for this option is that it is a small footprint solution. For instance, the biofilter system can be constructed between the existing primary clarifiers and existing storm water tanks.

The units of the wastewater treatment plant are illustrated on the process diagram on the following page and the units are briefly described hereunder to give an impression of the extent of the upgrading.

5.10.2. Inlet works and mechanical treatment As Option 1.

5.10.3. Secondary treatment This option includes construction of a new biofilter system consisting of six separate biofilter cells. Distribution between the existing CASS tanks and the new biofilters will take place in a new distribution chamber. The capacity of the existing blower system must be extended.

5.10.4. Tertiary treatment As Option 1.

5.10.5. Sludge treatment As Option 1.

5.10.6. Wastewater treatment facilities

Present New Total

no. units no. units no. units

Inlet pumps For inspection4 purposes only. 2 6 Consent of copyright owner required for any other use. Screens (and Screenings classifier) 2 + (1) 0 2+(1) Grit chambers (and Grit classifier) 2 1 3 Primary clarifiers 2 1 3 Intermediate pumping station 1 + (1) 0 + (1) 1 + (2) (and distribution chamber) CASS tanks 4 2 6 Submerged biofilter system 0 1 1 Storm water tanks 2 0 2 Figure in brackets indicate backup/storm systems

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5.10.7. Sludge treatment facilities

Present Total New units no. units units Collection and homogenisation tanks 2 0 2 Drum thickeners 2 0 2 Loading tank for digesters 1 0 1 Digesters 2 1 3 Gas storage tank 1 0 1 CHPs 2 0 2 Gas/oil boilers 2 0 2 Digested sludge storage tanks 2 0 2 Belt filter presses 2 1 3

5.10.8. Investment cost estimate The calculation of the investment costs for Option 3, based on a DB (design and build) contract, is summarised in Table 5.17 below:

Table 5.17 Preliminary estimate of Investment costs for Option 3 Present New units for option 1 Unit Size/nos. Price Inlet pumping – Upgrading 4*1,200 m3/h 2*1,200 m3/h 180,000 Grit chambers 2*52 m3 1*52 m3 30,000 Primary clarifiers 2*1,810 m3 1*1,810 m3 310,000

Biofilters system For inspection purposes only.- 1*1,350 m3 5,300,000 Consent of copyright owner required for any other use. Sandfilters incl. contact filtration equipment - 6*125 m² 4,000,000 Digesters incl. associated equipment 2*1,320 m3 1*1,320 m3 730,000 Belt filter press 2*550 kg/h 1*550 kg/h 300,000 Piping - - incl. SCADA – upgrading - - 400,000 Ground works, landscaping, pavement, etc. 5% 550,000 Total 11,800,000

Design, supervision and commissioning 12.5% 1,475,000 Contingency 20% 2,360,000

Grand Total, excl. VAT 15,635,000

Prices include all investment costs related to engineering, equipment, civil work and installation as part of a DB contract.

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5.10.9. Operations costs An estimate for the operation and maintenance costs for extended wastewater treatment plant is given in Table 5.18 below. The estimate includes the extra O&M cost related to the extension.

Table 5.18 O&M cost estimate – Option 3 Type Units Nos. IR£/unit IR£/year Electricity kWh/year 1,390,000 0.06 83,500 Precipitation chemicals tons/year 900 120 108,000 Polymers kg/year 6,000 5 30,000 tons/year Sludge transport and disposal 3,300 60 198,000 (20% DS) Staff persons/year 2 25,000 50,000 Miscellaneous % 10 - 47,000 % Maintenance 2.5 - 287,500 (of investment cost) Total 804,000

Notes: Compared to a conventional treatment plant (Option 2) it is the consultant’s experience that the power consumption for a plant based on submerged biofilters is approx. 25% higher due to less possibility for optimisation of the aeration system.

For this option it is assumed that the plant is operated with pre-precipitation, i.e. dosing of precipitation chemicals before the primary clarifiers. It is the consultant’s experience that efficient removal of primary sludge before the biofilter units is important for a satisfactory operation. Most of the phosphorus removal will thus be based on chemical precipitation.

The sludge production for submerged biofilter plant is approx. 2/3 of the sludge production from a conventional plant. Hence the operation costs for polymer consumption and sludge transport and disposal are correspondingly lower.

The biological phosphorus removal is assessed to be more efficient for the conventional activated sludge process compared to the SBR/CASS process, whereas the precipitation chemical consumption is lower than for Option 1. For inspection purposes only. Consent of copyright owner required for any other use. Polymer consumption and expenses for sludge transport and disposal are slightly lower than Option 1 due to less chemical sludge production.

The O&M cost estimate corresponds to approximately IR£0.26 per m3 of treated wastewater.

5.10.10. Evaluation of Option 3 The main advantage of Option 3 based on submerged biofilter technology is the small footprint solution that can easily be included in the existing plant. However, the available area for extension of the present plant is not regarded to be a problem. Another advantage is that the effluent from the biological stage contains very low suspended solids, which is important in relation to the more stringent effluent standards.

The main disadvantage is relatively high construction and O&M costs. Furthermore the plant is relatively complicated to operate.

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Figure 5.10 Process diagram – Option 3

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Figure 5.11 Process diagram – Option 3

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Figure 5.12 Layout plan – Option 3

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5.11. OPTION 4 - NEW SBR PROCESS LINE AND THERMOPHILIC DIGESTER

5.11.1. Plant description The wastewater treatment facilities for this option are similar to Option 1. Sludge treatment facilities differ from Option 1 as thermophilic digestion of sludge is used instead of the existing mesophilic digestion. This means that it will not be necessary to construct a new digester. However, the heat exchanger system has to be extended, including installation of a new sludge/sludge heat exchanger.

The units of the wastewater treatment plant are illustrated on the process diagram on the following page and the units are briefly described hereunder to give an impression of the extent of the upgrading.

5.11.2. Inlet works and mechanical treatment As Option 1.

5.11.3. Secondary treatment As Option 1.

5.11.4. Tertiary treatment As Option 1.

5.11.5. Sludge treatment Thermophilic digestion of all sludge. Installation of new sludge/sludge heat exchangers.

5.11.6. Wastewater treatment facilities

Present New Total

no. units no. units no. units Inlet pumps 4 2 6 Screens (and Screenings classifier) 2 + (1) 0 2+(1) For inspection purposes only. Consent of copyright owner required for any other use. Grit chambers (and Grit classifier) 2 1 3 Primary clarifiers 2 1 3 Intermediate pumping station 1 + (1) 0 + (1) 1 + (2) (and distribution chamber) CASS tanks 4 2 6 Storm water tanks 2 0 2 Figure in brackets indicate backup/storm systems

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5.11.7. Sludge treatment facilities

Present Total New units no. units units Collection and homogenisation tanks 2 0 2 Drum thickeners 2 0 2 Loading tank for digesters 1 0 1 Digesters 2 0 2 Gas storage tank 1 0 1 CHPs 2 0 2 Gas/oil boilers 2 0 2 Digested sludge storage tanks 2 0 2 Belt filter presses 2 1 3

5.11.8. Investment cost estimate The calculation of the investment costs for Option 4, based on a DB (design and build) contract, is summarised in Table 5.19 below:

Table 5.9 Preliminary estimate of Investment costs for Option 4 Present New units for option 1 Unit Size/nos. Price Inlet pumping – Upgrading 4*1,200 m3/h 2*1,200 m3/h 180,000 Grit chambers 2*52 m3 1*52 m3 30,000 Primary clarifiers 2*1,810 m3 1*1,810 m3 310,000 3 3 SBR tanks For inspection purposes4*5,050 only. m 2*5,050 m 2,600,000 Consent of copyright owner required for any other use. Sandfilters incl. contact filtration equipment - 6*125 m² 4,000,000 Blowers incl. building 13,200 Nm3/h 7,800 Nm3/h 190,000 Upgrading and extension of heating and heat - - 300,000 exchanger system Belt filter press 2*550 kg/h 1*550 kg/h 300,000 Piping - - incl. SCADA – upgrading - - 300,000 Ground works, landscaping, pavement, etc. 5% 395,000 Total 8,605,000

Design, supervision and commissioning 12.5% 1,076,000 Contingency 20% 1,721,000

Grand Total, excl. VAT 11,402,000

Prices include all investment costs related to engineering, equipment, civil work and installation as part of a DB contract.

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5.11.9. Operations costs An estimate for the operation and maintenance costs for extended wastewater treatment plant is given in Table 5.20 below. The estimate includes the extra O&M cost related to the extension.

Table 5.20 O&M cost estimate – Option 4 Type Units Nos. IR£/unit IR£/year Electricity kWh/year 1,500,000 0.06 90,000 Precipitation chemicals tons/year 370 120 44,500 Polymers kg/year 11,200 5 56,000 tons/year Sludge transport and disposal 5,200 60 312,000 (20% DS) Staff persons/year 2 25,000 50,000 Miscellaneous % 10 - 55,500 % Maintenance 2.5 - 208,000 (of investment cost) Total 816,000

Notes: As the demand for heating of the digesters will be higher for thermophilic digestion, the surplus gas production for power consumption will be less. The net power consumption is estimated to be approx. 15% higher than for Option 1.

Thermophilic digested sludge contains a higher amount of colloids compared to mesophilic digested sludge. This has a negative effect on the de-waterability of the sludge. Therefore the polymer consumption is estimated to be approx. 20% higher for Option 4 compared to Option 1.

The O&M cost estimate corresponds to approximately IR£0.26 per m3 of treated wastewater.

5.11.10. Evaluation of Option 4 This option is similar to Option 1 except for the sludge stabilisation and has therefore the same advantages and disadvantages. For inspection purposes only. Consent of copyright owner required for any other use. Thermophilic digestion has the advantages that it is not necessary to construct one additional digester, and that the sludge from the digesters will have a higher degree of sludge hygienisation. Dewatering of the sludge will, however, be more difficult.

The existing digesters are un-insulated, which means that the heat loss is relatively high. If thermophilic digestion is introduced, the heat loss will be even higher and it might be beneficial to insulate the digesters. This is not included in the cost estimate.

Operational problems in terms of blocking of the sludge/sludge heat exchangers might occur, which means that they have to be cleaned periodically.

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Figure 5.13 Process diagram – Option 4

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Figure 5.14 Process diagram – Option 4

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Figure 5.15 Layout plan – Option 4

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5.12. SUMMARY AND RECOMMENDATION Commonly used treatment technologies have described and assessed, and four realistic options for the extension of the plant have been investigated from both technical and economical viewpoints.

In general the conclusion is that there are no limiting conditions for the extension of the plant to a capacity of 130,000 PE at the current site using BATNEEC technologies.

The four suggested options for the extension of Osberstown WWTP to cater for 130,000 PE is summarised in Table 5.21 below:

O&M cost Investment Option estimate Advantages Disadvantages cost estimate per year

Option 1 IR£12m IR£0.8m • Process technology • Operational difficulties (€15m) (€1m) similar to existing plant for existing plant SBR/CASS process and • Flexible process with • CASS system not mesophilic good optimisation optimal for biological digester possibilities phosphorus removal

Option 2 IR£12m IR£0.8m • Simple operation with • Different process (€15m) (€1m) stable treatment technology compared to Conventional performance existing plant activated sludge and mesophilic • High biological digester phosphorus removal can be achieved • Lowest total price over an operational period of more than 6 years

For inspection purposes only. Consent of copyright owner required for any other use. Option 3 IR£16m IR£0.8m • Small footprint • High investment and (€20m) (€1m) O&M costs Submerged • Low suspended solids biofilter system content from biological • Significantly different and mesophilic stage process technology digesters compared to existing plant

Option 4 IR£11m IR£0.8m • Lowest investment • Possible operational (€14m) (€1m) cost problems with sludge SBR process and blocking thermophilic • Higher degree of digester sludge hygienisation • Poor de-waterability of sludge • Only one process technology at the plant • Relatively high energy consumption

It is recommended that all four options are considered for a future PPP procurement process.

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6. POLLUTER PAYS

6.1. INTRODUCTION This section was prepared as a framework for Kildare County Council to recover costs of improving and expanding wastewater treatment facilities at Osberstown. It has been prepared in accordance with circulars L/16/00 and L/4/00 from the Department of the Environment & Local Government (DoELG). These circulars advise local authorities of the policy framework agreed by Government for the development of a more comprehensive and transparent system for charging water and wastewater services in the non-domestic sector. In accordance with this policy, an assessment has been made of the portion of capital costs that the commercial/industrial sector should pay towards the Extension to Osberstown WWTP – Stage 3, together with the sectoral split for the overall operation and maintenance costs of the extended plant.

In order to calculate the portion that is recoupable by the Council, the capital costs of the proposed works at Osberstown are split into two parts: new collection systems and new treatment facilities. This report details the breakdown for the wastewater treatment facilities aspect. A further report will be issued following assessment of the required new collection systems in early 2002.

When charging the industry and developers for treatment facilities the portion of the load that is applicable to industry and new development is assessed and costed. The cost of providing the necessary facilities for extension of the plant is assessed first by estimating the cost attributable to the new domestic (residential) load, with the remaining cost attributable to industry and commercial sectors. This is discussed in detail further in the text.

6.2. LOADS Existing loads were estimated and reported on in the “Load Assessment and Categorisation” section using Osberstown WWTP influent sampling, house count information from GeoDirectory, and the results of an industrial sampling survey to determine the industrial portion of the load. The Urban Wastewater Treatment Directive defines 1 population equivalent (PE) as the load resulting from 60g of BOD5. The increase in load over the period 2000 to 2021 is summarised as follows: For inspection purposes only. Consent of copyright owner required for any other use. Table 6.1 Loads to Osberstown WWTP

Scenario Domestic Total load (PE) population Current Plant year 2000 45,500 60,500 Current Plant at capacity 61,300 80,000 Extension to 130k PE 79,400 130,000 Additional load 18,100 50,000

Projected future populations and other development in the Osberstown Catchment were also estimated in the Load Assessment and Categorisation section. The projections were based on the town development plans, the “Strategic Planning Guidelines for the Greater Dublin Area”, building capacities, and the proposed connection of urban areas to the Upper Liffey Valley Regional Sewerage Scheme in the future.

It may be noted that the current industry load of 25% (of total load) is projected to change significantly over the period to 2021, when it is projected to account for 39% of the total load, driven for the most part by significant areas of existing zoned industrial land.

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6.3. MARGINAL COSTS In keeping with current DoELG policy it is likely that the extension of the plant will be a DB (Design and Build Contract) or DBO (Design-Build-Operate) in order to ensure a transparent and cost effective process. This approach is in keeping with “User Charges” system for wastewater charges.

The marginal capital cost is somewhat difficult to accurately quantify and will vary depending on the process chosen by the Contractor. The WWTP section suggested four likely design options for extension with estimated costs in the range IR£12m to IR£16m (€15m to €20m). The costs presented here are based primarily on options 1 and 2 of the WWTP report, being the most likely designs, and summarily consisting of:

• primary clarification units • sequencing batch reactors (SBR) • additional sludge capacity • sand-filter phosphorus removal unit

The other two options recommended in the WWTP section are based on biofilm and SBR (with thermophilic digestion) technologies, respectively. The marginal cost will change according to the final design adopted and should be reviewed at that stage.

The proposed extension is from the existing (stage 2) plant with a capacity of 80,000 PE up to a future 130,000 PE. It is estimated that the current plant will reach capacity between 2003 and 2005. The current load is estimated to be 60,500 PE, with an available capacity remaining of 19,500 PE. The remaining capacity is relevant to the Stage 2 extension only, and is not considered in the marginal cost calculations.

The marginal cost is calculated on the basis of extending the plant for domestic development to 98,100 PE (current 80,000 PE plus new domestic of 18,100 PE). For the capital costs attributable to the domestic sector, the required capacities of all relevant units were calculated to meet this 98,100 PE capacity. The overall costs of extending the plant to 130,000 PE in terms of capital and operational aspects were calculated as part of the WWTP section. The difference between the requirements at 98,100 PE and 130,000 PE are taken as the marginal cost to industry and commercial sectors.

This marginal cost was then converted into a “long run marginal cost” (LRMC) according to the criteria discussed and detailed in the ESRI Paper No. 22 entitled “Wastewater Services : Charging Industry For inspection purposes only. the Capital Cost”. Consent of copyright owner required for any other use.

Operational costs are taken as the proportion of the overall 130,000 PE plant attributable to a sector by a direct proportion calculation.

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6.3.1. Marginal Capital costs The marginal capital costs are presented below.

Table 6.2 Estimated capital costs for extension to 130,000 PE

WWTP Price 130000 PE Inlet pumps - upgrading € 229,000 Grit chamber € 38,000 Primary clarifiers € 394,000 Secondary treatment € 3,428,000 Sandfilters incl. contact filtration equipment € 5,079,000 Digesters incl. associated equipment € 927,000 Belt filter press € 381,000 SCADA upgrading € 381,000 Ground works, landscaping, pavement etc. (5%) € 533,000

Total € 11,390,000

Design, supervision and commissioning € 1,424,000

Grand total € 12,814,000

The following assumptions are made:

• There is over-capacity in the grit chambers, primary clarifiers, and belt filter presses at 98,000 PE. The cost of providing extra capacity in these units is negligible, and installing units of differing sizes can lead to operational problems. It is therefore recommended that these units are taken at full cost at 98,000 PE. For inspection purposes only. • Ground works, landscaping,Consent pavement, of copyright owner design, required supervision,for any other use. and commissioning costs are

negligibly affected by the non-domestic element.

• Based on the required capacity of the listed elements, the percentage costs for non-domestic capacity are as follows: Inlet pumps upgrading at 44% of total, Secondary treatment at 49%, Sandfilters etc. at 20%, SCADA at 17%.

The net cost of the non-domestic units is thus €2,871,000.

The LRMC for the non-domestic load is calculated as follows:

Design PE of extension = 50,000 PE Marginal capital cost of plant = €2,871,000 Cost factor x PE0.75 = Marginal capital cost Cost factor x 500000.75 = €2,871,000 Cost factor = €859

Non-domestic PE of extension = 31,900 PE Domestic PE of extended plant = 18,100 PE Notional capital cost for domestic PE = Cost factor x PE0.75 = €859 x 181000.75 = €1,340,455 LRMC for non-domestic plant is €2,871,000 - €1,340,455 = €1,530,546

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In summary, the plant design options 1&2 are the most likely designs to be adopted in the DB/DBO process. The cost breakdown is:

• domestic 88% (€11.28m) • industrial and commercial 12% (€1.53m)

These figures should be reviewed following the adoption of a final design and tender.

6.4. OPERATION AND MAINTENANCE COSTS Table 6.3 shows the load breakdown for the current plant and proposed extension.

Table 6.3 Load proportions to Osberstown WWTP

Scenario Domestic Industry- population commercial Current Plant year 2000 75% 25% Current Plant at capacity 77% 23% Extension to 130k PE 61% 39%

The operational and maintenance costs for the extended plant (only) were estimated in the WWTP report. These are presented below, less the costs associated with sludge transport and disposal, which are now part of the proposed new sludge treatment plant project.

The costs estimated for the four options are as follows:

Table 6.4 Estimated operation and maintenance costs for the extension for different plant design options

Extension Cost Cost per m3 of per year wastewater Option 1 €625,000 €0.20 Option 2 €585,000 €0.19 Option 3 €769,000 €0.25 For inspection purposes only. Option 4Consent of copyright €640,000 owner required for any other €0.21 use.

Notes: The estimated costs are based on the assumptions detailed in the WWTP report. It may be noted that whilst Option 3 has comparatively higher operational costs, sludge production is approximately 2/3 of the other processes, and therefore could realise cost savings at sludge treatment stage. Wastewater volumes assumed to be 8,500 m3 per day The average of the costs of Options 1 and 2 (as the most likely design to be adopted) is €605,000 Costs do not include sludge disposal

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The costs for the current plant at current capacity and the estimated costs at full capacity are shown in Table 6.5 below:

Table 6.5 Estimated operation and maintenance costs for the current plant

Cost Domestic Cost Industry- per year commercial cost Current plant 60,000 PE (€1,234,000) Current plant 80,000 PE €1,632,000 Extended plant (net) €605,000

Total plant at 130,000 PE €2,237,000 €1,365,000 €872,000

Cost per m3 of wastewater €0.21 Notes: Wastewater volumes assumed to be 20,000 m3 per day at 80,000 PE Costs do not include sludge disposal

Thus, the overall extended plant at 130,000 PE is estimated have operational and maintenance costs of €2.2m per annum, and the likely sectoral split based on BOD is:

• domestic: €1.37m, 61% • industrial and commercial: €0.87m, 39%

6.5. IMPLEMENTING THE POLLUTER PAYS PRINCIPLE Regarding the capital costs of the proposed extension, the implementation of the ‘polluter pays principle’ should be applied to both existing and new industrial and commercial loads. The principle of charging existing industrial and commercial concerns is justified on the basis that the proposed extension to the plant is not only an extension of capacity, but is an upgrade in the overall treatment facilities. Improved treatment standards are needed to comply with River Liffey water quality objectives under the Phosphorus Regulations and recently For inspection adopted purposes only. Water Framework Directive, and necessitate Consent of copyright owner required for any other use. improved treatment particularly in regard to meeting phosphorus, ammonia, and BOD standards. These new treatment standards would require a plant upgrade irrespective of the need for additional capacity.

It is therefore recommended that the capital costs of the proposed extension are applied to existing and new industrial and commercial loads, over the period to 2021.

The standard method of recovering operational costs from industry and commercial using the ‘modified Mogden formula’ is recommended. This formula calculates charges based on the capital and operation/maintenance costs of the Osberstown network and treatment facilities, based on BOD, suspended solids, flow, and phosphorus. The formula is as follows:

C = R + V + (Ot/Os)xB + (St/Ss)xS + (Pt/Ps)xP

Where: C = total cost per cubic metre of trade effluent St = suspended solids (mg/l) of trade effluent R = reception and conveyance cost per cubic metre Ss = suspended solids (mg/l) of crude sewage V = volumetric and treatment cost per cubic metre S = treatment and disposal of sludges Ot = BOD (mg/l) of trade effluent Pt = phosphate concentration (mg/l) of trade effluent Os = BOD (mg/l) of crude sewage Pt = phosphate concentration (mg/l) of crude sewage B = biological oxidation cost per cubic metre P = phosphate removal cost per cubic metre

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It is recommended that this formula should also include ammonia as a key component of the upgraded/extended treatment. The formula would thus read as follows:

C = R + V + (Ot/Os)xB + (St/Ss)xS + (Pt/Ps)xP + (At/As)xA

Where: At = ammonia (mg/l) of trade effluent As = BOD (mg/l) of crude sewage A = treatment cost associated with nitrification

Kildare County Council have been applying this principle over the last number of years, and this has lead to significant changes in the characteristics of medium to large industry effluent discharges. Overall discharges are now more consistent and lower than the pre-1998 situation, which was causing operational problems at the old plant. Several industries have installed or upgraded their own treatment, having discussed the situation with the council, and concluded that in-house treatment was more cost effective than full council charges. This is certainly a positive trend towards encouraging source minimisation.

The continuing implementation of the polluter pays principle in this manner is recommended. Under normal circumstances, only medium to large industries and commercial premises are practical to monitor for effluent discharge (selected concerns are required to have in-house monitoring, validated by council checks). The monitoring programme that is currently in operation by the council on a yearly basis is fundamental to the recovery of treatment costs, and should be continued and extended as necessary to cover new industry and commercial as appropriate. This monitoring programme is detailed in the “Load Assessment and Categorisation” section.

The remainder of the small industry and commercial treatment costs should be recovered on a standard charge basis per business until such time as a improved system is available. The apportioning of this cost could be improved by using a water usage based system, and this system is currently being considered by the council.

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6.6. SUMMARY CONCLUSIONS AND RECOMMENDATIONS

1. Eighty-eight percent (88%) of the capital costs of the proposed extension are attributable to domestic sewage treatment – estimated at €11.28m (subject to the uncertainties of a probable design-build or design-build-operate contract process).

2. Twelve percent (12%) of the capital costs of the proposed extension are attributable to industrial and commercial sewage treatment – estimated at €1.53m.

3. The capital costs and marginal costs should be reassessed on acceptance of a final design and tender.

4. The sectoral split is set to change significantly from the current situation of 75%/25% domestic/non-domestic to 61%/39% for the extended plant.

5. Sixty-one percent (61%) of the operation and maintenance costs of the extended plant are attributable to domestic sewage treatment – estimated at €1.37m.

6. Thirty-nine percent (39%) of the operation and maintenance costs of the extended plant are attributable to industrial and commercial sewage treatment – estimated at €0.87m.

7. The operation and maintenance costs for industrial and commercial sewage treatment should continue to be recovered by the council from this sector under the ‘polluter pays principle’.

8. The current council programme of monitoring medium to large industry and commercial has significant advantages in both cost recovery and effluent minimisation at source. This should be continued and expanded as appropriate to cater for future development.

9. Small industry and commercial is not practical to monitor individually, as should be charged for sewage treatment on a standard charge basis until such time as other methods are available (such as in relation to water usage).

10. The capital costs of the proposed extension attributable to the industrial and commercial sectors should be recovered from both new development and existing concerns over an appropriate period. This is justified on the basis that the extension of the works is needed not For inspection purposes only. only for additional capacity,Consent butof copyright for owner improved required for treatment any other use. under recent regulations and directives.

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7. PLANNING, CONSTRUCTION, AND PROCUREMENT

7.1. PLANNING AND CONSTRUCTION

The design-build (DB) or design-build-operate (DBO) forms of contract are generally accepted as the most efficient forms of contract for this type of situation. These types of contract are intended to ensure appropriate risk transfer from the Client Authority to the Contractor for the provision of the service. It follows that the Contractor should be given as much freedom as possible, within essential physical and environmental constraints, to determine his preferred treatment process and arrangements to allow him to effectively manage his design, construction and operational risks, while delivering value for money.

Before such a contract can be procured, it is likely that the following steps will need to be completed;

• Completion of statutory process (EIS, site availability)

• Detailed site investigations

• Stakeholder requirements to be defined (staff, etc.)

The essence of the project is that it requires the provision of a technically advanced wastewater treatment facility at Osberstown to meet very demanding effluent quality standards. This will involve advanced treatment technologies and a matching sophistication in operational control and maintenance. The inherent difficulty and risk in operation will obviously be significantly influenced by the process selection, design, and construction. A whole life optimisation approach is needed, therefore, to obtain the best value for money consistent with meeting the technical objectives

7.1.1. Statutory processes For inspection purposes only. As a result of the European UnionConsent Directive of copyright owner on required environmental for any other use. assessment (85/337/EEC), Irish Government Regulations entitled “European Communities (Environmental Impact Assessment) Regulation”, 1989 (SI 349, of 1989) updated by the European Communities (Environmental Impact Assessment) (Amendment) Regulations 1999 and 2000 as well as the 1994 Local Government (Planning and Development) Regulations (SI 86, of 1994) require that an Environmental Impact Statement (EIS) is prepared for these works to be published and submitted to the Competent Authority for the assessment. In this case, that Authority is An Bord Pleanála.

In Circular L3 / 99, the Department of the Environment set out procedures for the carrying out of Water Services capital projects by means of design/build (DB) or design/build/operate (DBO) contract. This circular required assessment in all preliminary reports of use of the design build (DB) or design/build/operate (DBO) (Chapter 11). Clause 3.5 of the Circular requires that the design documentation and environmental impact assessment should reflect performance values rather than detailed design specifications in so far as this is possible. The use of alternative design options should be encouraged even within traditional procurement contracts.

The Circular requires that the performance specification should allow the competing contractors to submit alternative and innovative design options. More detailed guidance in this regard is currently being finalised by the Department for Public Private Partnership (PPP) contracts in the Roads, Water and Waste sections.

The preparation of the EIS will necessarily identify constraints to be applied to the project. The EIS will be carried out in accordance with the European Community’s (Environmental Impact Assessment) (Amendment) Regulations, 1999 and will have regard to the “Draft Guidelines on the Information to be

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Contained in Environmental Impact Statement” published by the EPA, together with their document entitled “Advice notes on Current Practice (in the Preparation of Environmental Impact Statements)”. In 1997, a second directive in relation to Environmental Impact Assessment was adopted by the European Communities (97/11/EC). In Circular 1/99 of the Department of the Environment and Local Government, advice is given on the principal changes contained in the new Directive.

There is a degree of conflict between the objectives of the EIS and those of retaining as far as possible flexibility for innovation in design by the DB/DBO Tenderers. In examples of similar projects to date, the following approach has been adopted:-

• The description of the works is illustrated by indicative layouts showing typical arrangements and details. The level of detail varies with the sensitivity of the site and issues and is governed by what is considered necessary in the particular context.

• Air and noise emissions are critical for a wastewater treatment plant and will be addressed by means of numerical modelling and the setting of performance standards to be achieved at the boundary of the site, without establishing precisely how these standards will be met in terms of process design or equipment. This approach is generally acceptable provided it is demonstrated that the limits can be achieved by available technology.

• Traffic and other social impacts can be assessed by reference to the predicted impact of the development in light of the process options to be considered. In this case, there are no significant differences in the various design options.

To summarise, in principle, reference to performance standards will be used as far as possible in preparing the EIS.

7.1.2. The EIS The EIS for the extension is currently being finalised and is expected to be submitted to An Bord Pleanala in January 2002. The EIS has considered all relevant regulations and guidance, and presents the different design options considered. The recommended constraints and performance standards reflect the likely DB or DBO contract type, and inherent uncertainties. Essentially, the highest degree of freedom in design is allowed for but within the strict performance targets set by the EIS.

For inspection purposes only. Consent of copyright owner required for any other use. 7.1.3. Technical investigations The construction of tankage to accommodate the wastewater treatment processes may involve deep excavations on the site depending on whether a sunken option or an ‘above-ground’ type of construction (as per the current CASS tanks) is adopted. Particular attention should (again) be paid to the risk of flotation of buried tanks.

The extent of excavations on the site will generate significant surplus spoil materials if the buried option is chosen. Some of this material will undoubtedly be used in reshaping the site contours, within the site boundary. Nevertheless, significant volumes of soil will have to be taken off site. This will generate significant traffic movements in the early stages of construction.

7.1.4. Construction impacts Experience of construction of major facilities in built up areas indicates significant public concern with environmental impacts during construction. The EIS will consider these impacts with particular reference to:

• Traffic management and public safety outside the site that would require a traffic management plan to be adhered to by the Contractor throughout the project. This would be particularly sensitive at times of peak traffic associated with disposal of excavated soil, delivery of concrete and other materials.

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• Construction noise and vibration limited by limitation on working hours, night-time and weekend working and by setting limits on noise and vibration limits which would be more stringent during sensitive periods.

• Water pollution from pumping of excavations would require the provision of sedimentation before discharge of pumped flows from the site.

• Construction safety is always critical, given the poor track record of site safety in construction and would require a site specific safety plan to be strictly implemented under the control of the Project Supervisor (Construction). Prior to construction, safety would be an integral consideration in the design stage under the control of a Project Supervisor (Design) in accordance with the Regulations (SI 138/1995).

7.1.5. Stakeholder issues The implications of a DB or DBO contract for existing Local Authority employees requires careful management and consideration. Kildare has a particular circumstance where the council has trained and experienced personnel capable of operating this type of plant, and the council’s personnel costs are low. If a DBO contract is chosen, various options exist including redeployment within the Council or transfer to the Contractor.

In a design-build-operate situation, staff transferring to the contractor would be entitled to protection of current employment conditions under the TUPE Regulations (Transfer of Undertakings Protection of Employment). This ensures that staff transferring would not be financially disadvantaged in a DBO option. Nonetheless, detailed stakeholder discussions are needed to address the impact on staff, determine the options open to them, and consider any aspects not fully covered by TUPE (e.g. pension entitlements).

Satisfactory operation of the sewerage works during the construction period will be a key requirement of the contract. This will involve detailed liaison between Council and Contractor staff. Kildare Co. Co. has experience in this regard from the recent works at both Osberstown and Leixlip. In a DB situation, Kildare Co. Co. would be responsible for plant operation at all times. In a DBO type contract, the optimum approach is for transfer of operation at the outset of the contract, with defined interim performance standards specified during the construction phase of the new plant.

For inspection purposes only. Consent of copyright owner required for any other use. 7.2. PROCUREMENT Circular L3/99 of the Department of the Environment and Local Government set out revised procedures for the carrying out of water services Capital Projects incorporating design/build or design/build/operate (DB and DBO) contract arrangements. This circular was issued in the context of the endorsement by Government of the Public Private Partnership (PPP) model as a way of meeting the major demands for increased investment in national infrastructure.

The wastewater and sludge treatment plants required in this project have the following characteristics;

• They require the application of the most up-to-date technologies available at reasonable cost to meet the discharge standards within the constraints of the site,

• These performance criteria can be satisfied by a range of technical solutions involving different processes and arrangement of plant and equipment,

• Achievement of the specified performance standards will be critically dependent on effective performance management of the plant. Since such plant will inevitably involve sophisticated, mechanical, electrical and control systems, it follows that considerable operational skill and expertise will be required throughout the operating life of the plant to ensure optimal performance,

• The statutory processes required before wastewater treatment plants can be constructed include Environmental Impact Assessment (EIA) approval by An Bord Pleanála in accordance with the

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latest regulations. Implementation of these processes should not preclude suitable treatment systems, as far as practicable.

7.2.1. Preliminary risk assessment A preliminary assessment of key risks to the project was carried out. These risks can be defined as any factor, event or influence that threatens the successful completion or operation of the project in terms of cost, time or quality. When considering PPP options, the scope for transfer of these risks must be evaluated. The key criterion is that the risk should lie with the party who is in the best position to manage it. This fundamental principle should usually result in the best value for money outcome.

At each stage of the project the general risk assessment outcome is identified in:

• Design; Transfer of design risk provides the opportunity for innovative solutions. It is imperative therefore, that the solutions should not be unnecessarily prescriptive. In order to ensure “fitness for purpose”, minimum quality and track record criteria should apply,

• Procurement; PPP options will require new contract and procurement arrangements, currently being developed. Key considerations will be qualification criteria for contractors, tender compliance requirements and evaluation criteria,

• Construction; The availability of the existing site should permit satisfactory definition of ground, archaeology, and other site conditions. Compliance with environmental standards during construction would be vital in this relatively built up rural area. A key consideration would be the maintenance of the existing plants operation at the best possible performance to minimise pollution risk to the streams & foreshores,

• Operation; Traditional and Design Build options effectively result in operational risk being retained by the client. In these options, achievement of performance standards, availability of plant capacity, and equipment maintenance, plays a significant burden on existing organisational structures and resources. As a result, failure to achieve the specified performance levels is a significant risk even for well designed and constructed plant facilities

Design Build (DB) permits transfer of some design and construction risk over and above the traditional approach. However, it would not mitigate and may in fact increase operational risk by virtue of the following factors: For inspection purposes only. Consent of copyright owner required for any other use. • Greater reliance on the Contractor for design standards and quality control,

• Reduced control over process and equipment selection which may result in less robust solution,

• The chosen solution may involve a higher level of operational skill and training than would be normal for a conventional design,

• Technological obsolescence risk could be increased, if spare parts are not guaranteed during the operational life of the plant,

• Sensitivity to price increases, for example energy, may increase the cost of operation compared with a conventional solution

Design/Build/Operate (DBO) procurement has the potential to successfully transfer these operational risks from the Client to the Contractor, by including a significant operational period in the contract. The Contractor must ensure that the choice of process, design and construction of the plant is capable of delivering the specified performance standards. By linking payment to performance criteria, the client is in a position to ensure that this risk transfer is affected.

As outlined, there is a possible advantage of a DB contract is the particular circumstance in Kildare where the council has trained and experienced personnel capable of operating this type of plant. The

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The optimum solution is considered to be that which satisfactorily addresses the technical and environmental constraints at the site while affording a reasonable cost solution. Ultimately, in a competitive tender process, the precise design arrangements offering the most cost effective solution would be determined by the contractor in accordance with the specification criteria. The tender process should be left open to both DB and DBO systems with a clear tender on both elements. A final decision on whether to opt for a DB or DBO contract can then be made. Strict performance objectives and standards are necessary ensure an acceptable final operation standard in either a DB or DBO contract, through appropriate contract monitoring and management systems.

7.2.2. Experience and recommendations from the current Stage 2 plant DB contract The main points noted from the Stage 2 DB contract were:

1. The influent load and treatibilty characteristics must be considered in detail, together with an evaluation of likely change over the construction process, and a range of acceptable influent characteristics and loads must be specified.

2. Any changes from original contract submission must be discouraged, or at least considered in detail and strictly controlled. Any agreed changes should not subsequently facilitate a contractor claim.

3. Notwithstanding the degree of freedom inherent in the DB process design, certain elements of the contract specification must be highly specific, e.g. sampling points/equipment/methodology.

7.3. CONCLUSION Either a DB or DBO contract could be used as the procurement model for future wastewater treatment. A DBO option would allow the Local Authority to shed the risk of operating the treatment plant satisfactorily and in compliance with the performance requirements. A DB contract may have an advantage in terms of operation and maintenance costs in the case of Kildare Co. Co. who have trained and experienced personnel operating For inspection on a lowpurposes cost only. base. Consent of copyright owner required for any other use.

This recommendation provides the best guarantee that the Local Authorities will be in a position to comply with its statutory requirements in respect of wastewater and sludge treatment at Osberstown.

A PPP Assessment report should be prepared at the outset of the contract stage to determine the optimum route to guarantee delivery of the effluent standard at lowest whole life cost, with an appropriate risk management strategy adopted. Provision for long-term upgrading of the plant should also be allowed for.

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8. CONCLUSIONS AND RECOMMENDATIONS

8.1. SUMMARY CONCLUSIONS

1. The option of extending the current treatment plant at Osberstown is considered to be the most practical and cost effective solution to the sewage treatment needs of The Upper Liffey Valley to the year 2021, due mainly to the configuration of the catchment sewerage system and the remaining available area on the site.

2. A receiving water study was carried out for the River Liffey with cognisance taken of all relevant water quality standards and objectives, including the Framework Directive, the Phosphorus Regulations, the Salmonid Regulations, the Urban Wastewater Treatment Directive, and the Liffey Water Quality Management Plan.

3. It was found that the river upstream of Osberstown is unpolluted, with both physico-chemical and biological characteristics supportive of this status.

4. With regard to achieving the objectives of the Phosphorus Regulations downstream of the effluent discharge, the target quality index for 2007 at Castlekeely Ford is Q4 – unpolluted status.

5. The current water quality in the Liffey downstream of the plant shows nutrient levels that are either within set standard limits or consistent with the values in the Liffey upstream of the plant, except for MRP and ammonia values.

6. The main assimilative capacity restriction of the Liffey at Osberstown is in terms of phosphorus capacity.

7. The current (Stage 2) WWTP is unlikely to meet the phosphorus targets for the Liffey at current phosphorus treatment levels and effluent standards. This plant was designed before the advent of stricter water quality standards - principally the Framework Directive and Phosphorus For inspection purposes only. Regulations – and cannot thereforeConsent of copyright be expected owner required to forbe any consistent other use. with target effluent treatment requirements for 2007.

8. The assimilative capacity of the Liffey at Osberstown would safely allow an upgraded WWTP plant with a maximum capacity of 130,000 PE, under the two main conditions that stormwater misconnection is minimised, and that a median concentration effluent standard for TP of 0.35 mg/l is adopted.

9. The upgraded plant requires state of the art treatment based on “P” removal assisted by chemical treatment to meet the best practicable standard. Reference plants for this standard have been identified in Denmark, characterised by expert process monitoring and management.

10. There is a current average influent load of 51,500 PE, out of a total of 60,500 PE connected to the plant. The difference in these actual and potential figures is explained by the weekday commuting of residential population to Dublin and other work-centres, and significant variation in the industrial weekday-weekend load. The capacity of the current plant is 80,000 PE.

11. There is significant variation in the daily loads connected to the plant, with approximately 20% of daily loads below 30,000 PE, and 20% of daily loads above 70,000 PE. The 95-percentile and maximum loads during the past year were 1.8 and 2.5 times the average load, respectively. The design of a future extension to the WWTP will have to allow for these variations.

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12. The analysis of sectoral loads concludes that there is current connection of 45,500 residential population, equivalent to approximately 38,000 PE (at 50g BOD per head), 15,000 PE large industrial-commercial, and 7,500 PE commercial connection.

13. There are significant extraneous inputs to the sewer system, most likely from storm misconnection and groundwater infiltration. A programme of extraneous flow reduction in the sewer system is essential and fundamental to ensuring that the full capacity of both the current and an upgraded plant can be realised. Failure to achieve this element will compromise the capacity of the current plant to below the 80,000 PE design figure, and the proposed upgraded plant to well below the 130,000 PE target.

14. The current plant is projected to reach capacity between 2003 and 2005. The proposed flow reduction programme should be implemented to ensure that the full capacity of this Stage II plant can be achieved, otherwise the timescale to reach capacity will certainly be closer to 2003.

15. The proposed upgraded plant (Stage III) is projected to reach capacity in 2018 at the earliest. Again, this is provisional on the proposed flow reduction programme.

16. The timescales for development in the Upper Liffey Valley catchment presented in this text are based on both the “Strategic Planning Guidelines” and building capacity. The projected growth to 2021 is in the range 112,000 PE to 135,000 PE. The range presented represents a reasonable low and high envelope. It may be noted that the building capacity in the catchment is subject to a fair degree of uncertainty given the multitude of driving forces behind this aspect.

17. It is recommended that the entire treatment plant shall be extended to treat the increasing hydraulic load increasing from the present DWF capacity of 20,000 m3/d to 28,500 m3/d. Depending on the change of concentration of pollutants in the raw wastewater, this will mean an increase from 65,000 PE to a future of 130,000 PE.

18. Assuming the present CASS biological treatment units fulfil the process guarantee, the extension of the biological treatment can be achieved by building a parallel line to the existing CASS tanks. The additional phosphorous removal should be performed in a subsequent polishing step.

19. Commonly used treatment technologies were described and assessed, and four realistic options for the extension of the plant were investigated from both technical and economical

viewpoints. Four design options are For inspectionpresented purposes as only. applicable to the extension under a DB or DBO process: Consent of copyright owner required for any other use.

a. Option 1 - New SBR process line and mesophilic digester b. Option 2 - Conventional Activated sludge process and mesophilic digester c. Option 3 - New Biofilter system d. Option 4 - New SBR process line and thermophilic digester

20. The design options are based on the following extension of capacity and upgraded treatment: a. Existing mechanical treatment b. Extension of primary clarifiers c. New biological treatment line d. New conventional sand filter system with contact filtration e. Extension of sludge digester capacity

21. The estimated capital costs (including sludge treatment extension) are in the range IR£12m to IR£16m (€15m to €20m).

22. The estimated operation and maintenance cost (including sludge treatment extension) is IR£0.8m per year (€1m).

23. It is concluded that there are no limiting conditions for the extension of the plant to a capacity of 130,000 PE at the current site using BATNEEC technologies.

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24. Eighty-eight percent (88%) of the capital costs of the proposed extension are attributable to domestic sewage treatment – estimated at €11.28m (subject to the uncertainties of a probable design-build or design-build-operate contract process).

25. Twelve percent (12%) of the capital costs of the proposed extension are attributable to industrial and commercial sewage treatment – estimated at €1.53m.

26. The capital costs and marginal costs should be reassessed on acceptance of a final design and tender.

27. The sectoral split is set to change significantly from the current situation of 75%/25% domestic/non-domestic to 61%/39% for the extended plant.

28. Sixty-one percent (61%) of the operation and maintenance costs of the extended plant are attributable to domestic sewage treatment – estimated at €1.37m.

29. Thirty-nine percent (39%) of the operation and maintenance costs of the extended plant are attributable to industrial and commercial sewage treatment – estimated at €0.87m.

30. The operation and maintenance costs for industrial and commercial sewage treatment should continue to be recovered by the council from this sector under the ‘polluter pays principle’.

31. The current council programme of monitoring medium to large industry and commercial has significant advantages in both cost recovery and effluent minimisation at source. This should be continued and expanded as appropriate to cater for future development.

32. Small industry and commercial is not practical to monitor individually, as should be charged for sewage treatment on a standard charge basis until such time as other methods are available (such as in relation to water usage).

33. The capital costs of the proposed extension attributable to the industrial and commercial sectors should be recovered from both new development and existing concerns over an appropriate period. This is justified on the basis that the extension of the works is needed not only for additional capacity, but for improved treatment under recent regulations and directives.

34. Either a DB or DBO contract could be used as the procurement model for future wastewater

treatment. A DBO option would For allow inspection the purposes Local only. Authority to shed the risk of operating the treatment plant satisfactorilyConsent and of incopyright compliance owner required with for any the other use. performance requirements. A DB contract may have an advantage in terms of operation and maintenance costs in the case of Kildare Co. Co. who have trained and experienced personnel operating on a low cost base.

35. A PPP Assessment report should be prepared at the outset of the contract stage to determine the optimum route to guarantee delivery of the effluent standard at lowest whole life cost, with an appropriate risk management strategy adopted. Provision for long-term upgrading of the plant should also be allowed for.

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8.2. SUMMARY RECOMMENDATIONS An extended and upgraded wastewater treatment plant should be developed at Osberstown to a total capacity of 130,000 PE, to cater for the sewage treatment needs of the Upper Liffey Valley area for the period to 2021. The extension should be procured under a ‘design-build’ or contract ‘design-build- operate’ contract, depending on the tender costs (whole life assessment). The extended plant should be in place no later than 2005.

A programme of extraneous flow reduction in the sewer system is essential and fundamental to ensuring that the full capacity of both the current and an upgraded plant can be realised. Failure to achieve this element will compromise the capacity of the current plant to below the 80,000 PE design figure, and the proposed upgraded plant to well below the 130,000 PE target. Without this programme, the current plant is likely to reach capacity by 2003.

There are several viable options for extension and upgrading of the plant. A high degree of phosphorus removal is needed to ensure consistency with the 2007 Phosphorus Regulations water quality targets, and therefore the extended plant will require a filtration system for phosphorus removal together with chemical dosing.

Given the tight timescale, both the plant extension and flow reduction programme should be adopted urgently.

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Appendices

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APPENDIX A Water Quality Standards

TABLE A1 STANDARDS FOR QUALITY OF RAW WATER FOR ABSTRACTION

Parameter Unit Standards for Categories

I A1 A2 A3 pH pH Unit 5.5-8.5 5.5-9.0 5.5-9.0 Colouration mg/l Pt scale 20(o) 100 (o) 150(o) Total Suspended mg/l SS 50 Solids Temperature oC 25 (o) 25 (o) 25 (o) Conductivity µs/cm-1 at 20oC 1000 1000 1000 Odour Dilution factor at 25oC 5 10 20 Nitrates mg/l NO3 50(o) 50(o) 50(o) Chlorides mg/l Cl 250 250 250 Phosphates mg/l P2 O5 0.5 0.7 0.7 COD mg/l O2 40 DO % O2 >60% >50% >30% BOD mg/l O2 5 5 7 Ammonium mg/l NH4 0.2 1.5 4 (o)

II Total Coliforms No/100 ml 5,000 25,000 100,000 Faecal Coliforms No/100 ml 1,000 5,000 40,000 Kjeldahl Nitrogen mg/l N 200 2,000 10,000 Dissolved iron mg/l Fe 0.2 2 2 Manganese mg/l Mn 0.05 0.3 1 Copper mg/l Cu 0.50(o) 0.1(o) 1(o) Zinc mg/l Zn 3 5 5 Sulphates mg/l SO4 200 200(o) 200(o) Phenols mg/l C6H5OH 0.0005 0.005 0.1 Surfactants (reacting mg/l laurysulphate 0.2 0.2 0.2 with Methylene blue)

For inspection purposes only. III Consent of copyright owner required for any other use. Fluorides mg/l F 1 1.7 1.7 Boron mg/l B 2 2 2 Arsenic mg/l As 0.05 0.05 0.1 Cadmium mg/l Cd 0.005 0.005 0.005 Total chromium mg/l Cr 0.05 0.05 0.05 Lead mg/l Pb 0.05 0.05 0.05 Selenium mg/l Se 0.01 0.01 0.01 Mercury mg/l Hg 0.001 0.001 0.001 Barium mg/l Ba 0.1 1 1 Cyanide mg/lCN 0.05 0.05 0.05 Dissolved or mg/l 0.01 0.2 1 emulsified hydrocarbons PAH mg/l 0.0002 0.0002 0.001 Total Pesticides mg/l 0.0005 0.0025 0.005 Substances mg/l SEC 0.2 0.4 1 extracted with chloroform Faecal Streptococci No/100 ml 200 2,000 10,000 Salmonella Not present Not present in 500ml in 100ml O = exceptional climatic or geographical conditions

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TABLE A2 STANDARDS FOR SALMONID WATERS

S.I. No. 293 of 1988

Parameter Units Standard Sampling Conformance Frequency to Standard

Temperature oC Downstream of Weekly 98% of time thermal discharge upstream and Discharge > 1.5oC downstream temperature of receiving water > 21.5oC May-Oct > 10oC Nov-April

Dissolved mg/l 02 > 9 Monthly 50% of time Oxygen (D.O.) Danger at 6, L.A. to representative prove no harm to fish of low 02 population conditions E.U. Directive – guidance limits > 7 100% of time pH ≥ 6 <9 Monthly 95% of monthly not exceed ± 0.5 samples change in receiving 100% when less water frequent monitoring

Suspended mg/l < 25 Monthly Average over 12 solids (SS) does not apply to SS months with harmful chemical properties

BOD5 mg/l 02 < 5 For inspection purposes only.Monthly 95% of monthly Consent of copyright owner required for any other use. E.U. directive samples guidance limit < 3 100% when less frequently monitored

Nitrites mg/l < 0.05 Monthly 95% of monthly E.U. Directive samples guidance limit 100% when less < 0.01 frequently monitored

Non-Ionised mg/l NH3 < 0.02 Monthly 95% of monthly Ammonia samples 100% when less frequently monitored

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Parameter Units Standard Sampling Conformance Frequency to Standard

Total Mg/l NH4 < 1 Monthly 95% of monthly Ammonium subject to conforming samples with non-ionised 100% when less ammonia standard frequently monitored

Total Residual mg/l HOC1 < 0.005 Monthly 95% of monthly Chloride samples 100% when less frequently monitored

Total Zinc mg/l zinc < 0.03 to < 0.5 Monthly 95% of monthly Dependant on water samples hardness 100% when less frequently monitored

Dissolved mg/l cu < 0.005 to < 0.112 Monthly 95% of monthly Copper Dependent on water samples hardness 100% when less frequently monitored

Phenolic Not adversely affect Monthly when Compounds fish flavour presence of phenolic compounds are suspended

Petroleum Not form visible film Monthly Hydrocarbons on water surface or benthic surfacesFor inspection not purposes only. Consent of copyright owner required for any other use. be detectable in fish flavour not produce harmful effects in fish

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Table A3 Threshold limits used by the EPA in assessing impaired water quality in Irish rivers

Determinand Min Med Max

pH <6.6 or >9.5 <6.6 or >9.5 <6.6 or >9.5 Conductivity (µS cm-1 ) none none none

Temperature (ºC) >21.5 >21.5 >21.5 Dissolved Oxygen (%) <70 or >130 <70 or >130 <70 or >130

-1 Dissolved Oxygen (mg O2 l ) <7 <9 <9

-1 BOD (mg O2 l ) >3 >3 >5 Cl (mg l-1 ) >50 >999 (saline) >999 (saline) Total ammonia (mg N l-1 ) >0.1 >0.1 >0.3

Un-Ionised ammonia >0.01 >0.01 >0.02 -1 (mg NH3 l ) Oxidised N (mg N l-1) >5.65 >5.65 >5.65 ortho-Phosphate (mg P l-1 ) >0.02 >0.03 >0.15

Colour (Hazen) >50 >50 >100

For inspection purposes only. Consent of copyright owner required for any other use.

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APPENDIX B Detailed report on large industrial/commercial monitoring in the Osberstown catchment

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B CURRENT INDUSTRIAL LOADS

B.1 INDUSTRIAL MONITORING PROGRAMME Table A1 below shows the industries/businesses monitored by City Analysts in December 2000 and January 2001. All major industry was monitored in the catchment. Both individual large industry and industrial estates were monitored. Automatic flow proportional automatic samplers were used to monitor 18 major businesses and 5 industrial estates in the Catchment.

The sampling was carried out for seven days on each of the industrial estates and for a range of 2-7 days for the other industries depending on their size. The parameters BOD, COD, pH, ammonia, total phosphorus (TP), ortho-phosphorus, total kjeldahl nitrogen (TKN), and suspended solids (SS) were analysed. Heavy metals (cadmium, chromium, copper, mercury, nickel, lead, zinc) were monitored at Donnely Mirrors, Champion Spark Plugs, and Newbridge Cutlery.

1.2. Table A1 Industries Monitored by City Analysts Ltd

Name Location Donnelly Mirrors Naas Green Isle Foods Monread Industrial Estate, Naas Monread Industrial Estate Naas Champion Spark Plugs Monread Industrial Estate, Naas Poldy Foods Naas Industrial Estate, Naas Naas Industrial Estate Naas Clongowes Wood College Clane Newbridge Cutlery Newbridge Industrial Estate, Newbridge Clane Hospital Clane Monread Lodge Naas Crogeen Newbridge Newbridge Business Park Newbridge Newbridge Industrial Estate Newbridge Clane Cleaners Ltd Newbridge Industrial Estate, Newbridge* For inspection purposes only. Ashbourne Meats Consent of copyrightNaas owner Industrialrequired for any Estate, other use. Naas Maudlins Industrial Estate Naas Ambassador Hotel Kill QK Foods Maudlins Industrial Estate, Naas Wyeth Medica Newbridge Mc Carthy Meats Clane Schloetter Newbridge Industrial. Estate, Newbridge Newbridge Foods Newbridge Industrial Estate, Newbridge * although Clane Cleaners is located within Newbridge Industrial Estate it’s effluent drains into a separate line to the one monitored, and therefore was considered separately to Newbridge Industrial Estate.

Many of the industries monitored lie within the major industrial estates of Naas and Newbridge (Naas Industrial Estate, Monread Industrial Estate, and Maudlins Industrial Estate (all Naas), and Newbridge Industrial Estate and Newbridge Business Park).

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B.2 OVERALL RESULTS The results of the survey are outlined in Table A2 below, with detailed results contained in the Daily Results Sheets at the end of this section:

1.3. Table A2 Summary industrial loads Industry Monitoring As surveyed PE (from BOD) 7-day days average Average Minimum Maximum QK Foods 6 4,497 3,703 11,911 5,984 Maudlins Industrial Estate 7 4,990 1,125 7,854 4,984 Monread Industrial Estate 6 2,505 787 4,421 2,505 Green Isle Foods 7 1,777 928 2,425 1,777 Clongowes Wood College 7 1,681 733 2,607 1,681 Newbridge Industrial Estate 7 1,503 289 4,017 1,503 Newbridge Foods 7 736 0 1,625 859 Wyeth Medica 7 840 443 1,512 840 Newbridge Business Park 8 836 23 2,121 836 Monread Lodge 2 764 676 851 764 Naas Industrial Estate 7 629 34 969 629 Donnelly Mirrors1 7 568 142 1,184 568 Mc Carthy Meats 4 482 166 1,020 482 Poldy Foods 6 358 160 627 358 Clane Cleaners Ltd 5 176 19 478 176 Crogeen 4 126 44 269 126 Ambassador Hotel 7 96 4 200 96 Clane Hospital 2 47 42 53 47 Ashbourne Meats 6 43 23 73 43 Champion Spark Plugs 7 27 4 76 27 Newbridge Cutlery 6 2 1 2 2 Schloetter 1 0 0 0 0 For inspection purposes only. 2 Consent of copyright owner required for any other use. Totals 14,676 4,384 26,371 14,670 Notes: 1. Donnely Mirrors is in the process of but not currently connected 2. The totals shown are not straight sums down the column, but allow for the industries that were both monitored individually and within industrial estates 3. Calculation of PE from BOD results taken at 60g BOD per PE

Table A3 shows the monitored industries within each industrial estate. Those industries that are part of industrial estates are thus contained in the load calculated from that industrial estate.

1.4. Table A3 Industries within each Industrial Estate

Industrial Estate Industries Naas Industrial Estate Ashbourne Meats Poldy's Foods Monread Industrial Estate Green Isle Foods Champion Spark Plugs Maudlins Industrial Estate QK Foods Newbridge Industrial Newbridge Foods Estate Newbridge Cutlery Schloetter

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From the results outlined in Table A2 it is clear that there are a number of industries contributing high loads to the treatment plant, in particular QK Foods, and notably Green Isle Foods, Wyeth Medica and Newbridge Foods. Clongowes Wood College is another large contributor with the third highest load of all premises surveyed.

The total estimated seven day industrial load of 14,670 PE represents almost 25% of the total load to the plant of 60,000 PE. There is considerable variation in loads from day-to-day, with an estimated range of 5,000 to over 26,000 PE. Both coincident high loads from several industries, or individual industries such as QK Foods and Green Isle Foods have the potential to cause shock loads to the plant, with QK Foods alone having a maximum load of almost 12,000 PE.

Table A4 presents the five and seven day average loads, given the possible variation therein because of the operating regimes of each industry. The weekday load is some 2,500 PE higher than the overall seven-day load. The corresponding average weekday and weekend loads are 17,164 PE and 7,779 PE, respectively, showing a significant bias towards weekday loads.

1.5. Table A4 Average 5-day and 7-day Industrial Loads PE 5-day 7-day Maudlins Industrial Estate 6,492 4,984 Monread Industrial Estate 2,455 2,505 Naas Industrial Estate 773 629 Monread Lodge 764 764 Ambassador Hotel 96 96 Clongowes Wood College 1,830 1,681 McCarthy Meats 483 483 Clane Hospital 47 47 Newbridge Business Park 1,094 836 Newbridge Industrial Estate 1,879 1,503 Crogeen Ltd 126 126 Clane Cleaners Ltd 176 176 Wyeth Medica 949 840

For inspection purposes only. Total LoadConsent of copyright owner required for17,164 any other use. 14,670

The heavy metals results for the three industries showed mainly insignificant levels, with some higher values for e.g. nickel at Newbridge Cutlery. Given the small number and low flows of these industries, heavy metals are not considered a problem in this catchment.

B.3 DISCUSSION OF BOD RESULTS The results of the survey are discussed town by town considering the loads from each of the major contributors.

Naas: Naas is by far the largest contributor in terms of industrial loads. Of the 17,164 PE for the average five- day load to the plant approximately 61% (10,484 PE) of the load is attributed to Naas. There are two major industries in Naas, which constitute a large proportion of the load from the town, QK Foods, and Green Isle Foods. The estimated average load from Green Isle Foods was 1,777 PE (seven day operation) and from QK Foods the average (5 day operation) load was 4,497 PE.

QK Foods was monitored in conjunction with Maudlins Industrial Estate. The results for the two corresponded reasonably well in general with the exception of one date (23/01/01) where the BOD load from the QK plant was higher than that from the Maudlins Industrial Estate. This could be attributed to a

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EPA Export 26-07-2013:00:24:10 Osberstown WWTP Preliminary Report Vol 1 Rev F Upper Liffey Valley Sewerage Scheme Preliminary Report – Volume 1 Extension to Osberstown WWTP - Stage 3 discharge between the sampling point at QK Foods and the sampling point at the end of the Maudlins Industrial Estate, which may be inhibiting the BOD reaction, possibly a heavy metal discharge. There is also a high suspended solids load from the QK site on that date, which may have caused a problem with the BOD results. The calculated five-day BOD Load from the Maudlins is 6,492 PE and the seven-day is 4,984 PE.

Another significant contributor in Naas is the Monread Lodge Pub, where the lack of a grease trap may be a contributing factor, but more likely the proximity to Christmas resulted in the high measurement. It has been assumed that this two day measurement is approximately equivalent to the normal seven day load. Ashbourne Meats is a meat processing factory, which did not exhibit as high a loading as one might have expected. Poldy’s Foods are a significant contributor with a load of 369 PE. It is understood that new treatment facilities are to be constructed in the future

Process effluent from Donnelly Mirrors Ltd is not currently connected to the Upper Liffey Valley Regional Sewerage Scheme, but they will be connecting in the near future. The BOD load is significant with an average PE of 568.

Newbridge: Newbridge is the second biggest industrial centre in the Catchment and has the second largest industrial load attributed to it. It accounted for approximately 25% of the average industrial BOD load for this survey. The major contributors were Wyeth Medica (840 PE), Newbridge Foods (859 PE), Clane Cleaners (176 PE) and Newbridge Business Park, where Barlo Packaging, Oral B and Lily O’Brien’s Chocolates Ltd are located (combined load of 836 PE). Crogeen Ltd are also located in the town. The loads produced from Crogeen were low (average 126 PE) but the BOD concentrations were consistently very high with the concentration reaching 35,200 mg/l on one day.

Clane: There is no large scale industry in the town but Clongowes Wood College boarding school located outside the town is connected to the Upper Liffey Valley Regional Sewerage Scheme. This effluent was found to have an average BOD load of 1,681 PE. Other contributors in the town are McCarthy Meats with an average BOD load of 483 PE. Clane Hospital was also monitored but the load from it was low (47 PE)

Kill: The only business monitored in Kill was the Ambassador Hotel. The average load calculated was 96 PE.

For inspection purposes only. B.4 DISCUSSION OF OTHERConsent PARAMETER of copyright owner RESULTS required for any other use.

Table A5 overleaf illustrates the average loads calculated for the other physico-chemical parameters that were analysed for as part of the survey. These parameters were Chemical Oxygen Demand (COD), Total Phosphorus (TP), Ammonia and Total Kjedahl Nitrogen (TKN).

COD Loads: The major contributors here are QK Foods, Green Isle Foods, Donnelly Mirrors (not yet connected), Clongowes Wood College, Newbridge Business Park, Newbridge Foods, Monread Lodge, McCarthy Meats, Poldy Foods. The COD results are generally indicative of the BOD results, which is as expected. QK Foods are by far the largest contributor.

TKN Load: QK Foods is the major contributor for TKN loads also with the rest of the Maudlins Industrial Estate also contributing quite a large load (approximately 9 kg/day). Clongowes Wood College has the next highest load (11 kg/day). Monread Lodge Pub also has a high load for TN (7.45 kg/day). The rest of the loads are relatively small with McCarthy Meats contributing 4.47 kg/day, and Wyeth Medica 4.13 kg/day. The load for Newbridge Industrial Estate is quite high but the major contributor in the estate Newbridge Foods has a low load indicating there must be other significant discharges coming from the estate. Similarly for Naas Industrial Estate where Poldy’s Foods and Ashbourne Meats are thought to be the major contributors but the load measured is greater than twice their combined load.

TP Load: QK Foods is once again the largest contributor in terms of Total Phosphorus (TP) with an average load of 17.26 kg/day for a period of 5 days. The next largest contributor (excluding Maudlins Industrial Estate) is Wyeth Medica with 2.43 kg/day. This is almost eight times less than the load from QK Foods. Clongowes Wood and the Monread Lodge Pub are both quite high in terms of TP. The load from

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Monread Industrial Estate is quite high and notably the portion contributed by Green Isle Foods is far less than that for the estate in total. The load from Newbridge Industrial Estate is also quite significant.

Ammonia Load: QK Foods is the largest ammonia contributor by far. Clongowes Wood College and the Monread Lodge Pub have the next largest load. The loads calculated for Monread Lodge are extremely high which is remarkable due to the modest size of the business. Wyeth Medica, McCarthy Meats, Newbridge Business Park, Newbridge Industrial Estate and Naas Industrial Estate were also significant contributors.

Table A5 Industrial Loads for other parameters

COD Load TKN Load TP Load Ammonia (kg/day) (kg/day) (kg/day) Load (kg/day) Donnelly Mirrors 150.15 8.49 0.68 0.75 Green Isle Foods 172.09 1.94 0.21 0.17 Monread Industrial Estate 260.52 5.94 1.09 0.59 Champion Spark Plugs 3.07 0.37 0.04 0.36 Poldy Foods 43.37 1.20 0.43 0.01 Naas Industrial Estate 62.61 3.69 0.79 2.19 Clongowes Wood College 149.45 11.95 2.41 7.58 Newbridge Cutlery 0.62 0.05 0.10 0.00 Clane Hospital 7.32 0.75 0.08 0.66 Monread Lodge 87.24 7.45 1.46 6.51 Crogeen 12.71 0.02 0.00 0.01 Newbridge Business Park 103.51 3.71 0.63 2.24 Newbridge Industrial Estate 137.52 6.16 1.18 1.51 Clane Cleaners Ltd 45.47 0.38 0.93 0.01 Ashbourne Meats 6.27 0.17 0.87 0.07 Maudlins Industrial Estate 552.87 40.35 13.55 18.33 Ambassador Hotel 9.56 0.23 0.06 0.01 QK Foods 503.60 31.78 17.26 18.07

Wyeth Medica 92.83 For inspection4.13 purposes only.2.43 2.21 Consent of copyright owner required for any other use. Mc Carthy Meats 58.59 4.47 0.57 2.52 Schloetter 0.04 0.00 0.00 0.00 Newbridge Foods 76.54 1.50 0.19 0.03

B.5 OUTSTANDING ISSUES From the monitoring data there are two dates on which the results for QK Foods do not appear correct, 18/01/01 and 22/01/01. The BOD loads from QK Foods on those dates are greater than the loads from Maudlins Industrial Estate. City Analysts were contacted about this and have assured us that quality checks and tracing of results revealed no errors on their part. Explanations for the problem on the 22/01/01 are as follows:

• That there is an input between QK Foods and Maudlins causing a reduction or inhibition of the BOD. • There was a problem with the BOD sample or sampling equipment

The results for the 18th of January is obviously a sampling error or booking error because the BOD concentration is higher than the COD concentration, which is not possible chemically.

It is recommended that Kildare County Council should carry out further monitoring on the QK Foods and Maudlins Industrial Estate sites. If there are significant discharges to the sewer that have not been

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B.6 SUMMARY The total 7-day averaged BOD load from the major industries and commercial premises in the catchment is 14,670 PE. There is considerable variation in loads from day-to-day, with an estimated range of 5,000 to 26,000 PE. As expected, the major contributors are QK Foods, Clongowes Wood College, and Green Isle Foods, contributing over 50% of the large industrial-commercial BOD load.

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Appendix B Daily Results Sheets

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PE Results Donnelly Green Isle Monread Champion Poldy Naas Clongowes Newbridge Clane Monread Crogeen Newbridge Newbridge Clane Ashbourne Maudlins Ambassador QK Foods Wyeth Mc Carthy Schloetter Newbridge (from BOD) Mirrors Foods Industrial Spark Plugs Foods Industrial Wood Cutlery Hospital Lodge Business Industrial Cleaners Meats Industrial Hotel Medica Meats Foods Estate Estate College Park Estate Ltd Estate

T 30/11/00 292 2,425 F 01/12/00 554 1,882 4,060 34 S 02/12/00 166 928 787 4 S 03/12/00 142 1,716 4,421 9 M 04/12/00 503 1,193 1,902 12 T 05/12/00 1,184 2,212 ragging 29 W 06/12/00 1,135 2,084 2,940 24 T 07/12/00 918 76 160 F 08/12/00 277 613 1,243 S 09/12/00 500 1,911 S 10/12/00 34 733 M 11/12/00 312 652 2,607 2 T 12/12/00 257 969 2,052 2 W 13/12/00 627 943 1,591 2 T 14/12/00 513 690 1,632 2 F 15/12/00 2 42 S 16/12/00 53 676 S 17/12/00 851 M 18/12/00 1

T 09/01/01 58 624 1,272 154 W 10/01/01 269 2,121 1,871 478 T 11/01/01 1,368 4,017 137 F 12/01/01 135 1,757 1,393 19 S 13/01/01 99 835 S 14/01/01 23 289 M 15/01/01 44 382 844 93 T 16/01/01 314 62 W 17/01/01 73 5,613 29 5,333 T 18/01/01 38 4,626 63 6,004 F 19/01/01 7,488 109 3,813 For inspection purposes only. S 20/01/01 Consent of copyright owner required for any other use. 1,125 200 S 21/01/01 1,346 190 M 22/01/01 23 7,854 4 11,911 T 23/01/01 35 6,880 79 3,703 W 24/01/01 27 5,138 T 25/01/01 1,512 F 26/01/01 890 S 27/01/01 693 S 28/01/01 443 M 29/01/01 847 166 0 T 30/01/01 897 559 W 31/01/01 599 185 T 01/02/01 1,020 283 F 02/02/01 916 S 03/02/01 0 S 04/02/01 308 M 05/02/01 961 T 06/02/01 1,625 W 07/02/01 1,059

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Donnelly Green Monread Champion Poldy Naas Clongowes Newbridge Clane Monread Crogeen Newbridge Newbridge Clane Ashbourne Maudlins Ambassador QK Wyeth Mc Schloetter Newbridge Mirrors Isle Industrial Spark Foods Industrial Wood Cutlery Hospital Lodge Business Industrial Cleaners Meats Industrial Hotel Foods Medica Carthy Foods Foods Estate Plugs Estate College Park Estate Ltd Estate Meats

T 30/11/00 17.5 145.5 F 01/12/00 33.3 112.9 243.6 2.0 S 02/12/00 10.0 55.7 47.2 0.2 S 03/12/00 8.5 103.0 265.3 0.6 M 04/12/00 30.2 71.6 114.1 0.7 T 05/12/00 71.0 132.7 ragging 1.7 W 06/12/00 68.1 125.0 176.4 1.5 T 07/12/00 55.1 4.5 9.6 F 08/12/00 16.6 36.8 74.6 S 09/12/00 30.0 114.7 S 10/12/00 2.0 44.0 M 11/12/00 18.7 39.1 156.4 0.1 T 12/12/00 15.4 58.1 123.1 0.1 W 13/12/00 37.6 56.6 95.5 0.1 T 14/12/00 30.8 41.4 97.9 0.1 F 15/12/00 0.1 2.5 S 16/12/00 3.2 40.6 S 17/12/00 51.1 M 18/12/00 0.1

T 09/01/01 3.5 37.5 76.3 9.2 W 10/01/01 16.1 127.3 112.3 28.7 T 11/01/01 82.1 241.0 8.2 F 12/01/01 8.1 105.4 83.6 1.1 S 13/01/01 5.9 50.1 S 14/01/01 1.4 17.3 M 15/01/01 2.6 22.9 50.7 5.6 T 16/01/01 18.8 3.7 W 17/01/01 4.4 336.8 1.7 320.0 T 18/01/01 2.3 277.5 3.8 360.2 F 19/01/01 449.3 6.6 228.8 S 20/01/01 67.5 12.0 S 21/01/01 80.8 11.4 M 22/01/01 1.4 471.2 0.2 714.7 T 23/01/01 2.1 412.8 4.7 222.2 For inspection purposes only. W 24/01/01 Consent of copyright owner required for any other use. 1.6 308.3 T 25/01/01 90.7 F 26/01/01 53.4 S 27/01/01 41.6 S 28/01/01 26.6 M 29/01/01 50.8 10.0 0.0 T 30/01/01 53.8 33.5 W 31/01/01 36.0 11.1 T 01/02/01 61.2 17.0 F 02/02/01 55.0 S 03/02/01 S 04/02/01 18.5 M 05/02/01 57.7 T 06/02/01 97.5 W 07/02/01 63.5

Average 34.1 106.6 150.3 1.6 21.5 37.7 100.9 0.1 2.8 45.8 7.6 50.2 90.2 10.6 2.6 299.4 5.8 269.8 50.4 28.9 0.0 51.5 BOD Load PE 568.1 1,777.2 2,504.6 26.8 357.7 628.6 1,681.4 1.7 47.5 763.7 126.5 835.9 1,503.0 176.1 43.1 4,990.2 96.2 4,496.7 840.2 482.5 0.0 858.8

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Donnelly Green Isle Monread Champion Poldy Naas Clongowes Newbridge Clane Monread Crogeen Newbridge Newbridge Clane Ashbourne Maudlins Ambassador QK Foods Wyeth Mc Carthy Schloetter Newbridge Mirrors Foods Industrial Spark Plugs Foods Industrial Wood Cutlery Hospital Lodge Business Industrial Cleaners Meats Industrial Hotel Medica Meats Foods Estate Estate College Park Estate Ltd Estate

T 30/11/00 186.78 222.26 F 01/12/00 110.57 181.02 296.10 3.19 S 02/12/00 45.30 103.77 273.00 0.36 S 03/12/00 25.92 133.92 328.30 0.83 M 04/12/00 147.84 129.376 151.26 1.23 T 05/12/00 251.90 214.37 ragging 5.54 W 06/12/00 282.77 219.91 289.80 4.67 T 07/12/00 224.66 5.65 51.24 F 08/12/00 24.96 78.38 121.0 S 09/12/00 48.90 220.2 S 10/12/00 3.33 73.6 M 11/12/00 36.48 69.44 297.9 0.4 T 12/12/00 53.47 95.24 141.4 0.6 W 13/12/00 48.51 73.28 84.9 0.5 T 14/12/00 45.56 69.73 107.1 0.4 F 15/12/00 0.8 5.6 S 16/12/00 9.1 71.0 S 17/12/00 103.5 M 18/12/00 1.0

T 09/01/01 5.8 83.2 126.2 59.5 W 10/01/01 31.3 228.8 196.4 112.1 T 11/01/01 180.0 261.6 31.4 F 12/01/01 9.6 227.0 157.9 8.6 S 13/01/01 9.5 101.8 S 14/01/01 2.7 22.9 M 15/01/01 4.1 62.1 95.8 15.8 T 16/01/01 34.7 8.9 W 17/01/01 13.0 1029.6 4.3 675.0 T 18/01/01 3.6 490.7 7.1 345.3 F 19/01/01 647.8 8.7 436.5 S 20/01/01 137.6 18.0 S 21/01/01 136.0 16.0 For inspection purposes only. M 22/01/01 Consent of copyright owner required for any other use. 2.7 669.9 0.8 737.3 T 23/01/01 6.8 758.4 12.1 353.3 W 24/01/01 2.7 474.3 T 25/01/01 166.3 F 26/01/01 89.7 S 27/01/01 71.0 S 28/01/01 56.4 M 29/01/01 34.8 16.8 0.0 T 30/01/01 100.2 64.7 W 31/01/01 131.4 40.7 T 01/02/01 112.1 37.2 F 02/02/01 136.8 S 03/02/01 S 04/02/01 53.8 M 05/02/01 110.2 T 06/02/01 66.8 W 07/02/01 54.5

Average 150.15 172.09 260.52 3.07 43.37 62.61 149.4 0.6 7.3 87.2 12.7 103.5 137.5 45.5 6.3 552.9 9.6 503.6 92.8 58.6 0.0 76.5 COD Load

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Donnelly Green Isle Monread Champion Poldy Naas Clongowes Newbridge Clane Monread Crogeen Newbridge Newbridge Clane Ashbourne Maudlins Ambassador QK Foods Wyeth Mc Carthy Schloetter Newbridge Mirrors Foods Industrial Spark Plugs Foods Industrial Wood Cutlery Hospital Lodge Business Industrial Cleaners Meats Industrial Hotel Medica Meats Foods Estate Estate College Park Estate Ltd Estate

T 30/11/00 10.4 2.9 F 01/12/00 7.0 1.1 11.1 0.2 S 02/12/00 2.7 1.3 3.0 0.0 S 03/12/00 1.7 1.8 9.1 0.1 M 04/12/00 9.9 1.1 4.3 0.4 T 05/12/00 13.1 1.7 ragging 0.6 W 06/12/00 14.5 3.8 2.1 0.4 T 07/12/00 6.1 0.8 1.1 F 08/12/00 0.8 4.3 11.0 S 09/12/00 3.5 11.0 S 10/12/00 0.4 6.6 M 11/12/00 1.3 4.8 18.0 0.1 T 12/12/00 1.6 4.7 14.1 0.0 W 13/12/00 1.4 4.3 11.7 0.1 T 14/12/00 1.0 3.8 11.3 0.0 F 15/12/00 0.0 0.6 S 16/12/00 0.9 6.6 S 17/12/00 8.4 M 18/12/00 0.1

T 09/01/01 0.0 2.2 3.3 0.4 W 10/01/01 0.1 9.9 6.4 0.8 T 11/01/01 7.4 19.9 0.4 F 12/01/01 0.0 6.0 4.7 0.1 S 13/01/01 0.5 3.1 S 14/01/01 0.2 2.0 M 15/01/01 0.0 2.1 3.6 0.1 T 16/01/01 1.5 0.2 W 17/01/01 0.3 36.3 0.1 30.4 T 18/01/01 0.1 33.4 0.3 22.5 F 19/01/01 61.1 0.1 30.5 S 20/01/01 11.2 0.4 S 21/01/01 9.4 0.3 For inspection purposes only. M 22/01/01 Consent of copyright owner required for any other use. 0.1 58.2 0.0 52.2 T 23/01/01 0.2 73.0 0.3 24.0 W 24/01/01 0.1 31.0 T 25/01/01 3.9 F 26/01/01 3.2 S 27/01/01 2.0 S 28/01/01 1.7 M 29/01/01 2.6 1.7 0.0 T 30/01/01 5.3 4.9 W 31/01/01 10.1 2.6 T 01/02/01 8.6 0.7 F 02/02/01 2.8 S 03/02/01 S 04/02/01 1.5 M 05/02/01 1.6 T 06/02/01 1.1 W 07/02/01 1.3

Average 8.5 1.9 5.9 0.4 1.2 3.7 12.0 0.1 0.7 7.5 0.0 3.7 6.2 0.4 0.2 40.4 0.2 31.8 4.1 4.5 0.0 1.5 TKN Load

MCOS/207-501-001/ Rp010 App.17 Rev F

EPA Export 26-07-2013:00:24:10 Osberstown WWTP Preliminary Report Vol 1 Rev F Upper Liffey Valley Sewerage Scheme Preliminary Report – Volume 1 Extension to Osberstown WWTP - Stage 3

Donnelly Green Monread Champion Poldy Naas Clongowes Newbridge Clane Monread Crogeen Newbridge Newbridge Clane Ashbourne Maudlins Ambassador QK Wyeth Mc Carthy Schloetter Newbridge Mirrors Isle Industrial Spark Foods Industrial Wood Cutlery Hospital Lodge Business Industrial Cleaners Meats Industrial Hotel Foods Medica Meats Foods Foods Estate Plugs Estate College Park Estate Ltd Estate T 30/11/00 0.74 0.11 F 01/12/00 0.55 0.19 0.39 0.08 S 02/12/00 0.21 0.01 0.02 0.01 S 03/12/00 0.19 0.01 0.06 0.09 M 04/12/00 0.68 0.07 0.07 0.32 T 05/12/00 1.58 0.18 ragging 0.61 W 06/12/00 1.31 0.62 0.10 0.77 T 07/12/00 2.93 0.63 0.01 F 08/12/00 0.00 2.98 8.21 S 09/12/00 2.38 5.44 S 10/12/00 0.13 4.60 M 11/12/00 0.01 2.44 9.80 0.00 T 12/12/00 0.01 1.91 8.97 0.00 W 13/12/00 0.04 2.96 7.43 0.00 T 14/12/00 0.01 2.53 8.61 0.01 F 15/12/00 0.00 0.48 S 16/12/00 0.85 5.17 S 17/12/00 7.86 M 18/12/00 0.00

T 09/01/01 0.00 1.41 0.67 0.01 W 10/01/01 0.00 6.15 2.01 0.03 T 11/01/01 4.76 4.02 0.01 F 12/01/01 0.03 3.33 0.80 0.00 S 13/01/01 0.25 1.11 S 14/01/01 0.19 1.29 M 15/01/01 0.00 1.05 0.67 0.00 T 16/01/01 0.77 0.09 W 17/01/01 0.16 10.01 0.00 10.06 T 18/01/01 0.05 7.72 0.00 5.48 F 19/01/01 21.32 0.00 19.18 S 20/01/01 6.15 0.01 S 21/01/01 2.81 0.01 M 22/01/01 0.00 47.20 0.01 41.32 T 23/01/01 0.08 33.12 0.01 9.66 W 24/01/01 0.05 22.72 T 25/01/01 2.67 For inspection purposes only. F 26/01/01 Consent of copyright owner required for any other use. 1.29 S 27/01/01 0.27 S 28/01/01 0.13 M 29/01/01 0.51 0.97 0.00 T 30/01/01 3.51 4.47 W 31/01/01 7.10 1.57 T 01/02/01 3.08 0.01 F 02/02/01 0.11 S 03/02/01 S 04/02/01 0.01 M 05/02/01 0.05 T 06/02/01 0.00 W 07/02/01 0.03

Average 0.75 0.17 0.59 0.36 0.01 2.19 7.58 0.00 0.66 6.51 0.01 2.24 1.51 0.01 0.07 18.33 0.01 18.07 2.21 2.52 0.00 0.03 Ammonia Load

MCOS/207-501-001/ Rp010 App.18 Rev F

EPA Export 26-07-2013:00:24:10 Osberstown WWTP Preliminary Report Vol 1 Rev F Upper Liffey Valley Sewerage Scheme Preliminary Report – Volume 1 Extension to Osberstown WWTP - Stage 3

Donnelly Green Isle Monread Champion Poldy Naas Clongowes Newbridge Clane Monread Crogeen Newbridge Newbridge Clane Ashbourne Maudlins Ambassador QK Foods Wyeth Mc Carthy Schloetter Newbridge Mirrors Foods Industrial Spark Plugs Foods Industrial Wood Cutlery Hospital Lodge Business Industrial Cleaners Meats Industrial Hotel Medica Meats Foods Estate Estate College Park Estate Ltd Estate

T 30/11/00 0.76 0.45 F 01/12/00 0.45 0.03 0.94 0.03 S 02/12/00 0.22 0.16 0.85 0.01 S 03/12/00 0.17 0.22 2.42 0.02 M 04/12/00 1.17 0.08 1.03 0.05 T 05/12/00 1.02 0.10 ragging 0.09 W 06/12/00 0.95 0.41 0.07 0.00 T 07/12/00 1.22 0.11 0.43 F 08/12/00 0.31 0.79 2.20 S 09/12/00 0.76 2.19 S 10/12/00 0.07 1.12 M 11/12/00 0.52 1.12 4.47 0.03 T 12/12/00 0.47 1.01 2.65 0.11 W 13/12/00 0.46 0.92 1.91 0.15 T 14/12/00 0.36 0.84 2.32 0.09 F 15/12/00 0.06 0.06 S 16/12/00 0.10 1.46 S 17/12/00 1.46 M 18/12/00 0.16

T 09/01/01 0.00 0.38 0.52 1.08 W 10/01/01 0.00 1.64 1.35 1.99 T 11/01/01 1.06 3.35 1.12 F 12/01/01 0.00 1.19 0.97 0.17 S 13/01/01 0.18 0.68 S 14/01/01 0.04 0.52 M 15/01/01 0.00 0.30 0.90 0.28 T 16/01/01 0.24 0.04 W 17/01/01 0.05 21.79 0.05 21.93 T 18/01/01 0.02 12.71 0.04 13.61 F 19/01/01 17.27 0.04 12.31 For inspection purposes only. S 20/01/01 Consent of copyright owner required for any other use. 4.18 0.13 S 21/01/01 1.87 0.09 M 22/01/01 1.36 13.30 0.00 19.71 T 23/01/01 2.11 23.72 0.09 18.03 W 24/01/01 1.65 17.97 T 25/01/01 2.91 F 26/01/01 2.95 S 27/01/01 1.89 S 28/01/01 1.26 M 29/01/01 1.82 0.10 0.00 T 30/01/01 2.53 0.73 W 31/01/01 3.69 0.48 T 01/02/01 0.97 0.14 F 02/02/01 0.31 S 03/02/01 S 04/02/01 0.13 M 05/02/01 0.28 T 06/02/01 0.10 W 07/02/01 0.16

Average TP 0.68 0.21 1.09 0.04 0.43 0.79 2.41 0.10 0.08 1.46 0.00 0.63 1.18 0.93 0.87 13.55 0.06 17.26 2.43 0.57 0.00 0.19 Load

MCOS/207-501-001/ Rp010 App.19 Rev F

EPA Export 26-07-2013:00:24:10 Osberstown WWTP Preliminary Report Vol 1 Rev F Upper Liffey Valley Sewerage Scheme Preliminary Report – Volume 1 Extension to Osberstown WWTP - Stage 3

Appendix C – Polluter Pays calculations

Extension only O&M costs

O&M cost estimate – Option 1 Type Units Nos. IR£/unit IR£/year Electricity kWh/year 1,310,000 0.06 79,000 Precipitation chemicals tons/year 370 120 44,500 Polymers kg/year 9,300 5 46,500 tons/year *Sludge transport and disposal 5,200 60 312,000 (20% DS) Staff persons/year 2 25,000 50,000 Miscellaneous % 10 - 53,000 % Maintenance 2.5 - 219,000 (of investment cost) IR£804,000 Total €1,021,000

Total less sludge* €625,000 Notes: In the calculation for power consumption it is assumed that approx. 30% of the total power consumption can be covered by the CPHs.

The precipitation chemicals include both chemical precipitations in the biological treatment unit as support to the biological phosphorus removal and chemical dosing for contact filtration.

Polymer consumption is both for the mechanical thickeners and for final dewatering.

The O&M cost estimate corresponds approximately to IR£0.26 per m3 of treated wastewater.

O&M cost estimate – Option 2 Type ForUnits inspection purposes only. Nos. IR£/unit IR£/year Consent of copyright owner required for any other use.

Electricity kWh/year 1,110,000 0.06 66,500 Precipitation chemicals tons/year 300 120 36,000 Polymers kg/year 8,900 5 44,500 tons/year Sludge transport and disposal 4,900 60 294,000 (20% DS) Staff persons/year 2 25,000 50,000 Miscellaneous % 10 - 49,000 % Maintenance 2.5 - 215,000 (of investment cost) IR£755,000 Total €959,000

Total less sludge* €585,000 Notes: Compared to Option 1 the power consumption is estimated to be approx. 15% lower due to more continuous and effective aeration and mixing of the process tanks.

The biological phosphorus removal is assessed to be more efficient for the conventional activated sludge process compared to the SBR/CASS process, whereas the precipitation chemical consumption is lower than for Option 1.

MCOS/207-501-001/ Rp010 App.20 Rev F

EPA Export 26-07-2013:00:24:10 Osberstown WWTP Preliminary Report Vol 1 Rev F Upper Liffey Valley Sewerage Scheme Preliminary Report – Volume 1 Extension to Osberstown WWTP - Stage 3

Polymer consumption and expenses for sludge transport and disposal are slightly lower than Option 1 due to less chemical sludge production.

The O&M cost estimate corresponds to approximately. IR£0.24 per m3 of treated wastewater.

O&M cost estimate – Option 3 Type Units Nos. IR£/unit IR£/year Electricity kWh/year 1,390,000 0.06 83,500 Precipitation chemicals tons/year 900 120 108,000 Polymers kg/year 6,000 5 30,000 tons/year Sludge transport and disposal 3,300 60 198,000 (20% DS) Staff persons/year 2 25,000 50,000 Miscellaneous % 10 - 47,000 % Maintenance 2.5 - 287,500 (of investment cost) 804,000 Total €1,021,000 Total less sludge* €769,000 Notes: Compared to a conventional treatment plant (Option 2) it is the consultant’s experience that the power consumption for a plant based on submerged biofilters is approx. 25% higher due to less possibility for optimisation of the aeration system.

For this option it is assumed that the plant is operated with pre-precipitation, i.e. dosing of precipitation chemicals before the primary clarifiers. It is the consultant’s experience that efficient removal of primary sludge before the biofilter units is important for a satisfactory operation. Most of the phosphorus removal will thus be based on chemical precipitation.

The sludge production for submerged biofilter plant is approx. 2/3 of the sludge production from a conventional plant. Hence the operation costs for polymer consumption and sludge transport and disposal are correspondingly lower. For inspection purposes only. Consent of copyright owner required for any other use.

The biological phosphorus removal is assessed to be more efficient for the conventional activated sludge process compared to the SBR/CASS process, whereas the precipitation chemical consumption is lower than for Option 1.

Polymer consumption and expenses for sludge transport and disposal are slightly lower than Option 1 due to less chemical sludge production.

The O&M cost estimate corresponds to approximately IR£0.26 per m3 of treated wastewater.

MCOS/207-501-001/ Rp010 App.21 Rev F

EPA Export 26-07-2013:00:24:10 Osberstown WWTP Preliminary Report Vol 1 Rev F Upper Liffey Valley Sewerage Scheme Preliminary Report – Volume 1 Extension to Osberstown WWTP - Stage 3

O&M cost estimate – Option 4 Type Units Nos. IR£/unit IR£/year Electricity kWh/year 1,500,000 0.06 90,000 Precipitation chemicals tons/year 370 120 44,500 Polymers kg/year 11,200 5 56,000 tons/year Sludge transport and disposal 5,200 60 312,000 (20% DS) Staff persons/year 2 25,000 50,000 Miscellaneous % 10 - 55,500 % Maintenance 2.5 - 208,000 (of investment cost) IR£816,000 Total €1,036,000 Total less sludge* €640,000 Notes: As the demand for heating of the digesters will be higher for thermophilic digestion, the surplus gas production for power consumption will be less. The net power consumption is estimated to be approx. 15% higher than for Option 1.

Thermophilic digested sludge contains a higher amount of colloids compared to mesophilic digested sludge. This has a negative effect on the de-waterability of the sludge. Therefore the polymer consumption is estimated to be approx. 20% higher for Option 4 compared to Option 1.

The O&M cost estimate corresponds to approximately IR£0.26 per m3 of treated wastewater.

Current (Stage 2) plant O&M costs

O&M costs 2002 – Current Plant at 60,500 PE = €1,520,000 Less Sludge disposal -€286,000 Costs 2001 €1,234,000

The increase in O&M costs to 80,000 PE Foris calculatedinspection purposes as only. a proportional increase. Consent of copyright owner required for any other use.

Estimate of O&M at 80,000 PE: €1,645,000.

MCOS/207-501-001/ Rp010 App.22 Rev F

EPA Export 26-07-2013:00:24:10