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Report to Public Protection Policy Development and

Review Panel Date: 23 June 2009 Report of: Director of Regulatory Services Subject: PEEL COMMON WASTE WATER TREATMENT WORKS

SUMMARY

This report provides Members with an update on the current situation relating to the control of odours from the operation of the Peel Common Waste Water Treatment Works.

RECOMMENDATION

(a) That the work that has been undertaken by the Peel Common Odour Forum over the last eight years in reducing the levels of odour emanating from the Peel Common Waste Water Treatment Works be noted; and

(b) That, given the improvements that have been made, the Peel Common Odour Forum now meets with representatives of Southern Water on an annual basis.

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INTRODUCTION

1. Since the inception of the Peel Common Odour Forum the number of odour complaints has steadily reduced and the Council has not received a complaint of odour from the site since 17 January 2009. This was attributed to a breakdown at the site. Prior to this the last complaint received was on 12 April 2007. Gosport Borough Council has not received any complaints since 2006. The last report to the Public Protection Review Panel was on 6 March 2007 and this report provides Members with an update. For information and included in the following table is the number of complaints received by Southern Water since 2002 :

Year No. of complaints

2002 111

2003 59

2004 37

2005 35

2006 19

2007 20

2008 27

2009 to date 10

PEEL COMMON WASTE WATER TREATMENT WORKS

2. Appendix A provides some background to the Peel Common Sewage Works.

It details the type of odour problems and complaints this Council has received in the past as a result of the operations undertaken on site.

3. A number of measures and controls have been put in place over recent years to address the odours and there has been a steady reduction in the numbers of complaints.

PEEL COMMON ODOUR FORUM

4. The Peel Common Odour Forum was established in April 2001. It had Member and Officer representation from Fareham and Gosport Borough Councils, Officer and Management representation from Southern Water and representatives from local residents and, occasionally, from HMS Collingwood.

5. The group has been very effective in highlighting the issues and problems experienced by the local community, as well as maintaining the impetus and commitment of Southern Water in working to resolve the problem. The Forum has been very successful in influencing Southern Water`s capital investment plans to ensure that odour reduction works were implemented. Without this, progress would have been much slower and may well have required either or both Councils having to take regulatory action for statutory nuisance.

6. Meetings of the Forum were initially held on a quarterly basis and this reduced to six monthly. However, given the work that has been undertaken on site and the improvements that have been made in addressing the odour problems, reflected in the reduction in the number of complaints received, it is recommended that the meeting of the Forum now takes place on an annual

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basis.

PROGRESS ON ODOUR REDUCTION AND CURRENT ODOUR REDUCTION MEASURES

7. Phase 1 of Southern Water’s odour reduction measures at Peel Common

consisted of two parts. Part 1 was concerned with trials in the use of Potassium Permanganate to neutralise odour forming compounds from sewage sludge. These trials were undertaken in 2003 by Southern Water, at locations within the process that were identified as a major source of the odour problem. These trials showed that the use of Potassium Permanganate was effective in reducing odours. Complaints almost halved. Therefore, in 2004 Southern Water invested a quarter of a million pounds to make this system permanent and it is still operational today. Covers and enclosures were also installed to contain odours from plant and chambers.

8. Further measures were proposed to be included in Part 2 of Phase 1. These were completed in 2005 at a cost to Southern Water of £250,000. The four measures were as follows:

Installation of purpose built permanent Potassium Permanganate dosing system;

Permanent tanker point for emergency tanker discharges;

Sludge screening skip to be covered and connected to treatment plant;

Inlet point (DC2) to be totally enclosed and odour to be drawn off into odour treatment plant.

9. Odour monitoring carried out by Southern Water Services (SWS) indicated

that the Phase 1 improvements had led to a reduction in the number of complaints. However, it was accepted by Southern Water that further improvements were still needed to reduce the impact of the site on local residents. A table showing the reduction in odour complaints is included in Appendix B.

10. Phase 2 improvements consisted of seven measures which were completed in

2008:

Replace existing ferric dosing plant;

Replace old bio-filters serving sludge storage tanks and general maintenance of covers;

Replace old bio-filter serving the inlet works and general maintenance of aluminium cover of screw pumps and inlet works;

Cover Distribution Chamber No. 3 and opening channel and provide odour treatment of extracted foul air;

Cover weir channels for primary tanks and provide odour treatment of extracted foul air;

Carry out permanent boundary Hydrogen Sulphide monitoring;

Provision of new cesspool reception area.

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REPLACEMENT BIO-FILTERS

11. In 2007 the old bio-filters on site were replaced with two different environmentally-friendly systems to treat odours from the sludge storage tanks and inlet works.

12. A sustainable, green technology solution has been employed which uses natural materials like bark, wood chips, seaweed and seashells as the filtering media. Bacteria live on these materials inside an enclosed tank and these break down gases such as hydrogen sulphide that cause the smells. This gas is drawn into the tanks by fans and the treated gas is eventually vented back to the atmosphere. This environmental friendly technology achieves over 90% odour reduction. A "polishing" carbon filter makes sure any remaining odour is removed.

13. The shell filter holds 95,000 litres of seashells gathered from around the coast of the UK and Ireland but after a period of three to six years the shells will dissolve and have to be replaced. The wood chip tank filter contains 183 cubic metres of pinewood chips, supplied from forests in Norfolk and Gloucester as a waste product from saw mills and some 30 cubic metres of seaweed, which comes from local beaches, Cornwall and the Irish Sea.

14. Odour monitoring at the site is carried out by measuring levels of hydrogen

sulphide from all around the site. Hydrogen sulphide can be used as an indicator of the odours that local residents experience.

Further Information on Phase 2 is provided in Appendix B. NUTRIENT REMOVAL SCHEME

15. In 2008, new plants for nutrient removal were commissioned at Peel Common wastewater treatment works as part of a £3O million scheme to improve water quality in the Solent. A brand new activated sludge plant was constructed to provide extra aeration and a carbon source was introduced to remove more pollutants from sewage. This means not only carbonaceous pollutants such as Biological Oxygen Demand are removed from the sewage; but now ammonia and nitrate are also removed, which should help protect the Solent from algae bloom. Recycling of aerobic sludge from the new plant to the primary settlement process helps control odours from these large open tanks. Thus, the biggest plant upgrade for Peel Common waste water treatment works in more than three decades has delivered both cleaner treated waste water and fresher air for the benefits of the local communities.

16. The process of nitrogen removal involves passing the sewage through anoxic tanks which starve the bacteria of oxygen. This forces the bacteria to use oxygen from other solids within the sewage resulting in nitrogen being released into the atmosphere rather than being discharged into receiving waters. The nitrogen released into the atmosphere has no adverse environmental effects.

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17. The nitrogen removal scheme was completed by March 2008. A 50% reduction in hydrogen sulphide emissions also resulted in further reductions in the odour from the operations undertaken on the site.

18. An article appeared in the Spring 2009 edition of Fareham Today that set out the improvements that had been made and this is attached as Appendix C. THE WAY FORWARD

19. Over recent years Southern Water has adopted a very positive approach to the odour problems and issues raised by the Council. The meetings that have taken place with Southern Water have been constructive and the Forum has seen the gradual progress made via the 2 phase staged improvements at the site, which appear to have resulted in a significant reduction in odour complaints. The Council will continue to monitor any complaints received and work with Southern Water where necessary to resolve any issues and it is recommended that the Peel Common Odour Forum now meets on an annual basis to be arranged in October/November of each year.

RISK ASSESSMENT

20. A Risk Assessment is attached as Appendix D.

CONCLUSION

21. This report provides members of the Panel with an update on the progress made in the control of odours from Peel Common waste water treatment works.

22. The Council will continue to monitor and investigate any complaints received from the public about odours from the site and will liaise closely with SWS in respect of any future problems. However as the level of complaints received has considerably reduced, it is now recommended that the meeting of the Peel Common Odour Forum takes place on an annual basis that will enable Southern Water to provide an annual update for Members and Officers of current work and future developments.

Background Papers: Report to Health and Environment Committee, Peel Common Waste Water Treatment Works, 23 May 2000. Report to Health and Environment Committee, Peel Common Waste Water Treatment Works, 5 March 2002. Report to Health and Environment Overview Panel Committee, Peel Common Waste Water Treatment Works, 17 March 2003 Report to the Executive, Peel Common Waste Water Treatment Works, 24 March 2003 Report to the Health and Environment Overview Panel, Peel Common Wastewater Treatment Works, 9 September 2003 Report to Public Protection Review Panel, Peel Common Wastewater Treatment Works, 6 March 2007

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Reference Papers: Appendix A: History of Peel Common Waste Water Treatment Works Appendix B: Peel Common Wastewater Treatment Works Odour Control

Phase II Appendix C: Article in Spring 2009 edition of Fareham Today Appendix D: Risk Assessment Enquiries: For further information on this report please contact Karen Brett (Ext 2399).

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APPENDIX A

HISTORY OF PEEL COMMON WASTE WATER TREATMENT WORKS

INTRODUCTION

1. The Peel Common Waste Water Treatment Works were commissioned in 1980. The site covers 37 acres and is designed for a dry weather flow of waste water of 1,000 litres every second. It currently serves a population of approximately a quarter of a million people and operates at an average flow of 591 litres per second. The works serve Hamble, Titchfield, Warsash, Fareham and Gosport catchment areas.

TREATMENT PROCESS

2. The process at Peel Common follows the conventional pattern of screening out debris (rags, wood, large stones), grit removal, settlement to remove solids or sludge, biological treatment and final sedimentation. The treated water is then released via a long outfall to the Solent.

3. Approximately 18 tonnes of sludge per day are processed at the site. The sludge solids are collected at various stages and retained in tanks where further separation takes place and water recovered. A further process at Peel Common is where the sewage sludge is taken from the primary and secondary treatment tanks and dewatered. The sludge is dewatered by passing through large mangle-like presses to produce a 'cake', which used to be incinerated. However, the incinerator was decommissioned in July 2001.

4. The dewatered sludge 'cake' is now put into enclosed skips and transported to a Sludge Treatment Centre in Havant for final treatment.

5. The treated waste water flows into the final tanks where further settlement to produce a cleared liquid takes place. This is then released via a long outfall into the Solent. The quality of the cleaned water is constantly monitored to ensure it complies with stringent environmental standards.

ODOUR PROBLEMS

6. The odour problem associated with the operation of this site results from the anaerobic biological decomposition of organic materials. Gases and vapours are formed as part of the breakdown of material; the typical odours are hydrogen sulphide, ammonia and methane. Hydrogen sulphide has a characteristically rotten egg smell and is a good indicator of odour intensity in the air. It occurs predominantly in areas where oxygen is not present such as stagnant areas and the sludge handling systems.

7. It is this that Southern Water has identified as being the source of what local residents refer to as the "Peel Common Pong".

8. A number of measures and controls have been put in place over the years to address the problem of odours from the operations undertaken on site. Since Peel Common was opened in 1980, significant investment has been put into place to address odour issues. This includes the dosing of an iron based chemical (ferric chloride), the covering of certain wells and the installation of

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four biological filter beds. Air from known odour causing areas of the site is removed by fans and piped through these filters.

COMPLAINTS

9. Because of the concern about the operation of the water treatment works generally, the Peel Common Joint Working Group was established in the 1980s. It was made up of officers and Members of both Fareham and Gosport Borough Councils.

10. Improvements were carried out at the request of the Joint Working Group and complaints received from local residents relating to the smell from the operation of the site reduced significantly from a peak in 1985 when 100 complaints a month were received to only a handful in recent years.

11. However, whilst improvements have been made the odour problem still exists. Whilst the number of complaints has significantly reduced, it is possible that local residents have grown to accept the smell and some may have become discouraged by the lack of progress in totally resolving the problem and have ceased to complain even though the problem still exists.

PEEL COMMON ODOUR FORUM

12. Following further complaints from local residents and local Ward Councillors a site visit and meeting was arranged at the Peel Common site in April 2001.

13. The purpose of the meeting was an opportunity for local residents and Fareham Borough Council to discuss direct with Southern Water issues and concerns relating to the ongoing odour complaints from the operation of the Peel Common Waste Water Treatment Works.

14. Southern Water acknowledges that there is a smell problem from the operation of the plant but local residents have either given up complaining or have become resigned to and have accepted it and put up with the problem.

15. One issue therefore was how better to inform local residents of what to do if they are affected by the smell and what to do to register their complaint to enable Southern Water and the Council to get a better picture of the problem and for Southern Water to devise a strategy for addressing the problem.

16. Therefore a number of press releases were made and the telephone number of Southern Water's Customer Service Centre was promoted in the local press and Fareham Today requesting local residents to report to Southern Water incidents when they are affected by the smell. This information has been used to gauge the extent and degree of the problem.

17. The objective was to identify the source and cause of any odour which local residents experience which would then assist Southern Water in identifying and investigating specific ways to address the problem.

18. Following on from this initial meeting in April 2001 the Peel Common Odour Forum was established. The group now has Member and Officer representation from Fareham and Gosport Borough Councils, Officer and Management representation from Southern Water, representatives from local

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residents and from HMS Collingwood.

19. The Forum has proved to be a very effective group in highlighting the issues and problems that the local community is experiencing and which are now being addressed by Southern Water.

20. As well as working with Southern Water in addressing the problem, the Forum is also ensuring that the impetus and commitment by Southern Water is maintained and the need to resolve the problem kept high on their agenda.

21. As a result Southern Water has commissioned two separate surveys of the site which have investigated the sources of odour identified by the Forum and has undertaken an independent study looking at hydrogen sulphide, a major constituent of the smell on the site The press houses have been identified as the predominant source.

22. Southern Water has emphasised its commitment to resolving the odour problem and the results of these studies have been used to put together an investment programme which has now been submitted to the Company's funding Board.

23. At the same time it has been stressed to Southern Water that if satisfactory progress is not made to address the odour problem then the Council would have no hesitation in forcing the issue by instigating the necessary enforcement action to require Southern Water to abate the odour problem.

POTASSIUM PERMANGANATE TRIAL

24. Southern Water's technical experts have considered various engineering and technical solutions. The favoured solution involves the use of a chemical potassium permanganate, a strong oxidising chemical, which would be added into the sludge pipeline as sludge is being piped to the processing area which has been identified as a major source of the odour problem. The potassium permanganate reacts rapidly with hydrogen sulphide and turns it into odourless sulphates. Southern Water felt confident that this would be successful in addressing the odour problem.

25. The Southern Water funding board has formally acknowledged the odour problems at Peel Common and has sanctioned the odour reduction trial ahead of implementing a proven long-term solution. During the trial other studies will run in parallel which will look at shrouding the presses with the extraction and treatment of the odorous air, monitoring and improving the performance of the existing bio filters and reviewing the performance of the sludge consolidation tanks.

26. The commencement of the trial and the addition of the chemical started in February 2002. As the chemical trial is carried out, Southern Water, as stated above, will also be looking into the feasibility of isolating the odour releasing sources and treating the affected air.

27. Southern Water monitored the site and the sludge during the trial as well as customer feedback on any problems associated with smell/odour from operations on site. Residents who experienced such problems were

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requested and advised to contact Southern Water's Call Centre on 0845 278 0845 with specific details of their name, address and contact details together with a description of the smell, how it is affecting them and the date(s) and time(s) the odour problem was experienced.

28. The Council, in highlighting the work that is being undertaken to address the odour problem issued press releases so that local residents knew what to do if they experience the odour problems. This assisted Southern Water and the Council to gauge how effective the trial had been.

29. The work of the Peel Common Odour Forum has been effective in not only highlighting the odour problems that the local community still experiences but also in Southern Water putting in place short and long-term measures that hopefully will now begin to address the odour.

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APPENDIX B

Peel Common WTW Odour Control Phase II

18/5/2006

Peel Common Odour Phase 2 Southern Water

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CONTENTS

EXECUTIVE SUMMARY ............................................................................................................. - 13 -

INTRODUCTION ........................................................................................................................... - 13 -

PURPOSE OF THIS PAPER ................................................................................................................. - 13 -

BACKGROUND ................................................................................................................................ - 13 -

PHASE 1 SCHEME AND IMPROVEMENT MADE .................................................................. - 14 -

ODOUR CONTROL MEASURES IMPLEMENTED .................................................................................. - 14 -

EFFECT OF PHASE 1 ........................................................................................................................ - 14 -

DRIVERS FOR PHASE 2 .............................................................................................................. - 17 -

OUTSTANDING ODOUR ISSUES ............................................................................................... - 17 -

ODOUR SOURCES IDENTIFIED .......................................................................................................... - 17 -

ODOUR IMPACT ASSESSMENT ......................................................................................................... - 17 -

PHASE 2 SOLUTIONS .................................................................................................................. - 18 -

OBJECTIVES OF THE SCHEME .......................................................................................................... - 18 -

TECHNICAL MEASURES ................................................................................................................... - 18 -

IMPACT OF THE NUTRIENT REMOVAL SCHEME ............................................................................... - 19 -

COSTS OF PHASE 2 SOLUTIONS .............................................................................................. - 21 -

CAPITAL COST ................................................................................................................................ - 21 -

CAPITAL COST ................................................................................................................................ - 21 -

IMPLEMENTATION OF PHASE 2 ............................................................................................. - 21 -

CONCLUSIONS AND RECOMMENDATIONS ......................................................................... - 22 -

CONCLUSION .................................................................................................................................. - 22 -

RECOMMENDATION ........................................................................................................................ - 22 -


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Executive Summary The technical brief for Phase 2 odour control at Peel Common, consists of 4 measures, has been agreed. The estimated total cost for implementing the measures is within or close to the company budget of £1.8 million provided the scheme were implemented in the most efficient manner. It is in the best interest of the company if the first three measures of Phase 2 are implemented as early as possible in 2006 and this ambition is achievable.

Introduction

Purpose of this paper

This paper presents information for the Phase 2 odour control scheme at Peel Common WTW, including:

a review of Phase 1

the driver for Phase 2

an assessment odour sources

solutions identified

costs, and

strategy for delivery

Background

Site location;

Peel Common WTW is located to the south of Fareham in the Gosport area of Hampshire.

Wastewater and sludge treatment processes

Peel Common WTW and serves the catchment of Farnham, Lee on Solent, Portchester, Gosport and the surrounding area with a population equivalent of about 236,000. The sewage treatment includes screening, grit removal, storm treatment, primary sedimentation, activated sludge and secondary sedimentation. Indigenous sludge is stored in four mixed-sludge storage tanks and dewatered by four belt presses. Raw sludge cake is transported off-site in open-topped skips. A nutrient removal scheme is underway to provide additional aeration lanes to achieve nitrification and denitrification. An asset maintenance scheme is


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planned to install 6-mm screening, macerator and new cesspool import facilities. No major change is anticipated for the sludge treatment processes.

History of the odour issue

The site had a long history of odour complaints. Phase 1 odour control scheme (250k) was completed between 2003 and 2004. A customer forum is regularly attended by local residents and senior managers of Southern Water.

Phase 1 scheme and improvements made

Odour control measures implemented

Phase 1 delivered four odour control measures, as below.

Table 1 Phase 1 odour control measures

Description of work Effects Issues

A potassium permanganate system was installed in the press house.

Typically 90-95% reduction of H2S emission from the press house was achieved, eliminating about half the site’s total H2S emission at daytimes

The new system suffered reliability problems after commissioning.

A liquid sludge tanker discharge line was installed.

Odour emission during reception of liquid sludge import is eliminated.

This system is used on emergencies but it allows a hatch of the sludge tank to be permanently closed.

A GRP/PVC enclosure was installed over the sludge screenings skip.

Odour is prevented from escaping from the screenings skip.

The tidiness of this area was improved.

GRP cover was installed on the sewage distribution chamber DC2.

The H2S concentration above the DC2 is reduced by 95%, eliminating about 5% of the site’s total H2S emission.

The quality of the cover and access provided are good

Effect of Phase 1

Odour complaints

Odour complaint information over a four-year period before and after Phase 1 was reviewed. Before Phase 1, the site receives in excess of 100 complaints per year. After the completion of Phase 1, the site receives less than 40 complaints per year. In particular, daytime complaints decreased by over 75% (where the main measures were aimed). There were no changes in night-time odour complaints (see table).


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Table 2 Odour complaints

Time of complaints

Year 07:00-13:00 13:00-19:00 19:00-07:00 Total

2002 55 46 10 111

2003 25 21 13 59

2004 12 13 12 37

2005 13 5 17 35

The extent of odour affected area decreased substantially as a result of Phase 1 (see figures).


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Figure 1. Odour complaint footprints before and after Phase 1

Summary

The Phase 1 scheme has achieved significant reduction of odour complaints.


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Drivers for Phase 2

Despite the improvement achieved by Phase 1, Peel Common is still among the top 10 sites in the company for odour complaints. The current odour complaint footprint affects an area of 3.2-m2 containing up to 3,000-properties. The residents have strong expectation for further improvement after OFWAT approved the K4 investment plan.

Outstanding odour issues

Odour sources identified

The remaining odour sources at Peel Common include the failed odour control filters, the primary tanks, the grit channels, DC3, DC4, the cesspool reception area and the belt press building. The relative impact of these odour sources was assessed and illustrated in the figure below.

Figure 1 Relative impact of odour sources

Relative impact from odour sources

Primary tanks

22.75%

Grit channels

10.41%

Cesspool reception

6.20%Biofilter 3 (inlet)

5.83%

Biofilters 1&2 (sludge)

29.77%

Storm tanks

2.91%

Flow distribution chamber

6.53%RAS screw pump

0.30%Final settlement tanks

0.00%

Aeration plant

5.89%

Belt presses

5.18%

Cake skips

1.32%

Sludge storage tanks

2.91%

Odour impact assessment

The odour impact of site is assessed using a dispersion model. The predicted area of potential impact according to the company standard is similar to the actual complaint footprint of 2004-5.


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Figure 3. Predicted odour impact footprint after Phase 1 scheme

Phase 2 Solutions

Objectives of the scheme

The Phase 2 is a ‘best endeavour effort’ with no guarantee to eliminate all complaints. However, a significant reduction of odour complaints must be achieved.

Technical measures

The following odour control measures have been identified, listed in order of priority: 1. Install a new ferric dosing plant to optimise septicity control, This will have

a much greater impact on odours form the grit channel and primary tank areas.

2. Replace the old odour control biofilters serving the sludge consolidation tanks area with a new odour treatment plant including refurbishing the tank covers and renewing odour collection ductworks

3. Replace the old odour control biofilter serving the inlet works area with a new odour treatment plant

4. Provide continuous H2S monitoring at site boundaries


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The above list targets the worst odour sources. The potential impact of each measure has been evaluated in the following table.

Table 2. H2S emissions from various odour sources (mg/s)

Source name Now (After Phase 1)

After Phase 2 Phase 2 measures contributing to

change

Cesspool reception 7.96 7.96 None

Grit channels 13.36 1.55 1, 4

Primary tanks 29.2 15.6 1, 5

Storm tanks 3.74 0.52 1


8.38 0 4

Aeration plant 7.56 7.56 None

RAS screw pump 0.38 0.38 None

Sludge storage tanks 3.74 0 2

Belt presses 6.65 6.65 None

Cake skips 1.7 1.7 None

Biofilters 1&2 (sludge) 38.22 0.38 2

Biofilter 3 (inlet) 7.48 0.37 3

Skips 0.2 0 6

Total 128 43

Reduction (%) - 67%

Impact of the Nutrient Removal Scheme

The Nutrient Removal scheme is expected to deliver odour control benefits in ways shown in the following table. Table 2. Anticipated odour reduction from the nutrient removal scheme

Source name After Phase 2 After Nutrient Scheme

Factors contributing to change

Cesspool reception 7.96 0.08 New cesspool reception facility will

be equipped with odour control

Grit channels 1.55 1.55 None

Primary tanks 15.6 10.9 More stable SAS containing nitrate will

be returned to the PSTs

Storm tanks 0.52 0.52 None


0 0 None

Aeration plant 7.56 0.01 Nitrifying activated sludge will emit less

odours

RAS screw pump 0.38 0 Nitrifying activated


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Source name After Phase 2 After Nutrient Scheme

Factors contributing to change

sludge will emit less odours

Sludge storage tanks 0 0 None

Belt presses 6.65 6.65 None

Cake skips 1.7 1.7 None

Biofilters 1&2 (sludge) 0.38 0.38 None

Biofilter 3 (inlet) 0.37 0.37 None

Total 43 22

Reduction (%) 50%

It is assumed that the Nutrient removal scheme will not create additional odour.

Residual odour impact after Phase 2

A re-run of the dispersion model indicate that the vast majority of the residents in the surrounding area previously affected will no longer be adversely affected by odour after both schemes have completed. A small number of properties closest to the site may still receive some impact but the potential exposure of odour will be less frequent and at lower concentrations than at the present.

Figure 3. Predicted odour impact footprint after Phase 2 and the nutrient removal scheme


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Costs of Phase 2 solutions

Capital cost

The net capital cost for the seven odour control measures is estimated by the Asset Planning team. Direct quotations were obtained from framework suppliers for all main equipment to ensure confidence of the estimates. Based on the information obtained, the total cost for implementing Phase 2 in its integrity should be within or close to the company budget of £1.8 million if the most efficient delivery route (i.e. one which incurs the lowest overhead cost) is selected.

Capital cost

The new ferric dosing plant provides scope for optimising the dosing rate of existing ferric dosing operation. The power consumption of the odour treatment plant will be equal or slightly reduced due to lower overall airflow rates and more efficient fans.

Implementation of Phase 2

In order to achieve the objective of Phase 2, adopting a suitable strategy of implementation is as important as identifying the right solutions. Progressive abatement with early delivery of visible improvements offers the best way forward. An example of such a programme is indicated below.

Table 5 Example programme for implementation

Work to be implemented 2006 2007 2008 2009

Implemented measures 1, 2, 3 and 4

Monitoring the result, evaluate and refine

Monitoring the result, evaluate the needs for further abatement

Prepare briefs of Phase 3 for PR05 funding if required

This strategy of implementation offers the following benefits:

prevent lack of progress in 2006, which could trigger enforcement actions, which in turn, might lead to stakeholder let expansion of the scope for Phase 2 (a financial risk to SW)

allow SW to monitor the benefits of the first sets of measures to refine the other measures, in particular, the effects of improved septicity control on odours from the grit channels and primary tanks (measures 4 and 5).

allow SW to re-evaluate measures 4, 5 and 6 after the new screens have been completed.

progressive abatement encourage positive communication with the residents during the investment period.


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Conclusions and recommendations

Conclusion

The technical brief for Phase 2 odour control at Peel Common, consists of 7 measures, has been agreed. The estimated total cost for implementing the measures is within or close to the company budget of £1.8 million provided the scheme were implemented in the most efficient manner.

Recommendation

The odour abatement solutions identified in this paper should be implemented in its integrity but in a progressive manner to achieve the objectives within the budget.

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Appendix - Table A1 Further design information

Odour control measure

Effect to be achieved

Other benefits and constraints

Design information Requirement

Replace existing ferric dosing plant with a new, larger new plant and relocate the dosing point upstream of the screw pumps

Reduce H2S emission from inlet works, grit channel, DC3 and PST by making the sewage less septic

Flow proportional dosing, new standby dosing pump and increased chemical storage will improve the reliability and cost-effectiveness of this operation.

Current ferric dosing rate 700 l/d. One dosing pump operating at fixed dosing rate. Maximum size of delivery is 21 tonnes

Duty and standby dosing pump rated at 100 l/h with flow proportional dosing control and low/high flow cut-off. Maximum size of delivery is 25 tonnes. Chemical storage should be equal or larger than 14 days usage plus one maximum size delivery.

Replace failed compost filters serving the sludge storage tanks with a new odour treatment plant and carry out general maintenance of the GRP covers of the sludge storage tanks.

Reduce H2S emission from the sludge storage area by 95-99%

Existing compost filters and its ventilation system have failed, allowing odour to escape from the sludge tanks.

Total volume of 4 no sludge consolidation tanks = 4000 m3. Volume of sludge reception tank = 120 m3. Volume of skip kiosk = 30 m3. Total volume of 2 no decant chambers = 10 m3. Total flow of existing biofilters = 12000 m3.

1.5 air changes per hour are required for sludge consolidation tanks and sludge reception tank, 3 air changes or 120% of the maximum decant flow for decant chambers and 6 air changes for the skip kiosk. Range of H2S according to PS4WT-022. Stack height and treatment efficiency to be determined by dispersion model

Replace failed compost filter serving the inlet works with a new odour treatment plant and carry out general maintenance of the aluminium cover of the screw pumps and inlet works.

Reduce H2S emission from the inlet works by 90%

The existing compost filter has failed, leaving untreated foul air being discharged into the atmosphere without proper treatment.

Total ventilated space (screw pumps, DC1, DC2) is about 3200 m3. The actual ventilation flow of the existing system is unknown but likely to be in excess of 12000 m3.

Range of H2S according to PS4WT-022. Stack height and treatment efficiency to be determined by dispersion model

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Odour control measure

Effect to be achieved

Other benefits and constraints

Design information Requirement

Cover DC3 and opening channel up to the grit channel bridge and provide odour treatment of extracted foul air

Eliminate H2S emission from the highly turbulent DC3

The need to retain the moving bridge carrying the grid pumps prevents a cost-effective solution to cover the grid channels. The combination of the new ferric plant and this measure will reduce the odour from the grit channel area by 75%.

Two channels operating as duty / standby, with a mixing chamber and a penstock at the end. Total surface area of channel and chamber about 60 m2.

Range of H2S according to PS4WT-022.Stack height and treatment efficiency to be determined by dispersion model. A small local odour control unit is required.

Cover the weir channels for 3 no primary tanks and provide odour treatment of extracted foul air in conjunction with odour controlled areas of the new nutrient treatment plant

Prevent high concentration H2S plumes formed above the PST weirs

The requirement to retain existing scraper bridges prevents a cost-effective solution to cover the PSTs.

3 no. PSTs discharging into common weir channel. Total surface area of weir channel approximately 80 m3.

3 air changes per hour are required. Range of H2S according to PS4WT-022. Odour may be treated together with odour extracted from the new mixing chambers and anoxic zones of the nutrient removal plant. Stack height and treatment efficiency to be determined by dispersion model

Overall scheme H2S emission will be reduced by two third

H2S emission will be further reduced after the Nutrient removal scheme is completed.

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APPENDIX C

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APPENDIX D RISK ASSESSMENT

Impact Description Potential Risks Comments Potential

Opportunities Comments

CORPORATE OBJECTIVES

Implications in relation to:

achieving Corporate Objectives and Priorities

Corporate Governance Responsibilities

No significant risks. Contributes to a safe and healthy place to live and work

PARTNERSHIPS

Implications for any existing partnership arrangements Risks or opportunities for new partnerships

No significant risks. This builds upon the joint working with GBC and SWS to address the odour problem

FINANCE AND RESOURCES


Budget Constraints

Funding

Contractual Obligations or Penalties

Use of Land or Assets

This proposal can be met within existing budget limits.

No significant opportunities.

LEGAL


Statutory or discretionary powers

National Legislation (e.g. Human Rights, Data protection etc)

Failing to comply with legislative requirements of service

Potential litigation action

No significant risks. No significant opportunities.

PERSONNEL


Organisational change

Employee policies and conditions

Skill availability

Training and Development


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SERVICE


performance targets

the operation of the service

the need for Change Management

Competitive advantage of the service

Technological impacts

Innovation

The needs of residents, businesses or visitors to the Borough

No significant risks. The work that has been undertaken by the forum has resulted in less complaints being received about odour

HEALTH & SAFETY

Implications for the Health & Safety of the Public, Employees or Members


CRIME & DISORDER


Council’s Section 17 Obligations

Community Safety

Anti-fraud and corruption


ENVIRONMENTAL


Sustainability

Public Health

Physical risks

No significant risks. The work that has been undertaken has addressed the odour problem and the associated work has also addressed the level of nitrates contained in the treated water.

EQUALITY AND DIVERSITY


Inclusion

Equality of access and opportunity


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Cohesion

Diversity

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