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ADVANCED DIGESTION IN ANGLIAN WATER – SUMMARY OF AMP 4 DELIVERY EXPERIENCE AND AMP 5 DELIVERY PLAN Riches, S.1, Oliver, B.2, Nossiter, P.³ and Newton, J.4 1Anglian Water, 2 Imtech, ³Black and Veatch, 4 Mott MacDonald, UK Corresponding Author Tel. 01543 496600 Email

Abstract

During AMP 4 Anglian Water delivered four Advanced Digestion plants at King’s Lynn, Cottonvalley, Great Billing and Whitlingham. Collectively these sites were designed to process up to 99,000 tonnes dry solids producing enhanced quality sludge and generating 40GWh/year of renewable power. Two of the plants included Monsal enhanced enzymic hydrolysis and two plants used Cambi thermal hydrolysis. This paper compares operational experience at these four sites and the basis for learning lessons and developing an optimised AMP 5 delivery plan. Early experience of the AMP 5 delivery programme is also presented. Overall Anglian Water has committed to generate almost 90 GWh/year by the end of AMP 5 through its Advanced Digestion plants.

Key words

Advanced Digestion, Enhanced enzymic hydrolysis, Cambi Thermal Hydrolysis, Carbon reduction, High Efficiency CHP, enhanced sludge quality, power self sufficient operation, operational savings and sustainability.

Introduction

Anglian Water has led the UK Water industry in successfully developing and delivering four full- scale Advanced Digestion plants in AMP4. These plants at King’s Lynn, Cottonvalley, Whitlingham, and Great Billing, were designed to process up to 99,000 tDS/y of raw sludge (approx 54% of all sludge produced across Anglian Water), to produce enhanced quality sludge cake, and deliver lowest sustainable cost of service with targeted operational savings of over £6M/yr and generate more than 40GWh of renewable power.

Both Enhanced Enzymic Hydrolysis and Thermal Hydrolysis plants have been delivered. This paper takes an overview of Anglian Water’s experience in developing, delivering, commissioning, improving performance, operating and maintenance experience associated with this programme. In turn, important lessons have been learned, allowing Anglian Water to optimise the development and delivery of its AMP5 Biosolids programme.

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Development of the AMP 4 Biosolids programme

Following agreement of the AMP 4 Business Plan Anglian Water appointed Mott MacDonald to help develop a procurement strategy for its Special Projects programme of work. Anglian Water chose to select delivery partners principally based on their proven technical capability and ability to work in a collaborative and innovative arrangement. Anglian Water, with assistance from its framework consultant, Mott MacDonald, selected two delivery partners, GTM (a joint venture between Galliford Try and Imtech) and Black and Veatch (formerly Gleeson ECL), working alongside AWS client staff and their programme management consultant Mott MacDonald.

The original business plan was to process 77,000tDS/y of sludge to enhanced quality within a capital budget of £86M, operational impact of £3M/y and hence whole life cost of approximately £180M.

The Special Projects team was invited to review the basis of the programme, seek innovation, and develop the lowest sustainable whole life solution. Innovation and collaboration with the Operations team and the principal supply chain partners including specialist enzymic and thermal hydrolysis pre-treatment technologies rather than pasteurization, with Advanced Digestion solutions at four sites (instead of five as originally planned) and substantial operational cost savings.

The optimized solution was to process up to 99,000tDS/y of sludge to enhanced quality within an increased capital budget of £95M, but with forecast operational savings of £6M/y and hence more than halving the whole life cost at approximately £75M.

Figure 1 provides a summary of development of the AMP4 Biosolids programme.

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Original five proposed sites – pasteurisation Final four sites – enhanced digestion only

King’s Lynn King’s Lynn 31 December 2007 Whitlingham 31 December 2009 19,000 tDS/year Whitlingham 19,000 tDS/year 19,000 tDS/year 20,900 tDS/year

Flag Fen 13,100 tDS/year

Corby/Broadholme Great Billing 12,600 tDS/year 31 December 2009 38,700 tDS/year

Cottonvalley Cottonvalley 31 March 2008 13,700 tDS/year 22,000 tDS/year

Figure 1: Summary of AMP4 sites – before and after optimisation

A highly collaborative framework (under an NEC umbrella) with an incentivized capital and operational commercial model was agreed which sought to share best practice, share pain and gain equitably and ensure that following handover the delivery partners were incentivized to support the local operations teams to fully optimize performance and maximize operational savings for a period of two years.

Actions were taken at both programme and project level. At programme level it was decided to use advanced sludge digestion technology combined with the most efficient CHP engines available – with the following environmental benefits:

• Reduced reliance on lime treatment of sludge which is not considered to be a long term sustainable solution • Increased biogas production from the digestion process – with very efficient use of the biogas to maximise renewable energy generation together with optimising the energy balance of the system and hence reduce carbon emissions associated with grid power use • Reduced quantities of treated biosolids which is then transported for agricultural use – resulting in significantly lower transport impacts than lime treatment or even conventional digestion • A stable high quality treated biosolid product that is virtually odourless and pathogen free that is safer and easier for farmers to apply.

At project level there were a number of activities which mitigated potential environmental impacts at the various sites, for example:

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• Optimisation of wastewater treatment processes (e.g. at Great Billing) or use of advanced liquor treatment technologies (e.g. at Whitlingham) to ensure that centrate returning from sludge treatment does not adversely affect the performance of the wastewater treatment plant at each site and hence impact on final effluent compliance and receiving watercourses. • Detailed ecological assessments at each site and species relocation in accordance with Natural requirements in order to reduce potential impacts on wildlife. • Use of landscaped bunding to reduce potential visual impacts and keep excavated material on site, also providing habitats for wildlife. • Careful use of natural drainage channels and SUDS solutions such as swales to reduce impacts due to surface water run-off from the new developments. • Reduced sludge cake vehicle movements and mileage through 40% reduction in cake volume. • Re-use of waste streams to reduce use of potable water. • Careful design of odour control, boiler building and exhaust stack heights in order to minimise potential odour and other air quality impacts • Re-use of existing structures and buildings – including foundations – in order to minimise new build and associated impacts (construction, embodied carbon). • Use of vibro-compacted stone columns instead of conventional piling – helping to reduce materials consumption.

Description of projects

Cottonvalley (Milton Keynes)

• 21,000 tDS/y capacity (treating approx 14,000 tDS/y) • Raw sludge dewatering and cake imports • Single stream four reactor Cambi plant with new steam plant and CHP (new 1750 KWe engine and existing 625 KWe engine) • Up-rated wastewater treatment to treat high strength liquors (by others) • Uprated existing digesters including jet mixing • Centrifuge dewatering and cake recycling achieving > 28%DS

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Photo one: Cottonvalley (Milton Keynes)

Whitlingham (Norwich)

• 20,900 tDS/y capacity (treating approx 14,000 tDS/y now the SHARON liquor treatment plant commissioning has been completed) • Raw sludge dewatering • Single stream four reactor Cambi plant with new steam plant and CHP (new 1750 KWe engine, old 840 KWe unit removed from service) • Specialised SHARON plant to treat high strength ammonia liquors • Uprated existing digesters including jet mixing • Use existing belt presses to dewater and cake recycling achieving >30%DS

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Photo two: Whitlingham (Norwich)

King’s Lynn

• 19,000 tDS/y capacity (treating approx 10-12,000 tDS/y) • No significant change to sludge tankering operations • Full greenfield development i.e. limited interfaces with existing assets • No additional liquor treatment • No reliance on satellite dewatering sites

Photo three: King’s Lynn

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Great Billing (Northampton)

• 38,700 tDS/y capacity (treating approx 28-34,000 tDS/y) • Significant change in operation & management of large satellite sites – converted to regional dewatering sites • Approx 2/3 sludge imported as cake • Multiple interface points with existing assets, e.g. thickening and digestion • Need to balance and dose Ferric Sulphate to treat high strength liquors

Photo four: Great Billing (Northampton)

Programme Delivery

Following agreement of the revised strategy the first two projects to be delivered were King’s Lynn and Cottonvalley. King’s Lynn was a greenfield site adjoining the existing wastewater treatment works and was the first example of enhanced enzymic hydrolysis including steam heating of the second stage pasteurisation system – a refinement developed by the Special Projects team to reduce capex and improve operation. Initial process commissioning commenced in November 2007 and following an extended period of commissioning to fully integrate the overall sludge treatment plant, handover and performance testing was completed in May 2008. This site then became the blueprint for the innovative SOOP (Sludge Opex Optimsation Plan) support service, whereby the team continued to support local operations to maximise performance and operational savings.

The second project to be successfully delivered was the Cambi thermal hydrolysis plant at Cottonvalley. This project had different challenges including integration within the existing anaerobic digestion plant and very congested site layout. This plant was commissioned in

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2008/9 and again required an extended period of process commissioning in order to overcome a series of operational challenges. Issues associated with biogas quality have reduced engine availability, a siloxane removal plant was installed and commissioned in April 2011 to resolve these issues, allowing the plant to operate at its full design capacity.

Great Billing was the third project to be delivered. This was a sensitive site and required improvements to overcome local concerns before planning approval was given. The project was then constructed within a challenging period of 13 months. This site included integration with existing digestion facilities, dewatering and transport of raw sludge cake from other large satellite works including Flag Fen (Peterborough) and Broadholme (Wellingborough). Full commissioning and integration of this project was very challenging. The team worked closely with local operations to integrate the site facilities and understand the importance and dependency of operating the major satellite sites. Ultimately, this project has been operated at its design throughput, achieving impressive levels of renewable power generation and operational savings.

The final project to be delivered was Whitlingham, which included Cambi thermal hydrolysis integrated into the existing digestion facility. Delivery of this project built on lessons learnt at Cottonvalley to maximise factory pre-assembly and minimise the site construction period. Challenges with liquor treatment required the installation of a specialised liquor treatment plant (SHARON). Unfortunately the construction of this plant was delayed due to planning and construction issues and construction commenced in summer of 2010. The process has now been fully commissioned allowing the Advanced Digestion plant to be operated at full throughput.

Each of the above projects has been subject to regular programme level review with full collaborative support and sharing of lessons learnt. In turn each project has been supported by a two year period of operational support to maximise performance and operational savings. The relationships built with local operational teams have been very good and certainly helped to maximise the operational benefits from this programme.

Performance

This programme has delivered industry leading performance, which is summarised below.

Capital cost

The original capital cost for this programme of work was approximately £120M and included only pasteurisation processes. In contrast, the project team has delivered optimised whole life cost treatment solutions based on both enzymic and thermal hydrolysis advanced digestion processes, including associated site specific works such as liquor treatment, for an overall out turn capital cost of approximately £100M.

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Enhanced quality

Although very limited previous experience was available additional features have been added to each of the four digestion plants, including steam heating for second stage enhanced hydrolysis and UV disinfection of final effluent for sludge dilution and polymer makeup. Regular testing of the treated biosolids cake has demonstrated that enhanced quality, as defined by the Safe Sludge Matrix, can be reliably produced at each of the four sites, safeguarding Anglian Water’s sustainable biosolids recycling operations.

Renewable power

Both enzymic and thermal hydrolysis has helped to maximise volatile solids destruction at each of the four Advanced Digestion plants. The measured volatile solids destruction has typically ranged from 50-55% for enhanced enzymic plants and 60-65% for Cambi thermal hydrolysis. This increased volatile solids destruction has in turn maximized biogas production at each site. High efficiency CHP units were selected for each project with an electrical conversion efficiency of over 40% under design load conditions. A combination of the above enhancements has helped to achieve industry leading levels of renewable power generation at each site.

Under test conditions the industry leading specific renewable power efficiency of 1 MWh/tDS has been measured at each plant. However, the challenge has been to maintain sludge throughput, and overall plant efficiency and availability on an ongoing basis. Target setting and enhanced operational management with support from the Special Projects team has helped to closely monitor the long term performance level at each site, identify issues, realize opportunities for improvement and implement risk mitigation measures. Understanding interdependencies and rigorous performance management including daily reporting and effective management has helped Anglian Water achieve long term efficiency levels of approximately 0.7MWh/tDS at King’s Lynn and Great Billing. Additional investment has been required across some of the sites to install siloxane removal plants to improve gas quality, and CHP availability, this work is now complete and the plants are on track to achieve their target levels of performance.

Table one shows the renewable power generation at each of the AMP4 sites from 2007/8 to 1010/11, together with the total renewable power generation from all Anglian Waters CHP plants. Clearly, the AMP4 biosolids programme has increased renewable energy generation from 13 to 39 GWh/y, from 2007 to 2010, approximately 300%. Recent improvements will allow the output to be increased to 54 GWh/y.

Good and consistent power generation has been maintained at King’s Lynn since commissioning, although less sludge was available long term efficiency levels of 0.7MWh/tDS have been achieved.

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Extended commissioning at Great Billing helped the team to understand the dependency of regular deliveries from satellite works, but improved logistics and focused management has helped to improve performance, driving renewable power generation from 3.6 GWh in 2007 to 19.3GWh in 2011, and is on track to exceed 20GWh in the current financial year.

Issues at Cottonvalley included limited liquor treatment capacity, gas quality and reduced CHP reliability. However, performance has steadily improved and gas cleaning technology should allow the target power generation to be achieved at this site.

Throughput at Whitlingham was restricted leading to lower power generation than originally forecast. However, successful delivery and commissioning of a specialized liquor treatment plant (SHARON) and the decision to take off line, clean and refurbish the existing digesters has removed the restriction and recent results show significantly increased renewable power generation.

Further improvements and performance improvements are planned over the next few years in order to maximize renewable power generation from the AMP 4 projects. The performance target for these projects has been set at 54GWh/y informed by periods of best performance at each site.

Table 1: Renewable Power generation (GWh/y)

Year Great Billing King’s Lynn Cotton valley Whitlingham Total Achievable 23.0 8.0 9.0 9.0 54.0 2010/11 19.3 6.7 6.2 2.6 39.0 2009/10 7.2 7.7 5.0 3.0 28.0 2008/9 4.0 7.1 3.7 3.6 23.0 2007/8 3.6 0.0 2.7 3.0 13.5

Sludge Production

The design basis for the AMP 4 projects was “DMPS” or design maximum production at each site which took account of measured sludge production, a peaking factor and growth forecasts. In practice there have been some significant changes at some sites, particularly King’s Lynn, due to closure of commercial facilities such as Campbell’s Foods and other companies installing their own treatment facilities. Also, the installation of weigh bridges and other improvements to data capture at key assets has helped to more precisely measure sludge production across the region. Long term performance data across several sites shows that “DAPS” (design average production of sludge plus growth allowance) is a better design basis for future projects). Also, we have found that early operational savings should be forecast based on 85% of DAPS.

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Measurements show that overall the AMP 4 biosolids projects are processing approximately 70,000tDS/y, approximately 70% of the original design basis. Fortunately, this shortfall has given opportunities to further optimize Anglian Water’s sludge treatment assets with additional satellite sites with raw sludge dewatering and additional cake reception facilities at the key Advanced Digestion sites.

Operational savings

The compelling case for optimising the AMP 4 Biosolids solution was driving industry leading best value for customers. Clearly, the key requirement was to deliver the operational savings in order to justify the increased capital investment and inform future investment programmes. The optimized solution halved the whole life cost of sludge treatment and disposal when compared to the final determination solution.

The optimum solution for AMP 4 targeted operational savings of approximately £2.7M/y across the programme, equivalent to £6M/y outperformance when compared to the original mandate. The delivery partners were incentivized to support the operations team and maximize both performance and operational savings over the first two years of service following Handover.

A threshold savings level of approximately £2M/y was set (equivalent to an outperformance of £5M/y). If this savings level was exceeded then the delivery partners would receive a bonus equivalent to an agreed percentage of the extra savings for a period of two years.

In practice this incentive has proved difficult to achieve due to a number of issues. The sludge throughput at all sites was lower than initially forecast, the better performing sites had to offset other sites where performance was lower than expected and there were some increased costs at some sites associated with liquor treatment and use of support fuel.

Overall it has taken longer than expected to increase sludge throughput and optimize plant performance at each site, but despite the challenges, this year the opex outperformance for this programme is on track to exceed the threshold value of £5M/y.

Whole Life Costs

Least whole life cost solutions at acceptable residual business risk were central to the decision making process. The project team embraced and enhanced Anglian Water’s capital delivery process and risk and value intervention process. The original solution had a whole life cost of £180M. The revised solution has a whole life cost of approximately £74M. This reduction was achieved by opening up and challenging the PR04 strategy (reducing the number of sites from five to four), considering innovative processes which provided a more sustainable solution, maximising biogas generation and increasing treatment capacity by 30%. Higher capital cost combined heat and power (CHP) generators had a demonstrable whole life cost benefit.

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Other key factors

Performance at the different sites has demonstrated the importance of maximising Dry Solids concentration prior to enzymic and thermal pretreatment. With Enzymic hydrolysis the optimum concentration of the raw sludge has been shown to be in the range of 7-8% DS. This has the advantage of minimising process heating requirements such that hot water and steam production from the CHP plant exceed the site requirements and no support fuel is required during normal operation. Similarly, with thermal hydrolysis, raw sludges are dewatered and then diluted at a controlled rate to achieve a target feed sludge of 16.5 to 17.5% DS in order to minimise the use of support fuel required. Long term performance monitoring has shown that the amount of support fuel for Cambi thermal hydrolysis can be reduced to less than 0.5 MWh/tDS when operated at target feed dry solids.

Long term operational experience across all sites has demonstrated the importance of levelling out sludge production and quality in order to optimise process performance. This is particularly important at the enhanced enzymic AD plants where unusually high proportions of secondary sludge or significant increases in sludge throughput have been found to adversely affect process stability and in some situations lead to foaming issues both in the pre-treatment stage and anaerobic digesters. Improvements have been made to improve the process stability and foam management at both King’s Lynn and Great Billing. However, it is clear that where sludge production levels and composition vary significantly then Cambi thermal hydrolysis is a much more flexible treatment process. In practise, Anglian Water has recognised the importance and logistics associated with management of sludge production and achieved very reliable performance at the enhanced enzymic plants.

Calculations have shown that the AMP4 Biosolids programme has delivered significant operational Carbon savings. These have mainly arisen from renewable power generation, reduced vehicle use and reduced lime usage, giving an overall saving of approximately 30,000tCO₂/y.

The combination of maximising biogas production through advanced digestion, maximising renewable power generation using high efficiency CHP engines and importing raw sludge from satellite sites has resulted in renewable power generation exceeding site power requirements at both King’s Lynn and Great Billing. Long term monitoring has demonstrated that power self sufficient wastewater service can be maintained at both of these sites. With similar optimisation of sludge imports it is likely that power self sufficient wastewater service can also be achieved at both Cottonvalley and Whitlingham.

Summary of lessons learnt from AMP 4

Special Projects has reviewed programme and project delivery in AMP4 particularly focussing on feedback from operations and performance achieved compared to initial forecasts. Some

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16th European Biosolids and Organic Resources Conference important achievements and lessons have been learnt both at programme and project level and these are summarised below:

Achievements

• Successful delivery of AMP4 Biosolids programme, capable of processing 99,000 tDS/y to enhanced quality cake, maximising volatile solids destruction and renewable power generation to drive lowest sustainable cost of service and produce more than 40GWh/y • Achieve industry leading performance – 0.9-1.0 MWh/tDS • Achieve power self sufficient wastewater service • A great example of extended support and working closely with operations to maximise performance and operational savings • Some important innovations included: • Steam heating • Optimised transport of raw sludge cake • Liquor treatment • SOOP

Lessons learnt

• More focus on sustainable sludge production levels • Importance of prethickening to minimise heating requirements, improve process stability and optimise downstream plant sizing • Improve design standardisation, preassembly and optimise construction activities • Importance of right first time process commissioning • Extended commissioning working as integrated team with operations • Performance support to local operations team to ensure full process acclimatisation • Ensure fully integrated solution including sludge imports and optimum liquor treatment • Optimise renewable power generation, long term plant availability, carbon savings, and lowest whole life cost of service.

Development of the AMP 5 programme

Anglian Water’s agreed challenge for AMP5 is to; • Process a further 66,000 tDS/y of raw sludge to enhanced quality, hence increasing the quantity of sludge treated by Advanced Digestion to > 80% of total sludge production by 2015 • Increase renewable power generation to almost 90 GWh/y • Reduce lime treatment to less than 1% of raw sludge production • Meet the above regulatory obligations for a mandated Capex of approximately £100M and Whole life Cost of approximately £140M

The PR09 initial plan was based on investment at five sludge treatment centres.

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N L I N C O L N S H I R E CHP Pyewipe N E Newton Canwick – shut lime plant, L I N C S Marsh provide new enhanced digestion plant N O T T S

LincolnCanwick X CHP

L I N C O L N S H I R E Seasonal King’s Lynn – provide cake reception, increase Boston Marston throughput Seasonal CHP N O R F O L K Spalding M King’s Lynn King’s Lynn Bedford – provide new Caister CHP enhanced digestion plant Norwich C R U T L A N D Whitlingham Gt.Yarmout P E T E R B O R O U G H h Peterborough CHP Flag Fen Lowestoft L E I C S Lowestoft Market HarboroughCorby Thetford

Part Thetford Kettering Huntingdon N O R T H A M P T O N S H I R E Cliff Quay – shut lime Wellingborough Broadholme Bury St Edmunds M M Cambridge plant, provide new Northampton Great Billing S U F F O L K CHP St Neots CambridgeCHP enhanced digestion plant B E D F O R D S H I R E CHP X Bedford M I L T O N Haverhill K E Y N E S Bedford Ipswich X C CHP Cliff Quay Cottonvalley CHP Milton Keynes Leighton Letchworth Linslade Chalton Harwich & Dovercourt O X O N B U C K S Hitchin Colchester Stevenage X DunstableLuton Colchester CHP Clacton E S S E X

Chelmsford Jaywick Chelmsford Chelmsford imports Colchester – new diverted to Rayleigh West Basildon – new enhanced Basildon CHP Rochford enhanced digestion plant digestion plant Basildon X Rayleigh SOUTHENDWest THURROCK Canvey Tilbury

Figure 2: AMP5 Programme based on PR09 Final Business Plan

Figure 2 shows a summary of both the original AMP 5 Plan and the optimised AMP5 Plan

Revised design assumptions were agreed for the AMP 5 Biosolids programme including;

• Design based on average sludge production with 10% strategic capacity in each operational area • Biological hydrolysis selected for all sites to deliver the lowest sustainable whole life cost and lowest carbon solution • Increased focus on pre-thickening to improve performance and optimise the use of downstream assets • Develop standard solution applied across the programme • Early delivery of CHP plant (achieved by March 2011) to secure full one ROC accreditation • Close working with local operations to understand particular site constraints • Operational savings forecast based on 85% of average sludge production and 70% overall long term availability

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An optimised programme has been developed for AMP 5 including;

• Four new Advanced Digestion Plants (Cliff Quay, Colchester, Basildon and Pyewipe) • Raw sludge dewatering at Bedford and transport to Cottonvalley and/or Great Billing • Uprating and optimisation of existing Advanced Digestion plants • The forecast capex is approximately £100M, with forecast opex saving of £1M/y, and whole life cost of approximately £85M

Figure 3 shows a summary of the latest optimised AMP 5 programme

N L I N C O L N S H I R E CHP Pyewipe Scunthorpe X Grimsby N E Newton L I N C S Marsh Replace Canwick ED 11,400 tDS/y

with Pyewipe ED 16,650 tDS/y N O T T S

Lincoln Ingoldmells Canwick Skegness L I N C O L N S H I R E

Grantham Boston Marston

CHP N O R F O L K Spalding M King’s Lynn King’s Lynn Caister CHP

Norwich C R U T L A N D Whitlingham Gt.Yarmout P E T E R B O R O U G H Indigenous h as cake Peterborough CHP Part (20%) Lowestoft L E I C S Lowestoft

Market HarboroughCorby Flag Fen Thetford

Part (80%) Thetford Reduce Cliff Quay ED Kettering Huntingdon N O R T H A M P T O N S H I R E 18,900 tDS/y to 14,800 tDS/y Wellingborough Broadholme Cambridge Bury St Edmunds M M Northampton Great Billing S U F F O L K CHP St Neots CambridgeCHP B E D F O R D S H I R E Bedford M I L T O N Haverhill K E Y N E S Bedford Ipswich X C CHP Cliff Quay Cottonvalley CHP Milton Keynes Close Bedford ADLeighton Letchworth Linslade Chalton Harwich & Dovercourt – TransferO X raw O N B U C K S Hitchin Stevenage Colchester Luton X Colchester cake to Dunstable E S S E X CHP Clacton

Cottonvalley Chelmsford Jaywick Chelmsford

Chelmsford imports diverted to Basildon Colchester – new Basildon CHP Basildon – new enhanced Rochford Basildon X enhanced digestion plant digestion plant Rayleigh SOUTHENDWest THURROCK Canvey Tilbury

Figure 3: Optimised AMP5 Programme

Active management throughout AMP 5 will; • improve data capture • improve thickening of raw sludges • review and optimise sludge transport logistics • consider further investment opportunities such as additional CHP units, as well biogas- to-grid options • continually monitor the journey to 90 GWh/y • drive industry leading efficiency and availability.

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Figure 4 shows the planned journey to approx 90 GWh/y from Advanced Digestion.

Renewable power generation from Advanced Digestion - The journey to 90GWh/y 100 90 80 70 60 50 40 30 20 10

0 Renewable powerfrom AD (GWh/y)

Figure 4: Renewable power generation from Advanced Digestion – the journey to 90 GWh/y

Conclusion

• Anglian Water’s original AMP4 mandate was to process 77,000tDS/y of raw sludge to enhanced quality within a capital budget of £86M, operational impact of £3M/y and whole life cost of approximately £180M. • Anglian Water decided to deliver the programme through its Special Project team and selected two delivery partners, GTM (a joint venture between Galliford Try and Imtech) and Black & Veatch, to work with Mott MacDonald and focus on technical innovation and collaborative delivery. • The combined Special Projects Team developed an optimised programme solution capable of processing 30% more sludge, by Advanced Digestion processes (Enzymic and Thermal Hydrolysis) which provided significant opex savings of £6M/y, and reduced the whole life cost from £180 to £75M. • The optimised AMP 4 Biosolids programme has been safely delivered by the Special Projects team. • Innovations include; • Steam heating to eliminate the risk of vivienite precipitation • High efficiency CHP • Sludge cake transport and reception facilities • Specialised liquor treatment facilities • Extended process commissioning and Opex Incentivisation (SOOP) to support delivery of the targeted operational savings.

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• There have been some challenges delivering the AMP 4 programme, there was less sludge than expected, we had to manage interdependencies, and it took longer than expected to optimise plant performance. • It takes time • But we’ve achieved a great outcome, we’ve delivered within budget, achieved 80% opex savings, demand for the product has increased, and improved operational practices have helped deliver Industry leading, award winning performance. • Lessons have been learned from AMP 4 delivery and applied to help optimise the design basis and delivery of the AMP 5 programme. We have focussed on average sludge load, further improvements in raw sludge pre-thickening, targeted power self sufficient waste water service and a closer partnership with operations to maximise performance and operational savings. • The optimised AMP5 Programme will process over 66,000 tDS/y of sludge to enhanced quality, use standardised solutions where possible, use a newly developed biological pre-treatment process (HPH) at all sites and increase renewable power generation from Advanced Digestion to approximately 90 GWh/y.

Acknowledgement

The authors wish to thank Anglian Water for its support and assistance in the development of this article. Imtech Process, as part of the GTM joint venture with Galliford Try, Black and Veatch and Mott MacDonald were pleased to be involved in helping Anglian Water to deliver their industry leading AMP4 Bio-solids programme. The successful delivery of this programme was only possible through the excellent commitment and performance of the programme, project and local operations team. We wish to thank everyone involved in the successful delivery and optimisation of this programme.

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