- Case Studies
New CHP upgrade and improvements made on-site, significantly improve plant serviceability, power generation, whilst reducing carbon emission at Mogden Sewage Treatment Works.
In 2014, Thames Water transformed how it was going to deliver capital investment, and set up an industry-leading alliance, under the operating name eight2O.
Comprising of five groupings, eight2O includes two design and build joint ventures consisting of Costain, Atkins, Black & Veatch (CABV) and Skanska, MWH and Balfour Beatty (SMB), as well as a programme manager in MWH and a technology innovator in IBM, plus Thames Water as both client and partner.
Following a competitive tendering process in 2015, Costain, one of the UK’s leading engineering solutions providers, awarded Edina Group the contract to supply, install and maintain 3 x 2MWe MWM TCG 2020 V20 biogas reciprocating CHP engines as part of the upgrades to the existing CHP system.
Edina is the official distributor in the UK and Ireland for MWM reciprocating gas engine technology. MWM is one of the world’s leading gas engine manufacturers, and are capable of achieving market leading electrical and thermal efficiencies, low operating and servicing costs and high reliability and availability, which is usually well in excess of 95%.
The project won the ‘Best Sewage Treatment AD Plant UK’ category at the UK AD & Biogas Industry Awards 2017.
The new £24.6million CHP plants replaced the existing dual fuel CHP system, improving serviceability, power generation, whilst reducing operational costs and reducing the sites environmental impact.
The Edina installed 6MW CHP plants was containerised individually at Edina’s manufacturing facility based in Lisburn, Northern Ireland. Due to the confined space restrictions available on-site, the containerised CHP plants were bespoke engineered to accommodate for the limitation in space.
The new CHP plants have been installed in an area adjacent to the existing CHP plant, and as a result, allowed for the installation, commissioning, and performance testing, whilst keeping the existing CHP plant operational.
A new gas feed was connected into the gas line feeding the power house, achieving a minimum of interruption to the 24/7 process of the sewerage treatment works. The gas line was fed into new coalescing filters onto new siloxane filtration before being split in a manifold, off to the new engines.
A new flue stack was erected to comply with the chimney heights regulations, and coolers from excess heat dump and intercoolers were all installed outside the 80 year old power house. Similar to the gas line, the hot water circuit was interrupted and a diversion circuit was created in the basement of the power house so that the heat from the new engines could be easily diverted into the boilers feeding the pasteurisation process whilst still maintaining the heating from both the old CHPs and the boilers.
By containerising the CHP engines in individual acoustic enclosures, and the shutting down of the old CHP engines, the noise level within the powerhouse has significantly reduced, with the Edina CHP engines operating at 65dBA.
In the event of a loss of power from the electricity grid, the supplied MWM engines are capable of running in Island Mode operation, isolated from the grid, providing critical standby power to the sites infrastructure.
The eight2O alliance have also replaced existing assets to further improve efficiency, serviceability and performance. Namely, improving the on-site infrastructure to accommodate a higher yield in gas production due to the efficiencies made to the existing boilers. Furthermore, the replacement of the air blower feed pipe work and blowers to battery activated sludge treatment processes, and reduced odours at the site.
Improvements to Mogden Sewage Treatment Works have enabled the facility to increase its sewage treatment capacity by more than 50 percent and meet the tighter effluent quality standards set by the Environmental Agency.
In April 2017, the CHP has just finished its 28 day trial period and is showing some significant results reported by Thames Water. In its first few weeks of operation, reports suggest that the CHP has generated a 47% increase in electricity when compared to the same period in 2015. Although the energy generated does vary week on week, it potentially represents a weekly cost reduction of £123,000 for Thames Water.
Also, Mogden Sewage Treatment Works is 1 of 27 digestion sites, and was reported to be responsible for 16% of the total Thames Water sites generation achieved by waste water.
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