WASTEWATER | HEAT RECOVERY Londons hidden heat source A new wastewater heat-recovery project announced by Thames Water and Kingston Council could provide a model for future schemes in London. Andy Pearson reports T hames Water and Kingston Council have unveiled plans to use heat recovered from a wastewater treatment plant (WWTP) in Kingston upon Thames, southwest London, to provide low carbon heating for more than 2,000 homes in the borough. the sewage-treatment process at the WWTP will provide clean, green heat and hot water to new homes soon to be built under the regeneration of the nearby Cambridge Road Estate. If successful, up to 7GWh of low carbon heat could be supplied per year. between 10-15C all year round. centre, where heat will be extracted before it is discharged. A heat pump will concentrate the reclaimed heat, which will then be piped to the district heating system being built to serve the 2,170 new homes on the redeveloped housing estate. If successful, the scheme could be expanded to public and commercial buildings in Kingston town centre. which reuse heat from the billions of litres of warmed water that end up in sewers every day. Closer to home, in Scotland, Borders College, Galashiels, has been recovering The value of gas saved is around 10,000 per year, while carbon savings as a result of the scheme are estimated to be 170 tonnes of CO2 a year. Resource dishwashers and washing machines, for example, goes down the drain, thermal energy are lost every year through the sewage system, corresponding a massive 350TWh of energy down the drain each year the equivalent of heating 30 million homes a year. in the sewers every day could, theoretically, provide more than 20TWh of heat energy annually. This is enough to provide space heating and hot water S Farman Ali and A Gillich at the 2020 CIBSE Technical Symposium.1 This paper states that the average temperature of wastewater in UK sewers varies between 10C and 25C, depending on the time of year and whether the sewer is combined to carry rainwater. By the time the wastewater has reached the treatment plants, which are often situated out of town, it will have cooled to approximately the WWTP to clean the water can reheat the wastewater by 2-3C, so the average temperature of water leaving the treatment plant is a consistently between 12C and 15C year round. Recovery wastewater can be performed either before the WWTP where the wastewater is 46 May 2021 www.cibsejournal.com CIBSE May 21 pp46-48 Sewage power Supp.indd 46 23/04/2021 16:07