Heat Recovery Opportunities from Wastewater Treatment Plants

Wastewater offers the potential of a widespread resource for low-temperature waste heat, with wastewater in sewers normally at temperatures greater than ambient due to the use of hot water in buildings. Heat can be recovered from wastewater from different locations, such as the wastewater pipework within a building, the sewage network or at wastewater treatment plants (WWTPs). The latter represents an interesting alternative as wastewater flow rates are generally much higher in the effluent of treatment plants than in sewers. Additionally, the temperatures may be above ambient, as the biological sewage treatment process results in some heat generation. This paper investigates the potential availability of waste heat from WWTPs across the UK, with a total thermal energy output of 26.2 TWh [89.5 MMDth (US)] per annum being estimated. A possible configuration for recovering waste heat from the WWTP effluent is also presented and used to assess the benefits that could be obtained against conventional heating technologies based on a case study in London. Although the case study is based in the UK, the methodology hereby described can also be applied to evaluate the potential for heat recovery from wastewater treatment plants in other countries.