The problem of energy efficiency and rational use of energy resources in housing and utilities sector remains relevant over the past years. In this regard, the reduction of heating and hot water costs remains under continuous review of specialists all over the world. The article discusses the issues of using low potential thermal energy of domestic wastewater for hot water heating. Data on wastewater temperature in various locations are presented. The main designs of wastewater heat recovery units and the features of their application are considered. It is shown that the temperature parameters of residential building wastewaters differ significantly and depend not only on the climatic zone, but also on the regional features of water consumption. It is concluded that in process of wastewater heat recovery it is possible to reduce wastewater temperature at least by 5 ºС, and in hot season ‒ by 10-15 ºС. The analysis of literature data lead to the conclusion that wastewater heat recovery units are more promising and viable at building level as well as sewer or wastewater treatment plant level. For these cases, greater efficiency can be reached by using heat recovery facilities with a heat pumps.

Keywords: hot water supply, sewage, low potential heat, wastewater temperature, heat pump, heat exchanger, waste water heat recovery, energy saving