Heat recovery from hot water

Tubular heat exchanger © KoenB, Wikipedia, April 2007

A large proportion of household wastewater is made up of hot water. That heat can be put to various uses. A simple technique that offers high yields is a shower heat retrieval system: as the hot water drains away, it heats the cold water flowing to the shower. Shower heat retrieval systems can offer yields of 50%. agentschap.nl

Heat exchangers can be used to extract heat from sewer water or from the effluent of sewage treatment plants. An additional benefit in the latter method of heat recovery is that less heat enters the surface water. VROM/TAUW, 2010

Potential savings are around 15%. According to a study performed by Stowa, the Dutch Foundation for Applied Water Research, the most efficient solution is to position the heat recovery systems directly at the drainage point, for example in a shower or where the effluent exits the sewage treatment plant or at pumps. Kluck, 2011