Waste-heat utilization

Wastewater is a cheap energy source continuously available in urban areas and production facilities. With appropriate technology, wastewater heat otherwise ending up as waste in the sewage system can be utilized.

Utilizing wastewater heat doesn’t affect the composition of wastewater, that is, conditions for cleaning or bioenergy production remain the same.

Communal, household and industrial wastewater can all be used as an energy source. The temperature of communal wastewater falls in the range between 10°C and 20°C, while industrial wastewater can be even warmer than that. Their temperature doesn’t sink below 10°C in winter either.

Due to its virtually constant temperature, wastewater heat offers much better energy efficiency than soil heat or groundwater. Typical values:

  • heating (COP):        5.0 – 6.5, with auxiliary energy: about 4.5
  • cooling (EER):         7.5 – 8.5, with auxiliary energy: about 6.5

As generating 1MW of power requires a daily wastewater volume of about 3,400 m3/day, a typical building’s own wastewater output is not enough to support its heating/cooling. As a result, projects need to be implemented close to the main collectors of large cities. 

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