New study in Upper Austria

Heat from wastewater could supply 55,000 homes

Energy could be recovered before the wastewater reaches the sewage treatment plant - here the plant in Marchtrenk.

(Bild: Markus Wenzel)

The environmental department of the province of Upper Austria is thinking about generating energy from wastewater. In Switzerland, 200 such plants are already in operation. The potential is certainly great. 

55,000 Upper Austrian households - that is around 8 percent - could be heated and supplied with hot water using waste heat from sewage treatment plants and sewers. This was the result of a survey commissioned by the state's environmental department. Provincial Councillor Stefan Kaineder (Greens) presented the "Wastewater Heat Potential Register" on Tuesday, which shows a theoretical thermal energy potential of around 485,000 MWh per year.

State Councillor for the Environment Stefan Kaineder commissioned the study.

(Bild: Dostal Harald/© Harald Dostal / 2023)

The survey was carried out by the Water Management Department, Drinking Water and Wastewater Group, based on data from the University of Natural Resources and Life Sciences in Vienna. Because the biological processes in sewage treatment plants require a certain temperature, it is advisable to extract heat only after the sewage treatment plant. This could then even counteract local warming of the waters into which the water is ultimately discharged. 

Technically, the use of wastewater heat could be implemented with a combination of heat exchanger and heat pump technologies. The Rabmer Group from Altenberg near Linz has experience with this. Managing Director Ulrike Rabmer-Koller assumes "that the practically feasible project potential could probably be even higher" than the 8 percent surveyed. Her experience shows that urban areas in particular offer optimal conditions for energy from wastewater.

Hundreds of plants already in operation in Europe
According to Rabmer-Koller, there are now several hundred plants across Europe that generate energy from sewage, with Switzerland leading the way. She also sees potential in the industrial state of Upper Austria in the use of industrial wastewater. At present, some of this wastewater is still cooled with additional energy input before it is discharged into the sewer instead of using the heat to generate energy.