Despite the optimised energy consumption and the use of biogas for local power and heat generation, the six sewage treatment plants in Berlin still make a significant contribution to Berlin’s energy requirements and greenhouse gas emissions.

In order to improve their carbon footprint, the E-VENT project has tested and evaluated in close cooperation with Berlin’s water utility Berliner Wasserbetriebe advanced processes for both wastewater and sewage sludge treatment in the last three years. Pilot tests with granular sludge at the Stahnsdorf wastewater treatment plant have yielded a very good biological cleaning performance with less energy consumption and more compact process technology compared to conventional treatment. To comply with the strict limit values, an additional tertiary treatment step would however, be required. The investigations regarding optimised sewage sludge treatment have shown that the biogas yield can be improved by up to 19% if the sludge is pre-treated by thermo-chemical or thermo-pressure hydrolysis processes. Thanks to these groundbreaking processes, the CO2 footprint of a sewage treatment plant can be reduced by up to 29%. The results of the project are now being incorporated into the planning for the reconstruction of the Stahnsdorf sewage treatment plant. All results of the project were presented at a public seminar in July 2020.