27.03.2026, Germany, Berlin - View of a filled and an empty aeration tank at the Ruhleben sewage treatment plant. These tanks belong to the biological treatment stage of the wastewater treatment. The tank on the right has been pumped empty for maintenance work and the pipes for surface aeration can be seen on the bottom. 00R260327D147CAROEX.JPG [MODEL RELEASE: NOT APPLICABLE, PROPERTY RELEASE: NO (c) caro images / Ruffer, http://www.caro-images.com, [email protected] - In case of using the picture for any purpose, please contact the agency - the picture is subject to royalty!]