Stock Photo - 10 September 2021, Brandenburg, Brandenburg/Havel: Water is purified in secondary clarifier 2 on the site of the Briest sewage treatment plant operated by Wasser- und Abwassergesellschaft Brandenburg GmbH (BRAWAG). The basin has a diameter of 42 metres and a maximum depth of 3.88 metres. A large-scale experimental plant for the removal of phosphorus, set up a few metres away, is intended to reduce the proportion of phosphorus and its compounds in the already purified water by a combination of phosphate precipitation and secondary treatment by means of sand filtration. In this process, the chemical element is converted by precipitation into large flakes, which are then separated out in a special sand filter and sucked out by a mammoth pump. The phosphorus can be recovered from the precipitated sludge. The project, entitled ""Zero-P"", is a cooperation between BRAWAG, Nordic Water and is funded by the German Federal Ministry of Education and Research. Photo: Soeren Stache/dpa-Zentralbild/ZB. - Brandenburg/Havel/Brandenburg/Germany