The so-called flake filter is primarily intended to further filter the nutrient phosphorus out of the water, 98 per cent of which has already been removed at this point, according to Wasserbetriebe. The UV system, in turn, is intended to render any germs and bacteria still present in the already purified water harmless. This means that the purified water can now be discharged into the Spree all year round. Previously, in summer, the purified water was channelled past the Havel bathing areas via a 16-kilometre-long clear water pipeline to the Teltow Canal.