Underground World with a System
Drinking water turns into wastewater. It flows through the building connection sewers in freefall to the collector sewer pipes in the roads and through ever larger sewers to the pumping stations, which then pump it to the local sewage treatment plants. The Berlin wastewater sewers are 9,700 kilometres long. This is equivalent to the distance between Berlin and Cape Town, South Africa.
Berlin is divided into honeycomb-like drainage areas, whose boundaries are not identical with those of the Berlin residential districts, but rather follow the courses of rivers and canals. They also follow varying levels of terrain. Sewers always lead to the lowest point of a drainage area. A pumping station is situated there, which then pumps then wastewater on to the sewage treatment plants. Altogether, the Berlin wastewater sewers are more than 9,700 kilometres long. This includes 4,400 kilometres of wastewater sewers, 3,400 kilometres of stormwater sewers and 2,000 kilometres of combined water sewers. Around threequarters of the city area of Berlin are set up as one separate sewer network system and one quarter as a combined sewer network system.
Green Intensive Cleaning
A special form of these treatment plants are retention ground filters. These filters clean dirty stormwater from heavily travelled roads and industrial areas by filtering and retaining removable dirt from the water using a substrate and reed plants. So far, Berliner Wasserbetriebe has built four retention ground filters at the Baggersee Lake in Biesdorf, in Adlershof, in Blankenburg and at Halensee Lake.
The stormwater collected in the sewers first flows into a tank, where the dirt that has flowed in with it settles. In the actual filter itself, the loosened dirt and contaminants, such as phosphorous, nitrogen and heavy metals, are bonded to the substrate and in the plants. The reed plants ensure that the filter does not become blocked. After passing through the filter, the water is then freed of 80 % of the filterable substances – among other things, heavy metals adhere to them – and 70 % of the phosphorus compounds. Together with extensive renovation work in the sewers, these plants serve the purpose of achieving a good ecological balance in the Spree-Havel river system. The sewers transport the wastewater to one of the pumping stations within the metropolitan area.
Tanks Catch the Rain
Emergency outlets and stormwater overflows in Berlin are located on the rivers Spree, Havel, Panke, and on the Landwehr Canal, the Teltow Canal, and the Neukölln and Berlin-Spandau shipping canals. There are also several stormwater retention tanks at strategically important points. They catch the combined water during short and heavy storms in order to prevent it from overflowing into local bodies of water. With weirs, throttles and increased overflow thresholds, the sewage system itself is used as a reservoir. During long, sustained heavy rainstorms, it is possible to treat stormwater in the tanks directly.
With Pressure to the Sewage Treatment Plant
The pumping stations are connected by a 2,000-kilometre-long network with pressure pipes up to 1.60 metres thick. Main pumping stations transport the wastewater through these pressure mains to the sewage treatment plants. The system for transporting the wastewater from more than 300 plants, comprising pumping stations, weirs and stormwater tanks, is monitored and controlled from a control centre in Friedrichshain.