Berlin’s sewage plants are extremely busy. Every day, they treat about 680,000 cubic metres of rainwater and waste water from industry, households and public institutions (as of 2022). Three weeks’ worth of waste water could fill the Großer Wannsee.
Almost 10,000 kilometres of sewerage network and 166 pumping stations transport the water to six treatment plants. Some pipes transport only waste water, some only rainwater. Others carry both simultaneously. Experts call the latter combined sewerage system. Based on the designs of city planner James Hobrecht, this kind of system was installed in Berlin’s city centre within the area of the S-Bahn ring starting in 1873.
Waste water and rainwater predominantly flow through different pipes as part of the separate sewerage system in cities and communities that lie outside the S-Bahn ring, which became part of Greater Berlin in 1920. While waste water ends up in the treatment plant, precipitation flows back directly into our rivers and lakes. One problem here is that pollutants are washed off the streets and into the waters.
In the combined system, however, everything is pumped towards the sewage plant. However, during extreme downpours, the drains cannot cope with the amount of rain. To prevent water from gushing out of manholes, additional overflow drains have been put in place, discharging water into the Landwehrkanal or Spree, for example. This happens to a total of up to 7.2 million cubic metres of untreated waste water every year. For years, the Berlin Waterworks (BWB) have been installing intermediate retention basins underground to counteract this phenomenon.
Four fifths of the areas connected to a sewerage system are part of a separate system, the rest is connected to a combined system. Only a few settlements are not connected to any sewerage system. Here, removal companies transport waste water to the sewage plants.