Waste waters from Berlin households and streets were drained by a primitive gutter drainage system up into the 1870’s. There were years of dispute over which process should be chosen for urban dewatering and sewage disposal. Field treatment of sewage and its parallel use for agricultural areas was generally accepted as the most favorable form of sewage disposal. A total of 10,000 ha were adapted for 20 sewage farms. The city of Berlin had bought the land for the fields and still owns most of them today.
The establishment of sewage treatment plants in Berlin led to the closure of the great majority of sewage farms by the middle of the 80’s. Many of these areas are now used agriculturally. Large areas of sewage farms were built-up within Berlin, in Marzahn, Hellersdorf, and Hohenschönhausen; or reforested, as around Buch forest.
Both the nutrients and pollutants in waste water are accumulated in sewage farm soils (cf. Maps 01.03) This accumulation, in both active and closed sewage farms, has disadvantages for current uses and, because of the size of the areas, far-reaching consequences on the economy of nature.
Sewage farms will be important spaces for urban development in the future. A diversity of concepts, some of them competing, are now being discussed for use of the remaining surfaces as residential areas, industrial parks, recreation spaces or for ground water accumulation. The pollution of sewage farm soils makes information about conditions and areas once used as sewage farms an important basis for planning, in order to avoid future conflict.
Functioning of Sewage Farms
The sewage farms followed a dewatering concept by J. Hobrecht. In 1869 the Berlin administration made him director of the Berlin Latrine System. Hobrecht divided the city into 12 districts, called radial systems. Each radial system had a pumping station. Pumping stations received domestic, commercial and industrial waste waters as well as precipitation water through gravity flow pipelines. Sewage effluents were conducted from the pumping station through pressure pipelines to sewage farms located outside the city. Some sewage farms were additionally supplied by direct pipelines.
Pressure pipelines discharge waste water at the sewage farms. Waste water is first collected in sedimentation basins made of concrete or earth. Water flows through the tank and most sediments settle to the bottom. Immersion panels hold back floating matter. Sediments settling in the sedimentation basin are regularly evacuated and dewatered at special sludge drying areas. Dewatered sludge was used as a soil conditioner for agriculture and horticulture in early years. The sewage farm trench system is also regularly cleaned, whereby removed sediments are usually deposited directly alongside the trench. After sewage water has passed through the sedimentation basin, e.g. has been mechanically cleaned, it flows through gravity feeders to the terraces.
The natural ground form was not automatically suited for processing sewage waters. Terraces were constructed horizontally or sloping, depending on the surface. They were about 0.25 ha large, and surrounded by embankments. There are three methods of sewage farm treatment. Horizontal terraces are flooded by surrounding distribution ditches. For slope terraces, sewage water overflows the upper bank and irrigates the sloped terrace. Bed terraces with ditch irrigation were also initially used. Waste water flowed through bed terraces in connected parallel furrows, about a meter apart. Only plant roots received water (cf. Fig. 1).