© RoofWaterFarm

„Block 6“ in Kreuzberg shows that separating and subsequent recycling is by no means a recent trend.

Kreuzberg is a trendy district and pioneer where trend-setting is asked. But Kreuzberg has also been a Berlin showpiece district in respect of technological issues. With its project ‘Block 6‘, Kreuzberg set a trend as far back as 1987.  ‘Block 6‘ is a building complex at the Dessauer Straße south-east of the Potsdamer Platz, consisting of an old building and a residential complex that was built in the 1960’s. Later, within the scope of the International Bauausstellung [International building exhibition], a further 106 flats were added in six new buildings. A grey water constructed wetland plant comprising 900 square meters with decorative bathing pond in the inner courtyard was something really special at the time and a construction-technical experiment for the city of Berlin - to treat waste water without chemical means and subsequently re-use it within the buildings.  

Disposing of grey- and black water within a building makes it possible to treat various qualities of waste waters and use these later on as process water in the building and on the open space. Waste water from the kitchen, shower, washing machine, and washbasin is collected as grey water and treated to become process water, used for toilet flushing or watering plants.  Due to this method up to 10,000 litres of potable water from the pipes could be saved. At the time black water containing phosphor and nitrogen from faeces and urine was disposed of directly into the sewage system.  

Reissue of a promising system of reprocessing water

Grey water treatment was technically re-designed and further developed for economic reasons in 2006. Today, a process water house in the inner courtyard is responsible that re-treated grey water can be turned into process water in bath water quality by means of a mechanical-biological process. The former constructed wetland plant evaporates rain water from the surrounding roofs today. The start of the research project ROOF WATER-FARM was a natural further development of the location. In 2013, ROOF WATER-FARM installed a greenhouse at the rear of the process water house for aquaponics.  It is here that technical possibilities and the hygienic safety are tested for using process water in the food production resp. in urban farming. But not only hygienically safe process water from grey water treatment is used for the production of fish and plants. But also the black water so far disposed of containing nutrients such as nitrogen and phosphor is treated to be used as liquid fertiliser for urban farming, for the first time. A monitoring programme checks the quality of process water, liquid fertiliser, produced vegetables and fish and during the process subjects these to an extensive hygienic control. This does, of course, include checking for remaining micro-pollutants.   

The objective of the ROOF WATER-FARM is to reprocess urban waste water and to use it as a resource for urban farming.  

Food production could take place in particular in densely populated city districts and on the roofs of Berlin. To this end, the research group has published extensive prototypical studies. The so-called ‘Block 6’ has a history as innovative location for de-centralised inner city water management. A further development of the location by ROOF WATER-FARM could be an inspiration for other projects.