Let's Clarify That

How wastewater is cleaned before it flows back into the bodies of water

Wastewater consists of used water from households, businesses and industry, as well as stormwater, i.e. rain. Stormwater contains dirt from roofs, roads and public spaces. Solid matter floats in water or sinks to the bottom. Soluble substances can only be biologically or chemically separated from water. There are also semi-soluble substances called colloids. Colloids cause the water to be turbid.

There are 6 wastewater treatment plants in Berlin, but only the one in Ruhleben is also located in the city, the other five are situated on former sewage fields in the surrounding area. The largest plants, Ruhleben and Waßmannsdorf, can be visited daily. Although the systems differ visually from one another, their technical principle is identical except for a few details: 97 % of solid and biodegradable substances can be removed. The following criteria are used in assessing the degree of wastewater pollution: biochemical oxygen demand (BOD), chemical oxygen demand (COD) as well as the level of phosphorus and ammonium. BOD is the quantity of oxygen which is consumed by microorganisms through the degradation of organic substances within five days at 20° C. 97 % of solid and biodegradable substances can be removed. The following criteria are used in assessing the degree of wastewater pollution: biochemical oxygen demand (BOD), chemical oxygen demand (COD) as well as the level of phosphorus and ammonium. BOD is the quantity of oxygen which is consumed by microorganisms through the degradation of organic sustances with five days at 20° C.

COD is the estimated consumption of potassium chromate, which is produced during the chemical oxidation of organic water compounds. To ensure the best treatment performance, the respective concentrations are checked regularly at the outlets of the sewage treatment plants. In Berlin's sewage treatment plants, the majority are under the specified limits.