Extraneous water
Extraneous water generally refers to water that is not in the intended location. So it is water that unintentionally penetrates the sewer system, mixes with the dirty water and flows off together. According to DIN 4045, this is groundwater that penetrates the sewer system through leaks, water that is not allowed through incorrect connections and, in the case of a waste water channel, through z. B. Covers of sewer shafts inflowing surface water. Stream or drainage water discharged through the sewer system is also counted as extraneous water.
The proportion of foreign water in the total wastewater is difficult to determine and the forecast of the amount that arises is also difficult because it fluctuates greatly depending on the weather and the quality of the sewer network. Since the extraneous water unnecessarily takes up the capacity of sewage pipes and sewage treatment plants , it represents an unnecessary economic and ecological burden. In older, only moderately monitored canals, it can make up many times the black water when it rains . In unfavorable cases it causes the rain overflow to start in the sewer or in the inlet of the sewage treatment plant and thus an entry of untreated wastewater into a body of water.
In the case of separate sewer systems , the operator always endeavors to minimize the proportion of extraneous water by keeping the sewers and manholes as watertight as possible. Bad connections can often be identified by filling the sewer with an artificial mist. If this gets out through a street gully or a gutter , there is a wrong connection. The property owner is then usually asked to correct this connection.
