Sewer networks serve the purpose of quickly and completely discharging storm water as well as domestic and industrial waste water, avoiding sewage exposure in the community. A properly working sewer system is essential for impeccable hygiene, a high standard of living, water pollution abatement, and healthy economic development. The sewer networks in the Ruhr catchment area are usually owned, maintained, and operated by the local communities.
Waste water is discharged to the sewage treatment plantin either a combined or a separate sewage system. In the combined system, waste water and storm water are discharged together in a single sewer with storm water treatment plants protecting the sewage treatment plant from peak run-offs. In the separate system, waste water is discharged in two separate sewers. The waste water is led to the sewage treatment plant in its own sewer while the non-contaminated storm water is discharged directly into a body of water from a parallel storm water sewer.
The communal sewer system usually ends at a sewage treatment plant located in a town or municipal area. Waste water from smaller towns is sometimes transferred to more distant sewage treatment plants using transfer collectors. Responsibility for transfer collectors lies with the Ruhrverband which operates sewers and pressure pipelines as connecting conduits, totalling 317 km in length.
In addition to waste water and storm water, a certain share of non-contaminated water that does not require treatment (extraneous water) is unavoidable. It is composed largely of ground water infiltrating through leakages and misconnected drainages in the sewers.