What is sewage

Water Management Office

Each of us transforms an average of 50 m3 Drinking water per year in wastewater. Together with trade and industry, the residents of Bavaria produce around a year
1.6 billion m3 Wastewater - an amount that corresponds to the Chiemsee.
This huge amount needs to be cleaned before we give it back to the natural water cycle.

Our waters are polluted by so-called punctual and diffuse pollutant inputs.
The most important punctual loads are wastewater discharges.
Depending on its origin, wastewater differs:

  • Domestic sewage
  • Industrial and commercial wastewater
  • Rainwater

Wastewater is polluted by:

  • Easily degradable, organic ingredients and nutrients (e.g. household waste water, food industry)
  • Organic ingredients that are difficult to break down (e.g. in wastewater from the chemical industry, pharmaceutical industry)
  • Heavy metals (e.g. in wastewater from the metal processing industry)
  • Organic halogen compounds (e.g. chlorinated substances in waste water from dry cleaning)
  • Mineral oils and fats (e.g. waste water from car workshops)
  • Temperature increase (e.g. cooling water of the power plants)
  • unpolluted extraneous water

The domestic sewage consists essentially of toilet water as well as kitchen and cleaning water with bacteria, viruses, detergents and cleaning agents including dirt and food residues. In addition, there is the wastewater from commercial operations
All natural organic compounds - proteins, fats and sugar as well as environmentally friendly detergents and cleaning agents - can be broken down relatively easily and almost completely by microorganisms in biological sewage treatment plants. The concentration of the nutrients nitrogen and phosphorus in the wastewater can also be largely reduced with the help of special bacteria. This happens with the more extensive biological wastewater treatment. However, other substances such as medication, caffeine or zinc compounds from baby creams pass through the sewage treatment plant or are deposited in the sewage sludge.

The sewage out Commercial establishments and industry may contain easily degradable organic compounds and sometimes difficult to breakdown substances such as halogenated organic compounds or heavy metals.
One distinguishes between indirect discharging companies, which feed their mostly pre-treated wastewater to the municipal sewage treatment plants, as well as the directly introducing companies, through their in-house sewage treatment plants an additional 1 billion m annually3 treated wastewater can be discharged into the Bavarian waters. In industrial and commercial operations, very special processes are often used to treat wastewater. A special case is the thermal load on the body of water caused by the discharge of cooling water.

Rainwater In built-up areas it gets from the roofs, sidewalks, streets and other paved areas into the sewer system or is increasingly fed back into the groundwater on site. The discharge takes place either in a mixed sewer system or a separate sewer system.

Local infiltration or direct discharge into surface water is not permitted under certain conditions.

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