Wastewater is generated when natural or tap water is used for domestic purposes and technological processes of industrial enterprises. Wastewater also includes atmospheric precipitation – rain and melt water falling in the territories of cities, towns and industrial enterprises. Wastewater is also groundwater extracted from mines during mining. Such waters are the source of various diseases and the spread of epidemics. Wastewater systems eliminate the negative effects of wastewater on the environment. After treatment, wastewater is usually discharged into water bodies. The most advanced systems are closed sewage systems that provide wastewater treatment to a quality that makes it possible to reuse water in industry or agriculture.