Over the past 50 years, water quality in surface and groundwaters has been significantly improved thanks to the construction of wastewater treatment facilities. In the years ahead, further challenges will have to be addressed, such as the problems associated with micropollutants or the need to design sustainable urban water management systems.

Polluted and unpolluted wastewater

Wastewater is water that has been altered by domestic, industrial, commercial, agricultural or other uses; this includes stormwater run-off from hard surfaces.
Polluted wastewater is wastewater that may contaminate a receiving waterbody and therefore has to be treated before it is discharged. In contrast, unpolluted wastewater (e.g. roof water or rainwater from traffic routes that are not heavily used) can generally be allowed to infiltrate into the ground untreated.

Where does wastewater come from?

Polluted wastewater can be divided into three categories, according to where it arises:

• Municipal wastewater mainly comes from households. In Switzerland, around 1450 million cubic metres of municipal wastewater is generated per year. 
• Industrial wastewater comprises wastewater from commercial and industrial establishments, and from comparable sources (e.g. laboratories and hospitals).
• Other polluted wastewater comprises those types that cannot be classified as municipal or industrial wastewater. These include wastewater from once-through and closed-circuit cooling systems, construction sites, facade and tunnel cleaning, landfills, gravel washing, fish farms and swimming pools, as well as unmixed polluted rainwater.

Urban drainage

Wastewater treatment is only one element of modern urban drainage systems. Comprehensive water protection efforts also include measures designed to minimize, for example, the adverse impacts of wet-weather discharges or pollutant inputs to waterbodies from heavily used traffic routes.

Responsibilities

The cantons are responsible for enforcement of the Water Protection Act, e.g. specifying conditions for discharges, monitoring wastewater treatment works and implementing the polluter-pays principle.

The federal authorities oversee the enforcement of the Water Protection Act and issue implementing regulations. For example, they support cantonal enforcement efforts by preparing recommendations and guidance, implement international resolutions and agreements, and promote the development of systems and procedures ensuring the application of the best available techniques.