Wastewater encompasses sewage from households, industries and leachate from landfills, cooling water and storm water. It contains lots of natural substances but in high concentrations that may cause eutrophication, oxygen deprivation and other negative effects on the eco-system. Unnatural substances that come from certain industries can interrupt the cleaning process in treatment plants which in itself is an environmental threat.

There are also certain maximum limits for the levels of heavy metals in waste water. The heavy metals affect the process in the treatment plants as well as the sludge the treatment plant produces.

The counties have a clear responsibility to make sure that the requirements from the authorities are met. The requirements on industries upstream from treatment plants are therefore very strict. The analysis of their wastewater must always be done by accredited laboratories and the testing must be conducted by qualified technicians.