Wastewater is treated efficiently
The residents and companies in the Helsinki Metropolitan Area generate a total of 100 million cubic metres of wastewater per year. This water is led through the sewer network for processing and treatment before being reintroduced into the local water bodies.
The wastewater is processed by HSY’s two wastewater treatment plants in Viikinmäki, Helsinki, and Suomenoja, Espoo.
The treatment is conducted by means of a biochemical process that produces sludge and biogas as by-products. The sludge is processed into soil, and the gas is utilised as an energy source. The treated wastewater is led through a tunnel into the sea.
In addition to everyday wastewater from households, industrial and other diverging wastewater is discharged into the sewers. Leading such wastewater into the sewer system is subject to permission and requires an industrial wastewater agreement.
Wastewater treatment is an integral part of protecting coastal waters and the Baltic Sea. The wastewater to be treated includes a great deal of phosphorous and nitrogen nutrients, which, if discharged into the sea, would cause abundant eutrophication.
Various limitations have been imposed on wastewater treatment in EU directives and national legislation. Furthermore, wastewater treatment plants are obligated to meet the requirements of plant-specific environmental permits. The fulfilment of the requirements is monitored by the Environment Centre.