yhdysviemärijärjestelmän

Yhdysviemärijärjestelmän, often translated as a combined sewer system, is a type of sewage system where both sanitary sewage and stormwater runoff are collected and transported in the same pipe. This differs from separate sewer systems, which have distinct pipes for each type of wastewater. In a combined sewer system, wastewater from homes, businesses, and industries, along with rainwater and meltwater from streets and other surfaces, all flow into a single collection network.

The primary advantage of a combined sewer system is its simpler construction compared to separate systems, as it requires only one set of pipes. Historically, many older urban areas were developed with combined sewers. However, these systems present significant challenges, especially during heavy rainfall events. When the volume of combined sewage exceeds the capacity of the treatment plant, untreated or partially treated wastewater can be discharged directly into local waterways. This event is known as a combined sewer overflow (CSO). CSOs can introduce pollutants such as raw sewage, debris, and chemicals into rivers, lakes, and oceans, negatively impacting water quality and aquatic ecosystems. Managing and mitigating CSOs is a major environmental concern for municipalities with combined sewer systems. Modern infrastructure development often favors separate sewer systems to prevent CSOs and ensure more efficient wastewater treatment.