sekaviemärien

Sekaviemärien, meaning combined sewers in Finnish, are a type of sewer system designed to carry both sanitary sewage and stormwater runoff in a single pipe. This contrasts with separate sewer systems, which have distinct pipes for each type of wastewater. Combined sewer systems were common in older urban areas constructed before the widespread adoption of separate systems.

The primary function of a combined sewer is to collect wastewater from homes, businesses, and industries, as well as rainwater and snowmelt from streets, roofs, and other surfaces. During dry weather, the flow consists primarily of sanitary sewage. However, during precipitation events, the volume of water entering the system increases significantly due to the addition of stormwater.

A significant challenge associated with combined sewers is the occurrence of combined sewer overflows (CSOs). When heavy rainfall causes the flow to exceed the capacity of the sewer system or the wastewater treatment plant, untreated or partially treated sewage and stormwater are discharged directly into nearby bodies of water. This can lead to water pollution, health risks, and environmental damage.

Modern urban planning increasingly favors separate sewer systems to mitigate the problems associated with CSOs. However, in cities with existing combined sewer infrastructure, efforts are often made to upgrade or manage these systems. This can involve constructing storage tanks to hold excess flow during storms, implementing green infrastructure solutions to reduce stormwater runoff, or undertaking costly projects to separate the existing combined sewers. The management of sekaviemärien remains an important aspect of urban infrastructure and environmental protection in many regions.