Ühiskanalisatsioonide

Ühiskanalisatsioonide, also known as combined sewer systems, are wastewater collection systems that carry both sanitary sewage and stormwater runoff in a single pipe. This design was common in many older urban areas, particularly in Europe and North America, due to its simplicity and cost-effectiveness during initial construction.

In a combined sewer system, everyday wastewater from homes, businesses, and industries, along with rainwater and snowmelt from streets, roofs, and other surfaces, all flow into the same underground pipes. These pipes then transport the mixed flow to a wastewater treatment plant.

The primary challenge with combined sewer systems arises during periods of heavy rainfall or rapid snowmelt. When the volume of stormwater exceeds the capacity of the pipes and the treatment plant, a condition known as a combined sewer overflow (CSO) occurs. During a CSO, untreated or partially treated wastewater is discharged directly into nearby rivers, lakes, or oceans to prevent the system from backing up and flooding streets and properties. This discharge can significantly impact water quality, harming aquatic life and posing risks to human health.

Many cities are now undertaking efforts to separate their combined sewer systems into two distinct networks: one for sanitary sewage and another for stormwater. This separation aims to improve water quality by ensuring that all sanitary sewage reaches treatment plants, even during wet weather events. However, the process of separating combined sewers is often expensive and disruptive.