ABSTRACT
Combined sewer systems are designed to carry sewage and storm water in a single system to a treatment facility. During dry weather, sewer systems convey wastewater to the treatment plant, without any problem. However, in periods of heavy rainfall, total water flows will exceed the capacity of the plant and the pipes and manholes needed to store water. When the storage capacity of the sewer system is exceeded, the water flows untreated to surface water bodies, such as lakes, rivers, estuaries, or coastal waters. These spillages called combined sewer overflows are a major source of pollution. In these periods of heavy rainfall, another problem is local inundation in the streets.
