Sewer systems

Paris sewer system

Japanese sewer system

A Word About Sewers: Besides having a set of sewer pipes-- called, strangely enough, sanitary sewers-- which carry wastewater to a treatment plant, cities and towns also need pipes to collect stormwater. These are needed to prevent street flooding and usually lead directly to a waterway without any treatment. The runoff of pollutants from streets and yards into these storm sewers contain oil and other automotive wastes, which may contain toxic metals and organic compounds-- as well as pesticides and nutrient-containing fertilizers from lawns and gardens, and pathogenic microorganisms from animal wastes. The problem of pollution from storm sewers is currently being addressed by the USEPA. Further complicating the situation is the fact that while some cities and towns have completely separate sanitary and storm sewer systems, many others have combined systems. During rainy periods, combined sewers cause two problems: overloading of the treatment plant with extra water and contaminating waterways with untreated sewage from overflows. Even in cities with separate sewer systems, the flows to the treatment plants often increase greatly when it rains because of cracks or separations in the pipes, which allow groundwater or stormwater from broken storm sewer pipes to infiltrate into the sanitary sewer-- or from direct inflow of stormwater into manholes and from illegal connections of roof drains and sump pumps in buildings.

How sewer system is work