Sewerage

Sewerage (or sewage system) is the infrastructure that conveys sewage or surface runoff (stormwater, meltwater, rainwater) using sewers. It encompasses components such as receiving drains, manholes, pumping stations, storm overflows, and screening chambers of the combined sewer or sanitary sewer. Sewerage ends at the entry to a sewage treatment plant or at the point of discharge into the environment. It is the system of pipes, chambers, manholes, etc. that conveys the sewage or storm water. In many cities, sewage (or municipal wastewater) is carried together with stormwater, in a combined sewer system, to a sewage treatment plant. In some urban areas, sewage is carried separately in sanitary sewers and runoff from streets is carried in storm drains. Access to these systems, for maintenance purposes, is typically through a manhole. During high precipitation periods a sewer system may experience a combined sewer overflow event or a sanitary sewer overflow event, which forces untreated sewage to flow directly to receiving waters. This can pose a serious threat to public health and the surrounding environment. The system of sewers is called sewerage or sewerage system in British English and sewage system or sewer system in American English. It was probably the need to get rid of foul smells rather than an understanding of the health hazards of human waste that led to the first proper sewage systems. Most settlements grew next to natural waterways into which waste from latrines was readily channeled, but the emergence of major cities exposed the inadequacy of this approach. Early civilizations like the Babylonians dug cesspits below floor level in their houses and created crude drainage systems for removing storm water. But it was not until 2000 BC in the Indus valley civilization that networks of precisely made brick-lined sewage drains were constructed along the streets to convey waste from homes. Toilets in homes on the street side were connected directly to these street sewers and were flushed manually with clean water.