Sewer

Sewers transport wastewater from buildings to treatment facilities. Sewers are pipelines that connect buildings to horizontal 'mains'. The sewer mains often connect to larger mains, and then to the wastewater treatment site. Vertical pipes, called manholes, connect the mains to the surface. Sewers are generally gravity powered, though pumps may be used if necessary.

Related Topics:
Transport - Wastewater - Treatment facilities - Pipeline - Manhole - Pump

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Storm sewers (also storm drains) are large pipes that transport storm water runoff from streets to natural bodies of water, to avoid street flooding. When the two systems are operated separately, the sewer system that is not the set of storm drains is called a sanitary sewer.

Related Topics:
Storm drain - Street - Sanitary sewer

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Catchbasins are immediately below the vertical pipes connecting the surface to the storm sewers. While sewer grates covering the vertical pipes prevent large objects from falling into the sewer system, the grates are spaced far enough apart that many small objects can fall through. The area immediately below the catchbasin "catches" such detritus. Water from the top of the catchbasin drains into the sewer proper. The catchbasin serves much the same function as the "trap" in household wastewater plumbing in trapping objects. Unlike the trap, the catchbasin does not necessarily prevent sewer gases such as hydrogen sulfide and methane from escaping. Catchbasins contain stagnant water and can be used by mosquitoes for breeding. Catchbasins require regular cleaning to remove the trapped debris. Municipalities typically have large vacuum trucks that clean out catchbasins.

Related Topics:
Catchbasin - Sewer grates - Detritus - Plumbing - Hydrogen sulfide - Methane

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Storm sewer water may be treated or not, depending on jurisdiction. Treatment helps purify the storm water before being restored to a natural body of water. Storm water may become contaminated while running down the road or other impervious surface, or from lawn chemical runoff, before entering the sewer. It is a good idea to separate storm sewers from waste sewers because the huge influx of water during a rainstorm can overwhelm the treatment plant, resulting in untreated sewage being discharged into the environment. Washington DC and other cities with older combined systems have this problem after every heavy rain.

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However, completely separating storm sewers from sanitary sewers often means no treatment of stormwater which is not desirable either, as the first flush from storm runoff can be extremely dirty. Runoff into storm sewers can be minimized by including Sustainable Urban Drainage Systems in to municipal plans. Eaves troughs should not discharge directly into the storm sewer system but rather onto the ground where it has a chance to soak into the soil. Where possible, storm water runoff should be directed to unlined ditches before flowing into the storm sewers, again to allow the runoff to soak into the ground.

Related Topics:
Sanitary sewer - Stormwater

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Separation of undesired runoff can be done within the storm sewer system, but such devices are new to the market and can only be installed with new development or during major upgrades. They are referred to as oil-grit separators (OGS) or oil-sediment separators (OSS). They consist of a specialized manhole chamber, and use the water flow and/or gravity to separate oil and grit.

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See also sewage treatment, infiltration gallery

Related Topics:
Sewage treatment - Infiltration gallery

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