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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.
Catchbasin s 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.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.
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.
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). They consist of a specialized manhole chamber, and use the water flow and/or gravity to separate oil and grit.
See also sewage treatment, infiltration galleryAn infiltration gallery is a structure used to supplement a storm sewer, by directing storm runoff from non-road areas. While the catchbasins under sewer grates work well on swift-flowing surfaces like asphalt and concrete, heavy storm water flow on grass
The earliest covered sewers uncovered by archeologists are in the regularly planned cities of the Indus Valley CivilizationIndus River in present-day Pakistan. The Mohenjo-daro ruins pictured above were once the center of this ancient society. The Indus Valley Civilization 2800 BC 1800 BC, was an ancient civilization thriving along the Indus River in the northwest Indian subc. In ancient Rome, the Cloaca MaximaThe Cloaca Maxima was one of the world's earliest sewage systems. Constructed in ancient Rome in order to drain local marshes and remove the waste of one of the world's most populous cities, it carried effluent to the River Tiber, which ran beside the cit, considered a marvel of engineering, disgorged into the TiberThe River Tiber ( Italian Tevere , the third longest river in Italy at 406 km (252 miles) after the Po, flows through the Campagna and Rome in its course from Mount Fumaiolo to the Tyrrhenian Sea, which it reaches in two branches that cross the suburbs of. In medieval European cities, small natural waterways used for carrying off wastewater were eventually covered over and functioned as sewers. London's Fleet is such a system. Open drains along the center of some streets were known as 'kennels' ('canals'). The 19th-century brick-vaulted sewer system of ParisEiffel Tower has become the symbol of Paris throughout the world. Paris is the capital and largest city of France. The city is built on an arc of the River Seine, and is thus divided into two parts: the Right Bank to the north and the smaller Left Bank to offers tours for tourists.