Sewage collection and disposal
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[[Urban area|Urban]] areas require some methods for collection and disposal of [[sewage]].
===Collection===
A sewage system may convey the [[wastewater]] by [[gravity]] to a [[sewage treatment]] plant. Where pipeline excavation is difficult because of [[rock (geology)|rock]] or there is limited topographic relief (i.e., due to flat terrain), gravity collection systems may not be practical and the sewage must be pumped through a pipeline to the treatment plant. In low-lying communities, wastewater may be conveyed by [[vacuum sewer|vacuum]]. Pipelines range in size from pipes of six inches (150 mm) in diameter to concrete-lined tunnels of up to thirty feet (10 m) in diameter.
Sewage can also be collected by low pressure [[pump]]s and vacuum systems. A low pressure system uses a small [[grinder pump]] located at each point of connection, typically a house or business. [[Vacuum sewer]] systems use differential [[atmospheric pressure]] to move the liquid to a central vacuum station. Typically a vacuum sewer station can service approximately 1,200 homes before it becomes more cost-effective to build another station.
===Design and Analysis of Collection Systems===
Design and sizing of [[sewage]] collection systems considers population served, commercial and [[industrial wastewater|industrial]] flows, flow peaking characteristics and wet weather flows. [[Combined sewer]] systems are designed to transport both [[stormwater]] [[surface runoff|runoff]] and sewage in the same pipe. Besides the projected sewage flow, the size and characteristics of the [[drainage basin|watershed]] are the overriding design considerations for combined sewers. Often, combined sewers can not handle the volume of runoff, resulting in [[Combined sewer#combined sewer overflow|combined sewer overflows]] and causing [[water pollution]] problems in nearby water bodies.
Separate [[sanitary sewer]] systems are designed to transport sewage alone. In communities served by separate sanitary sewers, another pipe system is constructed to convey stormwater runoff directly to surface waters. Most municipal sewer systems constructed today are separate sewer systems.
Although separate sewer systems are intended to transport only sewage, all sewer systems have some degree of inflow and infiltration of surface water and [[groundwater]], which can lead to [[sanitary sewer overflow]]s. Inflow and infiltration is highly affected by [[antecedent moisture]] conditions, which also represents an important design consideration in these systems.
===Historical sewage conveyance and disposal===
As recently as 100 years ago in major cities of developed countries, and up to the present day in many parts of the world, the primary concern with sewage was the matter of conveying it away from inhabited areas. Aside from its unpleasant [[odor]], even early humans were aware that health problems arose when human waste was allowed to contaminate [[drinking water]] supplies{{Fact|date=February 2007}}.
Therefore, the historical focus of sewage treatment was on conveyance of raw sewage to a natural body of water, such as a [[river]] or [[ocean]], where it would be satisfactorily diluted and dissipated. Early [[human]] habitations were often built next to water sources. [[River]]s could double as a crude form of natural sewage disposal.
Higher [[population density|population densities]] required more complex sewer collection and conveyance systems in order to maintain (somewhat) sanitary conditions in crowded cities. The ancient [[city|cities]] of [[Harappa]] and [[Mohenjo-daro]] of the [[Indus Valley civilization]] constructed complex networks of [[brick]]-lined sewage drains from around 2600 BC and also had outdoor flush [[toilet]]s connected to this network.
The urban areas of the Indus Valley civilization provided public and private baths, sewage was disposed through underground drains built with precisely laid bricks, and a sophisticated water management system with numerous reservoirs was established. In the drainage systems, drains from houses were connected to wider public drains.<ref>Rodda, J. C. and Ubertini, Lucio (2004). ''The Basis of Civilization - Water Science?'' pg 161. International Association of Hydrological Sciences (International Association of Hydrological Sciences Press 2004).</ref>
Ancient [[Minoan civilization]] had [[rock (geology)|stone]] sewers that were periodically flushed with clean water.
[[Ancient Rome|Roman]] towns and garrisons in the [[United Kingdom]] between 46 BC and 400 CE had complex sewer networks sometimes constructed out of hollowed out [[Elm]] logs which were shaped so that they butted together with the down-stream pipe providing a socket for the upstream pipe.
A significant development was the construction of a network of sewers to collect waste water, which began from the [[Indus Valley civilization]]. In some cities, including [[Rome]] and [[Istanbul]] ([[Constantinople]]), networked ancient sewer systems continue to function today as collection systems for those cities' modernized sewer systems. Instead of flowing to a river or the sea, the pipes have been re-routed to modern sewer treatment facilities.
However, many cities had no [[sewer]]s and relied on nearby [[river]]s or occasional [[rain]] to wash away sewage. In some cities, [[waste water]] simply ran down the streets, which had [[stepping stone]]s to keep pedestrians out of the muck, and eventually drained as runoff into the local [[drainage basin|watershed]]. This was enough in early cities with few occupants but the growth of cities quickly [[pollution|overpolluted]] streets and became a constant source of [[disease]]. Even as recently as the late 19th century sewerage systems in parts of the highly industrialised United Kingdom were so inadequate that [[water-borne disease]]s such as [[cholera]] and [[typhoid]] were still common. In [[Merthyr Tydfil]], a large town in [[South Wales]], most houses discharged their sewage to individual [[cess-pit]]s which persistently overflowed causing the pavements to be awash with foul sewage.
A '''sewer bed''' is a piece of land typically used by a municipality for the dumping of raw sewage. Usually raw sewage was brought by truck or drawn by horses to be dumped, but the practice stopped back in the 1940s.
==References==
<references/>
==See also==
*[[Pumping station]]
*[[Sewage]]
*[[Sewage treatment]]
*[[Sewer bed]]
*[[Select Society of Sanitary Sludge Shovelers]]
*[[William Lindley]] – pioneering 19th century engineer
*[[John Todd (biologist)|John Todd]]
==External links==
*[http://www.straightdope.com/mailbag/msolidwaste.html What happens to all the stuff that goes down the toilet?] (from [[The Straight Dope]])
*[http://www.yucatanliving.com/yucatan-survivor/mexican-fosa-septica.htm Why you do not put toilet paper in the toilet in Mexico]
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[[Category:Environmental engineering]]
[[Category:Physical infrastructure]]
[[Category:Sewerage]]
[[Category:Waste collection]]
[[Category:Water pollution]]
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[[de:Abwasser]]
[[fr:Épuration des eaux]]
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