Sanitary sewer overflow: Difference between revisions

Revision as of 18:17, 13 December 2015

Revision as of 16:34, 22 December 2015

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: ''Not to be confused with [[Combined sewer#Combined sewer overflows (CSOs)|combined sewer overflow (CSO)]]''

[[File:Sewer overflow RI EPA.jpg|thumb|right|A [[manhole]] cover unable to contain a sanitary sewer overflow]]

'''Sanitary sewer overflow''' ('''SSO''') is a condition in which untreated [[sewage]] is discharged from a [[sanitary sewer]] into the environment prior to reaching [[sewage treatment]] facilities. When caused by rainfall it is also known as '''wet weather overflow'''. It is primarily meaningful in [[developed countries]], which have extensive treatment facilities. Frequent causes of SSO spills include:

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===Blockages===

Decentralized failures in dry weather mainly occur from collection sewer line blockages, which can arise from a [[debris]] clog or tree root intrusion into the line itself. Approximately half of SSOs in the United States are caused by blockage.<ref name="EPARTC"/>{{rp|p. 4–26}} [[Brown grease|Grease]] is the blocking agent in approximately half of United States SSOs attributed to blockage, and solid debris is the blocking agent for another 25 percent. [[Root]]s are a contributing factor in approximately one-quarter of United States SSOs attributed to blockage. Grease deposits are caused by cooking fats liquified with hot water for discharge to sanitary sewers. These fats congeal as solid deposits in the cooler sewer. Solid debris includes soiled clothing, [[diaper]]s, and [[sanitary napkin]]s flushed into toilets. <ref name="EPARTC"/>{{rp|p. 4–28}}

One of the main problems of a decentralized line failure is the difficulty of defining the ___location of overflow, since a typical urban system contains thousands of miles of collection pipes, and the central treatment plant has no way of communicating with all the lines, unless expensive monitoring equipment has been installed. Companies in the UK have widely deployed bulk dielectric transducers suspended in the sewers to detect high levels and to report the events back over fixed wireless data networks. In certain locations it has been said that this practice has permitted the reduction of pollution events by up to 60%.

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[[Image:Overflowepa.gif|thumb|230px|left|Decentralized wet weather overflow event]]

Human health impacts include significant numbers of [[gastrointestinal]] illness]] each year, although death from one overflow event is uncommon. Additional human impacts include [[beach]] closures, [[human swimming|swimming]] restrictions and prohibition of the consumption of certain aquatic animals (particularly certain [[mollusc]]s) after overflow events. Ecological consequences include [[fish kill]]s, harm to [[plankton]] and other aquatic microflora and microfauna. Turbidity increase and dissolved oxygen decrease in receiving waters can lead to accentuated effects beyond the obvious [[pathogen]]ic induced damage to aquatic [[ecosystem]]s. It is possible that higher life forms such as [[marine mammal]]s can be affected since certain seals and [[sea lion]]s are known to experience peaks in pathogenic harm.<ref>Johnson, S. P., Jang, S., Gulland, F.M.D., Miller, M., Casper, D., Lawrence, J., Herrera, J., [http://www.jwildlifedis.org/cgi/reprint/39/1/136.pdf "Characterization and clinical manifestations of Arcanobacterium phocae infections in marine mammals stranded along the central California coast"], ''Journal of Wildlife Diseases'', 39:136-144 (2003).</ref>

===Worldwide perspective===

In [[developing countries]], most wastewater is still not treated properly but discharged into the environment. Even a country such as the [[People's Republic of China]] discharged in 2001 about 55 percent of all sewage without treatment of any type.<ref>"[[World Bank]] Supports China's Wastewater Treatment", ''The People’s Daily'', November 30, 2001, Beijing</ref> In a relatively developed [[Middle East]]ern country such as [[Iran]], the majority of [[Tehran]]'s population has totally untreated sewage injected to the city’s groundwater.<ref>Massoud Tajrishy and Ahmad Abrishamchi, "Integrated Approach to Water and Wastewater Management for [[Tehran]], [[Iran]]", [[Water Conservation]], Reuse, and Recycling: Proceedings of the Iranian-American Workshop, National Academies Press (2005)</ref> In [[Venezuela]], a below-average country in [[South America]] with respect to wastewater treatment, 97 percent of the country’s [[sewage]] is discharged untreated into the environment.<ref>Appropriate Technology for Sewage Pollution Control in the Wider [[Caribbean]] Region, Caribbean Environment Programme Technical Report #40 1998</ref>

Developed countries such as the United States, [[Canada]], most [[Western Europe]]an states, [[Australia]] and [[Japan]] are struggling with a public health problem of SSO prevention. However, the magnitue of the problem is much greater in most developing countries.

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==External links==

*[http://cfpub.epa.gov/npdes/home.cfm?program_id=4 EPA - Sanitary Sewer Overflows Program]

[[Category:Public health]]