Sanitary sewer overflow: Difference between revisions

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SSOs can cause [[gastrointestinal illness]]es ([[waterborne diseases]]), beach closures and restrictions on fish and [[shellfish]] consumption.

=== United States= ==

==Magnitude of the problem==

Developed countries such as the [[United States]], [[Canada]], most [[Western Europe]]an nations (e.g. [[Italy]] and [[France]]), [[Australia]], [[Singapore]], [[South Korea]] and [[Japan]] are struggling with public health problems of SSO prevention. The magnitude of the problem is much greater in most developing countries.

===United States===

The [[U.S. Environmental Protection Agency]] (EPA) estimates that at least 23,000 to 75,000 SSO events occur in the United States each year.<ref>{{cite web |url=https://www.epa.gov/npdes/sanitary-sewer-overflows-ssos |title=Sanitary Sewer Overflows |author=<!--Staff writer(s); no by-line.--> |date=2015-11-16 |access-date=2023-02-17 |website=National Pollutant Discharge Elimination System |publisher=U.S. Environmental Protection Agency (EPA) |___location=Washington, D.C.}}</ref> EPA estimated that upgrading every municipal treatment and collection system to reduce the frequency of overflow events to no more than once every five years would cost about $88 billion as of 2004.<ref name="EPA-RTC">{{cite report |date=August 2004 |title=Report to Congress: Impacts and Control of CSOs and SSOs |url=https://www.epa.gov/npdes/2004-npdes-cso-report-congress |access-date=2023-02-17 |publisher=EPA |id=EPA-833-R-04-001}}</ref> This cost would be in addition to approximately $10 billion already invested. Although the volume of untreated sewage discharged to the environment is less than 0.01 percent of all treated sewage in the United States, the total volume amounts to several billion gallons per annum and accounts for thousands of cases of gastrointestinal illness each year.<ref name="EPA-RTC" />{{rp|Ch. 6}}

=== Worldwide perspective= ==

Developed European countries and Japan have similar or somewhat larger percentages of SSO events compared to the U.S.{{citation needed|date=June 2015}}

In [[developing countries]], most wastewater is still not treated when discharged into the environment. The [[People's Republic of China]] discharged about 55 percent of all sewage without treatment of any type, as of 2001.<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’scity'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’scountry'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>

In many countries there are obligations to measure and report SSO occurrence using real-time [[telemetry]] to warn the public, bathers and shellfishery operators.{{citation needed|date=June 2016}}

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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="EPA-RTC"/>{{rp|p. 4–26}} [[Brown grease|Grease]] is the blocking agent in approximately half of U.S. 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 down the toilet rather than being put in a waste bin.<ref name="EPA-RTC"/>{{rp|p. 4–28}}

Many U.S. municipalities require restaurants and food processing businesses to use [[grease interceptor]]s and regulate the disposal of fats, oil and grease in the sewer system.<ref>For example, the [[Washington Suburban Sanitary Commission]] (WSSC) in Maryland, U.S.: {{cite web |title=Fats, Oils, & Grease |url=https://www.wsscwater.com/fog |website=Special Wastewater Discharge Requirements |date=2023-12-29 |publisher=WSSC |___location=Laurel, MD}}</ref>

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 [[transducer]]s suspended in the sewers to detect high levels and to report the events back over fixed wireless data networks. In certain locations this practice has permitted the reduction of pollution events by up to 60 percent.{{citation needed|date=June 2016}}