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: ''Not to be confused with combined sewer overflow (CSO)'' 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: * Blockage of sewer lines * Infiltration/Inflow of excessive stormwater into sewer lines during heavy rainfall * Malfunction of pumping station lifts or electrical power failure * Broken sewer lines In many countries there are obligations to measure and report SSO occurrence using real-time telemetry to warn the public, bathers and shellfishery operators. The concept of SSO containment valves has been pioneered in the UK and they are installed to mitigate dry spills, by correlating rainfall data with SSO spill activity. ==Magnitude of the problem== EPA estimates that about forty thousand SSO events occur in the United States each year.〔U.S. Environmental Protection Agency (EPA). Washington, DC. ("Sanitary Sewer Overflows and Peak Flows" ), Updated February 2012.〕 The 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.〔 EPA. ("Report to Congress: Impacts and Control of CSOs and SSOs" ), Executive Summary. August 2004. Document No. EPA-833-R-04-001.〕 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% 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.〔 Advanced European countries and Japan have similar or somewhat larger percentages of SSO events.〔(【引用サイトリンク】title=A Worldwide View Of Sanitary Sewer Overflow )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Sanitary sewer overflow」の詳細全文を読む スポンサード リンク
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