Sanitary sewer overflow

Developed countries such as the United States, Canada, most Western European nations (e.g. Italy and France), Australia, Singapore, South Korea and Japan are struggling with public health problems of SSO prevention.

[1] 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.

[3] In a relatively developed Middle Eastern country such as Iran, the majority of Tehran's population has totally untreated sewage injected to the city's groundwater.

[5] In many countries there are obligations to measure and report SSO occurrence using real-time telemetry to warn the public, bathers and shellfishery operators.

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.

Approximately one-quarter of United States SSOs occur during heavy rainfall events, which can cause inflow of stormwater into sanitary sewers through damage, improper connections, or flooding buildings and lift stations in low-lying areas of the collection system.

ES–3 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, swimming restrictions and prohibition of the consumption of certain aquatic animals (particularly certain molluscs) after overflow events.

Turbidity increase and dissolved oxygen decrease in receiving waters can lead to accentuated effects beyond the obvious pathogenic induced damage to aquatic ecosystems.

[citation needed] In the 19th century, sewage treatment plants were first developed and installed in the U.S. and parts of Europe, and the concept of SSO was identified.

Local governments heard complaints of citizens, and beach closure protocols were systematised to reduce risks to public health.

After passage of the Clean Water Act in 1972, the U.S. spent billions of dollars on upgrades to sewage treatment plants, with some associated repairs and improvements to the associated collection systems, where the overflows occur.