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{{Short description|Liquid waste or sewage discharged into a river or the sea}}
[[File:Discharge pipe.jpg|thumb|right|[[Wastewater]]
'''Effluent''' is [[wastewater]] from sewers or industrial outfalls that flows directly into [[surface water]]s, either untreated or after being [[Wastewater treatment|treated]] at a facility.<ref name="EPA effluent defn">{{cite web |title=Terms of Environment |url=https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=40000807.txt |date=February 1993 |publisher=United States Environmental Protection Agency (EPA) |location=Washington, D.C. |page=10 |id=EPA 175-B-93-001}}</ref> The term has slightly different meanings in certain contexts, and may contain various [[pollutant]]s depending on the source.<ref name="WWD-effluent">{{cite magazine |last=Tuser |first=Cristina |title=What is Effluent? |url=https://www.wwdmag.com/wastewater-treatment/wastewater-treatment/article/10939353/what-is-effluent |date=2021-10-27 |magazine=Water & Wastes Digest |publisher=Endeavor Business Media, LLC}}</ref>
==
Effluent is defined by the [[United States Environmental Protection Agency]] (EPA) as "
== Description ==
Effluent in the artificial sense is in general considered to be [[water pollution]], such as the outflow from a [[sewage treatment]] facility or an [[Industrial wastewater treatment|industrial wastewater]] discharge. An effluent [[sump pump]], for instance, pumps waste from toilets installed below a main sewage line. In the context of [[waste water treatment plants]], effluent that has been treated is sometimes called ''secondary effluent'', or ''treated effluent''. This cleaner effluent is then used to feed the [[bacteria]] in [[biofilters]].<ref>{{Cite book |title=Wastewater engineering: Treatment and reuse |date=2003 |publisher=McGraw-Hill |author=George Tchobanoglous |author2=Franklin L. Burton |author3=H. David Stensel |isbn=0-07-041878-0|edition=4th |location=Boston |oclc=48053912}}</ref>
In the context of a [[thermal power station]] and other industrial facilities, the output of the cooling system may be referred to as the effluent cooling water, which is noticeably warmer than the environment and is called [[thermal pollution]].<ref name="Laws-aquatic">{{cite book |url=https://books.google.com/books?id=V5D2DQAAQBAJ |title=Aquatic Pollution<nowiki>:</nowiki> An Introductory Text |last=Laws |first=Edward A. |date=2017 |publisher=John Wiley & Sons |isbn=978-1-119-30450-0 |edition=4th |location=Hoboken, NJ}}</ref>{{rp|375}} In [[chemical engineering]] practice, effluent is the stream exiting a [[chemical reactor]].<ref>{{cite book |last=Fogler |first=H. Scott |title=Elements of Chemical Reaction Engineering |date=2006 |publisher=Prentice Hall |isbn=978-0-13-127839-4 |location=Hoboken, NJ |page=43}}</ref>
Effluent may carry pollutants such as fats, oils and greases; solvents, detergents and other chemicals; heavy metal; other solids; and food waste.<ref name="WWD-effluent"/> Possible sources include a wide range of manufacturing industries, mining industries, oil and gas extraction, and service industries.<ref name="EPA EG categories">{{Cite web |title=Industrial Effluent Guidelines |url=https://www.epa.gov/eg/industrial-effluent-guidelines |date=2022-11-07 |publisher=EPA}}</ref>
== Treatment ==
{{Main|Wastewater treatment}}
There are several kinds of wastewater which are treated at the appropriate type of treatment plant. Domestic wastewater (also called municipal wastewater or [[sewage]]) is processed at a [[Sewage treatment|sewage treatment plant]]. For industrial wastewater, treatment either takes place in a separate [[industrial wastewater treatment]] facility, or in a sewage treatment plant (usually after some form of pre-treatment). Other types of wastewater treatment plants include [[agricultural wastewater treatment]] and [[leachate]] treatment plants.
Treating wastewater efficiently is challenging, but improved technology allows for enhanced removal of specific materials, increased [[Water reuse|re-use of water]], and energy production from waste.<ref name="WWD-effluent"/><ref name="Brandt">{{Cite book |last1=Brandt |first1=Malcolm J. |chapter=Chapter 10. Specialized and Advanced Water Treatment Processes |date=2017-01-01 |url=https://www.sciencedirect.com/science/article/pii/B9780081000250000107 |title=Twort's Water Supply (Seventh Edition) |pages=407–473 |editor-last=Brandt |editor-first=Malcolm J. |location=Boston |publisher=Butterworth-Heinemann |doi=10.1016/b978-0-08-100025-0.00010-7 |isbn=978-0-08-100025-0 |last2=Johnson |first2=K. Michael |last3=Elphinston |first3=Andrew J. |last4=Ratnayaka |first4=Don D. |editor2-last=Johnson |editor2-first=K. Michael |editor3-last=Elphinston |editor3-first=Andrew J. |editor4-last=Ratnayaka |editor4-first=Don D.}}</ref><ref name="Jegatheesan">{{cite encyclopedia |last1=Jegatheesan |first1=V. |last2=Shu |first2=L. |last3=Visvanathan |first3=C. |title=Aquaculture Effluent: Impacts and Remedies for Protecting the Environment and Human Health |encyclopedia=Encyclopedia of Environmental Health |year=2011 |publisher=Elsevier |doi=10.1016/b978-0-444-52272-6.00340-8 |isbn=978-0-444-52272-6 |page=123}}</ref><ref>{{Cite book |author=ProQuest LLC |title=Energy from Toxic Organic Water for Head and Power Generation |date=2018 |publisher=Woodhead Publishing |isbn=978-0-08-102529-1 |oclc=1096233045}}</ref>
== Pollution control regulation ==
=== United States effluent guidelines ===
In the United States, the [[Clean Water Act]] requires all direct effluent discharges to surface waters to be regulated with permits under the [[Clean Water Act#Point sources|National Pollutant Discharge Elimination System]] (NPDES).<ref>{{cite web |date=2021-10-11 |title=NPDES Permit Limits |url=https://www.epa.gov/npdes/npdes-permit-limits |website=National Pollutant Discharge Elimination System |publisher=EPA}}</ref><ref name="EPA-learn">{{Cite web |title=Learn about Effluent Guidelines |url=https://www.epa.gov/eg/learn-about-effluent-guidelines |date=2022-09-09 |publisher=EPA}}</ref> Indirect dischargers–facilities which send their wastewater to municipal sewage treatment plants–may be subject to pretreatment requirements.<ref name="EPA-pretreatment">{{cite web |title=National Pretreatment Program Overview |url=https://www.epa.gov/npdes/national-pretreatment-program-overview |date=2022-10-03 |website=NPDES |publisher=EPA}}</ref> NPDES permits require discharging facilities to limit or treat effluent to the levels that result from using the most effective [[Wastewater treatment|treatment technologies]] possible at a practical cost to mitigate the effects of discharges on the receiving waters.<ref name="EPA-learn" /> EPA has published technology-based regulations, called "[[effluent guidelines]]", for 59 industrial categories.<ref name="EPA EG categories"/> The agency reviews the standards annually, conducts research on various categories, and makes revisions as appropriate.<ref name="EPA-learn" /> Noncompliance with these standards and all other conditions in the permits is punishable by law.<ref>{{Cite web |title=Effluent Guidelines Implementation & Compliance |url=https://www.epa.gov/eg/effluent-guidelines-implementation-compliance |date=2022-09-09 |publisher=EPA}}</ref> Each year, effluent guidelines regulations prevent billions of pounds of contaminants from being released into bodies of water.<ref>{{Cite web |title=Effluent Guidelines Plan |url=https://www.epa.gov/eg/effluent-guidelines-plan |date=2022-11-18 |publisher=EPA}}</ref>
EPA regulations require effluent limitations to be expressed as mass-based limits (rather than concentration-based limits) in the permits, so that discharging facilities will not use dilution as a substitute for treatment. In cases where setting mass-based limits are infeasible, the permit authority must set conditions in the permit that prohibit dilution.<ref>EPA. "Calculating NPDES permit conditions." ''Code of Federal Regulations'', {{CodeFedReg|40|122|45|f}}</ref>
=== United States sewage treatment standards ===
The U.S. "Secondary Treatment Regulation" is the national standard for municipal sewage treatment plants.<ref>EPA. "Secondary Treatment Regulation." Code of Federal Regulations,'' {{USCFR|40|133}}</ref>
==See also==
{{Portal|Water}}
{{wiktionary}}
*[[Agricultural wastewater treatment]]
*[[Effluent guidelines]] (U.S. wastewater regulations)
*[[Effluent limitation]]
*[[Industrial wastewater treatment]]
*[[Stormwater]]
*[[Surface runoff]]
==References==
{{
{{Rivers, streams and springs}}
[[Category:Environmental science]]
[[Category:Environmental engineering]]
[[Category:Water pollution]]
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