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{{short description|Contamination of water bodies}}
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{{Pollution sidebar|Water}}
'''Water pollution''' (or '''aquatic pollution''') is the contamination of ], with a negative impact on their uses.<ref name="Von Sperling"/>{{rp|6}} It is usually a result of human activities. Water bodies include ]s, ]s, ]s, ]s, ]s and ]. Water ] results when ]s mix with these water bodies. Contaminants can come from one of four main sources. These are ] discharges, industrial activities, agricultural activities, and urban runoff including ].<ref name=Eckenfelder>{{Cite book |vauthors=Eckenfelder Jr WW |url=https://onlinelibrary.wiley.com/doi/book/10.1002/0471238961 |title=Kirk-Othmer Encyclopedia of Chemical Technology |publisher=] |year=2000 |isbn=978-0-471-48494-3 |doi=10.1002/0471238961.1615121205031105.a01}}</ref> Water pollution may affect either ] or ]. This form of pollution can lead to many problems. One is the ] of ]. Another is spreading ] when people use polluted water for drinking or ].<ref>{{Cite web |date=July 23, 2013 |title=Water Pollution |url=https://www.hsph.harvard.edu/ehep/82-2/ |access-date=September 18, 2021 |website=Environmental Health Education Program |publisher=] |location=Cambridge, MA |archive-date=September 18, 2021 |archive-url=https://web.archive.org/web/20210918005228/https://www.hsph.harvard.edu/ehep/82-2/ |url-status=live}}</ref> Water pollution also reduces the ]s such as ] provided by the ].


Sources of water pollution are either ]s or ]s.<ref>{{Cite journal |last1=Schaffner |first1=Monika |last2=Bader |first2=Hans-Peter |last3=Scheidegger |first3=Ruth |date=August 15, 2009 |title=Modeling the contribution of point sources and non-point sources to Thachin River water pollution |url=http://dx.doi.org/10.1016/j.scitotenv.2009.05.007 |journal=Science of the Total Environment |volume=407 |issue=17 |pages=4902–4915 |doi=10.1016/j.scitotenv.2009.05.007 |issn=0048-9697}}</ref> Point sources have one identifiable cause, such as a ], a ], or an ]. Non-point sources are more diffuse. An example is ].<ref name="Moss2008">{{cite journal |vauthors=Moss B |title=Water pollution by agriculture |journal=Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences |volume=363 |issue=1491 |pages=659–666 |date=February 2008 |pmid=17666391 |pmc=2610176 |doi=10.1098/rstb.2007.2176}}</ref> Pollution is the result of the cumulative effect over time. Pollution may take many forms. One would is toxic substances such as oil, metals, plastics, ]s, ]s, and industrial waste products. Another is stressful conditions such as changes of ], ] or anoxia, increased temperatures, excessive ], or changes of ]). The introduction of ] is another. Contaminants may include ] and ] substances. A common cause of ] is the use of water as a ] by ] and industrial manufacturers.
'''Water pollution''' is the contamination of ] bodies (e.g. ]s, ]s, ]s, ]).


Control of water pollution requires appropriate ] and management plans as well as legislation. ] solutions can include improving ], ], ], agricultural ], ], ] and control of ] (including stormwater management).
Water pollution affects plants and organisms living in these ]; and, in almost all cases the effect is damaging either to individual ] and populations, but also to the natural ].
{{TOC limit|3}}


== Definition ==
Water pollution occurs when ]s are discharged directly or indirectly into water bodies without adequate ] to remove harmful compounds.
A practical definition of water pollution is: "Water pollution is the addition of substances or energy forms that directly or indirectly alter the nature of the water body in such a manner that negatively affects its legitimate uses."<ref name="Von Sperling"/>{{rp|6}} Water is typically referred to as polluted when it is impaired by ] contaminants. Due to these contaminants, it either no longer supports a certain human use, such as ], or undergoes a marked shift in its ability to support its biotic communities, such as fish.


==Introduction== == Contaminants ==
].]]
Water pollution is a major problem in the global context. It has been suggested that it is the leading worldwide cause of deaths and diseases,<ref name="death">{{cite news |url=http://finance.yahoo.com/columnist/article/trenddesk/3748 |author=Pink, Daniel H. |publisher=Yahoo |title=Investing in Tomorrow's Liquid Gold |date=April 19, 2006}}</ref><ref name="death2">{{cite news |url=http://environment.about.com/od/environmentalevents/a/waterdayqa.htm |author=West, Larry |publisher=About |title=World Water Day: A Billion People Worldwide Lack Safe Drinking Water |date=March 26, 2006}}</ref> and that it accounts for the deaths of more than 14,000 people daily.<ref name="death2"/> An estimated 700 million ]ns have no access to a proper toilet, and 1,000 Indian children die of diarrheal sickness every day.<ref name="creaking">{{cite web|url=http://www.economist.com/specialreports/displaystory.cfm?story_id=12749787|title=A special report on India: Creaking, groaning: Infrastructure is India’s biggest handicap|date=11 December 2008|publisher=The Economist}}</ref> Some 90% of ]'s cities suffer from some degree of water pollution,<ref>"". Chinadaily.com.cn. 2005-06-07.</ref> and nearly 500 million people lack access to safe drinking water.<ref>"". The New York Times. August 26, 2007.</ref> In addition to the acute problems of water pollution in ], ] continue to struggle with pollution problems as well. In the most recent national report on ] in the ], 45 percent of assessed ] ]s, 47 percent of assessed lake ]s, and 32 percent of assessed ] and ] ]s were classified as polluted.<ref>United States Environmental Protection Agency (EPA). Washington, DC. October 2007. Fact Sheet No. EPA 841-F-07-003.</ref>


===Contaminants with an origin in sewage ===
Water is typically referred to as polluted when it is impaired by ] contaminants and either does not support a human use, like serving as ], and/or undergoes a marked shift in its ability to support its constituent biotic communities, such as ]. Natural phenomena such as ]es, ]s, ]s, and ]s also cause major changes in water quality and the ecological status of water.
{{Further|Waterborne diseases#Diseases by type of pathogen|Sewage#Pathogens}}


The following compounds can all reach water bodies via raw sewage or even treated sewage discharges:
==Water pollution categories==
* Various chemical compounds found in personal ] and ] products.
Surface water and groundwater have often been studied and managed as separate resources, although they are interrelated.<ref name="circ1139">United States Geological Survey (USGS). Denver, CO. USGS Circular 1139. 1998.</ref> Sources of surface water pollution are generally grouped into two categories based on their origin.
* ]s found in chemically ] ] (whilst these chemicals can be a pollutant in the ], they are fairly volatile and therefore not usually found in environmental waters).<ref>{{cite journal |vauthors=Alexandrou L, Meehan BJ, Jones OA |title=Regulated and emerging disinfection by-products in recycled waters |journal=] |volume=637–638 |pages=1607–1616 |date=October 2018 |pmid=29925195 |doi=10.1016/j.scitotenv.2018.04.391 |bibcode=2018ScTEn.637.1607A |s2cid=49355478}}</ref>
* ]s (from ] and residue from human ] methods) and synthetic materials such as ]s that mimic hormones in their action. These can have adverse impacts even at very low concentrations on the natural biota and potentially on humans if the water is treated and utilized for drinking water.<ref>{{cite web |title=Environment Agency (archive) – Persistent, bioaccumulative and toxic PBT substances |url=http://www.environment-agency.gov.uk/business/444304/1290036/1290100/1290353/1294402/1311542/?version=1&lang=_e |archive-url=https://web.archive.org/web/20060804195610/http://www.environment-agency.gov.uk/business/444304/1290036/1290100/1290353/1294402/1311542/?version=1&lang=_e |archive-date=August 4, 2006 |access-date=2012-11-14 |publisher=]}}</ref><ref> {{Webarchive|url=https://web.archive.org/web/20150427112251/http://planetearth.nerc.ac.uk/news/story.aspx?id=297 |date=April 27, 2015 }}. Planetearth.nerc.ac.uk. Retrieved on 2012-12-19.</ref><ref>{{cite web |title=Endocrine Disruption Found in Fish Exposed to Municipal Wastewater |url=http://toxics.usgs.gov/highlights/wastewater_fish.html |archive-url=https://web.archive.org/web/20111015161223/http://toxics.usgs.gov/highlights/wastewater_fish.html |archive-date=October 15, 2011 |access-date=2012-11-14 |publisher=] |location=Reston, VA}}</ref>
* ]s and ]s, often from agricultural runoff.
*Pathogens like '']'' (HAV may be present in treated wastewater outflows and receiving water bodies but is largely removed during further treatment of drinking water<ref>{{cite journal|vauthors=Takuissu GR, Kenmoe S, Ebogo-Belobo JT, Kengne-Ndé C, Mbaga DS, Bowo-Ngandji A, Ondigui JL, Kenfack-Momo R, Tcatchouang S, Kenfack-Zanguim J, Fogang RL, Menekem EZ, Kame-Ngasse GI, Magoudjou-Pekam JN, Veneri C, Mancini P, Ferraro GB, Iaconelli M, Orlandi L, Del Giudice C, Suffredini E, La Rosa G|display-authors=6|title=Occurrence of Hepatitis A Virus in Water Matrices: A Systematic Review and Meta-Analysis|year=2023|journal=International Journal of Environmental Research and Public Health|volume=20|issue=2|page=1054|id=Art. No. 1054|doi=10.3390/ijerph20021054|doi-access=free|pmid=36673812|pmc=9859052}}</ref>)


Inadequately treated wastewater can convey nutrients, pathogens, heterogenous suspended solids and organic fecal matter.<ref name="Von Sperling"/>{{rp|6}}
===Point source pollution===
]
] - ].]]
] refers to contaminants that enter a waterway through a discrete conveyance, such as a ] or ]. Examples of sources in this category include discharges from a ] plant, a ], or a city ]. The U.S. ] (CWA) defines point source for ] enforcement purposes.<ref>Clean Water Act, section 502(14), {{USC|33|1362}} (14).</ref> The CWA definition of point source was amended in 1987 to include ] ] systems, as well as industrial stormwater, such as from ] sites.<ref>CWA section 402(p), {{USC|33|1342(p)}}</ref>


{| class="wikitable"
===Non-point source pollution===
|+Pollutants and their effects*
] (NPS) pollution refers to diffuse contamination that does not originate from a single discrete source. NPS pollution is often accumulative effect of small amounts of contaminants gathered from a large area. The leaching out of ] compounds from agricultural land which has been fertilized is a typical example. Nutrient ] in ] from "sheet flow" over an ] or a ] are also cited as examples of NPS pollution.
!Pollutant
!Main representative parameter
!Possible effect of the pollutant
|-
|]
|]
|
* ] problems
* ] deposits
* Pollutants ]
* Protection of pathogens
|-
|Biodegradable organic matter
|] (BOD)
|
* Oxygen consumption
* Death of fish
* Septic conditions
|-
|]s
|
* ]
* ]
|
* ]
* Toxicity to fish (])
* Illnesses in new-born infants (] from ])
* ]
|-
|Pathogens
|
* Coliforms, such as '']'', may not be pathogenic in and of themselves, but are used as ] of co-occurring pathogens that should take slightly less time to die or degrade<ref name="Von Sperling"/>{{rp|51}}
* ]<ref name="Von Sperling"/>{{rp|55}}<ref name="World Health Organization">{{cite book |url=http://www.susana.org/en/resources/library/details/1004|title=Guidelines for the Safe Use of Wastewater, Excreta and Greywater, Volume 4 Excreta and Greywater Use in Agriculture |date=2006 |publisher=] |isbn=92-4-154685-9 |edition=third |location=Geneva}}</ref>
|Waterborne diseases
|-
|Non-biodegradable organic matter
|
* ]s
* Some detergents
* Others
|
* ] (various)
* Foam (]s)
* Reduction of oxygen transfer (detergents)
* Non-]
* Bad ]s (e.g.: ])
|-
|Inorganic dissolved solids
|
* ]
* ]
|
* Excessive ] – harm to plantations (])
* Toxicity to plants (some ions)
* Problems with ] (])
|-
| colspan=3 style="text-align: left;" |* Sources of these pollutants are household and industrial wastewater, urban runoff and stormwater drainage from agricultural areas<ref name="Von Sperling" />{{rp|7}}
|}


==== Pathogens ====
Contaminated storm water washed off of ]s, ]s and ]s, called ], is sometimes included under the category of NPS pollution. However, this runoff is typically channeled into storm drain systems and discharged through pipes to local surface waters, and is a point source. However where such water is not channeled and drains directly to ground it is a non-point source.
Bacteria, viruses, ]s and ]s are examples of pathogens that can be found in wastewater.<ref name="Von Sperling"/>{{rp|47}} In practice, ]s are used to investigate pathogenic pollution of water because the detection of pathogenic organisms in water sample is difficult and costly, because of their low concentrations. The indicators (]) of fecal contamination of water samples most commonly used are total coliforms (TC) or fecal coliforms (FC), the latter also referred to as thermotolerant coliforms, such as '']''.<ref name="Von Sperling"/>{{rp|52–53}}


Pathogens can produce waterborne diseases in either human or animal hosts.<ref>{{Cite book |url=https://pubs.rsc.org/en/content/ebook/978-1-84973-648-0 |title=Pollution: Causes, effects, and control |date=2013 |publisher=] |vauthors=Harrison RM |editor-first1=R. M. |editor-last1=Harrison |isbn=978-1-78262-560-5 |edition=5th |location=Cambridge, UK |doi=10.1039/9781782626527 |oclc=1007100256}}</ref> Some microorganisms sometimes found in contaminated surface waters that have caused human health problems include ''],'' ''],'' ''],'' ''],'' ] and other viruses, and parasitic worms including the '']'' type.<ref>Schueler, Thomas R. "Microbes and Urban Watersheds: Concentrations, Sources, & Pathways." Reprinted in {{webarchive|url=https://web.archive.org/web/20130108194041/http://www.cwp.org/documents/cat_view/75-articles-from-the-practice-of-watershed-protection.html?limit=40&order=name&dir=DESC&start=80 |date=January 8, 2013}} 2000. Center for Watershed Protection. Ellicott City, MD.</ref>
==Groundwater pollution==
Interactions between ] and surface water are complex. Consequently, groundwater pollution, sometimes referred to as '''groundwater contamination''', is not as easily classified as surface water pollution.<ref name="circ1139" /> By its very nature, groundwater ]s are susceptible to contamination from sources that may not directly affect surface water bodies, and the distinction of point vs. non-point source may be irrelevant. A spill of a chemical contaminant on soil, located away from a surface water body, may not necessarily create point source or non-point source pollution, but nonetheless may contaminate the aquifer below. Analysis of groundwater contamination may focus on ] characteristics and ], as well as the nature of the contaminant itself. ''See ].''


The source of high levels of pathogens in water bodies can be from ] (due to ]), sewage, ], or ] that has found its way into the water body. The cause for this can be lack of sanitation procedures or poorly functioning on-site ] systems (]s, ]s), ] without disinfection steps, ]s and ]s (CSOs)<ref name="EPARTC">{{cite report |url=https://www.epa.gov/npdes/2004-npdes-cso-report-congress |title=Report to Congress: Impacts and Control of CSOs and SSOs |date=August 2004 |publisher=] |id=EPA 833-R-04-001}}</ref> during storm events and ] (poorly managed livestock operations).
==Causes of water pollution==
The specific contaminants leading to pollution in water include a wide spectrum of ]s, ]s, and physical or sensory changes such as elevated temperature and discoloration. While many of the chemicals and substances that are regulated may be naturally occurring (], ], ], ], etc.) the ] is often the key in determining what is a natural component of water, and what is a contaminant.


=== Organic compounds ===
]-depleting substances may be natural materials, such as ] matter (e.g. leaves and grass) as well as man-made chemicals. Other natural and anthropogenic substances may cause ] (cloudiness) which blocks light and disrupts plant growth, and clogs the ]s of some fish species.<ref name="EPA-AGFact">EPA. Fact Sheet No. EPA-841-F-05-001. March 2005.</ref>
Organic substances that enter water bodies are often ].<ref name="Laws-aquatic">{{cite book |vauthors=Laws EA |url=https://books.google.com/books?id=V5D2DQAAQBAJ |title=Aquatic Pollution<nowiki>:</nowiki> An Introductory Text |date=2018 |publisher=] |isbn=978-1-119-30450-0 |edition=4th |location=Hoboken, NJ |via=]}}</ref>{{rp|229}}
* ] hydrocarbons, including fuels (], ], jet fuels, and ]) and lubricants (motor oil), and fuel ] byproducts, from ]s or ] runoff<ref name="Burton & Pitt">{{cite book |url=http://unix.eng.ua.edu/~rpitt/Publications/BooksandReports/Stormwater%20Effects%20Handbook%20by%20%20Burton%20and%20Pitt%20book/MainEDFS_Book.html |title=Stormwater Effects Handbook: A Toolbox for Watershed Managers, Scientists, and Engineers |chapter=2 |publisher=]/Lewis Publishers |year=2001 |isbn=0-87371-924-7 |location=New York |vauthors=Burton Jr GA, Pitt R |access-date=January 26, 2009 |archive-date=May 19, 2009 |archive-url=https://web.archive.org/web/20090519035716/http://unix.eng.ua.edu/~rpitt/Publications/BooksandReports/Stormwater%20Effects%20Handbook%20by%20%20Burton%20and%20Pitt%20book/MainEDFS_Book.html |url-status=dead}}</ref>
* ], such as improperly stored industrial ]s. Problematic species are ]s such as ] (PCBs) and ], a common solvent.


] (PFAS) are ]s.<ref name="ReferenceA">{{cite journal |vauthors = Johnson MS, Buck RC, Cousins IT, Weis CP, Fenton SE |title=Estimating Environmental Hazard and Risks from Exposure to Per- and Polyfluoroalkyl Substances (PFASs): Outcome of a SETAC Focused Topic Meeting |journal=] |volume=40 |issue=3 |pages=543–549 |date=March 2021 |pmid=32452041 |pmc=8387100 |doi=10.1002/etc.4784}}</ref><ref name="linkinghub.elsevier.com">{{cite journal |vauthors=Sinclair GM, Long SM, Jones OA |title=What are the effects of PFAS exposure at environmentally relevant concentrations? |journal=] |volume=258 |pages=127340 |date=November 2020 |pmid=32563917 |doi=10.1016/j.chemosphere.2020.127340 |s2cid=219974801 |bibcode=2020Chmsp.25827340S}}</ref>
Many of the chemical substances are ]. Pathogens can produce ] in either human or animal hosts. Alteration of water's physical chemistry includes acidity (change in ]), ], temperature, and eutrophication. ] is an increase in the concentration of chemical nutrients in an ecosystem to an extent that increases in the primary productivity of the ecosystem. Depending on the degree of eutrophication, subsequent negative environmental effects such as ] (oxygen depletion) and severe reductions in water quality may occur, affecting fish and other animal populations.


=== Inorganic contaminants ===
===Pathogens===
] is an ] that is dangerously alkaline and can lead to water pollution if not managed appropriately (photo from ], Germany).]]
] cover unable to contain a ].]]
]
] are a commonly-used ] of water pollution, although not an actual cause of disease. Other ]s sometimes found in surface waters which have caused human health problems include:
Inorganic water pollutants include:
* '']''
* ] from food processing waste
* '']''
* ] from ]s (via ])<ref name="Burton & Pitt" /><ref>Schueler, Thomas R. "Cars Are Leading Source of Metal Loads in California." Reprinted in {{webarchive|url=https://web.archive.org/web/20120312045934/http://www.cwp.org/documents/cat_view/75-articles-from-the-practice-of-watershed-protection.html|date=March 12, 2012}} 2000. Center for Watershed Protection. Ellicott City, MD.</ref> and ]
* '']''
* ] and ]s, from sewage and agriculture (''see'' ])
* '']''
* ] (]) in runoff from construction sites or sewage, logging, ] practices land clearing sites
* '']'' and other ]es
* Salt: ] is the process of salty runoff contaminating ]s.<ref name="Kaushal et al">{{cite journal |vauthors=Kaushal SS, Likens GE, Pace ML, Utz RM, Haq S, Gorman J, Grese M |title=Freshwater salinization syndrome on a continental scale |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=115 |issue=4 |pages=E574–E583 |date=January 2018 |pmid=29311318 |pmc=5789913 |doi=10.1073/pnas.1711234115 |bibcode=2018PNAS..115E.574K |doi-access=free}}</ref> Human-induced salinization is termed as secondary salinization, with the use of ] road salts as the most common form of runoff.<ref>{{cite journal |vauthors=Evans DM, Villamagna AM, Green MB, Campbell JL |title=Origins of stream salinization in an upland New England watershed |journal=] |volume=190 |issue=9 |pages=523 |date=August 2018 |pmid=30116969 |doi=10.1007/s10661-018-6802-4 |bibcode=2018EMnAs.190..523E |s2cid=52022441}}</ref><ref name="Cañedo-Argüelles">{{cite journal |vauthors=Cañedo-Argüelles M, Kefford B, Schäfer R |title=Salt in freshwaters: causes, effects and prospects - introduction to the theme issue |journal=Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences |volume=374 |issue=1764 |date=December 2018 |pmid=30509904 |pmc=6283966 |doi=10.1098/rstb.2018.0002}}</ref>
* ]s (helminths).<ref>USGS. Reston, VA. FS-027-01. March 2001.</ref><ref>Schueler, Thomas R. Reprinted in 2000. Center for Watershed Protection. Ellicott City, MD.</ref>
High levels of pathogens may result from inadequately treated ] discharges.<ref>EPA. Accessed 2009-02-20.</ref> This can be caused by a sewage plant designed with less than ] (more typical in less-developed countries). In developed countries, older cities with aging ] may have leaky sewage collection systems (pipes, pumps, valves), which can cause ]s. Some cities also have ]s, which may discharge untreated sewage during rain storms.<ref name="EPARTC">EPA. " August 2004. Document No. EPA-833-R-04-001.</ref>


=== Pharmaceutical pollutants ===
Pathogen discharges may also be caused by poorly-managed ] operations.
{{excerpt|Environmental impact of pharmaceuticals and personal care products|paragraphs=1-3|file=no}}
* ]s, which can include various ]s and their ]s (''see also'' ]), such as ] drugs, ]s or the ].
* Metabolites of ] (see also ]), for example ] and ]<ref name="journals.biologists.com">{{Cite journal |vauthors=Knight K |date=2021 |title=Freshwater methamphetamine pollution turns brown trout into addicts |url=https://journals.biologists.com/jeb/article/224/13/jeb242971/270754/Freshwater-methamphetamine-pollution-turns-brown |journal=] |volume=224 |issue=13 |pages=jeb242971 |doi=10.1242/jeb.242971 |issn=0022-0949 |doi-access=free}}</ref><ref name="De Lorenzo">{{Cite web |last=De Lorenzo |first=D |title=MDMA Gangs Are Literally Polluting Europe |url=https://www.vice.com/en/article/qj83jw/mdma-gangs-are-literally-polluting-europe |date=2021-06-18 |website=Vice World News |publisher=] |location=Brooklyn, NY}}</ref>


===Chemical and other contaminants=== === Solid waste and plastics ===
], Canada]]
].]]
{{Further|Sewage#Solid waste|Plastic pollution|Marine plastic pollution}}
Contaminants may include ] and ] substances.


] can enter water bodies through untreated sewage, combined sewer overflows, urban runoff, people discarding ] into the environment, wind carrying municipal solid waste from ]s and so forth. This results in ] pollution– large visible items polluting the water– but also ] pollution that is not directly visible. The terms ] and ] are used in the context of pollution of oceans.
'''Organic''' water pollutants include:
* ]
* ]s found in chemically ] ], such as ]
* ] waste, which can include oxygen-demanding substances, fats and grease
* ]s and ]s, a huge range of ]s and other ]
* ] hydrocarbons, including fuels (], ], jet fuels, and ]) and lubricants (motor oil), and fuel ] byproducts, from ] ]<ref name="Burton & Pitt">{{cite book|title=Stormwater Effects Handbook: A Toolbox for Watershed Managers, Scientists, and Engineers|authors=G. Allen Burton, Jr., Robert Pitt|publisher=CRC/Lewis Publishers|location=New York|year=2001|isbn=0-87371-924-7|
url=http://unix.eng.ua.edu/~rpitt/Publications/BooksandReports/Stormwater%20Effects%20Handbook%20by%20%20Burton%20and%20Pitt%20book/MainEDFS_Book.html}} Chapter 2.</ref>
* ] and bush debris from ] operations
* ] (VOCs), such as industrial ]s, from improper storage. ]s, which are dense non-aqueous phase liquids (]s), may fall to the bottom of reservoirs, since they don't mix well with water and are denser.
* Various chemical compounds found in personal ] and ] products


Microplastics persist in the environment at high levels, particularly in ] and ]s, where they cause water pollution.<ref name=":9">{{Cite web |title=Development solutions: Building a better ocean |url=https://www.eib.org/en/essays/plastic-pollution |access-date=2020-08-19 |website=European Investment Bank}}</ref> 35% of all ocean microplastics come from textiles/clothing, primarily due to the erosion of polyester, acrylic, or nylon-based clothing, often during the washing process.<ref>{{Cite web |vauthors=Resnick B |date=2018-09-19 |title=More than ever, our clothes are made of plastic. Just washing them can pollute the oceans |url=https://www.vox.com/the-goods/2018/9/19/17800654/clothes-plastic-pollution-polyester-washing-machine |access-date=2021-10-04 |website=]}}</ref>
'''Inorganic''' water pollutants include:
* ] caused by industrial discharges (especially ] from ])
* ] from food processing waste
* ] as industrial by-products
* ]s containing nutrients--] and ]s--which are found in stormwater runoff from ], as well as commercial and residential use<ref name="Burton & Pitt" />
* ] from ]s (via ])<ref name="Burton & Pitt" /><ref>Schueler, Thomas R. Reprinted in 2000. Center for Watershed Protection. Ellicott City, MD.</ref> and ]
* ] (]) in runoff from ] sites, ], ] practices or land clearing sites


Stormwater, untreated sewage and wind are the primary conduits for microplastics from land to sea. Synthetic fabrics, tyres, and city dust are the most common sources of microplastics. These three sources account for more than 80% of all microplastic contamination.<ref name=":0">{{Cite web|author=((European Investment Bank))|date=2023-02-27 |title=Microplastics and Micropollutants in Water: Contaminants of Emerging Concern |url=https://www.eib.org/en/publications/20230042-microplastics-and-micropollutants-in-water |language=EN|access-date=2024-04-12}}</ref><ref>{{Cite web |title=Microplastics from textiles: towards a circular economy for textiles in Europe — European Environment Agency |url=https://www.eea.europa.eu/publications/microplastics-from-textiles-towards-a |access-date=2023-03-24 |website=www.eea.europa.eu |language=en}}</ref>
'''Macroscopic''' pollution—large visible items polluting the water—may be termed "floatables" in an urban stormwater context, or ] when found on the open seas, and can include such items as:
* ] (e.g. paper, plastic, or food waste) discarded by people on the ground, and that are washed by ] into ]s and eventually discharged into surface waters
* ]s, small ubiquitous waterborne plastic pellets
* ]s, large derelict ships


== Types of surface water pollution ==
] discharges heated water into ].<ref>Selna, Robert (2009). ''],'' January 2, 2009.</ref>]]
Surface water pollution includes pollution of rivers, lakes and oceans. A subset of surface water pollution is ] which affects the oceans. ] refers to contamination by excessive inputs of ].

Globally, about 4.5&nbsp;billion people do not have ] as of 2017, according to an estimate by the ].<ref name="JMP2017">WHO and UNICEF (2017) . Geneva: World Health Organization (WHO) and the United Nations Children's Fund (UNICEF), 2017</ref> Lack of access to sanitation is concerning and often leads to water pollution, e.g. via the practice of ]: during rain events or floods, the ] are moved from the ground where they were deposited into surface waters. Simple ] may also get flooded during rain events.

As of 2022, ] and ] account for around 16% of global ]s discharge into the seas,<ref name=":0" /><ref>{{Cite web |last=Ferris |first=Robert |title=Half of plastic trash in oceans comes from 5 countries |url=https://www.cnbc.com/2016/01/13/half-of-plastic-trash-in-oceans-comes-from-5-countries.html |access-date=2023-03-24 |website=CNBC |date=January 13, 2016 |language=en}}</ref> and although management of plastic waste and ] is improving globally, the absolute amount of plastic pollution continues to increase unabated due to the large amount of plastic that is being produced and disposed of.<ref name=ritchie2023>{{Cite journal|last1=Ritchie |first1=Hannah|author1-link=Hannah Ritchie |last2=Samborska|first2=Veronika|last3=Roser |first3=Max |author3-link=Max Roser |year=2023|title=Plastic Pollution |url=https://ourworldindata.org/plastic-pollution |journal=Our World in Data|access-date=12 April 2024}}</ref> Even if sea plastic pollution were to stop entirely, microplastic contamination of the surface ocean would be projected to continue to increase.<ref name=ritchie2023/>

=== Marine pollution ===
{{Excerpt|Marine pollution|paragraphs=1|file=no}}

=== Nutrient pollution ===
{{Excerpt|Nutrient pollution|paragraphs=1|file=no}}


===Thermal pollution=== ===Thermal pollution===
] in Massachusetts discharged heated water to ] until 2011.]]
{{excerpt|Thermal pollution|paragraphs=1|file=no}}
Elevated water temperatures decrease ] levels (due to lower levels of ], as gases are less soluble in warmer liquids), which can kill fish (which may then rot) and alter ] composition, reduce species ], and foster invasion by new ] species.<ref>{{Cite book |vauthors=Goel PK |url=https://www.worldcat.org/oclc/85857626|title=Water pollution: causes, effects and control |date=2006 |publisher=New Age International |isbn=81-224-1839-2 |edition=Rev. 2nd |location=New Delhi |oclc=85857626}}</ref>{{rp|179}}<ref name="Laws-aquatic" />{{rp|375}}


{{Main|Thermal pollution}} === Biological pollution ===
The introduction of aquatic ] is a form of water pollution as well. It causes ].<ref>{{cite journal |vauthors=Olenin S, Minchin D, Daunys D |title=Assessment of biopollution in aquatic ecosystems |journal=] |volume=55 |issue=7–9 |pages=379–394 |date=2007 |pmid=17335857 |doi=10.1016/j.marpolbul.2007.01.010|bibcode=2007MarPB..55..379O }}</ref>


== Groundwater pollution ==
Thermal pollution is the rise or fall in the temperature of a natural body of water caused by human influence. A common cause of thermal pollution is the use of water as a ] by ] and industrial manufacturers.
{{excerpt|Groundwater pollution|paragraphs=1|file=no}}In many areas of the world, groundwater pollution poses a hazard to the wellbeing of people and ecosystems. One-quarter of the world's population depends on groundwater for drinking, yet concentrated recharging is known to carry short-lived contaminants into carbonate aquifers and jeopardize the purity of those waters.<ref>{{Cite journal |last1=Hartmann |first1=Andreas |last2=Jasechko |first2=Scott |last3=Gleeson |first3=Tom |last4=Wada |first4=Yoshihide |last5=Andreo |first5=Bartolomé |last6=Barberá |first6=Juan Antonio |last7=Brielmann |first7=Heike |last8=Bouchaou |first8=Lhoussaine |last9=Charlier |first9=Jean-Baptiste |last10=Darling |first10=W. George |last11=Filippini |first11=Maria |date=2021-05-18 |title=Risk of groundwater contamination widely underestimated because of fast flow into aquifers |journal=] |language=en |volume=118 |issue=20 |pages=e2024492118 |doi=10.1073/pnas.2024492118 |issn=0027-8424 |pmc=8158018 |pmid=33972438|bibcode=2021PNAS..11824492H|doi-access=free }}</ref>
Elevated water temperatures decreases oxygen levels (which can kill fish) and affects ] composition, such as invasion by new ] species. Urban runoff may also elevate temperature in surface waters.


== Pollution from point sources ==
Thermal pollution can also be caused by the release of very cold water from the base of ]s into warmer rivers.
] refers to contaminants that enter a waterway from a single, identifiable source, such as a ] or ]. Examples of sources in this category include discharges from a sewage treatment plant, a factory, or a city ].


The U.S. ] (CWA) defines point source for regulatory enforcement purposes (''see'' ]).<ref>United States. Clean Water Act (CWA), section 502(14), {{USC|33|1362}} (14).</ref> The CWA definition of point source was amended in 1987 to include municipal storm sewer systems, as well as industrial storm water, such as from construction sites.<ref>U.S. CWA section 402(p), {{USC|33|1342(p)}}</ref>
==Transport and chemical reactions of water pollutants==
{{seealso|Marine pollution}}
Most water pollutants are eventually carried by rivers into the oceans. In some areas of the world the influence can be traced hundred miles from the mouth by studies using ]s. Advanced ]s such as ] or the ] have been used in many locations worldwide to examine the fate of pollutants in aquatic systems. Indicator ] species such as ] have also been used to study pollutant fates in the ], for example. The highest ] loads are not directly at the mouth of the ], but 100 kilometers south, since several days are required for incorporation into ]ic tissue. The Hudson discharge flows south along the coast due to ]. Further south then are areas of ], caused by chemicals using up oxygen and by ]s, caused by excess ]s from algal cell death and decomposition. Fish and ] kills have been reported, because toxins climb the food chain after small fish consume ], then large fish eat smaller fish, etc. Each successive step up the food chain causes a stepwise concentration of pollutants such as ] (e.g. ]) and ] such as ]. This is known as biomagnification, which is occasionally used interchangeably with bioaccumulation.


=== Sewage ===
Large ]s (]es) in the oceans trap floating ]. The ] for example has collected the so-called "]" that is now estimated at 100 times the size of Texas. Many of these long-lasting pieces wind up in the stomachs of marine birds and animals. This results in obstruction of digestive pathways which leads to reduced appetite or even starvation.
Sewage typically consists of 99.9% water and 0.1% solids.<ref>{{cite book |vauthors=Scholz M |title=Wetlands for Water Pollution Control |year=2016 |isbn=978-0-444-63607-2 |pages=13–15 |chapter=Sewage Treatment |doi=10.1016/B978-0-444-63607-2.00003-4}}</ref> Sewage contributes many classes of nutrients that lead to ]. It is a major source of phosphate for example.<ref name="WPC2">{{cite book |title=Water Pollution Control |year=2014 |isbn=978-1-118-86383-1 |veditors=Nesaratnam ST |doi=10.1002/9781118863831}}</ref> Sewage is often contaminated with diverse compounds found in personal ], ], ]s (see also ]), and their metabolites<ref name="journals.biologists.com"/><ref name="De Lorenzo"/> Water pollution due to environmental persistent pharmaceutical pollutants can have wide-ranging consequences. When sewers overflow during storm events this can lead to water pollution from untreated sewage. Such events are called ]s or ].] on ]]]


=== Industrial wastewater ===
Many chemicals undergo reactive ] or chemically change especially over long periods of time in ] reservoirs. A noteworthy class of such chemicals is the ] such as ] (used in industrial metal degreasing and electronics manufacturing) and ] used in the dry cleaning industry (note latest advances in liquid carbon dioxide in dry cleaning that avoids all use of chemicals). Both of these chemicals, which are ] themselves, undergo partial decomposition reactions, leading to new hazardous chemicals (including dichloroethylene and vinyl chloride).
] (PFOS) is a global ] that has been found in drinking water. It appears not to biodegrade.<ref name="PR09May">{{Cite web |url=http://chm.pops.int/Convention/Pressrelease/COP4Geneva8May2009/tabid/542/language/en-US/Default.aspx |title=Governments unite to step-up reduction on global DDT reliance and add nine new chemicals under international treaty |date=8 May 2009 |publisher=Stockholm Convention Secretariat |location=Geneva |id=Press release}}</ref>]]{{Further|Industrial wastewater treatment}}


Industrial processes that use water also produce wastewater. This is called ]. Using the US as an example, the main industrial consumers of water (using over 60% of the total consumption) are power plants, petroleum refineries, iron and steel mills, pulp and paper mills, and food processing industries.<ref name=Eckenfelder/> Some industries discharge chemical wastes, including solvents and heavy metals (which are toxic) and other harmful pollutants.
Groundwater pollution is much more difficult to abate than surface pollution because groundwater can move great distances through unseen ]s. Non-porous aquifers such as ]s partially purify water of bacteria by simple filtration (adsorption and absorption), dilution, and, in some cases, chemical reactions and biological activity: however, in some cases, the pollutants merely transform to ]s. Groundwater that moves through cracks and ] is not filtered and can be transported as easily as surface water. In fact, this can be aggravated by the human tendency to use natural ]s as dumps in areas of ] topography.


<section begin=Pollutants in industrial wastewater/>Industrial wastewater could add the following pollutants to receiving water bodies if the wastewater is not treated and managed properly:
There are a variety of secondary effects stemming not from the original pollutant, but a derivative condition. An example is ]-bearing ], which can inhibit the penetration of sunlight through the water column, hampering ] in aquatic plants.
* ], including ], ], and ]
* ] matter and nutrients such as ]: Certain industries (e.g. ], ] waste, paper fibers, plant material, etc.) discharge high concentrations of BOD, ammonia nitrogen and oil and grease.<ref>{{Cite book |url=https://www.worldcat.org/oclc/48053912 |title=Wastewater engineering: treatment and reuse |date=2003 |publisher=McGraw-Hill |vauthors=Tchobanoglous G, Burton FL, Stensel HD |isbn=0-07-041878-0 |edition=4th |location=Boston |chapter=Chapter 3: Analysis and Selection of Wastewater Flowrates and Constituent Loadings |oclc=48053912}}</ref>{{rp|180}}<ref name="Laws-aquatic" />
* ] particles such as ], grit, metal particles, rubber residues from tires, ]s, etc.;
* ] such as ]s, ]s, ]s, etc.
* ], endocrine disrupting compounds, hormones, perfluorinated compounds, siloxanes, drugs of abuse and other hazardous substances<ref name="pmid25889547">{{cite journal |vauthors=Arvaniti OS, Stasinakis AS |title=Review on the occurrence, fate and removal of perfluorinated compounds during wastewater treatment |journal=] |volume=524–525 |issue= |pages=81–92 |date=August 2015 |pmid=25889547 |doi=10.1016/j.scitotenv.2015.04.023 |bibcode=2015ScTEn.524...81A}}</ref><ref name="pmid23320453">{{cite journal |vauthors=Bletsou AA, Asimakopoulos AG, Stasinakis AS, Thomaidis NS, Kannan K |title=Mass loading and fate of linear and cyclic siloxanes in a wastewater treatment plant in Greece |journal=] |volume=47 |issue=4 |pages=1824–32 |date=February 2013 |pmid=23320453 |doi=10.1021/es304369b |bibcode=2013EnST...47.1824B |s2cid=39997737}}</ref><ref name="pmid27236142">{{cite journal |vauthors=Gatidou G, Kinyua J, van Nuijs AL, Gracia-Lor E, Castiglioni S, Covaci A, Stasinakis AS |title=Drugs of abuse and alcohol consumption among different groups of population on the Greek Island of Lesvos through sewage-based epidemiology |journal=] |volume=563–564 |issue= |pages=633–40 |date=September 2016 |pmid=27236142 |doi=10.1016/j.scitotenv.2016.04.130 |bibcode=2016ScTEn.563..633G |hdl=10067/1345920151162165141|s2cid=4073701 |hdl-access=free }}</ref>
* ] such as polyethylene and polypropylene beads, polyester and polyamide<ref name="pmid30620926">{{cite journal |vauthors=Gatidou G, Arvaniti OS, Stasinakis AS |title=Review on the occurrence and fate of microplastics in Sewage Treatment Plants |journal=] |volume=367 |issue= |pages=504–512 |date=April 2019 |pmid=30620926 |doi=10.1016/j.jhazmat.2018.12.081 |bibcode=2019JHzM..367..504G |s2cid=58567561}}</ref>
* ] from ]s and industrial manufacturers
* ]s from ], processing ], operating ]s, or disposal of ].
* Some industrial discharges include ]s such as ] (PFAS).<ref name="ReferenceA" /><ref name="linkinghub.elsevier.com" /><section end=Pollutants in industrial wastewater/>


=== Oil spills ===
==Measurement of water pollution==
{{Excerpt|Oil spill|paragraphs=1|file=no}}
] preparing water autosamplers.]]
Water pollution may be analyzed through several broad categories of methods: physical, chemical and biological. Most involve collection of samples, followed by specialized analytical tests. Some methods may be conducted ''],'' without sampling, such as ]. Government agencies and research organizations have published standardized, validated analytical test methods to facilitate the comparability of results from disparate testing events.<ref>For example, see Clescerl, Leonore S.(Editor), Greenberg, Arnold E.(Editor), Eaton, Andrew D. (Editor). ''Standard Methods for the Examination of Water and Wastewater'' (20th ed.) American Public Health Association, Washington, DC. ISBN 0-87553-235-7. This publication is also available on CD-ROM and by subscription.</ref>


== Pollution from nonpoint sources ==
===Sampling===
{{Excerpt|Nonpoint source pollution|paragraphs=1|file=no}}
Sampling of water for physical or chemical testing can be done by several methods, depending on the accuracy needed and the characteristics of the contaminant. Many contamination events are sharply restricted in time, most commonly in association with rain events. For this reason "grab" samples are often inadequate for fully quantifying contaminant levels. Scientists gathering this type of data often employ auto-sampler devices that pump increments of water at either time or ] intervals.


=== Agriculture ===
Sampling for biological testing involves collection of plants and/or animals from the surface water body. Depending on the type of assessment, the organisms may be identified for ]s (population counts) and returned to the water body, or they may be dissected for ]s to determine ].
Agriculture is a major contributor to water pollution from nonpoint sources. The use of fertilizers as well as ] from farm fields, pastures and ]s leads to nutrient pollution.<ref>{{Cite book |veditors=Walters A |title=Nutrient Pollution From Agricultural Production: Overview, Management and a Study of Chesapeake Bay |url=https://novapublishers.com/shop/nutrient-pollution-from-agricultural-production-overview-management-and-a-study-of-chesapeake-bay/ |date=2016 |publisher=] |location=Hauppauge, NY |isbn=978-1-63485-188-6 |oclc=960163923}}</ref> In addition to plant-focused agriculture, fish-farming is also a source of pollution. Additionally, agricultural runoff often contains high levels of pesticides.<ref name=Eckenfelder/>


=== Atmospheric contributions (air pollution) ===
===Physical testing===
Air deposition is a process whereby air pollutants from industrial or natural sources settle into water bodies. The deposition may lead to polluted water near the source, or at distances up to a few thousand miles away. The most frequently observed water pollutants resulting from industrial air deposition are sulfur compounds, nitrogen compounds, mercury compounds, other heavy metals, and some pesticides and industrial by-products. Natural sources of air deposition include forest fires and microbial activity.<ref name="EPA air deposition">{{cite report |title=Frequently Asked Questions About Air Deposition |url=https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=2000NQU1.txt |date=September 2001 |pages=3–7 |publisher=] |id=EPA 453/R-01-009}}</ref>
Common physical tests of water include temperature, solids concentration like ] (TSS) and turbidity.


] is caused by emissions of ] and ], which react with the ] in the ] to produce acids.<ref name=":5">{{Cite web |date=2022-06-24 |title=What is Acid Rain? |url=https://www.epa.gov/acidrain/what-acid-rain |publisher=]}}</ref> Some governments have made efforts since the 1970s to reduce the release of sulfur dioxide and nitrogen oxide into the atmosphere. The main source of sulfur and nitrogen compounds that result in acid rain are ], but nitrogen oxides can also be produced naturally by ] strikes and sulphur dioxide is produced by ].<ref>{{Cite journal |vauthors=Sisterson DL, Liaw YP |date=1990-01-01 |title=An evaluation of lightning and corona discharge on thunderstorm air and precipitation chemistry |journal=] |volume=10 |issue=1 |pages=83–96 |bibcode=1990JAtC...10...83S |doi=10.1007/BF01980039 |issn=1573-0662 |s2cid=97714446}}</ref> Acid rain can have harmful effects on plants, aquatic ecosystems and infrastructure.<ref>{{Cite web |date=2022-04-24 |title=Effects of Acid Rain |url=https://www.epa.gov/acidrain/effects-acid-rain |publisher=EPA}}</ref><ref name=":6">{{cite book |vauthors=Kjellstrom T, Lodh M, McMichael T, Ranmuthugala G, Shrestha R, Kingsland S |chapter=Air and Water Pollution: Burden and Strategies for Control |date=2006 |chapter-url=http://www.ncbi.nlm.nih.gov/books/NBK11769/ |title= Disease Control Priorities in Developing Countries |veditors=Jamison DT, Breman JG, Measham AR, Alleyne G, Claeson M, Evans DB, Jha P, Mills A, Musgrove P |archive-url=https://web.archive.org/web/20200807014923/https://www.ncbi.nlm.nih.gov/books/NBK11769/ |edition=2nd |publisher=World Bank |isbn=978-0-8213-6179-5 |pmid=21250344 |archive-date=August 7, 2020 |url-status=live}}</ref>
===Chemical testing===
{{see also|water chemistry analysis|environmental chemistry}}
Water samples may be examined using the principles of ]. Many published test methods are available for both organic and inorganic compounds. Frequently-used methods include ], ] (BOD), ] (COD), nutrients (] and ] compounds), metals (including ], ], ], ] and ]), oil and grease, total petroleum hydrocarbons (TPH), and ]s.


] have increased since the 1850s due anthropogenic influences (]).<ref name="cald03" /> This leads to ] and is another form of water pollution from atmospheric contributions.<ref>{{cite journal |vauthors=Doney SC, Fabry VJ, Feely RA, Kleypas JA |title=Ocean acidification: the other CO2 problem |journal=] |volume=1 |issue=1 |pages=169–192 |date=2009-01-01 |pmid=21141034 |doi=10.1146/annurev.marine.010908.163834 |bibcode=2009ARMS....1..169D|s2cid=402398 }}</ref>
===Biological testing===
{{main|Bioindicator}}
Biological testing involves the use of plant, animal, and/or microbial indicators to monitor the health of an ].
:''For microbial testing of drinking water, see ].''


== Sampling, measurements, analysis ==
==Control of water pollution==
] preparing water autosamplers]]
===Domestic sewage===
{{Further|Water quality#Sampling and measurement|Environmental monitoring|Analysis of water chemistry|Water sampling station|Regulation and monitoring of pollution#Water pollution}}
{{main|Sewage treatment}}
] serving ] and vicinity.]]
Domestic sewage is 99.9% pure water, the other 0.1% are pollutants. While found in low concentrations, these pollutants pose risk on a large scale.<ref>"Environmental works: types of sewage.Encyclopaedia Britannica Online. N.p., 2009. Web. 9 Oct. 2009. <http://www.search.eb.com/eb/article-72342></ref> In urban areas, domestic sewage is typically treated by centralized ] plants. In the U.S., most of these plants are operated by local government agencies, frequently referred to as ] (POTW). Municipal treatment plants are designed to control ]s: BOD and suspended solids. Well-designed and operated systems (i.e., secondary treatment or better) can remove 90 percent or more of these pollutants. Some plants have additional sub-systems to treat nutrients and pathogens. Most municipal plants are not designed to treat toxic pollutants found in industrial wastewater.<ref>EPA (2004). Document No. EPA 832-R-04-001.</ref>


Water pollution may be analyzed through several broad categories of methods: physical, chemical and biological. Some methods may be conducted '']'', without sampling, such as temperature. Others involve collection of samples, followed by specialized analytical tests in the laboratory. Standardized, validated analytical test methods, for water and wastewater samples have been published.<ref>For example, see {{cite book |title=Standard Methods For the Examination of Water and Wastewater |edition=21 |editor-last1=Eaton |editor-first1=Andrew D. |editor-last2=Greenberg |editor-first2=Arnold E. |editor-last3=Rice |editor-first3=Eugene W. |editor-last4=Clesceri |editor-first4=Lenore S. |editor-last5=Franson |editor-first5=Mary Ann H. |year=2005 |publisher=American Public Health Association |isbn=978-0-87553-047-5 |id=Also available on CD-ROM and by subscription}}</ref>
Cities with sanitary sewer overflows or combined sewer overflows employ one or more ] approaches to reduce discharges of untreated sewage, including:
* utilizing a ] approach to improve stormwater management capacity throughout the system, and reduce the ] overloading of the treatment plant<ref>EPA. December 9, 2008.</ref>
* repair and replacement of leaking and malfunctioning equipment<ref name="EPARTC" />
* increasing overall hydraulic capacity of the sewage collection system (often a very expensive option).


Common physical tests of water include temperature, Specific conductance or ] (EC) or conductivity, solids concentrations (e.g., ] (TSS)) and ]. Water samples may be examined using ] methods. Many published test methods are available for both organic and inorganic compounds. Frequently used parameters that are quantified are ], BOD,<ref name="Newton">{{cite book |vauthors=Newton D |title=Chemistry of the Environment |publisher=Checkmark Books |year=2008 |isbn=978-0-8160-7747-2}}</ref>{{rp|102}} ] (COD),<ref name="Newton" />{{rp|104}} ] (DO), ], nutrients (] and ] compounds, e.g. ] and ]s), metals (including copper, ], ], lead and ]), oil and grease, total ] hydrocarbons (TPH), ]s and ]s.
A household or business not served by a municipal treatment plant may have an individual ], which treats the wastewater on site and discharges into the soil. Alternatively, domestic wastewater may be sent to a nearby privately-owned treatment system (e.g. in a rural community).


The use of a biomonitor or ] is described as ]. This refers to the measurement of specific properties of an organism to obtain information on the surrounding physical and chemical environment.<ref name=":22">{{Cite report |date=March 2016 |title=National Rivers and Streams Assessment 2008–2009: A Collaborative Study |url=https://www.epa.gov/sites/production/files/2016-03/documents/nrsa_0809_march_2_final.pdf |publisher=EPA |id=EPA 841/R-16/007}}</ref> Biological testing involves the use of plant, animal or microbial indicators to monitor the health of an ]. They are any biological species or group of species whose function, population, or status can reveal what degree of ecosystem or environmental integrity is present.<ref name="Karr">{{cite journal |vauthors=Karr JR |year=1981 |title=Assessment of biotic integrity using fish communities |journal=Fisheries |volume=6 |issue=6 |pages=21–27 |doi=10.1577/1548-8446(1981)006<0021:AOBIUF>2.0.CO;2 |bibcode=1981Fish....6f..21K |issn=1548-8446}}</ref> One example of a group of bio-indicators are the ]s and other small water ]s that are present in many water bodies. Such organisms can be monitored for changes (biochemical, physiological, or behavioral) that may indicate a problem within their ecosystem.
===Industrial wastewater===
{{main|Industrial wastewater treatment}}
] system for treating industrial wastewater.]]
Some industrial facilities generate ordinary domestic sewage that can be treated by municipal facilities. Industries that generate wastewater with high concentrations of conventional pollutants (e.g. oil and grease), toxic pollutants (e.g. heavy metals, volatile organic compounds) or other nonconventional pollutants such as ammonia, need specialized treatment systems. Some of these facilities can install a pre-treatment system to remove the toxic components, and then send the partially-treated wastewater to the municipal system. Industries generating large volumes of wastewater typically operate their own complete on-site treatment systems.


{{excerpt|Water quality#Sample collection|section=Sample collection|paragraphs=1|file=no}}
Some industries have been successful at redesigning their manufacturing processes to reduce or eliminate pollutants, through a process called ].


== Impacts ==
Heated water generated by power plants or manufacturing plants may be controlled with:
], resulting from ] and ], is a common cause of fish kills.]]
*]s, man-made bodies of water designed for cooling by ], ], and ]
*]s, which transfer waste heat to the ] through ] and/or ]
*], a process where waste heat is recycled for domestic and/or industrial heating purposes.<ref>
{{Cite report |title=Profile of the Fossil Fuel Electric Power Generation Industry |url=http://www.epa.gov/compliance/resources/publications/assistance/sectors/notebooks/fossil.html |author=EPA |year= 1997 |publisher= |accessdate= }} Document No. EPA/310-R-97-007. p. 24</ref>


=== Ecosystems ===
<div style="clear:right;">
Water pollution is a major global ] because it can result in the degradation of all ]s – fresh, coastal, and ocean waters.<ref name="HäderHelblingVillafañe2021">{{cite book |author1=Donat-P. Häder |author2=E. Walter Helbling |author3=Virginia E. Villafañe |date=30 September 2021 |title=Anthropogenic Pollution of Aquatic Ecosystems |publisher=Springer Nature |isbn=978-3-030-75602-4 |url=https://books.google.com/books?id=ZtxFEAAAQBAJ |access-date=9 August 2022 |page=1 |quote=Pollution is a major stress factor affecting all aquatic ecosystems including fresh, coastal and open ocean waters.}}</ref> The specific contaminants leading to pollution in water include a wide spectrum of ]s, pathogens, and physical changes such as elevated temperature. While many of the chemicals and substances that are regulated may be naturally occurring (], ], iron, ], etc.) the ] usually determines what is a natural component of water and what is a contaminant. High concentrations of naturally occurring substances can have negative impacts on aquatic flora and fauna. Oxygen-depleting substances may be natural materials such as plant matter (e.g. leaves and grass) as well as human-made chemicals. Other natural and anthropogenic substances may cause turbidity (cloudiness) which blocks light and disrupts plant growth, and clogs the ]s of some fish species.<ref name="Davies-ColleySmith2001">{{cite journal |last1=Davies-Colley |first1=R. J. |last2=Smith |first2=D. G. |title=Turbidity, Suspended Sediment and Water Clarity: A Review |journal=Journal of the American Water Resources Association |date=October 2001 |volume=37 |issue=5 |pages=1085–1101 |issn=1093-474X |eissn=1752-1688 |doi=10.1111/j.1752-1688.2001.tb03624.x |bibcode=2001JAWRA..37.1085D |s2cid=129093839 |url=https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1752-1688.2001.tb03624.x |access-date=9 August 2022}}</ref>] collected from pit latrines is dumped into a river at the Korogocho slum in ].]]


=== Public health and waterborne diseases ===
===Agricultural wastewater===
{{Further|WASH#Health aspects}}
{{main|Agricultural wastewater treatment}}
A study published in 2017 stated that "polluted water spread ]s and ] and killed 1.8&nbsp;million people" (these are also referred to as waterborne diseases).<ref>{{cite news |vauthors=Kelland K |date=2017-10-19 |title=Study links pollution to millions of deaths worldwide |publisher=Reuters |url=https://www.reuters.com/article/us-health-pollution/study-links-pollution-to-millions-of-deaths-worldwide-idUSKBN1CO39B}}</ref> Persistent exposure to pollutants through water are ] hazards, which can increase the likelihood for one to develop cancer or other diseases.<ref>Dovjak, Mateja; Kukec, Andreja (2019), "Health Outcomes Related to Built Environments", ''Creating Healthy and Sustainable Buildings'', Cham: Springer International Publishing, pp. 43–82, {{doi|10.1007/978-3-030-19412-3_2}}, {{ISBN|978-3-030-19411-6}}, {{S2CID|190160283}}</ref>
] lining a creek in ]]]
'''Nonpoint source controls'''<br />
] (loose ]) washed off fields is the largest source of agricultural pollution in the ].<ref name="EPA-AGFact" /> Farmers may utilize ]s to reduce runoff flows and retain soil on their fields. Common techniques include ], crop ]ing, ], planting ] crops and installing ]s.<ref name="NRCS-NCPS">U.S. Natural Resources Conservation Service (NRCS). Washington, DC. National Handbook of Conservation Practices. Accessed 2009-03-28.</ref><ref name="EPA-agmm"/>{{Rp|pp. 4-95–4-96|date=May 2009}}


=== Eutrophication from nitrogen pollution ===
Nutrients (] and ]) are typically applied to farmland as commercial ]; animal ]; or spraying of municipal or industrial wastewater (effluent) or sludge. Nutrients may also enter runoff from ]s, ] water, ], and ].<ref name="EPA-agmm">EPA. July 2003. Document No. EPA-841-B-03-004.</ref>{{Rp|p. 2-9|date=May 2009}} Farmers can develop and implement ] plans to reduce excess application of nutrients.<ref name="NRCS-NCPS" /><ref name="EPA-agmm" />{{Rp|pp. 4-37–4-38|date=May 2009}}
] can cause eutrophication, especially in lakes. Eutrophication is an increase in the concentration of chemical nutrients in an ] to an extent that increases the ] of the ecosystem. Subsequent negative environmental effects such as ] (oxygen depletion) and severe reductions in water quality may occur.<ref name="Von Sperling" />{{rp|131}} This can harm fish and other animal populations.


{{excerpt|eutrophication|paragraphs=1|file=no}}
To minimize pesticide impacts, farmers may use ] (IPM) techniques (which can include ]) to maintain control over pests, reduce reliance on chemical pesticides, and protect water quality.<ref>EPA. March 13, 2008.</ref>


=== Ocean acidification ===
]]]
] is another impact of water pollution. Ocean acidification is the ongoing decrease in the pH value of the Earth's oceans, caused by the uptake of ] ({{CO2}}) from the atmosphere.<ref name="cald03">{{cite journal |vauthors=Caldeira K, Wickett ME |title=Oceanography: anthropogenic carbon and ocean pH |journal=Nature |volume=425 |issue=6956 |pages=365 |date=September 2003 |pmid=14508477 |doi=10.1038/425365a |bibcode=2001AGUFMOS11C0385C |s2cid=4417880 |url=https://zenodo.org/record/1233227|doi-access=free }}</ref>
'''Point source wastewater treatment'''<br />
Farms with large ] and ] operations, such as ]s, are called ''concentrated animal feeding operations'' or ''confined animal feeding operations'' in the U.S. and are being subject to increasing government ].<ref>EPA. December 15, 2008.</ref><ref>Iowa Department of Natural Resources. Des Moines, IA. Accessed 2009-03-05.</ref> Animal ] are usually treated by containment in ] before disposal by spray or trickle application to grassland. ]s are sometimes used to facilitate treatment of animal wastes, as are ]. Some animal slurries are treated by mixing with ] and ] at high temperature to produce a bacteriologically sterile and friable manure for soil improvement.
</div>


== Prevalence ==
<div style="clear:left;">
Water pollution is a problem in ] as well as in ].


=== By country ===
===Construction site stormwater===
For example, ] and ] is widespread. About 90 percent of the water in the cities of China is polluted.<ref>{{cite news |url=http://www.chinadaily.com.cn/english/doc/2005-06/07/content_449451.htm |title=China says water pollution so severe that cities could lack safe supplies |work=China Daily |date=June 7, 2005}}</ref>{{world topic|Water pollution in|title=Water pollution by country|noredlinks=yes|state=expand}}
] installed on a construction site.]]
Sediment from construction sites is managed by installation of:
* ]s, such as ]ing and ], and
* ]s, such as ]s and ]s.<ref>Tennessee Department of Environment and Conservation. Nashville, TN. 2002.</ref>


==Control and reduction==
Discharge of toxic chemicals such as motor fuels and concrete washout is prevented by use of:
], Washington, D.C., United States. Seen in the distance are the sludge digester building and thermal hydrolysis reactors.]]
* spill prevention and control plans, and
* specially-designed containers (e.g. for concrete washout) and structures such as overflow controls and diversion berms.<ref>EPA (2006). National Menu of Stormwater Best Management Practices.</ref>
</div>


=== Pollution control philosophy ===
<div style="clear:right;">
One aspect of environmental protection is mandatory regulations, which are only part of the solution. Other important tools in pollution control include environmental education, economic instruments, market forces, and stricter enforcement. Standards can be "precise" (for a defined quantifiable minimum or maximum value for a pollutant), or "imprecise" which would require the use of ] (BAT) or ] (BPEO). Market-based economic instruments for pollution control can include charges, subsidies, deposit or refund schemes, the creation of a market in pollution credits, and enforcement incentives.<ref name="Jones OA et al">{{Cite book |vauthors=Jones OA, Gomes RL |editor-first1=R. M. |editor-last1=Harrison |url=https://pubs.rsc.org/en/content/ebook/978-1-84973-648-0|title=Pollution: Causes, Effects and Control|publisher=Royal Society of Chemistry |year=2013 |isbn=978-1-84973-648-0 |edition=5th|chapter=Chapter 1: Chemical Pollution of the Aquatic Environment by Priority Pollutants and its Control|doi=10.1039/9781782626527 }}</ref>


Moving towards a holistic approach in chemical pollution control combines the following approaches: Integrated control measures, trans-boundary considerations, complementary and supplementary control measures, ], the impacts of chemical mixtures.<ref name="Jones OA et al"/>
===Urban runoff (stormwater)===
{{main|Urban runoff}}
] for controlling ]]]
Effective control of urban runoff involves reducing the velocity and flow of stormwater, as well as reducing pollutant discharges. Local governments use a variety of stormwater management techniques to reduce the effects of urban runoff. These techniques, called ] (BMPs) in the U.S., may focus on water quantity control, while others focus on improving water quality, and some perform both functions.<ref name="EPA-PDS">EPA (1999). Chapter 5. Document No. EPA-821-R-99-012.</ref>


Control of water pollution requires appropriate ] and management plans. The infrastructure may include ], for example sewage treatment plants and ] treatment plants. ] for farms, and ] at construction sites can also help prevent water pollution. Effective control of urban runoff includes reducing speed and quantity of flow.
Pollution prevention practices include ] techniques, installation of ]s and improved chemical handling (e.g. management of motor fuels & oil, fertilizers and pesticides).<ref>EPA. October 9, 2008.</ref> Runoff mitigation systems include ]s, ] systems, constructed wetlands, ]s and similar devices.<ref>California Stormwater Quality Association. Menlo Park, CA. 2003.</ref><ref>New Jersey Department of Environmental Protection. Trenton, NJ. April 2004.</ref>


Water pollution requires ongoing evaluation and revision of ] at all levels (international down to individual aquifers and wells).
Thermal pollution from runoff can be controlled by stormwater management facilities that absorb the runoff or direct it into ], such as bioretention systems and infiltration basins. Retention basins tend to be less effective at reducing temperature, as the water may be heated by the sun before being discharged to a receiving stream.<ref name="EPA-PDS" />{{Rp|p. 5-58|date=May 2009}}


=== Sanitation and sewage treatment ===
{{See also|Green infrastructure}}
{{Further|Sanitation|WASH|Water issues in developing countries}}
</div>
]
Municipal wastewater can be treated by centralized sewage treatment plants, ]s, ]<ref name=":2">UN-Water (2018) , Geneva, Switzerland</ref> or in ] and septic tanks. For example, ]s can be a low cost treatment option for sewage.<ref name="Von Sperling">{{Cite journal|last=Von Sperling |first=Marcos |date=2007 |title=Wastewater Characteristics, Treatment and Disposal |journal=Water Intelligence Online |publisher=IWA Publishing|series=Biological Wastewater Treatment|volume=6 |doi=10.2166/9781780402086 |isbn=978-1-78040-208-6 |doi-access=free}}</ref>{{rp|182}} UV light (sunlight) can be used to degrade some pollutants in waste stabilization ponds (sewage lagoons).<ref>{{cite journal |vauthors=Wang Y, Fan L, Jones OA, Roddick F |title=Quantification of seasonal photo-induced formation of reactive intermediates in a municipal sewage lagoon upon sunlight exposure |journal=] |volume=765 |pages=142733 |date=April 2021 |pmid=33572041 |doi=10.1016/j.scitotenv.2020.142733 |s2cid=225156609 |bibcode=2021ScTEn.76542733W}}</ref> The use of ]s would prevent water pollution caused by lack of access to sanitation.<ref name="JMP2017" />


Well-designed and operated systems (i.e., with secondary treatment stages or more advanced tertiary treatment) can remove 90 percent or more of the ] in sewage.<ref>{{cite report |title=Primer for Municipal Wastewater Treatment Systems |url=https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=20017KBE.txt |date=2004 |publisher=] |page=11 |id=EPA 832-R-04-001}}</ref> Some plants have additional systems to remove ]s and pathogens. While such advanced treatment techniques will undoubtedly reduce the discharges of ]s, they can also result in large financial costs, as well as environmentally undesirable increases in energy consumption and ].<ref>{{cite journal |vauthors=Jones OA, Green PG, Voulvoulis N, Lester JN |title=Questioning the excessive use of advanced treatment to remove organic micropollutants from wastewater |journal=] |volume=41 |issue=14 |pages=5085–5089 |date=July 2007 |pmid=17711227 |doi=10.1021/es0628248 |bibcode=2007EnST...41.5085J}}</ref>
==See also==
{{portalpar|Water|Drinking water.jpg}}
{{Portal|Sustainable development|Sustainable development.svg}}
{{Portal|Environment|Devils Punchbowl Waterfall, New Zealand.jpg}}
{{Misplaced Pages-Books|Pollution}}
* ]
* ]
* '']'' (Supreme Court of Canada)
* ]
* ]
* ]
* ]
* ]
* ]
* ]
{{-}}


] during storm events can be addressed by timely maintenance and upgrades of the ]. In the US, cities with large combined systems have not pursued system-wide separation projects due to the high cost,<ref>{{cite web |vauthors=Renn AM |title=Wasted: How to Fix America's Sewers |url=https://media4.manhattan-institute.org/sites/default/files/R-AR-0216.pdf |date=2016-02-25 |page=7 |publisher=Manhattan Institute |location=New York, NY}}</ref> but have implemented partial separation projects and ] approaches.<ref>{{cite report |title=Greening CSO Plans: Planning and Modeling Green Infrastructure for Combined Sewer Overflow Control |url=https://www.epa.gov/sites/production/files/2015-10/documents/greening_cso_plans_0.pdf |date=March 2014 |publisher=] |id=832-R-14-001}}</ref> In some cases municipalities have installed additional CSO storage facilities<ref>{{cite web |url=https://www.dcwater.com/cleanrivers |title=Clean Rivers Project |author=<!--Not stated--> |publisher=District of Columbia Water and Sewer Authority |location=Washington, DC |access-date=2024-04-13}}</ref> or expanded sewage treatment capacity.<ref>{{cite web |title=United States and Ohio Reach Clean Water Act Settlement with City of Toledo, Ohio |url=http://yosemite.epa.gov/opa/admpress.nsf/b1ab9f485b098972852562e7004dc686/59f70abeaacc274885256c24005e6240?OpenDocument |date=2002-08-28 |publisher=EPA |archive-url=https://web.archive.org/web/20160113095352/http://yosemite.epa.gov/opa/admpress.nsf/b1ab9f485b098972852562e7004dc686/59f70abeaacc274885256c24005e6240?OpenDocument |archive-date=2016-01-13 |id=Press release.}}
==References==
</ref>
{{reflist}}

===Industrial wastewater treatment===
{{excerpt|Industrial wastewater treatment|paragraphs=1|file=no}}

===Agricultural wastewater treatment{{anchor|Agricultural wastewater}}===
{{excerpt|Agricultural wastewater treatment|paragraphs=1|file=no}}

===Management of erosion and sediment control===
] installed on a construction site]]
Sediment from construction sites can be managed by installation of ]s, such as ]ing and ], and ]s, such as ]s and ]s.<ref>Tennessee Department of Environment and Conservation. Nashville, TN (2012). </ref> Discharge of toxic chemicals such as motor fuels and concrete washout can be prevented by use of spill prevention and control plans, and specially designed containers (e.g. for concrete washout) and structures such as overflow controls and diversion berms.<ref>{{cite report |date=February 2012 |title=Concrete Washout |series=Stormwater Best Management Practice |url=https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P100E60V.txt |publisher=] |id=BMP fact sheet. EPA 833-F-11-006}}</ref>

Erosion caused by ] and changes in ] (soil loss due to water runoff) also results in loss of sediment and, potentially, water pollution.<ref>{{cite journal |vauthors = Mapulanga AM, Naito H |title=Effect of deforestation on access to clean drinking water |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=116 |issue=17 |pages=8249–8254 |date=April 2019 |pmid=30910966 |pmc=6486726 |doi=10.1073/pnas.1814970116 |doi-access=free |bibcode=2019PNAS..116.8249M}}</ref><ref>{{Cite web |author=University of Basel |title=Climate change and land use are accelerating soil erosion by water |url=https://www.sciencedaily.com/releases/2020/08/200824165633.htm |date=2020-08-24 |website=Science Daily}}</ref>

=== Control of urban runoff (storm water) ===
{{excerpt|Urban runoff#Prevention and mitigation|paragraphs=1,2|file=no}}
{{clear right}}] in 2020. A water body is classified as "good" quality if at least 80% of monitoring values meet target quality levels, see also ], Indicator 6.3.2.]]

=== Legislation ===
==== Philippines ====
In the Philippines, Republic Act 9275, otherwise known as the Philippine Clean Water Act of 2004,<ref name="LawPhil2004">{{Cite web |title=An Act Providing for a Comprehensive Water Quality Management And For Other Purposes |url=http://www.lawphil.net/statutes/repacts/ra2004/ra_9275_2004.html |url-status=live |archive-url=https://web.archive.org/web/20160921041418/http://www.lawphil.net/statutes/repacts/ra2004/ra_9275_2004.html|archive-date=21 September 2016 |access-date=September 30, 2016 |website=The LawPhil Project |df=dmy-all}}</ref> is the governing law on wastewater management. It states that it is the country's policy to protect, preserve and revive the quality of its fresh, brackish and marine waters, for which wastewater management plays a particular role.<ref name="LawPhil2004" />

==== United Kingdom ====
In 2024, The ] released a study into the effects wastewater on public health in the United Kingdom.<ref>{{cite web |title=Testing the waters Priorities for mitigating health risks from wastewater pollution |url=https://nepc.raeng.org.uk/media/qi2eyivp/testing-the-waters-priorities-for-mitigating-health-risks-from-wastewater-pollution.pdf |publisher=Royal Academy of Engineering |date=May 2024}}</ref> The study gained media attention, with comments from the UKs leading health professionals, including Sir ]. Outlining 15 recommendations for various UK bodies to dramatically reduce public health risks by increasing the water quality in its ]s, such as rivers and lakes.

After the release of the report, ] newspaper interviewed Whitty, who stated that improving water quality and sewage treatment should be a high level of importance and a "public health priority". He compared it to eradicating ] in the 19th century in the country following improvements to the ] network.<ref>{{cite web |title=Reducing sewage in rivers and seas is public health priority, says Chris Whitty |url=https://www.theguardian.com/society/article/2024/may/21/reducing-sewage-rivers-seas-public-health-priority-chris-whitty |publisher=The Guardian}}</ref> The study also identified that low water flows in rivers saw high concentration levels of ], as well as times of flooding or heavy rainfall. While heavy rainfall had always been associated with sewage overflows into streams and rivers, the British media went as far to warn parents of the dangers of ] in shallow rivers during warm weather.<ref>{{cite web |last1=Blakely |first1=Rhys |title=Paddling in rivers this summer could make children ill, warns Whitty |url=https://www.thetimes.com/uk/environment/article/paddling-in-rivers-this-summer-could-make-children-ill-warns-whitty |publisher=]}}</ref>

Whitty's comments came after the study revealed that the UK was experiencing a growth in the number of people that were using coastal and inland waters recreationally. This could be connected to a growing interest in activities such as ] or other ]s.<ref>{{cite web |last1=Speare-Cole |first1=Rebecca |title=Minimising sewage in UK waters is a ‘public health priority’ – Chris Whitty |url=https://www.independent.co.uk/climate-change/news/chris-whitty-people-devon-government-university-of-leeds-b2548414.html |publisher=]}}</ref> Despite this growth in recreation, poor water quality meant some were becoming unwell during events.<ref>{{cite web |title=Dozens of triathletes left severely ill after swimming in River Thames |url=https://www.independent.co.uk/news/uk/home-news/thames-water-pollution-river-thames-triathlon-b2561829.html |publisher=]}}</ref> Most notably, the ] had to delay numerous swimming-focused events like the triathlon due to high levels of sewage in the ].<ref>{{cite web |title=What's the problem with swimming in the Seine? |url=https://www.bbc.co.uk/news/articles/cn05d4k0l2qo#:~:text=It%20should%20be%20a%20stunning,be%20postponed%20for%20a%20day. |publisher=]}}</ref>

==== United States ====
{{excerpt|Water pollution in the United States#Current regulations|paragraphs=1|file=no}}

== See also ==
{{Portal|Water|Environment}}
* ]
* {{section link|Environmental impact of pesticides|Water}}
* ]
* ]
* ]
* ] (water quality indicator for lakes)
* ]
* ]
* ]


==External links== == References ==
{{Reflist}}
{{commons|Water pollution|Water pollution}}
'''Overview Information'''
* - Guides, news and reports from Natural Resources Defense Council (US nonprofit organization)
* - Video from "Strange Days on Planet Earth" by National Geographic & PBS
* - Report (2006) by Beyond Pesticides (US nonprofit organization)
* - Teaching resources for elementary & secondary education, from Colorado State University


== External links ==
'''Analytical Tools and Other Specialized Resources'''
{{commons}}
*
{{Library resources box |by=no |onlinebooks=no |others=yes lcheading=Water – Pollution}}
* - Peace Palace Library (Netherlands)
* – UN Environment Programme
* - Portal for Soil and Water Management in Europe
* - US EPA guide for identifying pollution problems (stressor identification)


{{Pollution}} {{pollution}}
{{marine pollution}} {{marine pollution}}
{{water}}
{{Natural resources}}
{{Environmental science}}
{{Public health}}

{{Authority control}}


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Latest revision as of 16:43, 14 January 2025

Contamination of water bodies "DWEL" redirects here. For the radio station in Ilocos Norte, Philippines, see DWEL-FM. "Clean water" redirects here. For water that is safe to drink, see Drinking water.

Raw sewage and industrial waste in the New River as it passes from Mexicali (Mexico) to Calexico, California
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Water pollution (or aquatic pollution) is the contamination of water bodies, with a negative impact on their uses. It is usually a result of human activities. Water bodies include lakes, rivers, oceans, aquifers, reservoirs and groundwater. Water pollution results when contaminants mix with these water bodies. Contaminants can come from one of four main sources. These are sewage discharges, industrial activities, agricultural activities, and urban runoff including stormwater. Water pollution may affect either surface water or groundwater. This form of pollution can lead to many problems. One is the degradation of aquatic ecosystems. Another is spreading water-borne diseases when people use polluted water for drinking or irrigation. Water pollution also reduces the ecosystem services such as drinking water provided by the water resource.

Sources of water pollution are either point sources or non-point sources. Point sources have one identifiable cause, such as a storm drain, a wastewater treatment plant, or an oil spill. Non-point sources are more diffuse. An example is agricultural runoff. Pollution is the result of the cumulative effect over time. Pollution may take many forms. One would is toxic substances such as oil, metals, plastics, pesticides, persistent organic pollutants, and industrial waste products. Another is stressful conditions such as changes of pH, hypoxia or anoxia, increased temperatures, excessive turbidity, or changes of salinity). The introduction of pathogenic organisms is another. Contaminants may include organic and inorganic substances. A common cause of thermal pollution is the use of water as a coolant by power plants and industrial manufacturers.

Control of water pollution requires appropriate infrastructure and management plans as well as legislation. Technology solutions can include improving sanitation, sewage treatment, industrial wastewater treatment, agricultural wastewater treatment, erosion control, sediment control and control of urban runoff (including stormwater management).

Definition

A practical definition of water pollution is: "Water pollution is the addition of substances or energy forms that directly or indirectly alter the nature of the water body in such a manner that negatively affects its legitimate uses." Water is typically referred to as polluted when it is impaired by anthropogenic contaminants. Due to these contaminants, it either no longer supports a certain human use, such as drinking water, or undergoes a marked shift in its ability to support its biotic communities, such as fish.

Contaminants

Contaminants with an origin in sewage

Further information: Waterborne diseases § Diseases by type of pathogen, and Sewage § Pathogens

The following compounds can all reach water bodies via raw sewage or even treated sewage discharges:

Inadequately treated wastewater can convey nutrients, pathogens, heterogenous suspended solids and organic fecal matter.

Poster to teach people in South Asia about human activities leading to the pollution of water sources
Pollutants and their effects*
Pollutant Main representative parameter Possible effect of the pollutant
Suspended solids Total suspended solids
Biodegradable organic matter Biological oxygen demand (BOD)
  • Oxygen consumption
  • Death of fish
  • Septic conditions
Nutrients
Pathogens
  • Coliforms, such as E. coli, may not be pathogenic in and of themselves, but are used as an indicator of co-occurring pathogens that should take slightly less time to die or degrade
  • Helminth eggs
Waterborne diseases
Non-biodegradable organic matter
Inorganic dissolved solids
* Sources of these pollutants are household and industrial wastewater, urban runoff and stormwater drainage from agricultural areas

Pathogens

Bacteria, viruses, protozoans and parasitic worms are examples of pathogens that can be found in wastewater. In practice, indicator organisms are used to investigate pathogenic pollution of water because the detection of pathogenic organisms in water sample is difficult and costly, because of their low concentrations. The indicators (bacterial indicator) of fecal contamination of water samples most commonly used are total coliforms (TC) or fecal coliforms (FC), the latter also referred to as thermotolerant coliforms, such as Escherichia coli.

Pathogens can produce waterborne diseases in either human or animal hosts. Some microorganisms sometimes found in contaminated surface waters that have caused human health problems include Burkholderia pseudomallei, Cryptosporidium parvum, Giardia lamblia, Salmonella, norovirus and other viruses, and parasitic worms including the Schistosoma type.

The source of high levels of pathogens in water bodies can be from human feces (due to open defecation), sewage, blackwater, or manure that has found its way into the water body. The cause for this can be lack of sanitation procedures or poorly functioning on-site sanitation systems (septic tanks, pit latrines), sewage treatment plants without disinfection steps, sanitary sewer overflows and combined sewer overflows (CSOs) during storm events and intensive agriculture (poorly managed livestock operations).

Organic compounds

Organic substances that enter water bodies are often toxic.

Per- and polyfluoroalkyl substances (PFAS) are persistent organic pollutants.

Inorganic contaminants

Bauxite residue is an industrial waste that is dangerously alkaline and can lead to water pollution if not managed appropriately (photo from Stade, Germany).
Muddy river polluted by sediment

Inorganic water pollutants include:

Pharmaceutical pollutants

This section is an excerpt from Environmental impact of pharmaceuticals and personal care products.

The environmental effect of pharmaceuticals and personal care products (PPCPs) is being investigated since at least the 1990s. PPCPs include substances used by individuals for personal health or cosmetic reasons and the products used by agribusiness to boost growth or health of livestock. More than twenty million tons of PPCPs are produced every year. The European Union has declared pharmaceutical residues with the potential of contamination of water and soil to be "priority substances".

PPCPs have been detected in water bodies throughout the world. More research is needed to evaluate the risks of toxicity, persistence, and bioaccumulation, but the current state of research shows that personal care products impact the environment and other species, such as coral reefs and fish. PPCPs encompass environmental persistent pharmaceutical pollutants (EPPPs) and are one type of persistent organic pollutants. They are not removed in conventional sewage treatment plants but require a fourth treatment stage which not many plants have.

In 2022, the most comprehensive study of pharmaceutical pollution of the world's rivers found that it threatens "environmental and/or human health in more than a quarter of the studied locations". It investigated 1,052 sampling sites along 258 rivers in 104 countries, representing the river pollution of 470 million people. It found that "the most contaminated sites were in low- to middle-income countries and were associated with areas with poor wastewater and waste management infrastructure and pharmaceutical manufacturing" and lists the most frequently detected and concentrated pharmaceuticals.

Solid waste and plastics

Solid waste and plastics in the Lachine Canal, Canada
Further information: Sewage § Solid waste, Plastic pollution, and Marine plastic pollution

Solid waste can enter water bodies through untreated sewage, combined sewer overflows, urban runoff, people discarding garbage into the environment, wind carrying municipal solid waste from landfills and so forth. This results in macroscopic pollution– large visible items polluting the water– but also microplastics pollution that is not directly visible. The terms marine debris and marine plastic pollution are used in the context of pollution of oceans.

Microplastics persist in the environment at high levels, particularly in aquatic and marine ecosystems, where they cause water pollution. 35% of all ocean microplastics come from textiles/clothing, primarily due to the erosion of polyester, acrylic, or nylon-based clothing, often during the washing process.

Stormwater, untreated sewage and wind are the primary conduits for microplastics from land to sea. Synthetic fabrics, tyres, and city dust are the most common sources of microplastics. These three sources account for more than 80% of all microplastic contamination.

Types of surface water pollution

Surface water pollution includes pollution of rivers, lakes and oceans. A subset of surface water pollution is marine pollution which affects the oceans. Nutrient pollution refers to contamination by excessive inputs of nutrients.

Globally, about 4.5 billion people do not have safely managed sanitation as of 2017, according to an estimate by the Joint Monitoring Programme for Water Supply and Sanitation. Lack of access to sanitation is concerning and often leads to water pollution, e.g. via the practice of open defecation: during rain events or floods, the human feces are moved from the ground where they were deposited into surface waters. Simple pit latrines may also get flooded during rain events.

As of 2022, Europe and Central Asia account for around 16% of global microplastics discharge into the seas, and although management of plastic waste and its recycling is improving globally, the absolute amount of plastic pollution continues to increase unabated due to the large amount of plastic that is being produced and disposed of. Even if sea plastic pollution were to stop entirely, microplastic contamination of the surface ocean would be projected to continue to increase.

Marine pollution

This section is an excerpt from Marine pollution. Marine pollution occurs when substances used or spread by humans, such as industrial, agricultural and residential waste, particles, noise, excess carbon dioxide or invasive organisms enter the ocean and cause harmful effects there. The majority of this waste (80%) comes from land-based activity, although marine transportation significantly contributes as well. It is a combination of chemicals and trash, most of which comes from land sources and is washed or blown into the ocean. This pollution results in damage to the environment, to the health of all organisms, and to economic structures worldwide. Since most inputs come from land, either via the rivers, sewage or the atmosphere, it means that continental shelves are more vulnerable to pollution. Air pollution is also a contributing factor by carrying off iron, carbonic acid, nitrogen, silicon, sulfur, pesticides or dust particles into the ocean. The pollution often comes from nonpoint sources such as agricultural runoff, wind-blown debris, and dust. These nonpoint sources are largely due to runoff that enters the ocean through rivers, but wind-blown debris and dust can also play a role, as these pollutants can settle into waterways and oceans. Pathways of pollution include direct discharge, land runoff, ship pollution, bilge pollution, dredging (which can create dredge plumes), atmospheric pollution and, potentially, deep sea mining.

Nutrient pollution

This section is an excerpt from Nutrient pollution.
Nutrient pollution caused by Surface runoff of soil and fertilizer during a rain storm
Nutrient pollution, a form of water pollution, refers to contamination by excessive inputs of nutrients. It is a primary cause of eutrophication of surface waters (lakes, rivers and coastal waters), in which excess nutrients, usually nitrogen or phosphorus, stimulate algal growth. Sources of nutrient pollution include surface runoff from farm fields and pastures, discharges from septic tanks and feedlots, and emissions from combustion. Raw sewage is a large contributor to cultural eutrophication since sewage is high in nutrients. Releasing raw sewage into a large water body is referred to as sewage dumping, and still occurs all over the world. Excess reactive nitrogen compounds in the environment are associated with many large-scale environmental concerns. These include eutrophication of surface waters, harmful algal blooms, hypoxia, acid rain, nitrogen saturation in forests, and climate change.

Thermal pollution

The Brayton Point Power Station in Massachusetts discharged heated water to Mount Hope Bay until 2011.
This section is an excerpt from Thermal pollution. Thermal pollution, sometimes called "thermal enrichment", is the degradation of water quality by any process that changes ambient water temperature. Thermal pollution is the rise or drop in the temperature of a natural body of water caused by human influence. Thermal pollution, unlike chemical pollution, results in a change in the physical properties of water. A common cause of thermal pollution is the use of water as a coolant by power plants and industrial manufacturers. Urban runoffstormwater discharged to surface waters from rooftops, roads, and parking lots—and reservoirs can also be a source of thermal pollution. Thermal pollution can also be caused by the release of very cold water from the base of reservoirs into warmer rivers.

Elevated water temperatures decrease oxygen levels (due to lower levels of dissolved oxygen, as gases are less soluble in warmer liquids), which can kill fish (which may then rot) and alter food chain composition, reduce species biodiversity, and foster invasion by new thermophilic species.

Biological pollution

The introduction of aquatic invasive organisms is a form of water pollution as well. It causes biological pollution.

Groundwater pollution

This section is an excerpt from Groundwater pollution. Groundwater pollution (also called groundwater contamination) occurs when pollutants are released to the ground and make their way into groundwater. This type of water pollution can also occur naturally due to the presence of a minor and unwanted constituent, contaminant, or impurity in the groundwater, in which case it is more likely referred to as contamination rather than pollution. Groundwater pollution can occur from on-site sanitation systems, landfill leachate, effluent from wastewater treatment plants, leaking sewers, petrol filling stations, hydraulic fracturing (fracking) or from over application of fertilizers in agriculture. Pollution (or contamination) can also occur from naturally occurring contaminants, such as arsenic or fluoride. Using polluted groundwater causes hazards to public health through poisoning or the spread of disease (water-borne diseases).

In many areas of the world, groundwater pollution poses a hazard to the wellbeing of people and ecosystems. One-quarter of the world's population depends on groundwater for drinking, yet concentrated recharging is known to carry short-lived contaminants into carbonate aquifers and jeopardize the purity of those waters.

Pollution from point sources

Point source water pollution refers to contaminants that enter a waterway from a single, identifiable source, such as a pipe or ditch. Examples of sources in this category include discharges from a sewage treatment plant, a factory, or a city storm drain.

The U.S. Clean Water Act (CWA) defines point source for regulatory enforcement purposes (see United States regulation of point source water pollution). The CWA definition of point source was amended in 1987 to include municipal storm sewer systems, as well as industrial storm water, such as from construction sites.

Sewage

Sewage typically consists of 99.9% water and 0.1% solids. Sewage contributes many classes of nutrients that lead to Eutrophication. It is a major source of phosphate for example. Sewage is often contaminated with diverse compounds found in personal hygiene, cosmetics, pharmaceutical drugs (see also drug pollution), and their metabolites Water pollution due to environmental persistent pharmaceutical pollutants can have wide-ranging consequences. When sewers overflow during storm events this can lead to water pollution from untreated sewage. Such events are called sanitary sewer overflows or combined sewer overflows.

A polluted river draining an abandoned copper mine on Anglesey

Industrial wastewater

Perfluorooctanesulfonic acid (PFOS) is a global pollutant that has been found in drinking water. It appears not to biodegrade.
Further information: Industrial wastewater treatment

Industrial processes that use water also produce wastewater. This is called industrial wastewater. Using the US as an example, the main industrial consumers of water (using over 60% of the total consumption) are power plants, petroleum refineries, iron and steel mills, pulp and paper mills, and food processing industries. Some industries discharge chemical wastes, including solvents and heavy metals (which are toxic) and other harmful pollutants.

Industrial wastewater could add the following pollutants to receiving water bodies if the wastewater is not treated and managed properly:

Oil spills

This section is an excerpt from Oil spill. An oil spill is the release of a liquid petroleum hydrocarbon into the environment, especially the marine ecosystem, due to human activity, and is a form of pollution. The term is usually given to marine oil spills, where oil is released into the ocean or coastal waters, but spills may also occur on land. Oil spills can result from the release of crude oil from tankers, offshore platforms, drilling rigs, and wells. They may also involve spills of refined petroleum products, such as gasoline and diesel fuel, as well as their by-products. Additionally, heavier fuels used by large ships, such as bunker fuel, or spills of any oily refuse or waste oil, contribute to such incidents. These spills can have severe environmental and economic consequences.

Pollution from nonpoint sources

This section is an excerpt from Nonpoint source pollution. Nonpoint source (NPS) pollution refers to diffuse contamination (or pollution) of water or air that does not originate from a single discrete source. This type of pollution is often the cumulative effect of small amounts of contaminants gathered from a large area. It is in contrast to point source pollution which results from a single source. Nonpoint source pollution generally results from land runoff, precipitation, atmospheric deposition, drainage, seepage, or hydrological modification (rainfall and snowmelt) where tracing pollution back to a single source is difficult. Nonpoint source water pollution affects a water body from sources such as polluted runoff from agricultural areas draining into a river, or wind-borne debris blowing out to sea. Nonpoint source air pollution affects air quality, from sources such as smokestacks or car tailpipes. Although these pollutants have originated from a point source, the long-range transport ability and multiple sources of the pollutant make it a nonpoint source of pollution; if the discharges were to occur to a body of water or into the atmosphere at a single location, the pollution would be single-point.

Agriculture

Agriculture is a major contributor to water pollution from nonpoint sources. The use of fertilizers as well as surface runoff from farm fields, pastures and feedlots leads to nutrient pollution. In addition to plant-focused agriculture, fish-farming is also a source of pollution. Additionally, agricultural runoff often contains high levels of pesticides.

Atmospheric contributions (air pollution)

Air deposition is a process whereby air pollutants from industrial or natural sources settle into water bodies. The deposition may lead to polluted water near the source, or at distances up to a few thousand miles away. The most frequently observed water pollutants resulting from industrial air deposition are sulfur compounds, nitrogen compounds, mercury compounds, other heavy metals, and some pesticides and industrial by-products. Natural sources of air deposition include forest fires and microbial activity.

Acid rain is caused by emissions of sulfur dioxide and nitrogen oxide, which react with the water molecules in the atmosphere to produce acids. Some governments have made efforts since the 1970s to reduce the release of sulfur dioxide and nitrogen oxide into the atmosphere. The main source of sulfur and nitrogen compounds that result in acid rain are anthropogenic, but nitrogen oxides can also be produced naturally by lightning strikes and sulphur dioxide is produced by volcanic eruptions. Acid rain can have harmful effects on plants, aquatic ecosystems and infrastructure.

Carbon dioxide concentrations in the atmosphere have increased since the 1850s due anthropogenic influences (emissions of greenhouse gases). This leads to ocean acidification and is another form of water pollution from atmospheric contributions.

Sampling, measurements, analysis

Environmental scientists preparing water autosamplers
Further information: Water quality § Sampling and measurement, Environmental monitoring, Analysis of water chemistry, Water sampling station, and Regulation and monitoring of pollution § Water pollution

Water pollution may be analyzed through several broad categories of methods: physical, chemical and biological. Some methods may be conducted in situ, without sampling, such as temperature. Others involve collection of samples, followed by specialized analytical tests in the laboratory. Standardized, validated analytical test methods, for water and wastewater samples have been published.

Common physical tests of water include temperature, Specific conductance or electrical conductance (EC) or conductivity, solids concentrations (e.g., total suspended solids (TSS)) and turbidity. Water samples may be examined using analytical chemistry methods. Many published test methods are available for both organic and inorganic compounds. Frequently used parameters that are quantified are pH, BOD, chemical oxygen demand (COD), dissolved oxygen (DO), total hardness, nutrients (nitrogen and phosphorus compounds, e.g. nitrate and orthophosphates), metals (including copper, zinc, cadmium, lead and mercury), oil and grease, total petroleum hydrocarbons (TPH), surfactants and pesticides.

The use of a biomonitor or bioindicator is described as biological monitoring. This refers to the measurement of specific properties of an organism to obtain information on the surrounding physical and chemical environment. Biological testing involves the use of plant, animal or microbial indicators to monitor the health of an aquatic ecosystem. They are any biological species or group of species whose function, population, or status can reveal what degree of ecosystem or environmental integrity is present. One example of a group of bio-indicators are the copepods and other small water crustaceans that are present in many water bodies. Such organisms can be monitored for changes (biochemical, physiological, or behavioral) that may indicate a problem within their ecosystem.

This section is an excerpt from Water quality § Sample collection. The complexity of water quality as a subject is reflected in the many types of measurements of water quality indicators. Some measurements of water quality are most accurately made on-site, because water exists in equilibrium with its surroundings. Measurements commonly made on-site and in direct contact with the water source in question include temperature, pH, dissolved oxygen, conductivity, oxygen reduction potential (ORP), turbidity, and Secchi disk depth.

Impacts

Oxygen depletion, resulting from nitrogen pollution and eutrophication, is a common cause of fish kills.

Ecosystems

Water pollution is a major global environmental problem because it can result in the degradation of all aquatic ecosystems – fresh, coastal, and ocean waters. The specific contaminants leading to pollution in water include a wide spectrum of chemicals, pathogens, and physical changes such as elevated temperature. While many of the chemicals and substances that are regulated may be naturally occurring (calcium, sodium, iron, manganese, etc.) the concentration usually determines what is a natural component of water and what is a contaminant. High concentrations of naturally occurring substances can have negative impacts on aquatic flora and fauna. Oxygen-depleting substances may be natural materials such as plant matter (e.g. leaves and grass) as well as human-made chemicals. Other natural and anthropogenic substances may cause turbidity (cloudiness) which blocks light and disrupts plant growth, and clogs the gills of some fish species.

Fecal sludge collected from pit latrines is dumped into a river at the Korogocho slum in Nairobi, Kenya.

Public health and waterborne diseases

Further information: WASH § Health aspects

A study published in 2017 stated that "polluted water spread gastrointestinal diseases and parasitic infections and killed 1.8 million people" (these are also referred to as waterborne diseases). Persistent exposure to pollutants through water are environmental health hazards, which can increase the likelihood for one to develop cancer or other diseases.

Eutrophication from nitrogen pollution

Nitrogen pollution can cause eutrophication, especially in lakes. Eutrophication is an increase in the concentration of chemical nutrients in an ecosystem to an extent that increases the primary productivity of the ecosystem. Subsequent negative environmental effects such as anoxia (oxygen depletion) and severe reductions in water quality may occur. This can harm fish and other animal populations.

This section is an excerpt from Eutrophication.

Eutrophication is a general term describing a process in which nutrients accumulate in a body of water, resulting in an increased growth of microorganisms that may deplete the oxygen in the water. Eutrophication may occur naturally or as a result of human actions. Manmade, or cultural, eutrophication occurs when sewage, industrial wastewater, fertilizer runoff, and other nutrient sources are released into the environment. Such nutrient pollution usually causes algal blooms and bacterial growth, resulting in the depletion of dissolved oxygen in water and causing substantial environmental degradation.

Ocean acidification

Ocean acidification is another impact of water pollution. Ocean acidification is the ongoing decrease in the pH value of the Earth's oceans, caused by the uptake of carbon dioxide (CO2) from the atmosphere.

Prevalence

Water pollution is a problem in developing countries as well as in developed countries.

By country

For example, water pollution in India and China is widespread. About 90 percent of the water in the cities of China is polluted.

Water pollution by country
  • Afghanistan
  • Albania
  • Algeria
  • Australia
  • Bangladesh
  • Belgium
  • Brazil
  • Canada
  • Chile
  • China
  • Colombia
  • Croatia
  • Denmark
  • Dominican Republic
  • Egypt
  • El Salvador
  • Georgia
  • Ghana
  • Guatemala
  • Haiti
  • Honduras
  • India
  • Indonesia
  • Iran
  • Japan
  • Kazakhstan
  • Kenya
  • Kuwait
  • Lebanon
  • Liberia
  • Libya
  • Mexico
  • Mongolia
  • Nepal
  • New Zealand
  • Nicaragua
  • Pakistan
  • Paraguay
  • Peru
  • Philippines
  • Poland
  • Russia
  • Serbia
  • Singapore
  • Sri Lanka
  • Syria
  • Taiwan
  • Thailand
  • Turkey
  • Uganda
  • United States
  • Uruguay
  • Uzbekistan
  • Venezuela
  • Vietnam
  • Zimbabwe
  • Control and reduction

    View of secondary treatment reactors (activated sludge process) at the Blue Plains Advanced Wastewater Treatment Plant, Washington, D.C., United States. Seen in the distance are the sludge digester building and thermal hydrolysis reactors.

    Pollution control philosophy

    One aspect of environmental protection is mandatory regulations, which are only part of the solution. Other important tools in pollution control include environmental education, economic instruments, market forces, and stricter enforcement. Standards can be "precise" (for a defined quantifiable minimum or maximum value for a pollutant), or "imprecise" which would require the use of Best available technology (BAT) or Best practicable environmental option (BPEO). Market-based economic instruments for pollution control can include charges, subsidies, deposit or refund schemes, the creation of a market in pollution credits, and enforcement incentives.

    Moving towards a holistic approach in chemical pollution control combines the following approaches: Integrated control measures, trans-boundary considerations, complementary and supplementary control measures, life-cycle considerations, the impacts of chemical mixtures.

    Control of water pollution requires appropriate infrastructure and management plans. The infrastructure may include wastewater treatment plants, for example sewage treatment plants and industrial wastewater treatment plants. Agricultural wastewater treatment for farms, and erosion control at construction sites can also help prevent water pollution. Effective control of urban runoff includes reducing speed and quantity of flow.

    Water pollution requires ongoing evaluation and revision of water resource policy at all levels (international down to individual aquifers and wells).

    Sanitation and sewage treatment

    Further information: Sanitation, WASH, and Water issues in developing countries
    Plastic waste on the big drainage, and air pollution in the far end of the drainage in Ghana

    Municipal wastewater can be treated by centralized sewage treatment plants, decentralized wastewater systems, nature-based solutions or in onsite sewage facilities and septic tanks. For example, waste stabilization ponds can be a low cost treatment option for sewage. UV light (sunlight) can be used to degrade some pollutants in waste stabilization ponds (sewage lagoons). The use of safely managed sanitation services would prevent water pollution caused by lack of access to sanitation.

    Well-designed and operated systems (i.e., with secondary treatment stages or more advanced tertiary treatment) can remove 90 percent or more of the pollutant load in sewage. Some plants have additional systems to remove nutrients and pathogens. While such advanced treatment techniques will undoubtedly reduce the discharges of micropollutants, they can also result in large financial costs, as well as environmentally undesirable increases in energy consumption and greenhouse gas emissions.

    Sewer overflows during storm events can be addressed by timely maintenance and upgrades of the sewerage system. In the US, cities with large combined systems have not pursued system-wide separation projects due to the high cost, but have implemented partial separation projects and green infrastructure approaches. In some cases municipalities have installed additional CSO storage facilities or expanded sewage treatment capacity.

    Industrial wastewater treatment

    This section is an excerpt from Industrial wastewater treatment. Industrial wastewater treatment describes the processes used for treating wastewater that is produced by industries as an undesirable by-product. After treatment, the treated industrial wastewater (or effluent) may be reused or released to a sanitary sewer or to a surface water in the environment. Some industrial facilities generate wastewater that can be treated in sewage treatment plants. Most industrial processes, such as petroleum refineries, chemical and petrochemical plants have their own specialized facilities to treat their wastewaters so that the pollutant concentrations in the treated wastewater comply with the regulations regarding disposal of wastewaters into sewers or into rivers, lakes or oceans. This applies to industries that generate wastewater with high concentrations of organic matter (e.g. oil and grease), toxic pollutants (e.g. heavy metals, volatile organic compounds) or nutrients such as ammonia. Some industries install a pre-treatment system to remove some pollutants (e.g., toxic compounds), and then discharge the partially treated wastewater to the municipal sewer system.

    Agricultural wastewater treatment

    This section is an excerpt from Agricultural wastewater treatment. Agricultural wastewater treatment is a farm management agenda for controlling pollution from confined animal operations and from surface runoff that may be contaminated by chemicals in fertilizer, pesticides, animal slurry, crop residues or irrigation water. Agricultural wastewater treatment is required for continuous confined animal operations like milk and egg production. It may be performed in plants using mechanized treatment units similar to those used for industrial wastewater. Where land is available for ponds, settling basins and facultative lagoons may have lower operational costs for seasonal use conditions from breeding or harvest cycles. Animal slurries are usually treated by containment in anaerobic lagoons before disposal by spray or trickle application to grassland. Constructed wetlands are sometimes used to facilitate treatment of animal wastes.

    Management of erosion and sediment control

    Silt fence installed on a construction site

    Sediment from construction sites can be managed by installation of erosion controls, such as mulching and hydroseeding, and sediment controls, such as sediment basins and silt fences. Discharge of toxic chemicals such as motor fuels and concrete washout can be prevented by use of spill prevention and control plans, and specially designed containers (e.g. for concrete washout) and structures such as overflow controls and diversion berms.

    Erosion caused by deforestation and changes in hydrology (soil loss due to water runoff) also results in loss of sediment and, potentially, water pollution.

    Control of urban runoff (storm water)

    This section is an excerpt from Urban runoff § Prevention and mitigation.

    Effective control of urban runoff involves reducing the velocity and flow of stormwater, as well as reducing pollutant discharges. Local governments use a variety of stormwater management techniques to reduce the effects of urban runoff. These techniques, called best management practices for water pollution (BMPs) in some countries, may focus on water quantity control, while others focus on improving water quality, and some perform both functions.

    Pollution prevention practices include low impact development (LID) or green infrastructure techniques - known as Sustainable Drainage Systems (SuDS) in the UK, and Water-Sensitive Urban Design (WSUD) in Australia and the Middle East - such as the installation of green roofs and improved chemical handling (e.g. management of motor fuels & oil, fertilizers, pesticides and roadway deicers). Runoff mitigation systems include infiltration basins, bioretention systems, constructed wetlands, retention basins, and similar devices.
    Share of water bodies with good water quality in 2020. A water body is classified as "good" quality if at least 80% of monitoring values meet target quality levels, see also SDG 6, Indicator 6.3.2.

    Legislation

    Philippines

    In the Philippines, Republic Act 9275, otherwise known as the Philippine Clean Water Act of 2004, is the governing law on wastewater management. It states that it is the country's policy to protect, preserve and revive the quality of its fresh, brackish and marine waters, for which wastewater management plays a particular role.

    United Kingdom

    In 2024, The Royal Academy of Engineering released a study into the effects wastewater on public health in the United Kingdom. The study gained media attention, with comments from the UKs leading health professionals, including Sir Chris Whitty. Outlining 15 recommendations for various UK bodies to dramatically reduce public health risks by increasing the water quality in its waterways, such as rivers and lakes.

    After the release of the report, The Guardian newspaper interviewed Whitty, who stated that improving water quality and sewage treatment should be a high level of importance and a "public health priority". He compared it to eradicating cholera in the 19th century in the country following improvements to the sewage treatment network. The study also identified that low water flows in rivers saw high concentration levels of sewage, as well as times of flooding or heavy rainfall. While heavy rainfall had always been associated with sewage overflows into streams and rivers, the British media went as far to warn parents of the dangers of paddling in shallow rivers during warm weather.

    Whitty's comments came after the study revealed that the UK was experiencing a growth in the number of people that were using coastal and inland waters recreationally. This could be connected to a growing interest in activities such as open water swimming or other water sports. Despite this growth in recreation, poor water quality meant some were becoming unwell during events. Most notably, the 2024 Paris Olympics had to delay numerous swimming-focused events like the triathlon due to high levels of sewage in the River Seine.

    United States

    This section is an excerpt from Water pollution in the United States § Current regulations. The Clean Water Act is the primary federal law in the United States governing water pollution in surface waters. The 1972 CWA amendments established a broad regulatory framework for improving water quality. The law defines procedures for pollution control and developing criteria and standards for pollutants in surface water. The law authorizes the Environmental Protection Agency to regulate surface water pollution in the United States, in partnership with state agencies. Prior to 1972 it was legal to discharge wastewater to surface waters without testing for or removing water pollutants. The CWA was amended in 1981 and 1987 to adjust the federal proportion of construction grant funding for local governments, regulate municipal storm sewer discharges and to later establish the Clean Water State Revolving Fund. The fund provides low-interest loans to improve municipal sewage treatment systems and finance other water quality improvements.

    See also

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