View source for Sewage

{{Short description|Wastewater that is produced by a community of people}}
{{About|a type of wastewater|the infrastructure to transport sewage|sewerage}}
{{Use dmy dates|date=June 2021}}
{{Pollution sidebar}}
'''Sewage''' (or '''domestic sewage''', '''domestic wastewater''', '''municipal wastewater''') is a type of [[wastewater]] that is produced by a [[community]] of people. It is typically transported through a [[sewerage|sewer system]].<ref name="Tilley-2014">{{cite book |last1=Tilley |first1=E. |last2=Ulrich |first2=L. |last3=Lüthi |first3=C. |last4=Reymond |first4=Ph. |last5=Zurbrügg |first5=C.|url=http://www.eawag.ch/en/department/sandec/publications/compendium/|title=Compendium of Sanitation Systems and Technologies |publisher=Swiss Federal Institute of Aquatic Science and Technology (Eawag), Duebendorf, Switzerland|year=2014|isbn=978-3-906484-57-0|edition=2nd Revised|archive-url=https://web.archive.org/web/20160408021403/http://www.eawag.ch/en/department/sandec/publications/compendium/|archive-date=8 April 2016|url-status=live}}</ref>{{rp|175}} Sewage consists of wastewater discharged from residences and from commercial, institutional and public facilities that exist in the locality.<ref name="Marcos">{{Cite journal |last=Von Sperling |first=M. |date=2007 |title=Wastewater Characteristics, Treatment and Disposal |url=https://iwaponline.com/ebooks/book/72/Wastewater-Characteristics-Treatment-and-Disposal |journal=Water Intelligence Online |language=en |volume=6 |doi=10.2166/9781780402086 |isbn=978-1-78040-208-6 |issn=1476-1777 |doi-access=free}} [[File:CC-BY_icon.svg|50x50px]] Text was copied from this source, which is available under a [[creativecommons:by/4.0/|Creative Commons Attribution 4.0 International License]]</ref>{{rp|10}} Sub-types of sewage are [[greywater]] (from sinks, bathtubs, showers, dishwashers, and clothes washers) and [[blackwater (waste)|blackwater]] (the water used to flush [[toilet]]s, combined with the [[human waste]] that it flushes away). Sewage also contains soaps and detergents. Food waste may be present from [[dishwashing]], and food quantities may be increased where [[garbage disposal unit]]s are used. In regions where [[toilet paper]] is used rather than [[bidet]]s, that paper is also added to the sewage. Sewage contains macro-pollutants and micro-pollutants, and may also incorporate some [[municipal solid waste]] and pollutants from [[Industrial wastewater treatment|industrial wastewater]].
Sewage usually travels from a building's [[plumbing]] either into a [[sewerage|sewer]], which will carry it elsewhere, or into an [[onsite sewage facility]]. Collection of sewage from several households together usually takes places in either [[sanitary sewer]]s or [[combined sewer]]s. The former is designed to exclude [[stormwater]] flows whereas the latter is designed to also take stormwater. The production of sewage generally corresponds to the water consumption. A range of factors influence water consumption and hence the sewage flowrates per person. These include: Water availability (the opposite of [[water scarcity]]), [[water supply]] options, [[climate]] (warmer climates may lead to greater water consumption), community size, economic level of the community, level of [[Industrialisation|industrialization]], [[Water metering|metering]] of household consumption, water cost and water pressure.<ref name="Marcos" />{{rp|20}}
The main parameters in sewage that are measured to assess the sewage strength or quality as well as treatment options include: solids, indicators of organic matter, nitrogen, phosphorus, and indicators of fecal contamination.<ref name="Marcos" />{{rp|33}} These can be considered to be the main macro-pollutants in sewage. Sewage contains [[pathogen]]s which stem from [[Human feces|fecal matter]]. The following four types of pathogens are found in sewage: pathogenic [[bacteria]], [[virus]]es, [[protozoa]] (in the form of cysts or oocysts) and [[helminths]] (in the form of eggs).<ref name="WHO-2006">{{Cite book |url=https://books.google.com/books?id=01B64IJhqY0C&pg=PA31 |title=Guidelines for the Safe Use of Wasterwater, Excreta and Greywater |date=2006|publisher=World Health Organization|isbn=92-4-154685-9|page=31|oclc=71253096}}</ref><ref name="Andersson">{{Cite book
|author=Andersson, K. |author2=Rosemarin, A. |author3=Lamizana, B. |author4=Kvarnström, E. |author5=McConville, J. |author6=Seidu, R. |author7=Dickin, S. |author8=Trimmer, C.
|title=Sanitation, Wastewater Management and Sustainability: from Waste Disposal to Resource Recovery
|url=https://www.susana.org/en/knowledge-hub/resources-and-publications/library/details/2636|access-date=2023-01-02
| isbn = 978-92-807-3488-1
| page = 56 | year = 2016
| publisher= United Nations Environment Programme and Stockholm Environment Institute
| place= Nairobi and Stockholm
| archive-url = https://web.archive.org/web/20170601071836/http://www.susana.org/en/resources/library/details/2636
|archive-date=2017-06-01
| url-status=live
}}</ref> In order to quantify the organic matter, indirect methods are commonly used: mainly the [[Biochemical oxygen demand|Biochemical Oxygen Demand]] (BOD) and the [[Chemical oxygen demand|Chemical Oxygen Demand]] (COD).<ref name="Marcos" />{{rp|36}}
Management of sewage includes collection and transport for release into the environment, after a [[Sewage treatment|treatment level]] that is compatible with the local requirements for discharge into water bodies, onto soil or for reuse applications.<ref name="Marcos" />{{rp|156}} Disposal options include dilution (self-purification of water bodies, making use of their [[assimilative capacity]] if possible), [[marine outfall]]s, land disposal and [[sewage farm]]s. All disposal options may run risks of causing [[water pollution]].
{{TOC limit|3}}
==Terminology==
=== Sewage and wastewater ===
Sewage (or domestic wastewater) consists of [[wastewater]] discharged from residences and from commercial, institutional and public facilities that exist in the locality.<ref name="Marcos" />{{rp|10}} Sewage is a mixture of water (from the community's [[water supply]]), [[Human waste|human excreta]] ([[Human feces|feces]] and [[urine]]), used water from [[bathroom]]s, food preparation wastes, laundry wastewater, and other waste products of normal living.
Sewage from municipalities contains wastewater from commercial activities and institutions, e.g. wastewater discharged from [[restaurant]]s, [[laundry|laundries]], [[hospital]]s, [[school]]s, [[prison]]s, [[office]]s, stores and establishments serving the local area of larger communities.<ref name="Marcos" />{{rp|21}}
Sewage can be distinguished into "untreated sewage" (also called "raw sewage") and "treated sewage" (also called "effluent" from a [[Sewage treatment|sewage treatment plant]]).
The term "sewage" is nowadays often used interchangeably with "wastewater" – implying "municipal wastewater" – in many textbooks, policy documents and the literature.<ref name="Marcos" /><ref name="Tchobanoglous-2003">{{Cite book|title=Wastewater engineering: treatment and reuse|date=2003|publisher=McGraw-Hill|others=George Tchobanoglous, Franklin L. Burton, H. David Stensel, Metcalf & Eddy|isbn=0-07-041878-0|edition=4th|location=Boston|oclc=48053912}}</ref><ref name="Henze-2008">{{Cite book|last1=Henze|first1=M.|url=http://iwaponline.com/ebooks/book/59/Biological-Wastewater-Treatment-Principles|title=Biological Wastewater Treatment: Principles, Modelling and Design|last2=van Loosdrecht|first2=M. C. M.|last3=Ekama|first3=G.A.|last4=Brdjanovic|first4=D.|date=2008|publisher=IWA Publishing
|isbn=978-1-78040-186-7|language=en|doi=10.2166/9781780401867|s2cid=108595515 }} Spanish and Arabic versions [https://iwaponline.com/ebooks/book/707/Tratamiento-biologico-de-aguas-residuales available free online]</ref> To be precise, wastewater is a broader term, because it refers to any [[water]] after it has been used in a variety of applications.<ref name="Tchobanoglous-2003" />{{rp|1}} Thus it may also refer to "[[Industrial wastewater treatment|industrial wastewater]]", [[Agricultural wastewater treatment|agricultural wastewater]] and other flows that are not related to household activities.
=== Blackwater ===
{{excerpt|blackwater (waste)|paragraphs=1-2|file=no}}
=== Greywater ===
{{excerpt|greywater|paragraphs=1-2|file=no}}
[[File:Pumping station lifting the wastewater (6908385151).jpg|thumb|Pumping station lifting sewage to the treatment plant in [[Bujumbura]], Burundi]]
[[File:Greywater settling tank and grease trap (3109542163).jpg|thumb|upright|[[Greywater]] (a component of sewage) in a settling tank]]
== Overall appearance ==
The overall appearance of sewage is as follows:<ref name="Marcos" />{{rp|30}} The temperature tends to be slightly higher than in drinking water but is more stable than the ambient temperature. The color of fresh sewage is slightly grey, whereas older sewage (also called "septic sewage") is dark grey or black. The [[odor]] of fresh sewage is "oily" and relatively unpleasant, whereas older sewage has an unpleasant foul odor due to [[hydrogen sulfide]] gas and other decomposition by-products.<ref name="lcu" />{{rp|9–38}} Sewage can have high [[turbidity]] from suspended solids.
The [[PH|pH value]] of sewage is usually near neutral, and can be in the range of 6.7–8.0.<ref name="Marcos" />{{rp|57}}
== Pollutants ==
Sewage consists primarily of water and usually contains less than one part of solid matter per thousand parts of water. In other words, one can say that sewage is composed of around 99.9% pure water, and the remaining 0.1% are solids, which can be in the form of either dissolved solids or [[suspended solids]].<ref name="Marcos" />{{rp|28}} The thousand-to-one ratio is an order of magnitude estimate rather than an exact percentage because, aside from variation caused by dilution, solids may be defined differently depending upon the mechanism used to separate those solids from the liquid fraction. [[Sludge]]s of settleable solids removed by [[settling]] or [[suspended solids]] removed by [[filtration]] may contain significant amounts of entrained water, while dried solid material remaining after evaporation eliminates most of that water but includes dissolved minerals not captured by filtration or gravitational separation.<ref>{{cite book |last1=Norton |first1=John F. |last2=Maxcy |first2=Kenneth F. |last3=Pirnie |first3=Malcolm |title =Standard Methods for the Examination of Water and Sewage |publisher =[[American Public Health Association]] |edition =Ninth |date =1947 |location =New York  |pages =145–146 }}</ref> The suspended and dissolved solids include organic and inorganic matter plus microorganisms.<ref name="Marcos" />{{rp|28}}
About one-third of this solid matter is suspended by [[turbulence]], while the remainder is [[Solution (chemistry)|dissolved]] or [[colloid]]al. For the situation in the United States in the 1950s it was estimated that the waste contained in domestic sewage is about half [[organic compound|organic]] and half [[inorganic compound|inorganic]].<ref name="lcu" />{{rp|9–38}}
=== Organic matter ===
The organic matter in sewage can be classified in terms of form and size: Suspended (particulate) or dissolved (soluble). Secondly, it can be classified in terms of [[biodegradability]]: either inert or biodegradable.<ref name="Marcos" />{{rp|35}} The organic matter in sewage consists of [[protein]] compounds (about 40%), [[carbohydrate]]s (about 25–50%), oils and grease (about 10%) and [[urea]], [[surfactant]]s, [[phenols]], [[pesticide]]s and others (lower quantity).<ref name="Marcos" />{{rp|35}} In order to quantify the organic matter content, it is common to use "indirect methods" which are based on the consumption of oxygen to oxidize the organic matter: mainly the [[Biochemical oxygen demand|Biochemical Oxygen Demand]] (BOD) and the [[Chemical oxygen demand|Chemical Oxygen Demand]] (COD).<ref name="Marcos" />{{rp|36}} These indirect methods are associated with the major impact of the discharge of organic matter into water bodies: the organic matter will be food for microorganisms, whose population will grow, and lead to the consumption of oxygen, which may then affect aquatic living organisms.
The mass load of organic content is calculated as the sewage flowrate multiplied with the concentration of the organic matter in the sewage.<ref name="Marcos" />{{rp|55}}
Typical values for physical–chemical characteristics of raw sewage is provided further down below.
=== Nutrients ===
Apart from organic matter, sewage also contains nutrients. The major nutrients of interest are [[nitrogen]] and [[phosphorus]]. If sewage is discharged untreated, its nitrogen and phosphorus content can lead to pollution of lakes and reservoirs via a process called [[eutrophication]].<ref name="Marcos" />{{rp|77}}
In raw sewage, nitrogen exists in the two forms of organic nitrogen or [[ammonia]]. The ammonia stems from the [[urea]] in [[urine]]. Urea is rapidly hydrolyzed and therefore not usually found in raw sewage.<ref name="Marcos" />{{rp|43}}
Total phosphorus is mostly present in sewage in the form of [[phosphate]]s.They are either inorganic (polyphosphates and orthophosphates) and their main source is from [[detergent]]s and other household chemical products. The other form is organic phosphorus, where the source is organic compounds to which the organic phosphorus is bound.<ref name="Marcos" />{{rp|45}}
=== Pathogens ===
[[Human feces]] in sewage may contain [[pathogen]]s capable of transmitting diseases.<ref name=lcu/>{{rp|9–38}} The following four types of pathogens are found in sewage:<ref name="WHO-2006" /><ref name="Andersson" />
* [[Bacteria]] like ''[[Salmonella]]'', ''[[Shigella]]'', ''[[Campylobacter]]'', or ''[[Vibrio cholerae]]'';
* [[Virus]]es like [[hepatitis A]], [[rotavirus]], [[coronavirus]],<ref>{{cite journal|last1=Naddeo|first1=Vincenzo|last2=Liu|first2=Haizhou|date=2020|title=Editorial Perspectives: 2019 novel coronavirus (SARS-CoV-2): what is its fate in urban water cycle and how can the water research community respond?|journal=Environmental Science: Water Research & Technology|volume=6|issue=5|pages=1213–1216|doi=10.1039/D0EW90015J|doi-access=free}}</ref> [[enteroviruses]];
* [[Protozoa]] like ''[[Entamoeba histolytica]]'', ''[[Giardia lamblia]]'', ''[[Cryptosporidium parvum]]''; and
* [[Helminths]] and their eggs including ''[[Ascaris]]'' (roundworm), ''[[Ancylostoma]]'' (hookworm), and ''[[Trichuris]]'' (whipworm)
In most practical cases, pathogenic organisms are not directly investigated in laboratory analyses. An easier way to assess the presence of fecal contamination is by assessing the [[most probable number]]s of [[fecal coliform]]s (called thermotolerant coliforms), especially ''[[Escherichia coli]]''. ''Escherichia coli'' are intestinal bacteria excreted by all warm blooded animals, including human beings, and thus tracking their presence in sewage is easy, because of their substantially high concentrations (around 10 to 100 million per 100 mL).<ref name="Marcos" />{{rp|52}}
=== Solid waste ===
[[File:Screening of the wastewater to remove larger objects. (6845984661).jpg|thumb|Screening of the sewage with bar screens at a sewage treatment plant to remove larger objects in Norton, [[Zimbabwe]]]]
[[File:Screen (6619766435).jpg|thumb|Screening of sewage at a sewage treatment plant in [[Bujumbura]], Burundi]]
The ability of a [[flush toilet]] to make things "disappear" is soon recognized by young children who may experiment with virtually anything they can carry to the toilet.<ref>{{cite web|last=Collins|first=Meg|title=The Infamous Toilet Lock|url=https://www.lucieslist.com/guides/baby-proofing/babyproofing-toilet-lock/|website=Lucie's List|access-date=24 August 2021}}</ref> Adults may be tempted to dispose of [[toilet paper]], [[wet wipe]]s, [[diaper]]s, [[sanitary napkin]]s, [[tampon]]s, tampon applicators, [[condom]]s, and expired [[medication]]s, even at the risk of causing blockages. The privacy of a toilet offers a clandestine means of removing embarrassing evidence by flushing such things as [[drug paraphernalia]], [[pregnancy test]] kits, [[combined oral contraceptive pill]] dispensers, and the packaging for those devices. There may be reluctance to retrieve items like children's toys or toothbrushes which accidentally fall into toilets, and items of clothing may be found in sewage from prisons or other locations where occupants may be careless.<ref>{{cite web |url=https://eponline.com/articles/2001/10/01/grinders-and-comminutors-an-evolving-technology.aspx?m=1 |title=Grinders and Comminutors: An Evolving Technology |last=Jamrock |first=Thomas E. |website=Environmental Protection |access-date=5 August 2021}}</ref> Trash and garbage in streets may be carried to combined sewers by stormwater runoff.
=== Micro-pollutants ===
Sewage contains [[environmental persistent pharmaceutical pollutant]]s. [[Trihalomethane]]s can also be present as a result of past [[disinfection]]. Sewage may contain [[microplastics]] such as polyethylene and polypropylene beads, or polyester and polyamide fragments<ref>{{Cite journal|last1=Gatidou|first1=Georgia|last2=Arvaniti|first2=Olga S.|last3=Stasinakis|first3=Athanasios S.|date=2019|title=Review on the occurrence and fate of microplastics in Sewage Treatment Plants|url=https://linkinghub.elsevier.com/retrieve/pii/S0304389418312305|journal=Journal of Hazardous Materials|language=en|volume=367|pages=504–512|doi=10.1016/j.jhazmat.2018.12.081|pmid=30620926|s2cid=58567561}}</ref> from synthetic clothing and bedding fabrics abraded by wear and laundering, or from [[plastic packaging]] and [[plastic-coated paper]] products disintegrated by [[lift station]] pumps. [[Pharmaceuticals]], endocrine disrupting compounds, and [[hormone]]s<ref>{{Cite journal|last1=Arvaniti|first1=Olga S.|last2=Stasinakis|first2=Athanasios S.|date=2015|title=Review on the occurrence, fate and removal of perfluorinated compounds during wastewater treatment|url=https://linkinghub.elsevier.com/retrieve/pii/S0048969715004593|journal=Science of the Total Environment|language=en|volume=524–525|pages=81–92|doi=10.1016/j.scitotenv.2015.04.023|pmid=25889547|bibcode=2015ScTEn.524...81A}}</ref><ref>{{Cite journal|last1=Bletsou|first1=Anna A.|last2=Asimakopoulos|first2=Alexandros G.|last3=Stasinakis|first3=Athanasios S.|last4=Thomaidis|first4=Nikolaos S.|last5=Kannan|first5=Kurunthachalam|date=2013-02-19|title=Mass Loading and Fate of Linear and Cyclic Siloxanes in a Wastewater Treatment Plant in Greece|url=https://pubs.acs.org/doi/10.1021/es304369b|journal=Environmental Science & Technology|language=en|volume=47|issue=4|pages=1824–1832|doi=10.1021/es304369b|pmid=23320453|bibcode=2013EnST...47.1824B|s2cid=39997737 |issn=0013-936X}}</ref><ref>{{Cite journal|last1=Gatidou|first1=Georgia|last2=Kinyua|first2=Juliet|last3=van Nuijs|first3=Alexander L.N.|last4=Gracia-Lor|first4=Emma|last5=Castiglioni|first5=Sara|last6=Covaci|first6=Adrian|last7=Stasinakis|first7=Athanasios S.|date=2016|title=Drugs of abuse and alcohol consumption among different groups of population on the Greek Island of Lesvos through sewage-based epidemiology|url=https://linkinghub.elsevier.com/retrieve/pii/S0048969716308233|journal=Science of the Total Environment|language=en|volume=563–564|pages=633–640|doi=10.1016/j.scitotenv.2016.04.130|pmid=27236142|bibcode=2016ScTEn.563..633G|hdl=10067/1345920151162165141|s2cid=4073701 |hdl-access=free}}</ref> may be excreted in urine or feces if not [[catabolized]] within the human body.
Some residential users tend to pour unwanted liquids like used [[cooking oil]],<ref name="Metcalf & Eddy">{{cite book|author=Metcalf & Eddy, Inc.|title=Wastewater Engineering|publisher=McGraw-Hill|year=1972|isbn=978-0-07-041675-8|location=New York}}</ref>{{rp|228}} [[lubricant]]s,<ref name="Metcalf & Eddy"/>{{rp|228}} [[adhesive]]s, [[paint]], [[solvent]]s, [[detergent]]s,<ref name="Metcalf & Eddy"/>{{rp|228}} and [[disinfectant]]s into their sewer connections. This behavior can result in problems for the treatment plant operation and is thus discouraged.
== Typical sewage composition ==
=== Factors that determine composition ===
The composition of sewage varies with climate, social and economic situation and population habits.<ref name="Marcos" />{{rp|28}} In regions where water use is low, the strength of the sewage (or pollutant concentrations) is much higher than that in the United States where water use per person is high.<ref name="Tchobanoglous-2003" />{{rp|183}} Household income and diet also plays a role: For example, for the case of Brazil, it has been found that the higher the household income, the higher is the BOD load per person and the lower is the BOD concentration.<ref name="Marcos" />{{rp|57}}
=== Concentrations and loads ===
Typical values for physical–chemical characteristics of raw sewage in [[Developing country|developing countries]] have been published as follows: 180 g/person/d for total solids (or 1100&nbsp;mg/L when expressed as a concentration), 50 g/person/d for BOD (300&nbsp;mg/L), 100 g/person/d for COD (600&nbsp;mg/L), 8 g/person/d for total nitrogen (45&nbsp;mg/L), 4.5 g/person/d for ammonia-N (25&nbsp;mg/L) and 1.0 g/person/d for total phosphorus (7&nbsp;mg/L).<ref name="Marcos" />{{rp|57}} The typical ranges for these values are: 120–220 g/person/d for total solids (or 700–1350&nbsp;mg/L when expressed as a concentration), 40–60 g/person/d for BOD (250–400&nbsp;mg/L), 80–120 g/person/d for COD (450–800&nbsp;mg/L), 6–10 g/person/d for total nitrogen (35–60&nbsp;mg/L), 3.5–6 g/person/d for ammonia-N (20–35&nbsp;mg/L) and 0.7–2.5 g/person/d for total phosphorus (4–15&nbsp;mg/L).<ref name="Marcos" />{{rp|57}}
For high income countries, the "per person organic matter load" has been found to be approximately 60 gram of BOD per person per day.<ref name="Henze-2008" /> This is called the [[population equivalent]] (PE) and is also used as a comparison parameter to express the strength of [[Industrial wastewater treatment|industrial wastewater]] compared to sewage.
Values for households in the United States have been published as follows, whereby the estimates are based on the assumption that 25% of the homes have [[Garbage disposal unit|kitchen waste-food grinders]] (sewage from such households contain more waste): 95 g/person/d  for total [[suspended solids]] (503&nbsp;mg/L concentration), 85 g/person/d for BOD (450&nbsp;mg/L), 198 g/person/d for COD (1050&nbsp;mg/L), 13.3 g/person/d for the sum of organic nitrogen and ammonia nitrogen (70.4&nbsp;mg/L), 7.8 g/person/d for ammonia-N (41.2&nbsp;mg/L) and 3.28 g/person/d for total phosphorus (17.3&nbsp;mg/L). The concentration values given here are based on a flowrate of 190 L per person per day.<ref name="Tchobanoglous-2003" />{{rp|183}}
A United States source published in 1972 estimated that the daily dry weight of solid wastes [[per capita]] in sewage is estimated as {{cvt|20.5|g}} in feces, {{cvt|43.3|g}} of dissolved solids in urine, {{cvt|20|g}} of toilet paper, {{cvt|86.5|g}} of greywater solids, {{cvt|30|g}} of food solids (if [[garbage disposal unit]]s are used), and varying amounts of dissolved minerals depending upon salinity of local water supplies, volume of water use per capita, and extent of [[water softener]] use.<ref name="Metcalf & Eddy" />{{rp|234}}
Sewage contains urine and feces. The mass of feces varies with dietary fiber intake. An average person produces 128 grams of wet feces per day, or a median dry mass of 29 g/person/day.<ref name="Rose-2015">{{Cite journal|last1=Rose|first1=C.|last2=Parker|first2=A.|last3=Jefferson|first3=B.|last4=Cartmell|first4=E.|date=2015|title=The Characterization of Feces and Urine: A Review of the Literature to Inform Advanced Treatment Technology|journal=Critical Reviews in Environmental Science and Technology|language=en|volume=45|issue=17|pages=1827–1879|doi=10.1080/10643389.2014.1000761|issn=1064-3389|pmc=4500995|pmid=26246784|bibcode=2015CREST..45.1827R }}</ref> The median urine generation rate is about 1.42 L/person/day, as was determined by a global literature review.<ref name="Rose-2015" />
== Flowrates ==
The volume of domestic sewage produced per person (or "[[per capita]]", abbreviated as "cap") varies with the water consumption in the respective locality.<ref name="Marcos" />{{rp|11}} A range of factors influence water consumption and hence the sewage flowrates per person. These include: Water availability (the opposite of [[water scarcity]]), [[water supply]] options, [[climate]] (warmer climates may lead to greater water consumption), community size, economic level of the community, level of [[Industrialisation|industrialization]], [[Water metering|metering]] of household consumption, water cost and water pressure.<ref name="Marcos" />{{rp|20}}
The production of sewage generally corresponds to the water consumption. However water used for landscape irrigation will not enter the sewer system, while [[groundwater]] and [[stormwater]] may enter the sewer system in addition to sewage.<ref name="Marcos" />{{rp|22}} There are usually two peak flowrates of sewage arriving at a treatment plant per day: One peak is at the beginning of the morning and another peak is at the beginning of the evening.<ref name="Marcos" />{{rp|24}}
With regards to water consumption, a design figure that can be regarded as "world average" is 35–90 L per person per day (data from 1992).<ref name="Tchobanoglous-2003" />{{rp|163}} The same publication listed the water consumption in [[China]] as 80 L per person per day, [[Africa]] as 15–35 L per person per day, [[Eastern Mediterranean]] in Europe as 40–85 L per person per day and [[Latin America]] and [[Caribbean]] as 70–190 L per person per day.<ref name="Tchobanoglous-2003" />{{rp|163}} Even inside a country, there may be large variations from one region to another due to the various factors that determine the water consumption as listed above.
A flowrate value of 200 liters of sewage per person per day is often used as an estimate in [[World Bank high-income economy|high income countries]], and is used for example in the design of sewage treatment plants.<ref name="Henze-2008" />
For comparison, typical sewage flowrates from urban residential sources in the [[United States]] are estimated as follows: 365 L/person/day (for one person households), 288 L/person/day (two person households), 200 L/person/day (four person households), 189 L/person/day (six person households).<ref name="Tchobanoglous-2003" />{{rp|156}} This means the overall range for this example would be {{cvt|189|-|365|L}}.
== Analytical methods ==
=== General quality indicators ===
{{excerpt|Wastewater quality indicators|paragraphs=1|file=no}}
=== Specific organisms and substances ===
Sewage can be monitored for both disease-causing and benign organisms with a variety of techniques. Traditional techniques involve filtering, staining, and examining samples under a microscope. Much more sensitive and specific testing can be accomplished with [[DNA sequencing]], such as when looking for rare organisms, attempting [[Eradication of infectious diseases|eradication]], testing specifically for drug-resistant strains, or discovering new species.<ref>[https://www.who.int/csr/don/2013_06_03/en/ Poliovirus detected from environmental samples in Israel] {{webarchive|url=https://web.archive.org/web/20131104191619/http://www.who.int/csr/don/2013_06_03/en/|date=2013-11-04}}</ref><ref>[http://healthmap.org/site/diseasedaily/article/drug-resistant-bug-review-ndm-1-new-delhi%E2%80%99s-sewage-who-calls-action-recent Drug resistant bug review: NDM-1 in New Delhi's sewage, WHO calls to action, recent outbreaks of antibiotic resistant bacteria] {{webarchive|url=https://web.archive.org/web/20131105042902/http://healthmap.org/site/diseasedaily/article/drug-resistant-bug-review-ndm-1-new-delhi%E2%80%99s-sewage-who-calls-action-recent|date=2013-11-05}}</ref><ref>[http://mbio.asm.org/content/2/5/e00180-11.full Raw Sewage Harbors Diverse Viral Populations] {{webarchive|url=https://web.archive.org/web/20130607085040/http://mbio.asm.org/content/2/5/e00180-11.full|date=2013-06-07}}</ref>  Sequencing DNA from an environmental sample is known as [[metagenomics]].
Sewage has also been analyzed to determine relative rates of use of prescription and illegal drugs among municipal populations.<ref>{{Cite web|title=Leading experts to review global developments in detecting illicit drugs in wastewater
|url=https://www.emcdda.europa.eu/news/2013/4_en|access-date=2023-01-02
| publisher= The European Monitoring Centre for Drugs and Drug Addiction
| archive-url = https://web.archive.org/web/20140209055215/http://www.emcdda.europa.eu/news/2013/4|archive-date=2014-02-09
| date = 2 May 2013
| url-status= live}}</ref> General socioeconomic demographics may be inferred as well.<ref>{{cite journal|last1=Choi|first1=Phil M.|date=7 October 2019|title=Social, demographic, and economic correlates of food and chemical consumption measured by wastewater-based epidemiology|journal=[[Proceedings of the National Academy of Sciences of the United States of America]]|volume=116|issue=43|pages=21864–21873|doi=10.1073/pnas.1910242116|pmc=6815118|pmid=31591193|bibcode=2019PNAS..11621864C |doi-access=free}}</ref>
== Collection ==
[[File:Wastewater in street (informal settlement near Cape Town), South Africa (2937833876).jpg|thumb|Lack of maintenance causing sewage to overflow from a manhole into the street of an informal settlement near [[Cape Town]], South Africa]]
Sewage is commonly collected and transported in [[gravity sewer]]s, either in a [[sanitary sewer]] or in a [[combined sewer]]. The latter also conveys [[urban runoff]] ([[stormwater]]) which means the sewage gets diluted during rain events.<ref name="Marcos" />{{rp|9}}
=== Sanitary sewer ===
{{excerpt|Sanitary sewer|paragraphs=1|file=no}}
=== Combined sewer ===
{{excerpt|Combined sewer|paragraphs=1|file=no}}
== Dilution in the sewer  ==
=== Infiltration of groundwater into the sewerage system ===
Infiltration is [[groundwater]] entering sewer pipes through defective pipes, connections, joints or [[manhole]]s.<ref name="Marcos" />{{rp|26}}<ref name="Tchobanoglous-2003" />{{rp|164}} Contaminated or [[saline water|saline]] groundwater may introduce additional pollutants to the sewage. The amount of such infiltrated water depends on several parameters, such as the length of the collection network, pipeline diameters, drainage area, soil type, water table depth, topography and number of connections per unit area.<ref name="Marcos" />{{rp|26}} Infiltration is increased by poor construction procedures, and tends to increase with the age of the sewer. The amount of infiltration varies with the depth of the sewer in comparison to the local [[groundwater table]].<ref name=lcu>{{cite book |last=Urquhart |first=Leonard Church |title =Civil Engineering Handbook |publisher =[[McGraw-Hill Book Company, Inc.]] |edition =Fourth |date =1959 |location =[[New York City]] }}</ref>{{rp|9-1, 9-9}} Older sewer systems that are in need of rehabilitation may also exfiltrate sewage into groundwater from the leaking sewer joints and service connections.<ref name="Tchobanoglous-2003" />{{rp|167}} This can lead to [[groundwater pollution]].<ref name="UNWATER2015">{{cite web|last=UN-Water|date=2015|title=Wastewater Management – A UN-Water Analytical Brief|url=http://www.unwater.org/fileadmin/user_upload/unwater_new/docs/UN-Water_Analytical_Brief_Wastewater_Management.pdf|archive-url=https://web.archive.org/web/20161130125232/http://www.unwater.org/fileadmin/user_upload/unwater_new/docs/UN-Water_Analytical_Brief_Wastewater_Management.pdf|archive-date=2016-11-30|access-date=2017-03-22}}</ref>
=== Stormwater ===
Combined sewers are designed to transport sewage and stormwater together. This means that sewage becomes diluted during rain events. There are other types of inflow that also dilute sewage, e.g. "water discharged from cellar and foundation drains, cooling-water discharges, and any direct stormwater runoff connections to the sanitary collection system".<ref name="Tchobanoglous-2003" />{{rp|163}} The "direct inflows" can result in peak sewage flowrates similar to combined sewers during wet weather events.<ref name="Tchobanoglous-2003" />{{rp|165}}
=== Industrial wastewater ===
{{main|Industrial wastewater treatment}}
Sewage from communities with industrial facilities may include some [[Industrial wastewater treatment|industrial wastewater]], generated by industrial processes such as the production or manufacture of goods. Volumes of industrial wastewater vary widely with the type of industry.<ref name="Marcos" />{{rp|27}} Industrial wastewater may contain very different pollutants at much higher concentrations than what is typically found in sewage.<ref name="Tchobanoglous-2003" />{{rp|188}} Pollutants may be [[toxic]] or non-[[Biodegradation|biodegradable]] waste including [[pharmaceutical]]s,<ref>{{Cite journal|last1=Naddeo|first1=V.|last2=Meriç|first2=S.|last3=Kassinos|first3=D.|last4=Belgiorno|first4=V.|last5=Guida|first5=M.|date=September 2009|title=Fate of pharmaceuticals in contaminated urban wastewater effluent under ultrasonic irradiation|journal=Water Research|language=en|volume=43|issue=16|pages=4019–4027|doi=10.1016/j.watres.2009.05.027|pmid=19589554|bibcode=2009WatRe..43.4019N |s2cid=23561392 }}</ref> [[biocide]]s, [[heavy metals]], [[radionuclide]]s, or [[thermal pollution]].
An industry may treat its wastewater and discharge it into the environment (or even use the treated wastewater for specific applications), or, in case it is located in the urban area, it may discharge the wastewater into the public sewerage system. In the latter case, industrial wastewater may receive pre-treatment at the factories to reduce the [[Measures of pollutant concentration|pollutant load]].<ref name="Marcos" />{{rp|27}} Mixing industrial wastewater with sewage does nothing to reduce the mass of pollutants to be treated, but the volume of sewage lowers the concentration of pollutants unique to industrial wastewater, and the volume of industrial wastewater lowers the concentration of pollutants unique to sewage.
== Disposal and dilution ==
[[File:FEMA - 42863 - Outfall tubes in Ocean City beach.jpg|thumb|upright|[[Marine outfall|Ocean outfall]] pipes in [[Cape May, New Jersey]], United States – pipes exposed after the sand was removed by severe storm]]
{{Further|Sewage treatment#Disposal or treatment options}}
=== Assimilative capacity of receiving water bodies or land ===
When wastewater is discharged into a [[Surface water|water body]] (river, lakes, sea) or land, its relative impact will depend on the [[assimilative capacity]] of the water body or [[ecosystem]].<ref name="Marcos" />{{rp|78}} Water bodies have a self-purification capacity, so that the concentration of a pollutant may decrease along the distance from the discharge point. Furthermore, water bodies provide a dilution to the pollutants concentrations discharged, although it does not decrease their mass. In principle, the higher the dilution capacity (ratio of volume or flow of the receiving water and volume or flow of sewage discharged), the lower will be the concentration of pollutants in the receiving water, and probably the lower will be the negative impacts. But if the water body already arrives very polluted at the point of discharge, the dilution will be of limited value.<ref>{{Cite book|last=Schmidt|first=Michael|title=Standards and thresholds for impact assessment|publisher=Springer Verlag|year=2008|isbn=978-3-540-31141-6|location=Berlin|oclc=261324614}}</ref>
In several cases, a community may treat partially its sewage, and still count on the assimilative capacity of the water body. However, this needs to be analyzed very carefully, taking into account the quality of the water in the receiving body before it receives the discharge of sewage, the resulting water quality after the discharge and the impact on the intended water uses after discharge. There are also specific legal requirements in each country. Different countries have different regulations regarding the specifications of the quality of the sewage being discharged and the quality to be maintained in the receiving water body.<ref name="Marcos" />{{rp|152}}The combination of treatment and disposal must comply with existing local regulations.
The assimilative capacity depends – among several factors – on the ability of the receiving water to sustain dissolved [[oxygen]] concentrations necessary to support organisms [[Catabolism|catabolizing]] organic waste.<ref name="Metcalf & Eddy" />{{rp|9, 673}} For example, fish may die if dissolved oxygen levels are depressed below 5&nbsp;mg/L.<ref name="l&f">{{cite book|last1=Linzley|first1=Ray K.|title=Water-Resources Engineering|last2=Franzini|first2=Joseph B.|date=1972|publisher=[[McGraw-Hill Book Company, Inc.]]|edition=Second|location=[[New York City]]}}</ref>{{rp|573}}
Application of sewage to land can be considered as a form of final disposal or of treatment, or both.<ref name="Marcos" />{{rp|189}} Land disposal alternatives require consideration of land availability, groundwater quality, and possible soil deterioration.<ref>{{cite book|last=Rich|first=Linville Gene|title=Low-Maintenance, Mechanically Simple Wastewater Treatment Systems|date=1980|publisher=[[McGraw-Hill Book Company, Inc.]]|isbn=0-07-052252-9|location=[[New York City]]|page=187}}</ref>
=== Other disposal methods ===
Sewage may be discharged to an [[evaporation]] or [[infiltration basin]].<ref name="lcu" />{{rp|9–41}} [[Groundwater recharge]] is used to reduce [[saltwater intrusion]], or replenish [[aquifer]]s used for agricultural [[irrigation]]. Treatment is usually required to sustain [[percolation]] capacity of infiltration basins, and more extensive treatment may be required for aquifers used as [[drinking water]] supplies.<ref name="Metcalf & Eddy" />{{rp|700–703}}
==== Marine outfall ====
{{excerpt|marine outfall|paragraphs=1|file=no}}
=== Global situation ===
{{excerpt|Sewage treatment#Global situation|paragraphs=1,2|file=no}}
== Treatment ==
{{main|Sewage treatment}}
Sewage treatment is beneficial in reducing environmental pollution. [[Bar screen]]s can remove large solid debris from sewage,<ref name="Metcalf & Eddy" />{{rp|274–275}} and [[Sewage treatment#Primary treatment|primary treatment]] can remove floating and [[settleable matter]].<ref name="Metcalf & Eddy" />{{rp|446}} Primary treated sewage usually contains less than half of the original solids content and approximately two-thirds of the BOD in the form of [[colloid]]s and [[Solvation|dissolved]] organic compounds.<ref>{{cite book|last=Abbett|first=Robert W.|title=American Civil Engineering Practice|date=1956|publisher=John Wiley & Sons|volume=II|location=New York|pages=19–28}}</ref> [[Secondary treatment]] can reduce the BOD of organic waste in undiluted sewage,<ref name="l&f" />{{rp|575}} but is less effective for dilute sewage.<ref>{{cite web|title=National Pollutant Discharge Elimination System (NPDES) Permit Writers' Manual|url=https://www.epa.gov/sites/default/files/2015-09/documents/pwm_chapt_05.pdf|publisher=[[United States Environmental Protection Agency]]|pages=5–11|access-date=14 September 2021}}</ref> [[Water disinfection]] may be attempted to kill pathogens prior to disposal, and is increasingly effective after more elements of the foregoing treatment sequence have been completed.<ref name="Metcalf & Eddy" />{{rp|359}}
== Reuse and reclamation ==
{{main|Reclaimed water}}
An alternative to discharge into the environment is to [[Reclaimed water|reuse]] the sewage in a productive way (for agricultural, urban or industrial uses), in compliance with local regulations and requirements for each specific reuse application. Public health risks of sewage reuse in agriculture can be minimized by following a "multiple barrier approach" according to guidelines by the [[World Health Organization]].<ref name="WHO2006">{{Cite book
|title=WHO Guidelines for the Safe Use of Wastewater, Excreta and Greywater (Volume IV: Excreta and greywater use in agriculture)
| author= World Health Organization
| date= 14 February 2024
| author-link= World Health Organization
|url=https://www.susana.org/en/knowledge-hub/resources-and-publications/library/details/1004|access-date=2023-01-02
| isbn =  978-92-4-154685-0
| url-status =live
| place= Geneva
| publisher= World Health Organization
| archive-url= https://web.archive.org/web/20141017235811/http://www.susana.org/en/resources/library/details/1004
| archive-date= 17 October 2014
}}</ref>
There is also the possibility of [[resource recovery]] which could make [[Sustainable agriculture|agriculture more sustainable]] by using [[carbon]], [[nitrogen]], [[phosphorus]], [[water]] and [[energy]] recovered from sewage.<ref name="Banwart-2021">{{Cite journal|last1=Banwart|first1=S.|last2=Carter|first2=L.|last3=Daniell|first3=T.|last4=Yong-Guan|first4=Z.|last5=Guo|first5=H.|last6=Guest|first6=J.|last7=Kirk|first7=S.|last8=Chen|first8=X.|last9=Evans|first9=B.|date=2021-09-14|title=Expanding the agricultural – sanitation circular economy: opportunities and benefits|url=http://www.leeds.ac.uk/info/130600/policy_leeds/879/policy_briefs|language=en|doi=10.5518/100/71|access-date=2021-09-16|website=www.leeds.ac.uk}}</ref><ref name="Andersson" />
===Sewage farm===
{{excerpt|sewage farm|paragraphs=1|file=no}}
== Regulations ==
{{Further|Sewage regulation and administration}}
Sewage management includes collection and transport for release into the environment after a [[Sewage treatment|treatment level]] that is compatible with the local requirements for discharge into water bodies, onto soil, or for reuse applications.<ref name="Marcos" />{{rp|156}} In most countries, uncontrolled discharges of wastewater to the environment are not permitted under law, and strict water quality requirements are to be met. For requirements in the United States, ''see [[Clean Water Act#Point sources|Clean Water Act]].''
Sewage management regulations are often part of a country's broader [[sanitation]] policies. These may also include the management of [[human excreta]] (from [[Fecal sludge management|non-sewered collection systems]]), [[Municipal solid waste|solid waste]] and stormwater.
== See also ==
{{Portal|Water}}
* [[Fecal sludge management]]
* [[History of water supply and sanitation]]
* [[Reuse of human excreta]]
* [[Urban Waste Water Treatment Directive]]
* [[Wastewater-based epidemiology]]
{{Clear}}
==References==
{{Reflist}}
==External links==
*[https://www.unep.org/resources/publication/sanitation-and-wastewater-atlas-africa Sanitation and Wastewater Atlas of Africa]
{{Wiktionary}}
{{Commons category|Wastewater}}
{{Scholia|topic}}
{{interwiki extra|qid=Q336191}}
{{Wastewater}}
{{Plumbing}}
{{Waste}}
{{Pollution}}
{{Authority control}}
[[Category:Anaerobic digestion]]
[[Category:Sanitation]]
[[Category:Sewerage]]
[[Category:Waste management]]
[[Category:Water pollution]]