Sewage

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Not to be confused with Sewerage.

Raw sewage arriving at a sewage treatment plant in Syria
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Sewage (or domestic sewage, domestic wastewater, municipal wastewater) is a type of wastewater that is produced by a community of people. It is characterized by volume or rate of flow, physical condition, chemical and toxic constituents, and its bacteriologic status (which organisms it contains and in what quantities). It consists mostly of greywater (from sinks, bathtubs, showers, dishwashers, and clothes washers), blackwater (the water used to flush toilets, combined with the human waste that it flushes away); soaps and detergents; and toilet paper (less so in regions where bidets are widely used instead of paper).

Sewage usually travels from a building's plumbing either into a sewer, which will carry it elsewhere, or into an onsite sewage facility. Whether it is combined with surface runoff in the sewer depends on the sewer design (sanitary sewer or combined sewer). In many developing countries the bulk of domestic and industrial wastewater is discharged without any treatment or after primary treatment only.

The term sewage is an older term and sometimes replaced by "wastewater" in modern usage.

Definitions[edit]

Domestic sewage is made up of the wastewater from residences and institutions, carrying bodily wastes (primarily feces and urine), washing water, food preparation wastes, laundry wastes, and other waste products of normal living. This is classified as sewage or domestic wastewater.[1]:9–1 Sewage is an older term often replaced by "wastewater", domestic wastewater or municipal wastewater in modern usage,[2] but useful to differentiate domestic sewage from the following terms:

  • Industrial wastewater, generated by industrial processes such as the production or manufacture of goods, may be significantly different from sewage and may be collected and treated or pre-treated separately.[4]:300
  • Infiltration is groundwater entering sewers through piping joints. Infiltration increases sewage volume and may contain soil particles of silt, sand, or clay. Contaminated or saline groundwater may introduce additional wastes to the sewage. 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.[1]:9–1&9–9 In areas with a low groundwater table, sewage may exfiltrate into groundwater from the leaking sewer joints.[5]:43&44
  • Combined sewers carry surface runoff in addition to sewage, which may significantly increase sewage volume during precipitation.[1]:9–1 Uncontaminated stormwater simply dilutes sewage, but runoff may dissolve or suspend virtually anything it contacts on roofs, streets, and storage yards.[4]:296 Combined sewers may receive dry weather drainage from landscape irrigation, construction dewatering, and washing buildings and sidewalks.
  • Sanitary sewers are typically much smaller than combined sewers, and they are not designed to transport stormwater. Backups of raw sewage can occur if excessive dilution by stormwater inflow and/or groundwater infiltration is allowed into a sanitary sewer system. Communities that have urbanized in the mid-20th century or later generally have built separate systems for sewage (sanitary sewers) and stormwater, because precipitation causes widely varying flows, reducing sewage treatment plant efficiency.[6] In general American English usage, the terms "sewage" and "sewerage" mean the same thing.[7][8][9] In common English usage, and in American technical and professional English usage, "sewerage" refers to the infrastructure that conveys sewage.[10]
  • Inflow is relatively clean water from roof, cellar, and yard drains[4]:303 diluting sewage by entering sanitary sewers intended to prevent such dilution.[1]:9–10
  • Wastewater, in the context of sanitation, is any water that has been contaminated by human use. Wastewater is "used water from any combination of domestic, industrial, commercial or agricultural activities, surface runoff or stormwater, and any sewer inflow or sewer infiltration".[11]

Pollutants[edit]

Greywater samples before and after treatment in a constructed wetland in Peru
Greywater (a type of wastewater) in a settling tank

Wastewater refers to the use of water to carry wastes away. Sewage consists primarily of water and usually contains less than one part solid matter per thousand parts of water.[1]:9–38 The daily dry weight of solid wastes per capita in sewage is estimated as 20.5 g (0.72 oz) in feces, 43.3 g (1.53 oz) of dissolved solids in urine, 20 g (0.71 oz) of toilet paper, 86.5 g (3.05 oz) of greywater solids, 30 g (1.1 oz) of food solids (if garbage disposal units are used), and varying amounts of dissolved minerals depending upon salinity of local water supplies, volume of water use per capita, amount and salinity of infiltration, and extent of water softener use.[5]:234 About one-third of this solid matter is suspended by turbulence, while the remainder is dissolved or colloidal. The waste contained in domestic sewage is about half organic and half inorganic. The organic content includes compounds of nitrogen[1]:9–38 with lesser amounts of phosphorus and sulfur providing nutrients for eutrophication.[5]:256–263 The organic content decomposes rapidly producing the unpleasant odor of hydrogen sulfide encouraging rapid removal of sewage from populated places.[1]:9–38 An average person produces sewage containing about 90 g (3.2 oz) of suspended solids and 77 g (2.7 oz) of biochemical oxygen demand per day, but populations using garbage disposal units for food waste disposal to sewers average 150 g (5.3 oz) suspended solids and 100 g (3.5 oz) biochemical oxygen demand per capita.[3] The volume of domestic sewage produced per person varies with the availability of water and cost of water,[12] and is typically within the range of 190–380 l (42–84 imp gal; 50–100 US gal) per capita per day.[4]:296 A community's commercial facilities may increase the volume or waste concentration of sewage if these facilities are used by populations from areas not served by the sewer system.[3]

Residential users may pour unwanted liquids like cooking oil,[5]:228 lubricants,[5]:228 adhesives, paint, solvents, detergents,[5]:228 disinfectants, or pesticides and herbicides into their sewer connections.

Pathogens[edit]

Domestic sewage includes greywater from bathing and from washing clothing and dishes, and blackwater containing feces, urine, blood and vomit from flush toilets. Blackwater is a unique environmental threat because of the likelihood it may contain pathogenic organisms that can transmit disease to humans and animals.[1]:9–38 Sewage contains pathogens of four types:[13][14]

Greywater may have lower concentrations of pathogens from laundering soiled diapers, clothing and bedding.

Micro-pollutants[edit]

Sewage contains environmental persistent pharmaceutical pollutants. Trihalomethanes 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[16] 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 hormones[17][18][19] may be excreted in urine or feces if not catabolized within the human body.

Solid waste[edit]

Households with flush toilets are often tempted to dispose of unwanted solid waste items through their toilet, even at the risk of causing blockages. For this reason the following solid waste items are often found in sewage: Toilet paper, wet wipes, diapers, sanitary napkins, tampons, tampon applicators, condoms, and expired medications. 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.[20]

Pollutants from industrial wastewater[edit]

Main article: Industrial wastewater treatment

Sewage from communities with industrial facilities may contain industrial wastewater with varying concentrations of raw materials, reagents, impurities, products, and by-products of manufacturing operations. Volumes of industrial wastewater vary widely with the type of industry.[1]:9–9 Industrial wastewater often includes blackwater from employees and customers, but may contain very different pollutants at much higher concentrations than what is typically found in sewage.[1]:9–92&9–96 Pollutants may be toxic or non-biodegradable waste including pharmaceuticals,[21] biocides, heavy metals, radionuclides, or thermal pollution. Industrial wastewater increases the volume of sewage per capita.

Quality indicators[edit]

Main article: Wastewater quality indicators

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, testing specifically for drug-resistant strains, or discovering new species.[22][23][24] 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.[25] General socioeconomic demographics may be inferred as well.[26]

Management[edit]

Sewage can cause water pollution when discharged to the environment. Proper collection and safe, nuisance-free disposal of the liquid wastes of a community are legally recognized as a necessity in an urbanized, industrialized society.[27] Management of sewage may include collection for release to surface water, infiltration to groundwater, or reuse,[5]:9 with or without sewage treatment.[28]:564 It is part of the broad term sanitation which includes not only the management of wastewater but also the management of human excreta, solid waste and stormwater.

Sewage may be collected and transported in a sanitary sewer or in a combined sewer that conveys stormwater runoff, sewage and industrial wastewater to an evaporation or infiltration basin, or to a stream, lake, or ocean.[1]:9–41 The amount of treatment required depends upon the perceived ability of the receiving water to dilute and assimilate wastes within the sewage, and perceptions of individuals generating the sewage may differ from other segments of the population. Sewage used for another purpose like irrigation or groundwater recharge may be called reclaimed water.[3]

Treatment[edit]

Main article: Sewage treatment

Sewage treatment is beneficial in reducing environmental pollution. Bar screens can remove large solid debris from sewage,[5]:274–275 and primary treatment can remove floating and settleable matter.[5]:446 Secondary treatment can reduce biochemical oxygen demand from concentrated sewage,[28]:575 but is less efficient for dilute sewage, or sewage containing toxic materials.

Dilution[edit]

Dilution remained the most common method of sewage disposal into the late 20th century. Most sewage produced globally remains untreated, causing widespread water pollution, especially in low-income countries: a global estimate by UNDP and UN-Habitat is that 90% of all wastewater generated is released into the environment untreated.[29] The larger suspended or floating solids may be removed rather than released to the receiving water.[28]:573 The amount of natural purification in receiving waters depends upon the volume of receiving water in comparison to the amount of waste, and the ability of the receiving water to sustain dissolved oxygen concentrations necessary to support organisms catabolizing organic waste.[5]:9&673 Fish may die if dissolved oxygen levels are depressed below 5 mg/l.[28]:573

Combined sewer systems dilute sewage with stormwater runoff or urban runoff. This design was common when urban sewerage systems were first developed, in the late 19th and early 20th centuries.[5]:119 As rainfall travels over roofs and the ground, it may pick up various contaminants including soil particles and other sediment, heavy metals, organic compounds, animal waste, and oil and grease.

Reclamation[edit]

Main article: Reclaimed water

Groundwater recharge is a common method of sewage disposal to reduce saltwater intrusion, or replenish aquifers 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.[5]:700–703 Sewage farming uses lower rates of infiltration in warm, arid climates. Land disposal alternatives require consideration of land availability, groundwater quality, and possible soil deterioration.[30]

Legislation[edit]

Further information: Reclaimed water § Guidelines and regulations, and Water pollution § Legislation

See also[edit]

References[edit]

  1. ^ a b c d e f g h i j k Urquhart, Leonard Church (1959). Civil Engineering Handbook (Fourth ed.). New York City: McGraw-Hill Book Company, Inc.
  2. ^ Wastewater engineering: treatment and reuse (4th ed.). Metcalf & Eddy, Inc., McGraw Hill, USA. 2003. p. 1807. ISBN 0-07-112250-8.
  3. ^ a b c d Sewage Treatment Plant Design. New York City: American Society of Civil Engineers and Water Pollution Control Federation. 1959. pp. 5–10.
  4. ^ a b c d e Hammer, Mark J. (1975). Water and Waste-Water Technology. New York City: John Wiley & Son. ISBN 0-471-34726-4.
  5. ^ a b c d e f g h i j k l m n Metcalf & Eddy, Inc. (1972). Wastewater Engineering. New York: McGraw-Hill. ISBN 978-0-07-041675-8.
  6. ^ Burrian, Steven J., et al. (1999). "The Historical Development of Wet-Weather Flow Management." US Environmental Protection Agency (EPA). National Risk Management Research Laboratory, Cincinnati, OH. Document No. EPA/600/JA-99/275.
  7. ^ Funk & Wagnall's Standard Dictionary (International Edition) New York, 1960, p. 1152.
  8. ^ Flexner, Sturat; Hauck, Leonore, eds. (1987) [1966]. The Random House Unabridged Dictionary (Second ed.). New York City: Random House (published 1993). p. 1754.
  9. ^ Neilson, William Allan; Knott, Thomas A., eds. (1934). Webster's new international dictionary of the English language. Second edition unabridged. An entirely new work (Hardocver) (Second ed.). Springfield, Mass: C. & C. Merriam Company. p. 2296.
  10. ^ "sewerage – definition of sewerage in English from the Oxford dictionary". Oxforddictionaries.com. Archived from the original on 24 September 2015. Retrieved 4 September 2015.
  11. ^ Tilley, E., Ulrich, L., Lüthi, C., Reymond, Ph., Zurbrügg, C. (2014). Compendium of Sanitation Systems and Technologies – (2nd Revised ed.). Swiss Federal Institute of Aquatic Science and Technology (Eawag), Duebendorf, Switzerland. p. 175. ISBN 978-3-906484-57-0. Archived from the original on 8 April 2016.CS1 maint: multiple names: authors list (link)
  12. ^ Steel, E.W.; McGhee, Terence J. (1979). Water Supply and Sewerage (Fifth ed.). New York City: McGraw-Hill Book Company, Inc. pp. 21–24. ISBN 0-07-060929-2.
  13. ^ World Health Organization (2006). Guidelines for the safe use of wastewater, excreta, and greywater. World Health Organization. p. 31. ISBN 9241546859. OCLC 71253096.
  14. ^ Andersson, K., Rosemarin, A., Lamizana, B., Kvarnström, E., McConville, J., Seidu, R., Dickin, S. and Trimmer, C. (2016). Sanitation, Wastewater Management and Sustainability: from Waste Disposal to Resource Recovery Archived 2017-06-01 at the Wayback Machine. Nairobi and Stockholm: United Nations Environment Programme and Stockholm Environment Institute. ISBN 978-92-807-3488-1, p. 56
  15. ^ Naddeo, Vincenzo; Liu, Haizhou (2020). "Editorial Perspectives: 2019 novel coronavirus (SARS-CoV-2): what is its fate in urban water cycle and how can the water research community respond?". Environmental Science: Water Research & Technology. 6 (5): 1213–1216. doi:10.1039/D0EW90015J.
  16. ^ Gatidou, Georgia; Arvaniti, Olga S.; Stasinakis, Athanasios S. (2019). "Review on the occurrence and fate of microplastics in Sewage Treatment Plants". Journal of Hazardous Materials. 367: 504–512. doi:10.1016/j.jhazmat.2018.12.081. PMID 30620926.
  17. ^ Arvaniti, Olga S.; Stasinakis, Athanasios S. (2015). "Review on the occurrence, fate and removal of perfluorinated compounds during wastewater treatment". Science of the Total Environment. 524–525: 81–92. Bibcode:2015ScTEn.524...81A. doi:10.1016/j.scitotenv.2015.04.023. PMID 25889547.
  18. ^ Bletsou, Anna A.; Asimakopoulos, Alexandros G.; Stasinakis, Athanasios S.; Thomaidis, Nikolaos S.; Kannan, Kurunthachalam (19 February 2013). "Mass Loading and Fate of Linear and Cyclic Siloxanes in a Wastewater Treatment Plant in Greece". Environmental Science & Technology. 47 (4): 1824–1832. Bibcode:2013EnST...47.1824B. doi:10.1021/es304369b. ISSN 0013-936X. PMID 23320453.
  19. ^ Gatidou, Georgia; Kinyua, Juliet; van Nuijs, Alexander L.N.; Gracia-Lor, Emma; Castiglioni, Sara; Covaci, Adrian; Stasinakis, Athanasios S. (2016). "Drugs of abuse and alcohol consumption among different groups of population on the Greek Island of Lesvos through sewage-based epidemiology". Science of the Total Environment. 563–564: 633–640. Bibcode:2016ScTEn.563..633G. doi:10.1016/j.scitotenv.2016.04.130. hdl:10067/1345920151162165141. PMID 27236142.
  20. ^ Jamrock, Thomas E. "Grinders and Comminutors: An Evolving Technology". Environmental Protection. Retrieved 5 August 2021.
  21. ^ Naddeo, V.; Meriç, S.; Kassinos, D.; Belgiorno, V.; Guida, M. (September 2009). "Fate of pharmaceuticals in contaminated urban wastewater effluent under ultrasonic irradiation". Water Research. 43 (16): 4019–4027. doi:10.1016/j.watres.2009.05.027. PMID 19589554.
  22. ^ Poliovirus detected from environmental samples in Israel Archived 2013-11-04 at the Wayback Machine
  23. ^ Drug resistant bug review: NDM-1 in New Delhi’s sewage, WHO calls to action, recent outbreaks of antibiotic resistant bacteria Archived 2013-11-05 at the Wayback Machine
  24. ^ Raw Sewage Harbors Diverse Viral Populations Archived 2013-06-07 at the Wayback Machine
  25. ^ 'Testing the waters': First International conference on drug wastewater analysis Archived 2014-02-09 at the Wayback Machine
  26. ^ Choi, Phil M. (7 October 2019). "Social, demographic, and economic correlates of food and chemical consumption measured by wastewater-based epidemiology". Proceedings of the National Academy of Sciences of the United States of America. 116 (43): 21864–21873. doi:10.1073/pnas.1910242116. PMC 6815118. PMID 31591193.
  27. ^ McGraw-Hill Encyclopedia of Science and Technology (View excerpt at Answers.com) Archived 2009-02-12 at the Wayback Machine
  28. ^ a b c d Linzley, Ray K.; Franzini, Joseph B. (1972). Water-Resources Engineering (Second ed.). New York City: McGraw-Hill Book Company, Inc.
  29. ^ Corcoran, E.; C. Nellemann; E. Baker; R. Bos; D. Osborn; H. Savelli, eds. (2010). Sick water? The central role of wastewater management in sustainable development. A rapid response assessment (PDF). Arendal, Norway: UNEP/GRID-Arendal. ISBN 978-82-7701-075-5. Archived from the original (PDF) on 18 December 2015.
  30. ^ Rich, Linville Gene (1980). Low-Maintenance, Mechanically Simple Wastewater Treatment Systems. New York City: McGraw-Hill Book Company, Inc. p. 187. ISBN 0-07-052252-9.
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