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Raw sewage arriving at a sewage treatment plant in Syria


All sewage ends up back in the environment (from which its constituents came), by any of several routes. A basic distinction in its route is whether it undergoes sewage treatment to mitigate its effect on the environment before arriving there. Sewage usually travels from a building's plumbing either into a sewer, which will carry it elsewhere, or into an onsite sewage facility (of which there are many kinds). Whether it is combined with surface runoff in the sewer depends on the sewer design (sanitary sewer or combined sewer). Before the 20th century, sewers usually discharged into a body of water such as a stream, river, lake, bay, or ocean. There was no treatment, so the breakdown of the human waste was left to the ecosystem. Today, the goal is that sewers route their contents to a wastewater treatment plant rather than directly to a body of water. In many countries, this is the norm; in many developing countries, it may be a yet-unrealized goal. In general, with passing decades and centuries, humanity seeks to be smarter about the route of sewage on its way back to the environment, in order to reduce environmental degradation and achieve sustainability. Thus other goals of modern sewage routing include handling surface runoff separately from sewage, handling greywater separately from toilet waste, and coping better with abnormal events (such as peaks in use from internal displacement and peaks in stormwater volumes from extreme weather).

The term sewage is nowadays regarded as an older term and is being more and more replaced by "wastewater".[1] In general American English usage, the terms "sewage" and "sewerage" mean the same thing.[2][3][4] Both words are descended from Old French assewer, derived from the Latin exaquare, "to drain out (water)". In American technical and professional English usage, "sewerage" refers to the infrastructure that conveys sewage.[5]


Greywater samples before and after treatment in a constructed wetland in Peru
  • The wastewater from residences and institutions, carrying body wastes (primarily feces and urine), washing water, food preparation wastes, laundry wastes, and other waste products of normal living, are classed as domestic or sanitary sewage.
  • Liquid-carried wastes from stores and service establishments serving the immediate community, termed commercial wastes, are included in the sanitary or domestic sewage category if their characteristics are similar to household flows. Wastes that result from an industrial processes such as the production or manufacture of goods are classed as industrial wastewater, not as sewage.


Organic pollutants and nutrients[edit]

Sewage is a complex mixture of chemicals, with many distinctive chemical characteristics. These include high concentrations of ammonium, nitrate, phosphorus, high conductivity (due to high dissolved solids), high alkalinity, with pH typically ranging between 7 and 8. The organic matter of sewage is measured by determining its biological oxygen demand (BOD) or the chemical oxygen demand (COD). Sewage also contains the nutrients nitrogen and phosphorus

Pathogens and micro-pollutants[edit]

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,[6] attempting eradication,[7] testing specifically for drug-resistant strains,[8] or discovering new species.[9] Sequencing DNA from an environmental sample is known as metagenomics.

Sewage has also been analyzed to determine relative rates of use of prescription[10] and illegal[11] drugs among municipal populations.

Sewage also contains environmental persistent pharmaceutical pollutants.

Trihalomethanes are also likely to be present as a result of past disinfection.

Disease potential[edit]

All categories of sewage are likely to carry pathogenic organisms that can transmit disease to humans and other animals; contain organic matter that can cause odor and nuisance problems; hold nutrients that may cause eutrophication of receiving water bodies; and can lead to ecotoxicity. 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.[12] The reality is, however, that around 90% of wastewater produced globally remains untreated causing widespread water pollution, especially in low-income countries. Fecal matter can potentially cause disease.

Reuse in agriculture[edit]

Further information: Reuse of excreta



Collection and disposal[edit]

Further information: Sewerage




Main article: Sewage treatment



In developed countries sewage collection and treatment is typically subject to local, state and federal regulations and standards.

See also[edit]


  4. ^ Neilson, William Allan; Knott, Thomas A., eds. (1934). Webster's new international dictionary of the English language. Second edition unabridged. An entirely new work (Hardcover) (Second ed.). Springfield, Mass: C. & C. Merriam Company. p. 2296. 
  5. ^ "sewerage - definition of sewerage in English from the Oxford dictionary". Retrieved 2015-09-04. 
  6. ^ Environmental Occurrence of the Whipple’s Disease Bacterium (Tropheryma whippelii)
  7. ^ Poliovirus detected from environmental samples in Israel
  9. ^ Raw Sewage Harbors Diverse Viral Populations
  10. ^ Miao, X. S.; Metcalfe, C. D. (2003). "Determination of cholesterol-lowering statin drugs in aqueous samples using liquid chromatography-electrospray ionization tandem mass spectrometry". Journal of chromatography. A 998 (1–2): 133–141. doi:10.1016/S0021-9673(03)00645-9. PMID 12862379. 
  11. ^ 'Testing the waters': First International conference on drug wastewater analysis
  12. ^ McGraw-Hill Encyclopedia of Science and Technology (View excerpt at