Wastewater (or waste water) 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". Therefore, wastewater is a byproduct of domestic, industrial, commercial or agricultural activities. The characteristics of wastewater vary depending on the source. Types of wastewater include: domestic wastewater from households, municipal wastewater from communities (also called sewage) and industrial wastewater. Wastewater can contain physical, chemical and biological pollutants.
Households may produce wastewater from flush toilets, sinks, dishwashers, washing machines, bath tubs, and showers. Households that use dry toilets produce less wastewater than those that use flush toilets.
Wastewater may be conveyed in a sanitary sewer that conveys only sewage. Alternatively, wastewater can be transported in a combined sewer that conveys both stormwater runoff and sewage, and possibly also industrial wastewater. After treatment at a wastewater treatment plant, treated wastewater (also called effluent) is discharged to a receiving water body. The terms "wastewater reuse" and "water reclamation" apply if the treated waste is used for another purpose. Wastewater that is discharged to the environment without suitable treatment can cause water pollution.
In developing countries and in rural areas with low population densities, wastewater is often treated by various on-site sanitation systems and not conveyed in sewers. These systems include septic tanks connected to drain fields, on-site sewage systems (OSS), vermifilter systems and many more.
The extremely broad term sanitation includes the management of wastewater, human excreta, solid waste and stormwater. The term sewerage refers to the physical infrastructure required to transport and treat wastewater.
Sources of wastewater include the following domestic or household activities:
- Human excreta (feces, urine, blood and other bodily fluids) often mixed with used toilet paper or wet wipes; this is known as blackwater if it is collected from flush toilets
- Washing water (personal hygiene, clothes, floors, dishes, cars, etc.), also known as greywater or sullage
- Surplus manufactured liquids from domestic sources (drinks, cooking oil, pesticides, lubricating oil, paint, cleaning detergents, etc.)
Activities producing industrial wastewater include:
- Industrial site drainage (silt, sand, alkali, oil, chemical residues);
- Industrial cooling waters (biocides, heat, slimes, silt)
- Industrial processing waters
- Organic or biodegradable waste including waste from hospitals, abattoirs, creameries, and food factories.
- Organic or non bio-degradable waste that is difficult-to-treat from pharmaceutical  or pesticide manufacturing
- Extreme pH waste from acid and alkali manufacturing
- Toxic waste from metal plating, cyanide production, pesticide manufacturing, etc.
- Solids and emulsions from paper mills, factories producing lubricants or hydraulic oils, foodstuffs, etc.
- Water used in hydraulic fracturing
- Produced water from oil & natural gas production
Other related activities or events:
- Urban runoff from highways, roads, railway tracks, car parks, roofs, pavements (contains oils, animal feces/manure, food waste, litter, petrol, diesel or rubber residues from tyres, soapscum, metals from vehicle exhausts, de-icing agents, herbicides and pesticides from gardens, etc.)
- Agricultural pollution, direct and diffuse
Wastewater can be diluted or mixed with other types of water through the following mechanisms:
The composition of wastewater varies widely. This is a partial list of pollutants that may be contained in wastewater:
Chemical or physical pollutantsEdit
- Heavy metals, including mercury, lead, and chromium
- Organic particles such as feces, hairs, food waste, vomit, paper fibers, plant material, humus, etc.;
- Soluble organic material such as urea, fruit sugars, soluble proteins, drugs, pharmaceuticals, etc.;
- Inorganic particles such as sand, grit, metal particles, rubber residues from tires, ceramics, etc.;
- Soluble inorganic material such as ammonia, road-salt, sea-salt, cyanide, hydrogen sulfide, thiocyanates, thiosulfates, etc.;
- Macro-solids such as sanitary napkins, nappies/diapers, condoms, needles, children's toys, dead animals or plants, etc.;
- Gases such as hydrogen sulfide, carbon dioxide, methane, etc.;
- Emulsions such as paints, adhesives, mayonnaise, hair colorants, emulsified oils, etc.;
- Toxins such as pesticides, poisons, herbicides, etc.
- Pharmaceuticals, endocrine disrupting compounds, hormones, perfluorinated compounds, siloxanes, drugs of abuse and other hazardous substances 
- Microplastics such as polyethylene and polypropylene beads, polyester and polyamide 
- Thermal pollution from power stations and industrial manufacturers
- Bacteria (for example Salmonella, Shigella, Campylobacter, Vibrio cholerae),
- Viruses (for example hepatitis A, rotavirus, enteroviruses),
- Protozoa (for example Entamoeba histolytica, Giardia lamblia, Cryptosporidium parvum) and
- Parasites such as helminths and their eggs (e.g. Ascaris (roundworm), Ancylostoma (hookworm) and Trichuris (whipworm));
Since all natural waterways contain bacteria and nutrients, almost any waste compounds introduced into such waterways will initiate biochemical reactions such as detailed above. Those biochemical reactions create what is measured in the laboratory as the biochemical oxygen demand (BOD). Such chemicals are also liable to be broken down using strong oxidizing agents and these chemical reactions create what is measured in the laboratory as the chemical oxygen demand (COD). Both the BOD and COD tests are a measure of the relative oxygen-depletion effect of a waste contaminant. Both have been widely adopted as a measure of pollution effect. The BOD test measures the oxygen demand of biodegradable pollutants whereas the COD test measures the oxygen demand of oxidizable pollutants.
Any oxidizable material present in an aerobic natural waterway or in an industrial wastewater will be oxidized both by biochemical (bacterial) or chemical processes. The result is that the oxygen content of the water will be decreased.
Aquatic toxicology tests are used to provide qualitative and quantitative data on adverse effects on aquatic organisms from a toxicant. Testing types include acute (short-term exposure), chronic (life span) and bioaccumulation tests. Many industrial facilities in the US conduct "whole effluent toxicity" tests on their wastewater discharges, typically in combination with chemical tests for selected pollutants.
There are numerous processes that can be used to clean up wastewaters depending on the type and extent of contamination. Wastewater can be treated in wastewater treatment plants which include physical, chemical and biological treatment processes. Municipal wastewater is treated in sewage treatment plants (which may also be referred to as wastewater treatment plants). Agricultural wastewater may be treated in agricultural wastewater treatment processes, whereas industrial wastewater is treated in industrial wastewater treatment processes.
One type of aerobic treatment system is the activated sludge process, based on the maintenance and recirculation of a complex biomass composed of micro-organisms able to absorb and adsorb the organic matter carried in the wastewater. Anaerobic wastewater treatment processes (UASB, EGSB) are also widely applied in the treatment of industrial wastewaters and biological sludge. Some wastewater may be highly treated and reused as reclaimed water. Constructed wetlands are also being used.
This section needs additional citations for verification. (May 2019) (Learn how and when to remove this template message)
In many cities, municipal wastewater is carried together with stormwater, in a combined sewer system, to a sewage treatment plant. In some urban areas, municipal wastewater is carried separately in sanitary sewers and runoff from streets is carried in storm drains. Access to these systems, for maintenance purposes, is typically through a manhole.
During high precipitation periods a combined sewer system may experience a combined sewer overflow event, which forces untreated sewage to flow directly to receiving waters. This can pose a serious threat to public health and the surrounding environment.
In less-developed or rural regions, sewage may drain directly into major watersheds with minimal or no treatment. This usually has serious impacts on the quality of an environment and on human health. Pathogens can cause a variety of illnesses. Some chemicals pose risks even at very low concentrations and can remain a threat for long periods of time because of bioaccumulation in animal or human tissue.
Wastewater from factories, power plants and other industrial activities is extensively regulated in developed nations, and treatment is required before discharge to surface waters. (See Industrial wastewater treatment.) Some facilities such as oil and gas wells may be permitted to pump their wastewater underground through injection wells. Wastewater injection has been linked to induced seismicity.
Treated wastewater can be reused in industry (for example in cooling towers), in artificial recharge of aquifers, in agriculture and in the rehabilitation of natural ecosystems (for example in wetlands). In rarer cases it is also used to augment drinking water supplies. There are several technologies used to treat wastewater for reuse. A combination of these technologies can meet strict treatment standards and make sure that the processed water is hygienically safe, meaning free from bacteria and viruses. The following are some of the typical technologies: Ozonation, ultrafiltration, aerobic treatment (membrane bioreactor), forward osmosis, reverse osmosis, advanced oxidation.
Some water demanding activities do not require high grade water. In this case, wastewater can be reused with little or no treatment. One example of this scenario is in the domestic environment where toilets can be flushed using greywater from baths and showers with little or no treatment.
Irrigation with recycled wastewater can also serve to fertilize plants if it contains nutrients, such as nitrogen, phosphorus and potassium. In developing countries, agriculture is using untreated wastewater for irrigation - often in an unsafe manner. There can be significant health hazards related to using untreated wastewater in agriculture. The World Health Organization developed guidelines for safe use of wastewater in 2006.
As part of the Environmental Protection Act 1994, the Environmental Protection (Water) Policy 2009 is responsible for the water management of Queensland, Australia.
In Nigeria, the Water Resources Act of 1993 is the law responsible for all kinds of water management.
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.
The Clean Water Act is the primary federal law in the United States governing water pollution in surface waters. It is implemented by the U.S. Environmental Protection Agency in collaboration with states, territories, and tribes. Groundwater protection provisions are included in the Safe Drinking Water Act, Resource Conservation and Recovery Act, and the Superfund act.
|Wikimedia Commons has media related to Wastewater.|
|Scholia has a topic profile for Wastewater.|
- 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)
- 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.
- Arvaniti and Stasinakis, 2015. Review on the occurrence, fate and removal of perfluorinated compounds during wastewater treatment. Science of the Total Environment vol. 524-525, August 2015, p. 81-92. Arvaniti and Stasinakis, 2015
- Bletsou et al., 2013. Mass loading and fate of linear and cyclic siloxanes in a wastewater treatment plant in Greece. Environmental Science and Technology vol. 47, January 2015, p. 1824-1832. Bletsou et al., 2013
- Gatidou et al., 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 vol. 563-564, September 2016, p. 633-640. Gatidou et al., 2016
- Gatidou et al. 2019. Review on the occurrence and fate of microplastics in Sewage Treatment Plants. Journal of Hazardous Materials, vol. 367, April 2019, p. 504-512. Gatidou et al., 2019
- World Health Organization (2006). Guidelines for the safe use of wastewater, excreta, and greywater. World Health Organization. p. 31. ISBN 978-9241546850. OCLC 71253096.
- 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 1 June 2017 at the Wayback Machine. Nairobi and Stockholm: United Nations Environment Programme and Stockholm Environment Institute. ISBN 978-92-807-3488-1, p. 56
- Rand, Gary M., ed. (1995). Fundamentals of Aquatic Toxicology (2nd ed.). London: Taylor & Francis. ISBN 1-56032-091-5.
- "Whole Effluent Toxicity (WET)". National Pollutant Discharge Elimination System (NPDES). Washington, D.C.: U.S. Environmental Protection Agency (EPA). 17 September 2019.
- WWAP (United Nations World Water Assessment Programme) (2017). The United Nations World Water Development Report 2017. Wastewater: The Untapped Resource. Paris. ISBN 978-92-3-100201-4. Archived from the original on 8 April 2017.
- U.S. Environmental Protection Agency, Washington, D.C. (2008). "Septic Systems Fact Sheet." Archived 12 April 2013 at the Wayback Machine EPA publication no. 832-F-08-057.
- van der Baan, Mirko; Calixto, Frank J. (1 July 2017). "Human-induced seismicity and large-scale hydrocarbon production in the USA and Canada". Geochemistry, Geophysics, Geosystems. 18 (7): 2467–2485. Bibcode:2017GGG....18.2467V. doi:10.1002/2017gc006915. ISSN 1525-2027.
- WHO (2006). WHO Guidelines for the Safe Use of Wastewater, Excreta and Greywater – Volume IV: Excreta and greywater use in agriculture Archived 17 October 2014 at the Wayback Machine. World Health Organization (WHO), Geneva, Switzerland
- "Environmental policy and legislation". Department of Environmental and Heritage Protection. Queensland Government. 25 September 2015. Archived from the original on 20 October 2017. Retrieved 20 October 2017.
- "An Act Providing For A Comprehensive Water Quality Management And For Other Purposes". The LawPhil Project. Archived from the original on 21 September 2016. Retrieved 30 September 2016.
- United States. Clean Water Act. 33 U.S.C. § 1251 et seq. Pub.L. 92-500 Archived 16 May 2013 at the Wayback Machine, 18 October 1972; as amended.
- Jim Hanlon, Mike Cook, Mike Quigley, Bob Wayland. “Water Quality: A Half Century of Progress.” EPA Alumni Association. March 2016.