Wastewater: Difference between revisions
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{{For|the lake in Northwestern England|Wastwater}} |
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{{Public Infrastructure}} |
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'''Wastewater''' is any [[water]] that has been adversely affected in quality by [[human impact on the environment|anthropogenic]] influence. It comprises liquid waste discharged by domestic residences, commercial properties, industry, and/or agriculture and can encompass a wide range of potential contaminants and concentrations. In the most common usage, it refers to the municipal wastewater that contains a broad spectrum of contaminants resulting from the mixing of wastewaters from different sources. |
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'''Sewage''' is correctly the subset of wastewater that is contaminated with [[feces]] or [[urine]], but is often used to mean any waste water. "[[Sewage]]" includes domestic, municipal, or industrial [[waste|liquid waste product]]s disposed of, usually via a [[pipeline transport|pipe]] or [[sanitary sewer|sewer]] or similar structure, sometimes in a [[cesspool emptier]]. |
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The physical infrastructure, including pipes, [[pump]]s, screens, channels etc. used to convey sewage from its origin to the point of eventual treatment or disposal is termed [[sanitary sewer|sewerage]]. |
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==Origin== |
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Wastewater or sewage can come from (text in brackets indicates likely inclusions or contaminants): |
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* [[Human waste]] ([[Human fæces|fæces]], used [[toilet paper]] or wipes, [[urine]], or other bodily fluids), also known as [[Blackwater (waste)|blackwater]], usually from [[lavatory|lavatories]]; |
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*[[Cesspit]] leakage; |
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*[[Septic tank]] discharge; |
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*[[Sewage treatment]] plant discharge; |
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* Washing water (personal, clothes, floors, dishes, etc.), also known as [[greywater]] or [[sullage]]; |
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* Rainfall collected on roofs, yards, hard-standings, etc. (generally clean with traces of [[oil]]s and [[fuel]]); |
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* [[Groundwater]] infiltrated into sewage; |
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* Surplus manufactured liquids from domestic sources (drinks, cooking oil, [[pesticide]]s, [[Lubricant|lubricating oil]], [[paint]], cleaning liquids, etc.); |
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* Urban [[rainfall]] runoff from [[road]]s, carparks, roofs, sidewalks, or pavements (contains oils, animal fæces, [[litter]], fuel or [[rubber]] residues, [[metal]]s from vehicle [[exhaust gas|exhausts]], etc.); |
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* [[Seawater]] ingress (high volumes of salt and micro-biota); |
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* Direct ingress of [[river]] water (high volumes of micro-biota); |
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* Direct ingress of manmade liquids (illegal disposal of pesticides, used oils, etc.); |
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*[[Highway]] drainage (oil, de-icing agents, rubber residues); |
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*[[Storm]] drains (almost anything, including cars, shopping trolleys, trees, cattle, etc.); |
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*[[blackwater (waste)|Blackwater]] (surface water contaminated by sewage); |
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*Industrial waste |
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*[[Industry|industrial]] site drainage (silt, sand, alkali, oil, chemical residues); |
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**Industrial cooling waters (biocides, heat, slimes, silt); |
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**Industrial process waters; |
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**Organic or bio-degradable waste, including waste from [[abattoir]]s, [[creamery|creameries]], and [[ice cream]] manufacture; |
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**Organic or non bio-degradable/difficult-to-treat waste ([[pharmaceutical]] or [[pesticide]] manufacturing); |
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**extreme [[pH]] waste (from [[acid]]/[[alkali]] manufacturing, metal plating); |
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**[[Toxic]] waste (metal [[plating]], [[cyanide]] production, [[pesticide]] manufacturing, etc.); |
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**[[Solids]] and [[Emulsion]]s ([[paper]] manufacturing, foodstuffs, lubricating and hydraulic [[oil]] manufacturing, etc.); |
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**[[Agriculture|agricultural]] drainage, direct and diffuse. |
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==Wastewater constituents== |
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The composition of wastewater varies widely. This is a partial list of what it may contain: |
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* Water ( > 95%) which is often added during [[flush toilet|flushing]] to carry waste down a drain; |
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* [[Pathogens]] such as bacteria, [[virus]]es, [[prion]]s and [[parasite|parasitic worms]]; |
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* Non-pathogenic [[bacteria]]; |
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* [[Organic material|Organic]] particles such as [[feces]], [[hair]]s, [[food]], [[vomit]], paper fibers, plant material, [[humus]], etc.; |
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* [[Soluble]] organic material such as [[urea]], fruit sugars, soluble [[protein]]s, [[medication|drugs]], [[pharmaceuticals]], etc.; |
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* [[Inorganic]] particles such as [[sand]], grit, metal particles, [[ceramic]]s, etc.; |
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* Soluble inorganic material such as [[ammonia]], road-salt, sea-salt, [[cyanide]], [[hydrogen sulfide]], [[thiocyanate]]s, [[thiosulfate]]s, etc.; |
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* Animals such as [[protozoa]], [[insect]]s, [[arthropod]]s, small [[fish]], etc.; |
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* Macro-solids such as [[sanitary napkin]]s, [[Diaper|nappies/diapers]], [[condom]]s, [[Hypodermic needle|needle]]s, children's toys, dead animals or plants, etc.; |
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* [[Gases]] such as [[hydrogen sulfide]], [[carbon dioxide]], [[methane]], etc.; |
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* [[Emulsion]]s such as [[paint]]s, [[adhesive]]s, [[mayonnaise]], [[hair]] colorants, emulsified oils, etc.; |
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* [[Toxins]] such as [[pesticide]]s, [[poison]]s, [[herbicide]]s, etc. |
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* [[Pharmaceuticals]] and other hormones. |
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==Wastewater quality indicators== |
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{{Main|Wastewater quality indicators}} |
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Any [[Redox|oxidizable]] material present in a natural waterway or in an industrial wastewater will be oxidized both by [[Biochemistry|biochemical]] (bacterial) or chemical processes. The result is that the oxygen content of the water will be decreased. Basically, the reaction for biochemical oxidation may be written as: |
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:'''Oxidizable material + bacteria + nutrient + O<sub>2</sub> → CO<sub>2</sub> + H<sub>2</sub>O + oxidized [[Inorganic chemistry|inorganics]] such as NO<sub>3</sub> or SO<sub>4</sub>''' |
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Oxygen consumption by reducing chemicals such as sulfides and nitrites is typified as follows: |
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:'''S<sup>--</sup> + 2 O<sub>2</sub> → SO<sub>4</sub><sup>--</sup>''' |
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:'''NO<sub>2</sub><sup>-</sup> + ½ O<sub>2</sub> → NO<sub>3</sub><sup>-</sup>''' |
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Since all natural waterways contain bacteria and nutrients, almost any waste compounds introduced into such waterways will initiate biochemical reactions (such as shown 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 [[biodegradation|biodegradable]] pollutants whereas the COD test measures the oxygen demand of oxidizable pollutants. |
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The so-called 5-day BOD measures the amount of oxygen consumed by biochemical oxidation of waste contaminants in a 5-day period. The total amount of oxygen consumed when the biochemical reaction is allowed to proceed to completion is called the Ultimate BOD. Because the Ultimate BOD is so time consuming, the 5-day BOD has been almost universally adopted as a measure of relative pollution effect. |
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There are also many different COD tests of which the 4-hour COD is probably the most common. |
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There is no generalized correlation between the 5-day BOD and the ultimate BOD. Similarly there is no generalized correlation between BOD and COD. It is possible to develop such correlations for specific waste contaminants in a specific waste water stream but such correlations cannot be generalized for use with any other waste contaminants or waste water streams. This is because the composition of any waste water stream is different. As an example an effluent consisting of a solution of simple [[sugar]]s that might discharge from a [[confectionery]] factory is likely to have organic components that degrade very quickly. In such a case, the 5 day BOD and the ultimate BOD would be very similar since there would be very little organic material left after 5 days. However a final effluent of a sewage treatment works serving a large industrialised area might have a discharge where the ultimate BOD was much greater than the 5 day BOD because much of the easily degraded material would have been removed in the sewage treatment process and many industrial processes discharge difficult to degrade organic molecules. |
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The laboratory test procedures for the determining the above oxygen demands are detailed in many standard texts. American versions include the "Standard Methods For the Examination Of Water and Wastewater" <ref>[http://www.standardmethods.org Standard Methods of the Examination of Water and Wastewater]</ref> |
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==Sewage disposal== |
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[[File:Wastewater effluent.JPG|thumb|right|Industrial wastewater effluent with neutralized pH from tailing runoff. Taken in Peru.|300px]] |
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In some urban areas, sewage is carried separately in [[sanitary sewer]]s and runoff from streets is carried in [[storm drain]]s. Access to either of these is typically through a [[manhole]]. During high precipitation periods a [[sanitary sewer overflow]] can occur, forcing untreated sewage to flow back into the environment. This can pose a serious threat to [[public health]] and the surrounding environment. |
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Sewage may drain directly into major [[drainage basin|watershed]]s with minimal or no treatment. When untreated, sewage can have serious impacts on the quality of an environment and on the health of people. [[Pathogen]]s 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. |
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==Treatment== |
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{{Further|[[Sewage treatment]] and [[Industrial wastewater treatment]]}} |
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There are numerous processes that can be used to clean up waste waters depending on the type and extent of contamination. Most wastewater is treated in industrial-scale [[sewage treatment|wastewater treatment plants]] (WWTPs) which may include physical, chemical and biological treatment processes. However, the use of [[septic tank]]s and other On-Site Sewage Facilities ([[OSSF]]) is widespread in rural areas, serving up to one quarter of the homes in the U.S.<ref>[http://cfpub.epa.gov/owm/septic/septic.cfm?page_id=261 "Septic Systems" US EPA. 2011]</ref> The most important aerobic treatment system is the activated sludge process, based on the maintenance and recirculation of a complex biomass composed by micro-organisms able to absorb and adsorb the organic matter carried in the wastewater. Anaerobic processes are widely applied in the treatment of industrial wastewaters and biological sludge. Some wastewater may be highly treated and reused as [[reclaimed water]]. For some waste waters [[ecological]] approaches using [[reed bed]] systems such as [[constructed wetland]]s may be appropriate. Modern systems include tertiary treatment by micro filtration or synthetic membranes. After membrane filtration, the treated wastewater is indistinguishable from waters of natural origin of drinking quality. [[Nitrate]]s can be removed from wastewater by microbial [[denitrification]], for which a small amount of [[methanol]] is typically added to provide the bacteria with a source of carbon. Ozone Waste Water Treatment is also growing in popularity, and requires the use of an ozone generator, which decontaminates the water as Ozone bubbles percolate through the tank. |
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Disposal of wastewaters from an industrial plant is a difficult and costly problem. Most petroleum refineries, chemical and petrochemical plants<ref>{{cite book | author=Beychok, Milton R. | title=[[Aqueous Wastes from Petroleum and Petrochemical Plants]] | edition=1st | publisher=John Wiley & Sons | year=1967 | id= [[LCCN]] 67019834}}</ref><ref>{{cite book|author=Tchobanoglous, G., Burton, F.L., and Stensel, H.D.|title=Wastewater Engineering (Treatment Disposal Reuse) / Metcalf & Eddy, Inc.|edition=4th|publisher=McGraw-Hill Book Company|year=2003|isbn=0-07-041878-0}}</ref> have onsite facilities to treat their wastewaters so that the pollutant concentrations in the treated wastewater comply with the local and/or national regulations regarding disposal of wastewaters into community treatment plants or into rivers, lakes or oceans. Other Industrial processes that produce a lot of waste-waters such as paper and pulp production has created environmental concern leading to development of processes to recycle water use within plants before they have to be cleaned and disposed of.<ref>J. F. Byrd, M. D. Ehrke, J. I. Whitfield. (1984) [http://www.jstor.org/stable/25042250 "New Bleached Kraft Pulp Plant in Georgia: State of the Art Environmental Control"] ''Water pollution control federation'' '''56'''(4): 378–385.</ref> |
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==Reuse== |
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Treated wastewater can be reused as [[drinking water]], in industry ([[cooling towers]]), in artificial recharge of aquifers, in agriculture (70% of Israel's [[irrigated]] agriculture is based on highly purified wastewater){{Citation needed|date=February 2007}} and in the rehabilitation of natural ecosystems (Florida's [[Everglades]]). |
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===Algal fuel=== |
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{{Main|Algal fuel}} |
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[[Woods Hole Oceanographic Institution]] and [[Harbor Branch Oceanographic Institution]], following the conclusions of the [[USDOE]]´s [[Aquatic Species Program]], use wastewater for breeding [[algae]]. The wastewater from domestic and industrial sources contain rich organic compounds, which accelerate the growth of algae. This algae can be used to produce [[algal fuel]]s<ref>[http://www.merinews.com/catFull.jsp?articleID=135399 Biofuels from industrial/domestic wastewater<!-- Bot generated title -->]</ref> |
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[[Algaewheel]], based in [[Indianapolis, Indiana]], presented a proposal to build a new wastewater treatment facility in [[Cedar Lake, Indiana]] that uses algae to treat municipal wastewater and uses the [[sludge]] [[byproduct]] to produce biofuel.<ref>{{cite web |
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| url= http://www.algaewheel.com | title= Algaewheel — Wastewater Treatment Specialists |
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| accessdate= 2008-06-18 }}</ref><ref> |
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{{cite web |
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| url= http://www.ewire.com/display.cfm/Wire_ID/4808 |
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| title= Indiana Company to Submit Proposal to Utilize Algae to Treat Wastewater and Create Renewable Energy |
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| date= 2008-06-12 |publisher= E-Wire |
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| accessdate= 2008-06-18 }}</ref> |
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==Etymology== |
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The words "sewage" and "[[sanitary sewer|sewer]]" came from [[Old French]] ''essouier'' = "to drain", which came from [[Latin]] ''exaquāre''. Their formal Latin antecedents are ''exaquāticum'' and ''exaquārium''. |
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==Legislation== |
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===European Union=== |
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{{Main|Directive on Urban Waste Water Treatment}} |
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Council [[Directive 91/271/EEC]] on Urban Waste Water Treatment was adopted on 21 May 1991,<ref>http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:31991L0271:EN:NOT</ref> amended by the Commission [[Directive 98/15/EC]].<ref>http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:31998L0015:EN:NOT</ref> |
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[[Commission Decision 93/481/EEC]] defines the information that Member States should provide the Commission on the state of implementation of the Directive.<ref>http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:31993D0481:EN:NOT</ref> |
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==See also== |
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{{Portal|Water}} |
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* [[APHA color]] |
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* [[ATP Test]] |
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* [[Directive on Urban Waste Water Treatment]] in European Union |
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* [[Ecological sanitation]] |
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* [[Industrial water treatment]] |
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* [[List of waste types]] |
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* [[List of waste water treatment technologies]] |
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* [[Pt/Co scale]] |
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* [[Rain garden]]s |
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* [[Sanitation]] |
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* [[Septic tank]] |
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* [[Sewage treatment]] |
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* [[combined sewer|Sewer]] |
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* [[sanitary sewer|Sewerage]] |
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* [[The Environmental Institute]] |
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* [[Waste management]] |
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* [[Water management]] |
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* [[Water pollution]] |
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* [[Water resources]] |
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* [[Water treatment]] |
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{{Commons category|Wastewater}} |
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==References== |
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{{Reflist|2}} |
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{{Pollution}} |
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{{Use dmy dates|date=January 2011}} |
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[[Category:Chemical engineering]] |
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[[Category:Environmental engineering]] |
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[[Category:Aquatic ecology]] |
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[[Category:Sewerage]] |
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[[Category:Water pollution]] |
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[[Category:Technical terminology]] |
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[[ar:مخلفات سائلة]] |
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[[cs:Odpadní voda]] |
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[[de:Abwasser]] |
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[[et:Reovesi]] |
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[[eu:Ur zikin]] |
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[[fa:پساب]] |
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[[fr:Eaux usées]] |
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[[it:Acque reflue]] |
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[[he:שפכים]] |
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[[lt:Nuotekos]] |
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[[hu:Szennyvíz]] |
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[[nl:Afvalwater]] |
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[[no:Avløpsvann]] |
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[[oc:Aigassas]] |
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[[pl:Ścieki]] |
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[[pt:Águas residuais]] |
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[[ru:Сточные воды]] |
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[[sc:Abas residuales]] |
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[[sk:Odpadová voda]] |
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[[sr:Отпадне воде]] |
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[[sv:Avloppsvatten]] |
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[[ta:கழிவு நீர்]] |
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[[uk:Стічні води]] |
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