Water treatment
239926
225975915
2008-07-16T08:08:50Z
81.244.203.8
/* Desperate need in developing countries */
{{mergefrom|Appropriate_technology#Water_treatment}}
[[Image:Bragança43.jpg|thumb|300px|A water treatment plant in northern [[Portugal]].]]
'''Water treatment''' describes a process used to make water more acceptable for a desired end-use. These can include use as [[drinking water]], industrial processes, medical and many other uses. The goal of all water treatment process is to remove existing contaminants in the water, improving it for subsequent use.
The goal may be to allow treated water to discharge into the [[natural environment]] without adverse ecological impact. These processes may be physical such as [[settling]], chemical such as [[disinfection]] or [[coagulation]], or biological such as lagooning, [[slow sand filter|slow sand filtration]] or [[activated sludge]].
==Desperate need in developing countries==
As of 2006, waterborne diseases are estimated to cause 1.8 million deaths each year. These deaths are attributable to bad public sanitation systems and it is clear that proper [[sewerage]] (or other options as [[greywater treatment|small-scale water treatment]]) need to be installed. <ref>http://www.cdc.gov/safewater/publications_pages/fact_sheets/WW4.pdf "Safe Water System,"] US Centers for Disease Control and Prevention Fact Sheet, June 2006.</ref>
Water may need treatment before use, depending on the source and the intended use (eg drinking water, mere discharge of used water into streams/rivers by factories, ...). High standards are required for purposes as [[drinking water]], yet other applications as redispersement of used water by factories may only require a lower degree of purification. Also, water obtained from [[household connection]]s or [[community water point]]s in low-income countries may not be (reliably) safe for direct human consumption. Water extracted directly from [[surface water]]s and open hand-dug shallow wells nearly always requires treatment.
[[Appropriate technology]] options in water treatment include both community-scale and household-scale point-of-use (POU) designs.<ref name=cawstHWT>Centre for Affordable Water and Sanitation Technology, [http://webmail.cawst.org/documents/Camille/New%20Training%20Materials/HWT%20Manual_Mar%2008.pdf "Household Water Treatment Guide," March 2008.</ref>
The most reliable way to kill microbial pathogenic agents is to heat water to a rolling boil<ref>[http://www.who.int/water_sanitation_health/dwq/GDWQ2004web.pdf] WHO’s Guidelines for Drinking Water Quality</ref>. Other techniques, such as varying forms of filtration, chemical disinfection, and exposure to ultraviolet radiation (including solar UV) have been demonstrated in an array of randomized control trials to significantly reduce levels of waterborne disease among users in low-income countries.<ref>Clasen, T., Schmidt, W., Rabie, T., Roberts, I., Cairncross, S. Interventions to improve water quality for preventing diarrhoea: a systematic review and meta-analysis. British Medical Journal, doi:10.1136/bmj.39118.489931.BE (published 12 March 2007)</ref>
Over the past decade, an increasing number of field-based studies have been undertaken to determine the success of POU measures in reducing waterborne disease. The ability of POU options to reduce disease is a function of both their ability to remove microbial pathogens if properly applied and such social factors as ease of use and cultural appropriateness. Technologies may generate more (or less) health benefit than their lab-based microbial removal performance would suggest.
The current priority of the proponents of POU treatment is to reach large numbers of low-income households on a sustainable basis. Few POU measures have reached significant scale thus far, but efforts to promote and commercially distribute these products to the world's poor have only been under way for a few years.
Parameters for drinking water quality typically fall under two categories: chemical/physical and microbiological. Chemical/physical parameters include heavy metals, trace organics, [[total suspended solids]] (TSS), and turbidity. Microbiological parameters include [[Coliform bacteria]], ''[[E. coli]]'', and specific pathogenic species of [[bacteria]] (such as [[cholera]]-causing ''[[Vibrio cholerae]]''), [[viruses]], and [[protozoan]] [[parasites]].
Chemical parameters tend to pose more of a chronic health risk through buildup of heavy metals although some components like nitrates/nitrites and [[arsenic]] may have a more immediate impact. Physical parameters affect the aesthetics and taste of the drinking water and may complicate the removal of microbial pathogens.
Originally, fecal contamination was determined with the presence of [[coliform bacteria]], a convenient marker for a class of harmful [[feces|fecal]] [[pathogen]]s. The presence of [[fecal coliforms]] (like ''[[Escherichia coli|E. Coli]]'') serves as an indication of contamination by [[sewage]]. Additional contaminants include [[protozoan]] [[oocysts]] such as ''[[Cryptosporidium]] sp.'', ''[[Giardia]] lambia'', ''[[Legionella]]'', and [[viruses]] (enteric)<ref>www.epa.gov/safewater/contaminants/index.html#listmcl</ref>. Microbial pathogenic parameters are typically of greatest concern because of their immediate health risk.
==Drinking water==
{{main|water purification}}
[[Image:Water plant.jpg|right|thumb|Abandoned Water Purification Plant [[Springfield, Tennessee]]]]
'''Water purification''' is the removal of contaminants from untreated water to produce drinking water that is [[purity|pure]] enough for its intended use, most commonly human consumption. Substances that are removed during the process of '''drinking water treatment''' include [[bacteria]], [[algae]], [[virus]]es, [[fungi]], minerals such as iron and sulphur, and man-made chemical [[pollutants]].
==Sewage==
{{main|Sewage treatment}}
'''Sewage treatment''' is the process that removes the majority of the contaminants from wastewater or [[sewage]] and produces both a liquid effluent suitable for disposal to the natural environment and a [[sludge]]. To be effective, sewage must be conveyed to a treatment plant by appropriate [[Sewage collection and disposal|pipes and infrastructure]] and the process itself must be subject to [[Sewage - regulation and administration|regulation and controls]]. Some wastewaters require different and sometimes specialized treatment methods. At the simplest level, treatment of sewage and most wastewaters is carried out through separation of solids from liquids, usually by settlement. By progressively converting dissolved material into solids, usually a biological floc which is then settled out, an effluent stream of increasing purity is produced.
==External links==
{{commons|Water treatment}}
*[http://cohesion.rice.edu/centersandinst/cben/events.cfm?doc_id=10142 Nanotechnology-enabled Water Treatment]-Project NeWT, [http://cben.rice.edu Center for Biological and Environmental Nanotechnology (CBEN), Rice University]
*[http://www.nsf.org National Safety Foundation], rules for equipment that contacts drinking water
*[http://www.water-treatment.org.uk/water_softeners.html Water Softener Reviews]
*[http://watertank.net/why-we-use-plastic.html Code of Federal Register - CFR Title 21 Part 129 Helpful information and water tank installation instructions]
*[http://www.fresh-water-filters.com/municipal_water_treatment.html Health Assessment of Municipal Water Treatment]
*[http://www.marcsteinmetz.com/pages/wasser/ewasser_minis.html picture story by German photographer Marc Steinmetz]
*Stormwater management Tools:
**[http://www.toolkit.net.au/music Model for Urban Stormwater Improvement Conceptualisation (MUSIC)]
[[Category:Physical infrastructure]]
[[Category:Water pollution]]
[[Category:Waste treatment technology]]
[[Category:Water treatment]]
[[fr:Traitement de l'eau]]
[[zh:水处理]]