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'''Pre-treatment is the preliminary removal of wastewater or sludge constituents, such as oil, grease, and various solids (e.g., sand, fibres and trash). Built before a Conveyance or Treatment technology, pre-treatment units can retard the accumulation of solids and minimize subsequent blockages. They can also help reduce abrasion of mechanical parts and extend the life of the sanitation infrastructure.'''
An under-the-sink grease trap is relatively low cost, but must be cleaned frequently (once a week to once a month), whereas a larger grease interceptor has
a higher capital cost, but is designed to be pumped out every 6 to 12 months. If designed to be large enough, grease traps can also remove grit and other settleable solids through sedimentation, similar to [[Septic Tank | Septic Tanks ]] (S.9).
====Screen====
inclined screens or bar racks. The spacing between the bars usually is 15 to 40 mm, depending on cleaning patterns. Screens can be cleaned by hand or mechanically raked. The latter allows for a more frequent solids removal and, correspondingly, a smaller design.
====Grit Chamber====
Where subsequent treatment technologies could be hindered or damaged by the presence of sand, grit chambers (or sand traps) allow for the removal of heavy inorganic fractions by settling. There are three general types of grit chambers: horizontal-flow, aerated, or vortex chambers. All of these designs allow heavy grit particles to settle out, while lighter, principally organic particles remain in suspension.
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===Appropriateness===
Grease traps should be applied where considerable amounts of oil and grease are discharged. They can be installed at single households, restaurants or industrial sites. Grease removal is especially important where there is an immediate risk of clogging (e.g., a constructed wetland for the treatment of greywater). Screening is essential where solid waste may enter a sewer system, as well as at the entrance of treatment plants. Trash traps, e.g., mesh boxes, can also be applied at strategic locations like market drains. A grit chamber helps prevent sand deposits and abrasion in wastewater treatment plants, particularly, where roads are not paved and/or stormwater may enter the sewer system. As laundries release high amounts of fabric fibres and particles with their wastewater, they should be equipped with lint trap devices.
===Health Aspects/Acceptance=== The removal of solids and grease from pre-treatment technologies is not pleasant and, if households or community members are responsible for doing this, it may not be done regularly. Hiring professionals to do the removal may be the best option though it is costly. The people involved in the cleaning may come in contact with pathogens or toxic substances; therefore, adequately protecting oneself with safety clothes, i.e., boots and gloves, is essential.
===Operation & Maintenance===
===References===
* Crites, R. and Tchobanoglous, G. (1998). Small and Decentralized Wastewater Management Systems. WCB/McGraw-Hill, New York, US. * Morel, A. and Diener, S. (2006Book). Greywater Management in Low and Middle-Income Countries. Review of Different Treatment Systems for Households or Neighbourhoods. Eawag (Department Sandec), Dübendorf, CH.:Available at: [http://www.sandec.ch sandec.ch]
* RobbinsMorel, D. MA. and LigonDiener, G.CS. (20142006). How to Design Wastewater [https://www.susana.org/en/knowledge-hub/resources-and-publications/library/details/947 Greywater Management in Low and Middle-Income Countries]. Review of Different Treatment Systems for Local Conditions in DevelopingCountriesHouseholds or Neighbourhoods. IWA PublishingEawag (Department Sandec), LondonDübendorf, UKCH.
* TchobanoglousRobbins, G., Burton, FD. LM. and StenselLigon, HG. DC. (20042014). How to Design Wastewater Engineering: Treatment and ReuseSystems for Local Conditions in Developing Countries. IWA Publishing, Metcalf & EddyLondon, 4th EdUK. (Internat. Ed.Book). McGraw-Hill, New York, US.
* UlrichTchobanoglous, AG. (Ed.), ReuterBurton, SF. (EdL.)and Stensel, Gutterer, BH. D. (Ed.2004), Sasse, L.Wastewater Engineering: Treatment and Reuse, PanzerbieterMetcalf & Eddy, T4th Ed. and Reckerzügel, T(Internat. (2009)Ed. DecentralisedWastewater Treatment Systems (DEWATS) and Sanitation in Developing Countries. A Practical Guide. WEDC, LoughboroughUniversityMcGraw-Hill, LeicestershireNew York, UKUS.(Book)
* Wastewater Solutions for DevelopmentUlrich, A. (Ed.), Reuter, S. (Ed.), Gutterer, B. (Ed.), Sasse, L., Panzerbieter, T. and Reckerzügel, T. (2009).:[httphttps://watsanexpwedc-knowledge.lboro.ningac.comuk/resources/pagebooks/pretreatmentandDEWATS_-grease watsanexp_Chapter_01.ningpdf Decentralised Wastewater Treatment Systems (DEWATS) and Sanitation in Developing Countries.com/page/pretreatmentand-greaseA Practical Guide] (last accessed February 2014). WEDC, Loughborough University, Leicestershire, UK.
===Acknowledgements===
{{:Acknowledgements Sanitation}}
