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Septic Tank

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Input1=Blackwater|Input2=GreywaterBrownwater|Input3=Greywater| Input4= |Input5=|Output1=Faecal SludgeEffluent |Output2=Effluent Sludge | Output3= | Output4= | Output5=

|english_link=Septic_Tank

|french_link=Fosse_Septique

[[Image:Icon_septic_tank.png |right|80px]]

[[Image:Aqua_privyss.PNG|thumb|right|200px|[[Aqua privy |Aqua privy]]]]

'''A Septic Tank septic tank is a watertight chamber made of concrete, fibreglass, PVC or plastic, for the storage and treatment of through which blackwater and greywaterflows for primary treatment. Settling and anaerobic processes reduce solids and organics, but the treatment is only moderate.'''

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A Septic Tank should typically have at least two chambers. The first chamber should be at least 50% of Liquid flows through the total length tank and when there are only two chambersheavy particles sink to the bottom, it should be 2/3 of while scum (mostly oil and grease) floats to the total lengthtop. Most of Over time, the solids that settle out in to the first chamberbottom are degraded anaerobically. The baffleHowever, or the separation between rate of accumulation is faster than the chambersrate of decomposition, is to prevent scum and solids from escaping with the accumulated sludge and scum must be periodically removed. The effluentof the septic tank must bedispersed by using a [[Soak Pit]] (D. A T7) or [[Leach Field]] (D.8), or transported to another treatment technology via a [[Solids-free Sewer | Solids-shaped outlet pipe will further reduce Free Sewer]] (C.5). Generally, the scum removal of 50% of solids, 30 to 40% of BOD and a 1-log removal of E. coli can be expected in a well-designed and maintained septic tank, although efficiencies vary greatly depending on operation and maintenance and solids that are dischargedclimatic conditions.

Liquid flows into the ===Design Considerations=== A septic tank and heavy particles sink to should have at least two chambers. The first chamber should be at least 50% of the bottomtotal length, while scum (oil and fat) floats to when there are only two chambers, it should be two thirds of the toptotal length. With time, Most of the solids that settle to out in the bottom are degraded anaerobicallyfirst chamber. HoweverThe baffle, or the rate of accumulation is faster than separation between the rate of decompositionchambers, is to prevent scum and solids from escaping with the accumulated sludge must be removed at some pointeffluent. A T-shaped outlet pipe further reduces the scum and solids that are discharged. Generally, Septic Tanks should be emptied every 2 Accessibility to 5 years, although they should be checked yearly to ensure proper functioningall chambers (through access ports) is necessary for maintenance.

Septic tanks should be vented for controlled release of odorous and potentially harmful gases. The design of a Septic Tank septic tank depends on the number of users, the amount of water used per capita, the average annual temperature, the pumping desludging frequency and the characteristics of the wastewater. The retention time should be designed for 48 hours to achieve moderate treatment. ===Aqua privy===A variation of the Septic Tank is called an aqua privy, which is a simple storage and settling tank located directly below the toilet, so that the excreta fall into the tank. A housing or shed is built over the tank. A vent pipe with a fly screen at the top end is attached to the housing. To prevent odours from surfacing, a water seal must be maintained by adding sufficient water per toilet visit to the tank via the drop-pipe to replace any losses. However, this may not completely prevent smells and the tank must be frequently desludged. The effluent must be dispersed by using a [[Soak Pit]] or [[Leach Field]] or by transporting the effluent to another treatment technology via a [[Simplified Sewers]] or [[Solids-free Sewer|Solids-Free]].

A variation of the septic tank is called an [[Aqua privy | Aquaprivy]]. This is a simple storage and settling tank that is located directly below the toilet so that the excreta fall into it. The Aquaprivy has a low treatment efficiency.

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{{procontable | pro=

- Can be built Simple and repaired with locally available materials. <br> - Long service life. robust technology<br> - No real problems with flies or odours if used correctly. electrical energy is required<br> - Low capital costs, moderate operating costs depending on water and emptying. <br> - Small land area required. Long service life<br> - No electrical energy Small land area required. (can be built underground)| con=- Low reduction in pathogens, solids and organics. <br> - Regular desludging must be ensured<br>- Effluent and sludge require secondary further treatment and/or appropriate discharge. <br> - Requires constant source of water.

}}

===AdequacyAppropriateness===This technology is most commonly applied at the household level. Larger, multi-chamber septic tanks can be designed for groups of houses and/ or public buildings (e.g., schools). A Septic Tank septic tank is appropriate where there is a way of dispersing or transporting the effluent. Because the Septic Tank must be desludged regularly, a vacuum truck should be able to access the location. Often Septic Tanks are installed in the home, under the kitchen or bathroom which makes emptying difficult. If Septic Tanks septic tanks are used in densely populated areas, on-site onsite infiltration should not be used , otherwise , the ground will become oversaturated and excreta contaminated, and wastewater may rise up to the surface , posing a serious health risk. Instead, the Septic Tank septic tanks should be connected to a sewer and some type of Conveyance technology, through which the effluent should be is transported to a subsequent treatment Treatment or disposal Disposal site. Larger, multi-chamber Septic Tanks can be designed for groups of houses and/or public buildings (i.e. schools). Generally, the removal of 50% of solids, 30 to 40 % of biochemical oxygen demand (BOD) and a 1-log removal of E.coli can be expected in a well designed Septic Tank although efficiencies vary greatly depending on operation and maintenance and climactic conditions.

Septic Tanks can be installed in every type of climate although the efficiency will be affected in colder climates. Even though the Septic Tank is septic tanks are watertight, it should is not be constructed recommended to construct them in areas with high groundwater tables or where there is frequent flooding. Aquaprivies can Because the septic tank must be built indoors and above ground and are appropriate for rocky or floodregularly de-prone areas where pits or other technologies would not sludged, a vacuum truck should be appropriateable to access the location. HoweverOften, septic tanks are installed in the home, under the kitchen or bathroom, because they require frequent which makes emptying and constant maintenancedifficult. Septic tanks can be installed in every type of climate, they although the efficiency will be lower in colder climates. They are only recommended for very specific applicationsnot efficient at removing nutrients and pathogens.

===Health Aspects/Acceptance===

Although the removal of pathogens is not highUnder normal operating conditions, the entire tank is below the surface so users do not come in contact with any the influent or effluent. Effluent, scum and sludge must behandled with care as they contain high levels of the wastewaterpathogenic organisms. Users should be careful when opening the tank because noxious and flammable gases may be released. Septic Tanks should have a vent. A vacuum truck should be used to empty the sludge from the Septic Tank. Users should not attempt to empty the pit themselves except with a manual technology like the [[Human-Powered Emptying and Transport|Gulper]]. ===Upgrading===A Septic Tank that is connected to a [[Leach Field]] or a [[Soak Pit]] can later be connected to a [[Solids-free Sewer]] if/when one is installed.

===Operation & Maintenance===Septic Tanks Because of the delicate ecology, care should be checked taken not to ensure that they are watertight and discharge harsh chemicals into the levels of the scum septic tank. Scum and sludge should levels need to be monitored to ensure that the tank is functioning well. Because of the delicate ecologyGenerally, care septic tanks should be taken not emptied every 2 to discharge harsh chemicals into the 5 years. This is best done by using a [[Motorized Emptying and Transport | Motorized Emptying and Transport]] technology (C.3), but [[Human-Powered Emptying and Transport | Human-Powered Emptying]] (C.2) can also be an option. Septic Tank. The sludge tanks should be removed annually using a vacuum truck checked from time to time to ensure proper functioning of the Septic Tankthat they are watertight.

===Field experiences===

===References===

Detailed Design Information:* MaraCrites, DDR. and Tchobanoglous, G. (19961998). [http://books.googleSmall and Decentralized Wastewater Management Systems.com/books/aboutWCB/Low_cost_urban_sanitation.html?id=WOgeAQAAIAAJ LowMcGraw-Cost Urban Sanitation]. Wiley, Chichester, UK. SizingHill, volume and emptying calculations and example design solutionsNew York, Chapter 6US.

* PolprasertMara, CD. and Rajput, VSD. (19821996). [http://docs.watsan.net/Scanned_PDF_Files/Class_Code_3_Sanitation/323.2Low-82SE-884.pdf Environmental Cost Urban Sanitation Reviews: Septic Tank and Septic Systems]. Environmental Sanitation Information CenterWiley, BangkokChichester, AITUK. (Sizing, Thailand. pp 68–74. Comprehensive volume and emptying calculations and exampledesign manual.solutions – Chapter 6)

* Sasse, L. Oxfam (19982008). DEWATSSeptic Tank Guidelines. Technical Brief. Oxfam GB, Oxford, UK. :Available at: [http://wwwpolicy-practice.indiawaterportaloxfam.org/sites/indiawaterportal.uk policy-practice.oxfam.org/files/Decentralised_%20wastewater_%20treatment_%20in_%20developing_%20countries_A_%20handbook_%20by_%20BORDA_1998.pdf Decentralised Wastewater Treatment in Developing Countriesuk]. BORDA, Bremen Overseas Research and Development Association, Bremen, Germany. Excel® Spreadsheet codes for sizing septic tanks.

General * Polprasert, C. and Rajput, V. S. (1982). Environmental Sanitation Reviews. Septic Tank and Septic Systems. Environmental Sanitation Information:Center, AIT, Bangkok, TH. pp. 68-74. (Comprehensive design manual)

* CritesUlrich, RA. and Tchobanoglous(Ed.), Reuter, GS. (1998Ed.), Gutterer, B. [http://books(Ed.google), Sasse, L.com/books/about/Small_and_decentralized_wastewater_manag, Panzerbieter, T.html?id=yx9SAAAAMAAJ Small and Decentralized Reckerzügel, T. (2009). Decentralised Wastewater Management Treatment Systems](DEWATS) and Sanitation in Developing Countries. A Practical Guide. WCB and McGraw-HillWEDC, Loughborough University, New YorkLeicestershire, USAUK.

===Acknowledgements===

{{:Acknowledgements Sanitation}}

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