'''The Single Pit is one of the most widely used sanitation technologies. Excreta, along with anal cleansing materials (water or solids) are deposited into a pit. Lining the pit prevents it from collapsing and provides support to the superstructure.'''
This system is based on As the use of a single pit technology to collect and store Excreta. The system can be used with or without Flushwaterfills, depending on two processes limit the User Interfacerate of accumulation: leaching and degradation. Inputs to the system can include Urine, Faeces, Anal Cleansing Water, Flushwater and Dry Cleansing Materials. The use water percolate into the soil through the bottom of Flushwater and/or Anal Cleansing Water will depend on water availability the pit and local habit. The User Interface for this system can either be a Dry Toilet (U.1) or a Pour Flush Toilet (U.4). A Urinal (U.3) could additionally be used. The User Interface is directly connected to a Single Pit (S.2) or a Single Ventilated Improved Pit (VIPwall, S.3) for Collection and Storage/Treatmentwhile microbial action degrades part of the organic fraction.
When '''Design Considerations''': On average, solids accumulate at a rate of 40 to 60 L per person/year and up to 90 L per person/year if dry cleansing materials such as leaves or paper are used. The volume of the pit is full there are several optionsshould be designed to contain at least 1,000 L. If there is spaceTypically, the pit can be filled with soil is at least 3 m deep and a fruit or ornamental tree can be planted, which will thrive 1 m in diameter. If the nutrient rich environment (Dpit diameter exceeds 1.1)5 m, and a new pit builtthere is an increased risk of collapse. This is generally only possible when the superstructure is mobileDepending on how deep they are dug, some pits may last 20 or more years without emptying. AlternativelyTo prevent groundwater contamination, the faecal Sludge that is generated from bottom of the Collection and Storage/Treatment technology has to pit should be removed and transported for further treatment. The Conveyance technologies that can be used include Human-Powered Emptying and Transport (C.at least 2) or Motorized Emptying and Transport m above groundwater level (C.3rule of thumb). A vacuum truck can only empty liquid faecal SludgeIf the pit is to be reused, it should be lined.
As Pit lining materials can include brick, rot-resistant timber, concrete, stones, or mortar plastered onto the soil. If the untreated faecal Sludge soil is highly pathogenicstable (i.e., no presence of sand or gravel deposits or loose organic materials), human contact and direct agricultural application should the whole pit need not be avoidedlined. The Sludge that is removed bottom of the pit should be transported remain unlined to a dedicated faecal Sludge treatment facility (Tallow for the infiltration of liquids out of the pit.13-T.17)As liquid leaches from the pit and migrates through the unsaturated soil matrix, pathogenic germs are sorbed to the soil surface. In the event that such a facility is not easily accessiblethis way, the faecal Sludge pathogens can be discharged removed prior to a Transfer Station (Ccontact with groundwater.7). From thereThe degree of removal varies with soil type, distance travelled, moisture and other environmental factors and, thus, it will be transported is difficult to estimate the treatment facility by distance necessary between a motorized vehicle (C.3)pit and a water source. A technology selection tree for faecal Sludge treatment plants minimum horizontal distance of 30m is provided in Strande et al., 2014 (see Sector Development Tools, p. 9). (Semi-) Centralized Treatment technologies (T.1-T.17) produce both Effluent and Sludge, which may require further treatment prior normally recommended to limit exposure to Use and/or Disposal. For example, Effluent from a faecal Sludge treatment facility could be co-treated with wastewater in Waste Stabilization Ponds (T.5) or Constructed Wetlands (T.7-T.9)microbial contamination.
Options for the Use and/When it is not possible to dig a deep pit or Disposal of the treated Effluent include Irrigation (D.6)groundwater level is too high, Fish Ponds (Da raised pit can be a viable alternative: the shallow pit can be extended by building the pit upwards with the use of concrete rings or blocks.9), Floating Plant Ponds (D.10) or discharge A raised pit can also be constructed in an area where flooding is frequent in order to a keep water body (Water Disposal/Groundwater Recharge, Dfrom flowing into the pit during heavy rain.11)Another variation is the unlined shallow pit that may be appropriate for areas where digging is difficult. After adequate treatmentWhen the shallow pit is full, Sludge it can either be used in agriculture (D.5) or brought to covered with leaves and soil, and a Storage/Disposal site small tree can be planted (see Arborloo, D.121).
A [[Single Ventilated Improved Pit|Ventilated Improved Pit]] (VIP, S.3) is slightly more expensive than a single pit, but greatly reduces the nuisance of flies and odours, while increasing comfort. If a urine-diverting User Interface is used, only faeces are collected in the pit and leaching can be minimized.
[[Image:single pit system - compendium.png|none|1000px|]]
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====Considerations====
This system should be chosen only where there is either enough space to continuously dig new pits or when there is an appropriate way to empty, treat and dispose of the faecal Sludge. In dense urban settlements, there may not be sufficient space to access a pit for desludging or to make a new pit. This system is, therefore, best suited to rural and peri-urban areas where the soil is appropriate for digging pits and absorbing the leachate. It is not recommended for areas prone to heavy rains or flooding, which may cause pits to overflow.
Some Greywater in the pit may help degradation, but excessive amounts of Greywater may lead to quick filling of the pit and/or excessive leaching. All types of Dry Cleansing Materials can be discarded into the pit, although they may shorten the pit life and make it more difficult to empty. Whenever possible, Dry Cleansing Materials should be disposed of separately. This system is one of the least expensive to construct in terms of capital cost. However, the maintenance costs may be considerable, depending on the frequency and method of pit emptying. If the ground is appropriate and has good absorptive capacity, the pit may be dug very deep (> 5m) and can be used for several years without emptying (up to 20 or more years). However, the groundwater level and use should be taken into consideration when digging pits in order to avoid contaminating it. Although different types of pits are common in most parts of the world, a well-designed pit-based system with appropriate transport, treatment and use or disposal is rare.
Another variation is the unlined shallow pit that may be appropriate for areas where digging is difficult. When the shallow pit is full, it can be covered with leaves and soil and a small tree can be planted. This concept is called the Arborloo and is a successful way of avoiding costly emptying, while containing excreta, and reforesting an area. The Arborloo is discussed in more detail on the [[Fill and Cover - Arborloo]] section.
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{{procontable | pro=- Can be built and repaired with locally available materials.<br> - Does not require a constant source of water.<br> - Can be used immediately after construction. <br> - Low (but variable) capital costs depending on materialsand pit depth. <br> - Small land area required. <br> | con=- Flies and odours are normally noticeable. <br> - Sludge requires secondary treatment Low reduction in BOD and/or appropriate dischargepathogens with possible contamination of groundwater. <br> - Costs to empty may be significant compared to capital costs. <br> - Low reduction in BOD Sludge requires secondary treatment and pathogens/or appropriate discharge.
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===AdequacyAppropriateness=== Treatment processes in a single pit (aerobic, anaerobic, dehydration, composting or otherwise) are limited and, therefore, pathogen reduction and organic degradation is not significant. However, since the excreta are contained, pathogen transmission to the user is limited.
Treatment processes in the Single Pit (aerobic, anaerobic, dehydration, composting or otherwise) are limited and therefore, pathogen reduction and organic degradation is not significant. However, since the excreta are contained, pathogen transmission to the user is limited. Single Pits pits are appropriate for rural and peri-urban areas; Single Pits in urban or dense densely populated areas they are often difficult to empty and/or have sufficient insufficient space for infiltration. Single Pits pits are especially appropriate when water is scarce and where there is a low groundwater table. They are not suited for rocky or compacted soils (that are difficult to dig) , or for areas that flood frequently.
===Health Aspects/Acceptance===
A simple Single Pit is an improvement to open defecation; however, it still poses health risks:
A simple Single Pit is an improvement to open defecation; however, it still poses health risks:
* Leachate can contaminate groundwater;
* Stagnant water in pits may promote insect breeding;
*Pits are susceptible to failure/overflowing during floods.
Single Pits pits should be constructed at an appropriate distance from homes to minimize fly and odour nuisances and to ensure convenience and safe travelsafety.
===Upgrading===
A [[Single Ventilated Improved Pit|Ventilated Improved Pit (VIP)]] is slightly more expensive but greatly reduces the nuisance of flies and odours, while increasing comfort and usability. For more information on the VIP please refer to the [[Single Ventilated Improved Pit|Single Pit VIP]] page. When two pits are dug side-by-side, one can be used while the contents of the other pit are allowed to mature for safer emptying. For more information on dual pit technologies refer to [[Double Ventilated Improved Pit|Double Pit VIP]] and [[Twin Pits for Pour Flush]] pages.
===Operation & Maintenance=== There is no daily maintenance associated with a simple Single Pitsingle pit apart from keeping the facility clean. However, when the pit is full it can be a) pumped out and reused or b) the superstructure and squatting plate can be moved to a new pit and the previous pit covered and decommissioned, which is only advisable if plenty of land area is available.
===Field experiences===
===References ===
* ARGOSS (2001). Guidelines for Assessing the Risk to Groundwater from on-Site Sanitation. British Geological Survey Commissioned Report, CR/01/142, Keyworth, UK. Available at: www.bgs.ac.uk* Brandberg, B. (1997). Latrine Building. A Handbook for Implementation of the Sanplat System. Intermediate Technology Publications, London, UK. (A good summary of common construction problems and how to avoid mistakes.) * Franceys, R., Pickford, J. and Reed, R. (1992). A guide Guide to the development Development of on-site sanitationSite Sanitation. WHO, Geneva, CH. Available at: www. susana.org/library (For information on accumulation rates, infiltration rates, general construction and example design calculations.) * LewisGraham, JWJ. P.and Polizzotto, et alM. L. (19822013). The Risk of Pit Latrines and Their Impacts on Groundwater Pollution by on-site Sanitation in Developing CountriesQuality: A Systematic Review. International Reference Centre for Waste DisposalEnvironmental Health Perspectives, DübendorfNational Institute of Environmental Health Sciences, Switzerland. (Detailed study regarding the transport and die-off of microorganisms and implications for locating technologies.) * MorganResearch Triangle Park, PUS. (2007). Toilets That Make CompostAvailable at: Low-cost, sanitary toilets that produce valuable compost for crops in an African contextwww. Stockholm Environment Institute, Swedenehponline. (Describes how to build a support ring/foundation.)org* Pickford, J. (1995). Low Cost Sanitation. A Survey of Practical Experience. Intermediate Technology Publications, London, UK. (Information on how to calculate pit size and technology life)* Robens Institute (1996).)Fact Sheets on Environmental Sanitation. Fact Sheet 3.4: Simple Pit Latrines. University of Surrey, UK and WHO, Geneva, CH. Available at: www.who.int
===Acknowledgements===
{{:Acknowledgements Sanitation}}