<!{|style="float: left;"|{{Language-- table at top of page with logo, picture, Application level, Management level, and input-output tables -->box|english_link=Single_Ventilated_Improved_Pit|french_link=Latrine_VIP_à_fosse_unique|spanish_link=Pozo_Simple_Mejorado_Ventilado|hindi_link=coming soon|malayalam_link=coming soon|tamil_link=coming soon | korean_link=coming soon chinese_link=Coming soon | indonesian_link=Coming soon | japanese_link=Coming soon }}|}
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Input1=Excreta|Input2=Blackwater |Input3=Faeces |Input3Input4=Anal cleansing water| Input4= |Input5=Dry Cleansing Materials|Output1=Faecal sludgeSludge| Output2= | Output3= | Output4= | Output5=|english_link=Single_Ventilated_Improved_Pit|french_link=Latrine_VIP_à_fosse_unique|spanish_link=Pozo_Simple_Mejorado_Ventilado
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<br>[[Image:Icon_single_ventilated_improved_pit.png |right|95px80px]]'''The Single VIP is a Ventilatedventilated, Improved Pitimproved pit. It is an improvement over the [[Single Pit | Single Pit ]] (S.2) because continuous airflow through the ventilation pipe vents odours and acts as a trap for flies as they escape towards the light.'''
Despite their simplicity, well-designed Single single VIPs can be completely smell free, and be more pleasant to use than some other water-based technologies. Flies that hatch in the pit are attracted to the light at the top of the ventilation pipe. When they fly towards the light and try to escape, they are trapped by the flyscreen and die. The ventilation also allows odours to escape and minimizes the attraction for flies.
Flies '''Design Considerations:''' The vent pipe should have an internal diameter of at least 110 mm and reach more than 300 mm above the highest point of the toilet superstructure. Wind passing over the top creates a suction pressure within the vent pipe and induces an air circulation. Air is drawn through the User Interface into the pit, moves up inside the vent pipe and escapes into the atmosphere. Care should be taken that hatch objects, such as trees or houses, do not interfere with the air stream. The vent works best in windy areas, but where there is little wind, its effectiveness can be improved by painting the pipe black. The heat difference betweenthe pit are attracted to (cool) and the vent (warm) creates an updraft that pulls the air and odours up and out of the light at pit. To test the top efficacy of the ventilation pipe. When they fly towards , a lit cigarette can be held over the User Interface; the smoke should be pulled down into the pit and up into the light vent and try to escape they are trapped by not remain in the superstructure. The mesh size of the fly-screen must be large enough to prevent clogging with dust and dieallow air to circulate freely. Aluminium screens, with a hole-size of 1.2 to 1. The ventilation also allows odours 5 mm, have proven to escape be the most effective. Typically, the pit is at least 3 m deep and minimizes 1 to 1.5 m in diameter, depending on the attraction for fliesnumber of users. Deep pits can last up to 20 or more years.
The vent pipe should have an internal diameter of at least 110mm to a maximum of 150mm As liquid leaches from the pit and reach more than 300mm above migrates through the highest point of unsaturated soil matrix, pathogenic germs are sorbed to the toilet superstructuresoil surface. The vent works better in windy areas but where there is little windIn this way, its effectiveness pathogens can be improved by painting removed prior to contact with groundwater. The degree of removal varies with soil type, distance travelled, moisture and other environmental factors and, thus, it is difficult to estimate the pipe black; the heat difference distance necessary between the a pit (cool) and the vent (warm) creates an updraft that pulls the air and odours up and out of the pita water source. To test the efficacy A minimum horizontal distance of the ventilation, 30 m between a small, smoky fire can be lit in the pit; and a water source and 2 m between the smoke should be pulled up and out bottom of the vent pipe pit and not remain in the pit or the superstructuregroundwater table is normally recommended to limit exposure to microbial contamination.
The mesh size of When it is not possible to dig a deep pit or the groundwater level is too high, a raised pit can be a viable alternative: the fly screen must shallow pit can be large enough to prevent clogging extended by building the pit upwards with dust and allow air to circulate freely. Aluminum screens, with a hole-size the use of 1concrete rings or blocks.2 A raised pit can also be constructed in an area where flooding is frequent in order to 1.5mm have proven to be keep water from flowing into the most effectivepit during heavy rain.
Care during superstructure design must A single VIP toilet can be taken upgraded to ensure a [[Double Ventilated Improved Pit | Double VIP]] (S.4). A Double VIP has an extra pit so that flies inside while one is in use, the contents of the full pit are not unduly attracted allowed to light through the defecation hole either through utilization of small windows drain, mature and degrade. If a urine-diverting User Interface is used, only faeces are collected in the superstructure or provision of a removable cover for the defectation holepit and leaching can be minimized.
The top diameter of the Single VIP should be between 1 to 1.5mand be dug at least 3mdeep, although the deeper the better. Deep pits can last up to 15, 20, 30 or more years. As the effluent leaches from the Single VIP and migrates through unsaturated soils, faecal organisms are removed. The degree of faecal organism removal varies with soil type, distance traveled, moisture and other environmental factors and thus, it is difficult to estimate the necessary distance between a pit and a water source. A minimum distance of 30m between the pit and a water source is recommended to limit exposure to chemical and biological contamination.<br>{{procontable | pro=- Flies and odours are significantly reduced (compared to non-ventilated pits). <br> - Does not require a constant source of water. <br> - Suitable for all types of user (sitters, squatters, washers and wipers). <br> - Can be built and repaired with locally available materials <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= - 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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==Adequacy=Appropriateness= ==Treatment processes in the single VIP (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. This technology is a significant improvement over Single Pits or open defecation.
Treatment processes in the Single VIP (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. This technology is a significant improvement over Single Pits or open defecation. Single VIPs 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 insufficient space for infiltration. Depending on the pit depth, depth to the water table, number of users and soil conditions, some pits can be used for 20 years without emptying. VIPs are especially appropriate when water is scarce and where there is a low groundwater table. They should be located in an area with a good breezeto ensure effective ventilation. They are not suited for rocky or compacted soils (that are difficult to dig) or for areas that flood frequently. ==Health Aspects/Acceptance==
===Health Aspects/Acceptance===
A Single VIP can be a very clean, comfortable, and well accepted sanitation option. However some health concerns exist:
* Latrine leachate can contaminate groundwater;
* Health risks from flies are not completely removed by ventilation.
===Upgrading===
A Single VIP toilet can be upgraded to a [[Double Ventilated Improved Pit|Double VIP]], a [[Urine Diverting Dry Toilet|Urine Diverting Dry Toilet (UDDT)]] if there is a use for urine, or a water-based [[Pour Flush Toilet|Pour Flush Toilet]] if water is available. A Double VIP has the addition of an extra pit so that while one pit is in use, the contents of the full pit are draining, maturing and undergoing degradation. Pathogens are destroyed much more thoroughly in a Double VIP and therefore, the contents are less hazardous to remove from the pit, although because the contents are so solid, the contents cannot be pumped, but rather, must be manually emptied.
===Operation & Maintenance===
To keep the Single VIP free of flies and odours, regular cleaning and maintenance is required. Dead flies, spider webs, dust and other debris should be removed from the ventilation screen to ensure a good flow of air.
===Origins===
The VIP latrine was developed in the 1970s at the Blair Research Laboratory in Zimbabwe.
==References =Field experiences==={{RSR_table* Mara, DD|1image= rsr 476.jpg|1link=http://rsr. (1996)akvo. Low-Cost Urban Sanitationorg/project/476/ |1project#=476 |1project name=Ensure access to safe water and sanitation ||2image= rsr 474. Wiley, Chichester, UKjpg|2link=http://rsr. (Provides detailed design informationakvo.)org/project/474/ |2project#=474 |2project name=Health & Sanitation project| * Mara DD|3image= rsr 360. (1984)jpg|3link=http://rsr. The Design of Ventilated Improved Pit Latrines (UNDP Interregakvo. Project INTorg/project/360/ |3project#= 360|3project name= WASH Facilities at Kajiado Schools||4image= rsr 727.jpg|4link=http:/81/047)rsr. The World Bank + UNDP, Washingtonakvo.org/project/727/ |4project#= 727|4project name=ESO North School and Community WASH Project | * Morgan, PR|5image= rsr 467. (1977)jpg|5link=http://rsr. The Pit Latrine – Revived. Central African Journal of Medicine, 23(1)akvo.org/project/467/ |5project#=467 |5project name=Community Water and Sanitation Project |}}
===References ===* MorganMara, PRD. D. (19791984). A [https://www.pseau.org/outils/ouvrages/world_bank_the_design_of_ventilated_lmproved_pit_latrines_1984.pdf The Design of Ventilated Improved Pit PrivyLatrines]. Appropriate TechnologyUNDP Interregional Project INT/81/047, 6 (3)The World Bank and UNDP, Washington, D.C., US.
* Morgan PR. and Mara, DDD. D. (19821996). Ventilated Improved Pit Latrines: Recent Developments in ZimbabweLow-Cost Urban Sanitation. World Bank Technical Paper noWiley, Chichester, UK.3. Available: http://www.worldbank.org(Book; provides detailed design information)
* Morgan PR, P. R. (19902009). Rural Water Supplies [http://www.ecosanres.org/pdf_files/EcologicalToilets-PeterMorgan-Mar2009.pdf Ecological Toilets. Start Simple and SanitationUpgrade from Arborloo to VIP]. Blair Research Laboratory & Ministry of Health + MacMillanStockholm Environment Institute, HarareStockholm, ZimbabweSE.
* FranceysMorgan, R., Pickford, JP. and Reed, R. (19922011). A guide to the development of on-site sanitation[http://www.ecosanres. WHOorg/pdf_files/Builders_Detailed_Manual_Upgradeable_%20Blair_VIP.pdf The Blair VIP toilet]. Manual for Upgradeable BVIP Model with Spiral Superstructure and Tubular Vent. Stockholm Environment Institute, GenevaStockholm, SE.(Provides detailed design and construction information)
* LewisRyan, JWB.A. and Mara, et alD. D. (19821983). [http://documents1.worldbank.org/curated/en/412331468199470290/pdf/TAG6000Ventila0pe0design0guidelines.pdf Ventilated Improved Pit Latrines: Vent Pipe Design Guidelines]. UNDP Interregional Project INT/81/047, The Risk of Groundwater Pollution by on-site Sanitation in Developing Countries. International Reference Centre for Waste DisposalWorld Bank and UNDP, DübendorfWashington, SwitzerlandD. (A detailed study regarding the transport and die-off of microorganisms and implications for locating technologiesC., US.)
* The World Bank (1986)See S. Information and Training 2 for Low-Cost Water Supply and Sanitation (UNDP Project INT/82/002). The World Bank, Washingtonadditional reading materials.
===Acknowledgements===
{{:Acknowledgements Sanitation}}
