Pit latrine

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Schematic of the pit of a pit latrine.[1] The defecation hole in the slab is shown at the top, and the user squats or sits above this defecation hole. Pits can be lined with a support ring at the top of the pit like it is shown in this schematic.

A pit latrine or pit toilet is a type of toilet that collects human feces in a hole in the ground. They use either no water or 1-3 liters per flush if it has a water seal in the case of pour-flush pit latrines.[1] It is a low cost method of separating feces from people. This separation is not always complete and groundwater pollution may occur. When properly built and maintained they can decrease the spread of disease by reducing the amount of human feces in the environment and thereby decreasing the transfer of pathogens between feces and food.[2] Not using toilets, known as open defecation, is a major factor in causing infectious diarrhea and intestinal worm infections.[3] Infectious diarrhea in turn resulted in about 0.7 million deaths in children under five years old in 2011 and 250 million lost school days.[3][4]

A pit toilet is made up of three major parts: a hole in the ground, a slab or floor and a building.[1] The pit is typically at least 3 meters (10 feet) deep and 1 m (3.2 feet) in diameter.[1] The World Health Organization recommends they be built about a reasonable distance from the house balancing issues of easy access versus that of smell.[2] The distance from groundwater and surface water source should be as large as possible to decrease the risk of pollution. It is generally recommended that the bottom of the pit should be at least 2 m above groundwater level and the horizontal distance between a pit and a water source should be at least 30 m (100 feet).[1] The hole in the slab should not be larger than 25 centimeters (9.8 inches) to prevent children falling in. Light should be prevented from entering the pit to reduce access by flies. This may require the use of a lid to cover the hole in the floor when not in use.[2] When the pit fills to within 0.5 meters (1.6 feet) of the top, it should be emptied or a new hole dug and the structure moved. If the pit is to be emptied by hand, two years must pass after last usage before this can be considered relatively safe.[5] Using protective equipment including gloves and boots is still recommended during emptying. Pit toilets may fall into disrepair and be abandoned when full if there are no mechanisms to empty or build a new pit. Also, safe disposal of the fecal sludge from the pit may be difficult.[6]

A basic pit toilet can be improved in a number of ways. One includes adding a ventilation pipe from the pit to above the structure. This improves airflow and decreases the smell of the toilet. It also can reduce flies when the top of the pipe is covered with mesh (usually made out of fiberglass). In these types of toilets a lid need not be used to cover the hole in the floor.[5] Other possible improvements include a floor constructed so fluid drains into the hole and a reinforcement of the upper part of the pit with bricks or cement rings to improve stability.[1][5]

As of 2013 pit toilets are used by an estimated 1.77 billion people.[7] This is mostly in the developing world as well as in rural and wilderness areas. In 2011 about 2.5 billion people did not have access to a proper toilet and one billion defecate outside.[8] Southern Asia and Sub-Saharan Africa have the poorest access to toilets.[9] In the developing world the cost of a simple pit toilet is between 25 and 60 USD.[10] In India the "No Toilet, No Bride" slogan is used successfully to promote toilets by encouraging women to refuse to marry a man who does not own a toilet.[11]

Terminology[edit]

Pit latrines are sometimes also referred to as "dry toilets" but this is not recommended because a "dry toilet" is an overarching term used for several types of toilets and strictly speaking only refers to the user interface.[1] Depending on the region, the term "pit latrine" may be used to denote a toilet that has a squatting pan with a water seal or siphon (more accurately termed a pour-flush pit latrine - very common in South East Asia for example) or simply a hole in the ground without a water seal (also called a simple pit latrine) - the common type in most countries in sub-Saharan Africa. Whilst a dry toilet can be with or without urine diversion, a pit latrine is almost always without urine diversion. The key characteristic of a pit latrine is the use of a pit which infiltrates liquids into the ground and acts as a device for storage and very limited treatment.[1]

Recommendations[edit]

A common problem: The groundwater well is in close proximity to the pit latrine at this household in peri-urban area of Lusaka, Zambia

Size of the drop hole[edit]

The size of the feces drop hole in the floor or slab should not be larger than 25 centimeters (9.8 inches) to prevent children falling in. Light should be prevented from entering the pit to reduce access by flies.This requires the use of a lid to cover the hole in the floor when not in use.[2] However, in practice, such a lid is not commonly used as it is easy to lose it or for the lid to get very filthy.

On top of the small hole there can either be nothing (this is the simplest form of a pit latrine) or there can be a squatting pan, seat (pedestal) or bench which can be made of concrete, ceramic, plastic or wood.

Groundwater considerations[edit]

As liquid leaches from the pit and through the unsaturated soil matrix, pathogens are sorbed to the soil surface. However, the degree of removal varies with soil type, distance travelled, moisture and other encironmental factors.[1] For this reason, it is difficult to estimate the "safe" distance between a pit and a water source - a problem that also applies to septic tanks. Detailed guidelines have been developed to estimate safe distances to protect groundwater sources from pollution from on-site sanitation[12] but these are often ignored by those building pit latrines. In addition to that, household plots are of a limited size and therefore, pit latrines are often built much closer to groundwater wells than what can be regarded as safe, with resulting groundwater pollution and household members falling sick when using this groundwater as a source of drinking water.[13] As a very general guideline it is recommended that the bottom of the pit should be at least 2 m above groundwater level and the horizontal distance between a pit and a water source should be at least 30 m to limit exposure to microbial contamination.[1]

However, no general statement should really be made regarding the minimum lateral separation distances required to prevent contamination of a well from a pit latrine for an entire country. For example, even 50 m lateral separation distance migth not be sufficient in a strongly karstified system with a downgradient supply well or spring, while 10 m lateral separation distance is completely sufficient if there is a well developed clay cover layer and the annular space of the groundwater well is well sealed. To give an example, the peri-urban areas of Lusaka, the capital of Zambia, have ground conditions which are strongly karstified and for this reason - together with the increasing population denstiy in these peri-urban areas - pollution of wells from pit latrines is a major public health threat there.[14]

If the local hydrogeological conditions (which can vary within a space of a few square kilometres) are ignored, pit latrines can cause greater public health damage (via contaminated groundwater) than they solve. In addition to the issue of pathogens, there is also the issue of nitrate pollution in groundwater from pit latrines, which has led to numerous cases of blue baby syndrome in children, notably in rural countries such as Romania and Bulgaria.[15]

Types[edit]

Pit latrines collects human feces in a hole in the ground. The principle of a pit latrine is that all liquids that enter the pit - in particular urine and water used for anal cleansing - seep into the ground (the only exception are fully lined pit latrines, see below).

Slit-trench latrine[edit]

A slit-trench latrine is not strictly a pit latrine (because it has no pit) but it is closely related. It consists of a relatively shallow trench (1–2 metres or 3–6 feet in depth) narrow enough to stand with one leg on either side (for the slit-trench latrine). This type is used either by squatting, with the users' legs straddling the pit, or by various arrangements for sitting or leaning against a support structure. Such support may vary from the simplest forms such as a log, plank, branch or similar arrangement placed at right angles to the long axis of the pit. This type of latrine is not commonly found in developing countries but can be used for emergency sanitation.

Shallow-trench latrine[edit]

The shallow-trench latrine also not strictly a pit latrine and is similar to the slit-trench latrine but is shallower (150 mm deep) but wider (200-300mm wide) compared to the slit-trench latrine. This type of latrine is often used in the initial phases of emergencies and is a simple improvement on open defecation fields.[16]  A rule of thumb in emergency sanitation provision is to allow 0.25 m2 of land per person per day. This means 2,500m2 per 10,000 people per day, or nearly two hectares per week. Men’s and women’s areas should always be separated.[16]

Cathole[edit]

A cathole is a one-time use pit toilet often utilized by campers, hikers and other outdoor recreationalists. It is also called the "cat method" and simply means digging a little hole just large enough for the faeces of one defecation event which is afterwards covered with soil.

Advanced designs[edit]

An advanced pit toilet is more complex forms, or higher capacity forms - commonly associated with outhouses though sometimes used underneath a house, or as a central collection area for several outhouses or other waste collection arrangements - the pit will be larger, and covered with a supporting structure. This structure may be simply a metal plate, or board floor - with a hole over which the user positions themselves during use. A provision for seating is often placed above a pit toilet, this may be a simple hole, or several holes, in a board surface at sitting height. In bitter cold Arctic climates, honey buckets are used inside the home and carried to such covered pits outside.

A more substantial structure may also be built. Commonly known as an outhouse, these small enclosed buildings (also called superstructure) provide a roof for shelter, one or more seats with a hole in it, and occasionally access to water for washing.

Ventilated improved pit[edit]

The ventilated improved pit latrine (VIP), is a pit toilet with a black pipe (vent pipe) fitted to the pit, and a screen (flyscreen) at the top outlet of the pipe. VIP latrines are an improvement to overcome the disadvantages of simple pit latrines, i.e. fly and mosquito nuisance and unpleasant odors. The smell is carried upwards by the chimney effect and flies are prevented from leaving the pit and spreading disease.[17]

The principal mechanism of ventilation in VIP latrines is the action of wind blowing across the top of the vent pipe. The wind creates a strong circulation of air through the superstructure, down through the squat hole, across the pit and up and out of the vent pipe. Unpleasant faecal odors from the pit contents are thus sucked up and exhausted out of vent pipe, leaving the superstructure odor-free. In some cases solar-powered fans are added giving a constant outwards flow from the vent pipe.

Flies, searching for an egg-laying site are attracted by faecal odors coming from the vent pipe, but they are prevented from entering by the flyscreen at the outlet of the vent pipe. Some flies may enter into the pit via the squat hole and lay their eggs there. When new adult flies emerge they instinctively fly towards light. However, if the latrine is dark inside the only light they can see is at the top of the vent pipe. Since the vent pipe is provided with a fly screen at the top, flies will not be able to escape and eventually they will die and fall back into the pit.

To ensure that there is a flow of air through the latrine there must be adequate ventilation of the superstructure. This is usually achieved by leaving openings above and below the door, or by constructing a spiral wall without a door.[18]

Covering the feces with an absorbent decreases smell and discourages flies. These may include soil, sawdust, ash or lime among others.[5] In developing countries, the use of absorbents in pit toilets is not commonly practiced.

Twin pit designs[edit]

A further possible improvement is the use of a second pit which is used in alternation with the first pit. It means that the first pit can rest for the duration of time it takes to fill up the second pit. When the second pit is also full, then the first pit is emptied. The faecal sludge collected in that first pit has in the meantime undergone some degree of pathogen reduction although this is unlikely to be complete. This is a common design for so-called twin-pit pour flush toilets and increases the safety for those having to enter the pit.[1] Also VIPs are sometimes built with two pits, although for VIP toilets one problem can be that the users may not stick to this alternation method and fill up both pits at the same time.

Pour-flush pit latrine[edit]

In a pour-flush pit latrine, a squatting toilet with a water seal (U-trap or siphon) is used over one or two offset pits instead of a plain hole or seat. Therefore, these types of toilets do required water for flushing but otherwise have many of the same characteristics as simple pit latrines and are therefore subsumed under the term "pit latrine". The faecal sludge that is removed from the full pits of twin-pit pour-pour flush pit latrines is somewhat safer to handle and reuse than the faecal sludge from single pit pour-flush latrines, although significant health risks remain in either case and are a cause for great concern.[19]

Pit lining[edit]

Partial[edit]

Digging the pit for an Arborloo, a type of pit toilet in Cap-Haitien, Haiti.

A "partially lined" pit latrine is one where the upper part of the hole in the ground is lined. Pit lining materials can include brick, rot-resistant timber, concrete, stones, or mortar plastered onto the soil.[1] This partial lining is recommended for those pit latrine used by a great number of people — such as a public restroom in rural areas, or in a woodland park or busy lay-by, rest stop or other similarly busy location — or where the soils are unstable in order to increase permanence and allow emptying of the pit without it collapsing easily. The bottom of the pit should remain unlined to allow for the infiltration of liquids out of the pit.

In Dar es Salaam, Tanzania pit latrines costing up to $300 are 10 ft (3.0 m) deep and lined with concrete slabs, while cheaper “temporary toilets” consist of a pits lined with two stacked oil drums or a stack of tires.[20] These latrines, which are often used by several households, may be emptied by vacuum truck, manual digging, or overflowing into streets during rains.[20]

Fully[edit]

A fully lined pit latrine has concrete lining also at the base so that no liquids infiltrate into the ground. One could argue that this is no longer a "pit" latrine in the stricter sense. The advantage is that no groundwater contamination can occur. The major disadvantage is that a fully lined pit latrine fills up very fast (as the urine cannot escape the pit) which results in high costs to empty and maintain the latrine. Increased odour can also be an issue as the pit content is much wetter and therefore emits more odour. This type of pit latrine is therefore used only in special cirumstances, e.g. in denser settlements where groundwater protection is paramount.

Pit emptying and faecal sludge management[edit]

An unprotected worker emptying the pit of a pit latrine in Fada N'Gourma in the East of Burkina Faso. The man works without gloves, boots and mask, because these are too expensive. Boots would be useless as in the beginning of the emptying process the sludge normally reaches up too the emptiers' knees
Faecal sludge that has been manually removed from pits is dumped into the local river at Korogocho slum near Nairobi, Kenya

Pits can be either covered and abandoned or periodically emptied when full, usually by a pump mounted on a large truck which also carries a tank for storage (called a vacuum tanker or in some countries "honey sucker"). The waste is transported by road to a sewage treatment facility, or to be composted elsewhere. There are numerous licensed waste hauling companies providing such service in areas where it is needed in developed countries, although in developing countries such services are not well regulated and are often carried out by untrained, unskilled and unprotected informal workers.

The requirements for safe pit emptying and faecal sludge management are often forgotten by those building pit latrines, as the pit will "only" fill up in a few years time. However, still today in many developing countries safe faecal sludge management practices are sorely lacking and causing public health risks as well as environmental pollution.[6] Faecal sludge that has been removed from pits manually or with vacuum tankers is often dumped into the environment indiscriminately, leading to what has been called "institutionalised open defecation".

When managed and treated correctly to achieve a high degree of pathogen kill, faecal sludge from pit latrines could be used as a fertiliser due to its high nitrogen, phosphorus and organic matter content. However, it is hard to ensure that this is done in a safe manner. The number of viable helminth eggs is commonly used as an indicator pathogen to make a statement about the pathogen load in a faecal sludge sample, as these helminth eggs are very persistent to the treatment methods in use and therefore a good indicator.

User experiences[edit]

Pit latrines may or may not be an enjoyable experience to use. Problems may occur when the pit latrine is shared by too many people, is not cleaned daily and not emptied when the pit is full. In such cases, flies and odour can be a massive nuisance. Also, pit latrines are usually dark places which are difficult to keep clean. Often, handwashing facilities are missing. Therefor shared pit latrines can be quite uncomfortable to use in developing countries. Also, there might be cultural preferences for open defecation and these may be difficult to overcome with unattractive toilet designs. This is currently being discussed amongst experts for the example in the case of rural India where behaviour change campaigns are needed to reduce open defecation.[21]

Ashes or sawdust can also be added on top of the feces to decrease the smell.[5] However, this is rarely done for pit latrines (more commonly done for dry toilets) as the users find that too much hassle and generally do not expect a pit latrine to be odour free and therefore are willing to put up with some smell. In the case of Arborloos it is recommended to add some leaves, soil or compost into the pit after defecation.

Advantages[edit]

Advantages of pit latrines may include:[1]

  • Can be built and repaired with locally available materials
  • Low (but variable) capital costs depending on materials and pit depth
  • Small land area required

Measures to improve access to safe water, sanitation and better hygiene, which includes the use of pit latrines instead of open defecation, is believed to be able to prevent nearly 90% of deaths due to infectious diarrhea.[22]

Disadvantages[edit]

Disadvantages of pit latrines may include:[1]

  • Flies and odours are normally noticeable to the users
  • The toilet has to be outdoors with the associated security risks if the person is living in an insecure situation
  • Low reduction in organic matter content and pathogens
  • Possible contamination of groundwater with pathogens and nitrate
  • Costs to empty the pits may be significant compared to capital costs
  • Pit emptying is often done in a very unsafe manner
  • Sludge (called faecal sludge) requires further treatment and/or appropriate discharge

Situations where not suitable[edit]

Pit latrines are often built in developing countries even in situations where they are not recommended. These include (adapted from [23]):

  • Frequent flooding, resulting in inoperable toilet systems and the contamination of water resources;
  • Unfavourable soil conditions, such as unstable or rocky soil and high water table, making pit-based sanitation difficult and expensive;
  • When groundwater is the primary source of drinking water and is likely to be contaminated by pit-based sanitation (for example in denser settlements or with unfavourable hydrogeological conditions);
  • Limited land space restricts the excavation of new pits if full pit latrines are usually not emptied;
  • Indoor installations are preferred as they provide greater comfort and security at night thus making them more accessible for all

In conditions where pit latrines are not suitable for the above mentioned reasons, the installations of other types of toilets should be considered, e.g. the urine-diverting dry toilet (UDDT).[23]

Costs[edit]

In the developing world the cost of the construction of a simple pit toilet is between 25 and 60 USD.[10] However, rather than looking only at the construction cost, the whole of life cost (or life-cycle cost) should be considered, as the regular emptying or re-building of pit latrines may add a significant expense to the households in the longer term.[24]

Promotional activities[edit]

In 2011 about 2.5 billion people did not have access to a proper toilet and one billion defecate outside.[8] Southern Asia and Sub-Saharan Africa have the poorest access to toilets.[9] Therefore, pit latrines are often promoted by government agencies and NGOs in rural areas as a low-cost quick fix solution (even in areas where other types of toiles, such as dry toilets, might be the better solution for example due to high groundwater table). In India the "No Toilet, No Bride" slogan is used successfully to promote toilets (usually pour flush pit latrine toilets) by encouraging women to refuse to marry a man who does not own a toilet.[11]

The community-led total sanitation campaigns which have been successful in many developing countries usually also result in the construction of pit latrines (typically with pour flush in Asia, without pour flush in sub-Saharan Africa) as a first step to get away from open defecation.

References[edit]

  1. ^ a b c d e f g h i j k l m Tilley, E., Ulrich, L., Lüthi, C., Reymond, Ph. and Zurbrügg, C. (2014). Compendium of Sanitation Systems and Technologies (2 ed.). Dübendorf, Switzerland: Swiss Federal Institute of Aquatic Science and Technology (Eawag). ISBN 9783906484570. 
  2. ^ a b c d "Simple pit latrine (fact sheet 3.4)". who.int. 1996. Retrieved 15 August 2014. 
  3. ^ a b "Call to action on sanitation" (pdf). United Nations. Retrieved 15 August 2014. 
  4. ^ Walker, CL; Rudan, I; Liu, L; Nair, H; Theodoratou, E; Bhutta, ZA; O'Brien, KL; Campbell, H et al. (Apr 20, 2013). "Global burden of childhood pneumonia and diarrhoea.". Lancet 381 (9875): 1405–16. PMID 23582727. 
  5. ^ a b c d e François Brikké (2003). Linking technology choice with operation and maintenance in the context of community water supply and sanitation. World Health Organization. p. 108. ISBN 9241562153. 
  6. ^ a b Still, David; Foxon, Kitty (2012). Tackling the challenges of full pit latrines : report to the Water Research Commission. Gezina [South Africa]: Water Research Commission. ISBN 9781431202935. 
  7. ^ Graham, JP; Polizzotto, ML (May 2013). "Pit latrines and their impacts on groundwater quality: a systematic review.". Environmental health perspectives 121 (5): 521–30. PMID 23518813. 
  8. ^ a b "Sanitation" (pdf). United Nations. 2013. Retrieved 15 August 2014. 
  9. ^ a b Progress on sanitation and drinking-water - 2014 update. (pdf). WHO. 2014. pp. 16–20. ISBN 9789241507240. 
  10. ^ a b Selendy, edited by Janine M. H. (2011). Water and sanitation-related diseases and the environment challenges, interventions, and preventive measures ([Elektronische Ressource] ed.). Hoboken, N.J.: Wiley-Blackwell. p. 25. ISBN 9781118148600. 
  11. ^ a b Global Problems, Smart Solutions: Costs and Benefits. Cambridge University Press. 2013. p. 623. ISBN 9781107435247. 
  12. ^ ARGOSS (2001). Guidelines for assessing the risk to groundwater from on-site sanitation. NERC, British Geological Survey Commissioned Report, CR/01/142, UK
  13. ^ Mayumbelo, K. (2008). C ost analysis for applying ecosan in peri-urban areas to achieve the MDGs - Case study of Lusaka, Zambia. MSc Thesis, UNESCO-IHE Institute for Water Education, The Netherlands
  14. ^ Nick, A. (2011). Methodology and results of the vulnerability map for Lusaka and suroundings using the PI-method - a documentation and manual - Technical note no. 6. Department of Water Affairs (DWA), Zambia & Federal Institute for Geosciences and Natural Resources (BGR), Germany
  15. ^ Buitenkamp, M., Richert Stintzing, A. (2008). Europe's sanitation problem - 20 million Europeans need access to safe and affordable sanitation. Women in Europe for a Common Future (WECF), The Netherlands
  16. ^ a b Harvey, P. A. Excreta Disposal in Emergencies: A field manual. WEDC, Loughborough University, UK. p. 232. ISBN 978 1 84380 113 9. 
  17. ^ Drains Not Disease - Zambia, Television Trust for the Environment website.
  18. ^ Ahmed,M.F. & Rahman,M.M. (2003). Water Supply & Sanitation: Rural and Low Income Urban Communities, 2nd Edition, ITN-Bangladesh. ISBN 984-31-0936-8.
  19. ^ "Discussion about the safety of sludge from twin pit pour flush toilets amongst sanitation experts". SuSanA Discussion Forum. 11 Sep 2013. Retrieved 15 Oct 2014. 
  20. ^ a b George, Rose (7 July 2009). The Big Necessity: The Unmentionable World of Human Waste and Why It Matters. Henry Holt and Company. pp. 83–85. ISBN 978-1-4299-2548-8. 
  21. ^ Clasen, Thomas; Boisson, Sophie; Routray, Parimita; Torondel, Belen; Bell, Melissa; Cumming, Oliver; Ensink, Jeroen; Freeman, Matthew; Jenkins, Marion; Odagiri, Mitsunori; Ray, Subhajyoti; Sinha, Antara; Suar, Mrutyunjay; Schmidt, Wolf-Peter. "Effectiveness of a rural sanitation programme on diarrhoea, soil-transmitted helminth infection, and child malnutrition in Odisha, India: a cluster-randomised trial". The Lancet Global Health. doi:10.1016/S2214-109X(14)70307-9. 
  22. ^ Organization, UNICEF, World Health (2009). Diarrhoea : why children are still dying and what can be done. New York: United Nations Children's Fund. p. 2. ISBN 978-92-806-4462-3. 
  23. ^ a b Rieck, C., von Münch, E., Hoffmann, H. (2012). Technology review of urine-diverting dry toilets (UDDTs) - Overview on design, management, maintenance and costs. Deutsche Gesellschaft fuer Internationale Zusammenarbeit (GIZ) GmbH, Eschborn, Germany
  24. ^ McIntyre, P., Casella D., Fonseca, C. and Burr, P. Priceless! Uncovering the real costs of water and sanitation. The Hague: IRC. ISBN 978-90-6687-082-6. 

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