Pit latrine

Drawing of a simple pit latrine with a squatting pan and shelter.[1]

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 one to three liters per flush with pour-flush pit latrines.[2] When properly built and maintained they can decrease the spread of disease by reducing the amount of human feces in the environment from open defecation.[3][4] This decreases the transfer of pathogens between feces and food by flies.[3] These pathogens are major causes of infectious diarrhea and intestinal worm infections.[4] Infectious diarrhea resulted in about 0.7 million deaths in children under five years old in 2011 and 250 million lost school days.[4][5] Pit latrines are the lowest cost method of separating feces from people.[3]

A pit latrine generally consists of three major parts: a hole in the ground, a slab or floor with a small hole, and a shelter.[2] The pit is typically at least 3 meters (10 feet) deep and 1 m (3.2 feet) across.[2] The World Health Organization recommends they be built a reasonable distance from the house balancing issues of easy access versus that of smell.[3] The distance from groundwater and surface water should be as large as possible to decrease the risk of groundwater pollution. 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.[3] When the pit fills to within 0.5 meters (1.6 feet) of the top, it should be either emptied or a new pit constructed and the shelter moved or re-built at the new location.[6] The management of the fecal sludge removed from the pit is complicated. There are both environment and health risks if not done properly.

A basic pit latrine 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.[6] 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.[2][6]

As of 2013 pit latrines 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 resort to open defecation in their surroundings.[8] Southern Asia and Sub-Saharan Africa have the poorest access to toilets.[8] In developing countries the cost of a simple pit toilet is typically between 25 and 60 USD.[9] Ongoing maintenance costs are between 1.5 and 4 USD per person per year which are often not taken into consideration.[10] In some parts of rural India the "No Toilet, No Bride" campaign has been used to promote toilets by encouraging women to refuse to marry a man who does not own a toilet.[11][12]

Terminology

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.[2] 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.[2]

Design considerations

Size of the drop hole

The user positions himself or herself over the small drop hole during use. 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.[3] 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.

Squatting pan or toilet seat

On top of the drop 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.

Shelter

Main article: Outhouse

A shelter, shed, small building or "super-structure" houses the squatting pan or toilet seat and provides privacy and protection from the weather for the user. Ideally, the shelter or small building should have handwashing facilities available inside or on the outside (e.g. supplied with water from a rainwater harvesting tank on the roof of the shelter) although this is unfortunately rarely the case in practice. In the shelter, anal cleansing materials (e.g. toilet paper) and a solid waste bin should also be available. A more substantial structure may also be built, commonly known as an outhouse.

Additives

Wood ash or sawdust can also be added on top of the feces to decrease the smell.[6] 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.

Pit additives based on "effective microorganisms" have also been promoted by some manufacturers with the aim to slow down the pit filling rate and to reduce odors. However they are usually costly in the longer term and fail to live up to expectations.[1]

Locating the pit

Common problem: groundwater well (forefront) in close proximity to the pit latrine (brick building at the back) in peri-urban area of Lusaka, Zambia

Liquids leach from the pit and pass the unsaturated soil zone (which is not completely filled with water). Subsequently, these liquids from the pit enter the groundwater where they may lead to groundwater pollution. This is a problem if a nearby water well is used to supply groundwater for drinking water purposes. During the passage in the soil, pathogens can die off or be adsorbed significantly, mostly depending on the travel time between the pit and the well.[13] Most, but not all pathogens die within 50 days of travel through the subsurface.[14]

The degree of pathogen removal strongly varies with soil type, aquifer type, distance and other environmental factors.[7] 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.[15][16] However, these are mostly 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 This results in groundwater pollution and household members falling sick when using this groundwater as a source of drinking water.

As a very general guideline it is recommended that the bottom of the pit should be at least 2 m above groundwater level, and a minimum horizontal distance of 30 m between a pit and a water source is normally recommended to limit exposure to microbial contamination.[1] However, no general statement should be made regarding the minimum lateral separation distances required to prevent contamination of a well from a pit latrine.[17] For example, even 50 m lateral separation distance might 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.

If the local hydrogeological conditions (which can vary within a space of a few square kilometres) are ignored, pit latrines can cause significant public health risks via contaminated groundwater. 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.[18]

Pit lining

Partial

Schematic of the pit of a pit latrine.[2] 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.
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.[2] 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.[19] These latrines, which are often used by several households, may be emptied by vacuum truck, manual digging, or overflowing into streets during rains.[19]

Fully

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.

Appropriateness

Pit latrines are often built in developing countries even in situations where they are not recommended. These include (adapted from [20]):

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).[20]

Types

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).

Ventilated improved pit

The ventilated improved pit latrine (VIP), is a pit latrine 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.[2]

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.[21]

Covering the feces with an absorbent decreases smell and discourages flies. These may include soil, sawdust, ash or lime among others.[6] In developing countries, the use of absorbents in pit toilets is not commonly practiced.

Twin pit designs

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.[2] 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

Pour-flush pit latrine schematic showing squatting pan with water seal[1]

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 concern.

Cat hole

A cat hole 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.

Maintenance

Manual pit emptying of a pit latrine near Durban, South Africa
Bad practice example: 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 to the emptier's knees.
Bad practice example: Faecal sludge that has been manually removed from pits is dumped into the local river at Korogocho slum near Nairobi, Kenya

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, in many developing countries safe faecal sludge management practices are lacking and causing public health risks as well as environmental pollution.[22] 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".

Pit emptying

When the pit of a pit latrine is full, the pit latrine stops being usable. The time it takes to fill the pit depends on the volume of the pit, the number of users but also on the soil permeability and groundwater level. It can typically take between one to ten years or even longer in some exceptional cases to fill up the pit of a pit latrine. At that point, the pit latrine is either covered and abandoned, and a new pit latrine built if space on the property permits this. The new pit latrine may reuse the shelter (super-structure) of the previous pit latrine in some cases. For pit latrines in more densely populated areas or at schools, the full pits are more likely to be emptied so that the toilets can be continued to be used at the same location. The emptying can be done manually with shovels and buckets, with manually powered pumps or with motorised pumps mounted on a vacuum truck which carries a tank for storage.[22] For the faecal sludge to be pumpable, water usually needs to be added to the pit and the content stirred up, which is a messy and smelly business.

Sludge management

The faecal sludge may be 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.

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.

Advantages

Advantages of pit latrines may include:[2]

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.[23]

Disadvantages

Disadvantages of pit latrines may include:[2]

Costs

In developing countries the construction cost for a simple pit toilet is between about 25 and 60 USD.[9] This cost figure has a wide range because the costs vary a lot depending on the type of soil, the depth and reinforcement of the pit, the superstructure that the user is willing to pay for, the type of toilet squatting pan or toilet seat chosen, the cost of labour, construction materials (in particular the cost of cement can dfifer a lot from one country to the next), the ventilation system and so forth.

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]

Society and culture

User experiences

School pit latrine after maintenance has been neglected, Ambira Boys High School, Nyanza Province, Kenya

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.[25]

Promotion

In 2011 about 2.5 billion people did not have access to a proper toilet and one billion defecate outside.[26] Southern Asia and Sub-Saharan Africa have the poorest access to toilets.[8] 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 the rural part of Haryana state in India the "No Toilet, No Bride" or "No loo, no "I do"" slogans has been used 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][12]

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

  1. ↑ 1.0 1.1 1.2 WEDC. Latrine slabs: an engineer’s guide, WEDC Guide 005 (PDF). Water, Engineering and Development Centre The John Pickford Building School of Civil and Building Engineering Loughborough University. p. 22. ISBN 978 1 84380 143 6.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 2.10 2.11 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.
  3. ↑ 3.0 3.1 3.2 3.3 3.4 3.5 "Simple pit latrine (fact sheet 3.4)". who.int. 1996. Retrieved 15 August 2014.
  4. ↑ 4.0 4.1 4.2 "Call to action on sanitation" (PDF). United Nations. Retrieved 15 August 2014.
  5. ↑ Walker, CL; Rudan, I; Liu, L; Nair, H; Theodoratou, E; Bhutta, ZA; O'Brien, KL; Campbell, H; Black, RE (Apr 20, 2013). "Global burden of childhood pneumonia and diarrhoea.". Lancet 381 (9875): 1405–16. doi:10.1016/s0140-6736(13)60222-6. PMID 23582727.
  6. ↑ 6.0 6.1 6.2 6.3 6.4 François Brikké (2003). Linking technology choice with operation and maintenance in the context of community water supply and sanitation (PDF). World Health Organization. p. 108. ISBN 9241562153.
  7. ↑ 7.0 7.1 Graham, JP; Polizzotto, ML (May 2013). "Pit latrines and their impacts on groundwater quality: a systematic review.". Environmental health perspectives 121 (5): 521–30. doi:10.1289/ehp.1206028. PMID 23518813.
  8. ↑ 8.0 8.1 8.2 Progress on sanitation and drinking-water - 2014 update. (PDF). WHO. 2014. pp. 16–20. ISBN 9789241507240.
  9. ↑ 9.0 9.1 Selendy, Janine M. H. (2011). Water and sanitation-related diseases and the environment challenges, interventions, and preventive measures. Hoboken, N.J.: Wiley-Blackwell. p. 25. ISBN 9781118148600.
  10. ↑ Sanitation and Hygiene in Africa Where Do We Stand?. Intl Water Assn. 2013. p. 161. ISBN 9781780405414.
  11. ↑ 11.0 11.1 Global Problems, Smart Solutions: Costs and Benefits. Cambridge University Press. 2013. p. 623. ISBN 9781107435247.
  12. ↑ 12.0 12.1 Stopnitzky, Yaniv (12 December 2011). "Haryana's scarce women tell potential suitors: "No loo, no I do"". Development Impact. Blog of World Bank. Retrieved 17 November 2014.
  13. ↑ DVGW (2006) Guidelines on drinking water protection areas - Part 1: Groundwater protection areas. Bonn, Deutsche Vereinigung des Gas- und Wasserfaches e.V. Technical rule number W101:2006-06
  14. ↑ Nick, A., Foppen, J. W., Kulabako, R., Lo, D., Samwel, M., Wagner, F., Wolf, L. (2012). Sustainable sanitation and groundwater protection - Factsheet of Working Group 11. Sustainable Sanitation Alliance (SuSanA)
  15. ↑ ARGOSS (2001). Guidelines for assessing the risk to groundwater from on-site sanitation. NERC, British Geological Survey Commissioned Report, CR/01/142, UK
  16. ↑ Moore, C., Nokes, C., Loe, B., Close, M., Pang, L., Smith, V., Osbaldiston, S. (2010) Guidelines for separation distances based on virus transport between on-site domestic wastewater systems and wells, Porirua, New Zealand, p. 296
  17. ↑ Wolf, L., Nick, A., Cronin, A. (2015). How to keep your groundwater drinkable: Safer siting of sanitation systems - Working Group 11 Publication. Sustainable Sanitation Alliance
  18. ↑ 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
  19. ↑ 19.0 19.1 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.
  20. ↑ 20.0 20.1 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
  21. ↑ 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.
  22. ↑ 22.0 22.1 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.
  23. ↑ WHO, UNICEF (2009). Diarrhoea : why children are still dying and what can be done (PDF). New York: United Nations Children's Fund. p. 2. ISBN 978-92-806-4462-3.
  24. ↑ McIntyre, P., Casella D., Fonseca, C. and Burr, P. Priceless! Uncovering the real costs of water and sanitation (PDF). The Hague: IRC. ISBN 978-90-6687-082-6.
  25. ↑ 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 (2014). "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 2 (11): e645. doi:10.1016/S2214-109X(14)70307-9.
  26. ↑ "Sanitation" (PDF). United Nations. 2013. Retrieved 15 August 2014.

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