< Resource Topic 7: Rural Sanitation and Water Supplies

I first became really aware of the problems to be faced when providing sanitation and water supplies to rural development projects when I was appointed the manager of the Bo Teacher’s College project in Sierra Leone (more details of the project can be found under the Sierra Leone section of this web-site).  As part of that project we constructed new facilities for ten primary schools situated in the rural areas around Bo Town and among these facilities were school toilets and drinking water supplies.

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There was no running water at any of the sites and therefore the only way to provide toilets was to construct pit-latrines.  I carried out a lot of research into the design and construction of VIP latrines (ventilated, improved pit latrines) which seemed to be the most promising solution to the problem of providing effective toilets and came up with a design for three and four compartment latrines.

 

VIP latrines were first developed in Zimbabwe in the 1970s and a description of their development can be found in ‘VIP latrines in Zimbabwe’. The basic principles of the design of VIP latrines are that the compartments are dark with the only light being provided by external vents to the pits (usually large diameter, dark-coloured PVC pipes) that rise to above roof level with insect mesh to the top of the vents.  These provide ventilation to the pits (necessary to avoid odour) and the light at the top of the vent should attract any flies that breed in the pit and the insect screen will trap them and they will die.

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The BTC latrines were constructed, as were the other school buildings, of stabilised-soil blocks with profiled steel sheet roofs.  The floors were of pre-cast concrete slabs (which were removable to allow the pits to be emptied) sitting on a reinforced concrete ring beam.  The soils in that part of the country where we were building the schools were very stable laterite soils and therefore foundation walls were not required.  The pits were three metres deep ventilated through blockwork ‘chimneys’ or vents that rose directly from the pits (large diameter PVC pipes were not available) and these provided the only source of light to the pits.  The latrines seemed to work very well with not much odour and my only regret is that we did not paint the outside of the vents black in order to increase the flow of air up the vents.

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I designed other, simpler VIP latrines for the clinics were built in the Solomon Islands (more details of the project can be found under the Solomon Islands section of this web-site).  These were one-compartment latrines constructed of timber over a 3 metre deep pit.  The timber panels had to be heavily braced and bolted down to the concrete ring beam in order to withstand cyclones.

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An improved version of the VIP latrine is the ‘double-pit latrine’ that originated in Vietnam; see TAG Technical Note and BRE Note 70/79 and a good example is shown in the Lesotho schools example.  The problem with the standard VIP latrine is that, once the pit is full, it cannot be used until the pit has been emptied and this can take 6 to 12 months, depending on the climate, for the contents to be rendered innocuous.  The advantage of the double-pit latrine is that the latrines can be used continuously by sealing one pit when it is full and then using the other pit.  The full pit can be emptied when the contents have settled and become innocuous.

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Whatever design is used, there are, in my experience, a few basic rules that should be followed in the design and construction of VIP latrines: 1) the pit should be as deep as possible in order to increase the periods of time required between emptying; 2) the pit should be accessible so that it can be emptied when the contents have dried out and become innocuous; 3) the vent from the pit must be vertical; the pipe used for the vent should be at least 15 cm in diameter; the vent should end at least 1 metre above roof level and the top of the vent should be closed with insect-proof mesh in order to trap flies; 4) the cubicle should be kept dark so that the only light visible is from the top of the vent pipe so that any flies breeding in the pit are attracted to the top of the vent where they will die; 5) the latrines should be at least 30 metres from any water source (more if the site is wet) and down-hill from any water source if the site slopes; 6) a water supply of some sort should be provided (if only a bucket) for hand-washing.

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An example of a design for a VIP latrine that will not work as it should is shown in one from Papua New Guinea.  This has numerous problems: 1) the pit cannot be emptied; 2) the vent is angled and therefore the light at the top will not attract flies from the pit; 3) the walls do not go up to the roof and therefore the cubicle will not be dark; 4) the plywood boxing around the pit opening will soon rot.

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A variant of the VIP latrine is the ‘pour-flush privy’ which uses a small quantity of water to flush solids into a pit and these can again be single or double pit.  The latrines have a water-seal in the pipe leading to the pit and although they do not use much water, they do require a water supply of some sort close to the latrine.  We used a variation of these in the clinics constructed by the East Timor health project (see the section of this web-site that covers this project).  We provided Asian-style squatting toilets next to small water storage tanks and the toilets were flushed with water from ladles; see Ross Bulletin 8: Small Excreta Disposal Systems for details.  This is a very useful publication and covers various options for the disposal of excreta in the rural areas.

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A problem that I have encountered several times with both VIP latrines and systems that use water and empty into septic tanks and soakaways, is where the ground water level is very high.  In these situations, VIP latrines should not be used especially if wells are being used at the same location for supplying water, as the latrines will probably infect the wells and cause disease.  Other solutions will have to be found which is not easy as I know.  In the Solomon Islands where the water table is often high and takes the form of a ‘bubble’ below the surface which must not be broken, beaches are used as latrines; one for males and one for females and the beaches are cleared by the tides.  Not an ideal solution but the only one in that situation.

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Where it is intended to use septic tanks and soakaways with a high water table, I have found two possible solutions.  The first is one that I used for the Autonomous Medical Store in East Timor (for further details see the East Timor section of this web-site) which was sited on ground where the water table was barely below ground level during the rainy season.  This is to raise the septic tank above ground level and construct soakaway mounds above the level of the existing ground.  These mounds should be planted with grass and then combine absorption and evapo-transpiration.  We tried this at the AMS and eventually go it to work after we had greatly extended the original mounds; see ‘Ross Bulletin 8: Small Excreta Disposal Systems’, pages 42 and 43 for details. The other solution which we are using in Tajikistan at the sites for two health centres with high water tables where we cannot use soakaway mounds, is to construct large, sealed, water-proof concrete tanks to store the effluent which then has to be pumped out by tankers.

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Some useful publications when considering the provision of toilets to rural schools are the following: UNICEF: Child-Friendly Hygiene and Sanitation Facilities in Schools; UNESCO EBD E5: Latrines for Schools; UNICEF: A Manual on School Sanitation and Hygiene and Technical Guide for Construction of School Sanitation Facilities in Nigeria.

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Some more general publications that are worth consulting are: Ventilated Improved Pit Latrines developed for a Nigerian community project; TAG Technical Note 6: Vent Pipe Design Guidelines; Sanitation Marketing Lessons from Cambodia and Rural Sanitation for Developing Countries.  Decentralised Waste Water Treatment is a comprehensive guide to water-based effluent disposal systems. Publications from the British Research Establishment that are also worth consulting are: OBN 189: Sanitation for Developing Communities; OBN 193: Mechanised Emptying of Pit Latrines; OBN 195: Disposal of Domestic Effluent and OBN 196: Health Aspects of Latrine Construction.

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My experience of the supply of water in rural areas also started with the Bo Teacher’s College Project where we constructed deep wells with hand-pumps to provide water to the schools.  The design of the wells was based on a design being used at the time in the country and worked very well.  We trained a team to construct the wells and purchased high-quality German-made pumps that sat on the concrete slab over the wells and were used to pump up the water.  A design guide for similar wells developed for a Nigerian community project is also very useful.

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In the Solomon Islands rural health project, the clinics and nurses’ houses were provided with large, aluminium water storage tanks on elevated stands supplied by roof gutters.  The country has rainfall throughout the year and this is a common way to provide water.  I do not like using roof gutters as they get blocked up and provide places for mosquitoes to breed but there was very little alternative.  An alternative to aluminium or plastic tanks are ferro-cement tanks that can be constructed on site.

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Other useful publications relevant to the provision of rural water supplies are: a design guide for rainwater catchment water supplies from Vanuatu (26); ‘Ross Bulletin 10: Small Water Supplies’ is a very useful publication that provides a variety of options for rural water supplies; BRE publication OBN 178: Village Water Supplies; Water Treatment and Sanitation that also covers rural sanitation; hand-pump maintenance  does what it says and  PACMEDIA Waste Water Treatment is a compact commercial system for water treatment that we used for Dili Hospital that was renovated and extended under the East Timor health project.