|Primary School Physical Environment and Health - WHO Global School Health Initiative (SIDA - WHO, 1997, 96 p.)|
The main purpose of school environmental sanitation is to prevent the exposure of students and staff to pathogenic organisms. Meeting this objective requires: effective human excreta disposal facilities; a regular water supply; safe drinking-water; easy-to-use handwashing arrangements; good drainage; and a functioning system for cleaning the premises and removing waste. Any physical improvements must of course be accompanied by hygiene education.
All these points, but particularly the management of human excreta and related behavioural issues, are heavily influenced by the local natural environment and cultural traditions. Universal prescriptions are of limited value and production of a meaningful manual to cover every situation would be impossible. The purpose of this appendix, therefore, is merely to outline some general principles and indicate the range of technical solutions available.
Human excreta disposal
Human excreta consists of urine and faeces. These two substances have quite different properties.
· Urine is basically water and dissolved nutrients. From a health point of view it is reasonably safe, as long as it is not directly deposited in ponds, streams or lakes. In fact, it is of potential value as a fertilizer. Urine is fairly easy to dispose of within a school compound. It can be infiltrated into the ground, evaporated, or collected in a container for use (diluted with water) as a fertilizer.
· Faeces consist of water, cellulose fibres, nutrients, bacteria, viruses and parasite eggs. From a health point of view faecal matter is extremely dangerous and many cultures have strong taboos about handling it or cleaning up a faecally-contaminated environment. It is difficult to dispose of and there are no easy, low-cost methods.
Schools basically have three options for human excreta disposal: drop-and-store, flush-and-discharge, or sanitize-and-reuse.
A drop-and-store toilet is basically a storage chamber for isolating the pathogens contained in faeces so that they cannot spread in the environment. There are three types: the ventilated improved pit toilet (VIP), the traditional pit toilet (TPT) and the toilet with urine separation (TUS).
The VIP toilet. Where site, soil and groundwater conditions permit the digging of pits 2-4 m deep, the VIP toilet is a well-tested, robust and long-lasting solution. If properly built and maintained, it is almost odour-free and fly-breeding reduced to a minimum. Variations on the VIP theme have been in use in west Africa since at least the 1940s.(18) In eastern and southern Africa, particularly in Zimbabwe, the VIP toilet has been in use since the 1970s. A full description, including a version for schools with several compartments, can be found in Morgan(19) and in a number of manuals on sanitation published over the past 20 years.(20, 21, 22)
© Ministry of Health, Zimbabwe.
The main disadvantage of the VIP toilet is its high initial cost. Many poor communities claim that they cannot afford to provide their school with toilets of a VIP standard.
The TPT. A low-cost alternative to the VIP toilet is the traditional pit toilet. It is reasonably easy to build, given favourable site, soil and groundwater conditions. Its functioning is easy to understand and, like the VIP, it can withstand considerable abuse and still function. The main disadvantages of the traditional pit toilet are that it smells unpleasant and that it generally produces considerable amounts of flies.
The TUS. With some modification in design, and changes in user behaviour, it is possible to eliminate or considerably reduce the two aforementioned faults of the pit toilet. A bacterium present in human faeces, Micrococcus ureae, uses its urease enzyme to split the carbamide in urine into ammonia and carbon dioxide. It is this process that produces the unpleasant smell when human faeces and urine are mixed. The modified toilet, therefore, involves keeping urine and faeces separate. It is most appropriate in areas with a fairly dry climate, and where water is not used for anal cleaning (as the pit must be kept dry).
Pit toilets with urine diversion have recently been developed in El Salvador.(23) The pit and superstructure are no different from those of ordinary toilets. The difference is in the squatting slab or the seat and bowl, which are designed in such a way that urine is collected separately and drained off into a soakage trench. Where this type of toilet is used, a sufficient number of urinals must also be provided, for girls as well as boys.
To reduce the risk of fly-breeding, some dry material (for example, ash, soil, husks or yard sweepings) should be added at the end of every day that the toilet is in use.
A flush toilet is a machine for mixing water, urine and faeces. The water is used to transport the excreta through pipes to a septic tank on site, or to a lake, river or the ocean via a municipal sewerage system. A water seal prevents odours from coming back up the pipe.
The WC. A typical school in a developing country has no access to a municipal sewerage system. There is usually not enough water to run sewered WCs, nor enough money to operate and maintain them. They would therefore not be a realistic option in most of the situations described in this document.
The pour-flush toilet. In communities where water is traditionally used for anal cleaning, some kind of pour-flush toilet can be an option. The pour-flush toilet has a water seal and is therefore odour-free and fly-proof.(20, 22, 24)
These toilets are based on the destruction of pathogens and the reuse of urine and/or processed human faeces as fertilizer and soil conditioner. Pathogen destruction is accomplished either through a dehydration process or decomposition (composting).(25)
In most sanitize-and-reuse systems, urine and faeces are treated separately. The best method is never to let the two substances mix. Use of modified squatting slabs and toilet seats will achieve this (see above, the TUS). More examples of toilets designed for urine separation can be found in Winblad and Kilama.(20) When urine is collected separately it remains relatively sterile and can often be used as a fertilizer without any further treatment.
So far, toilets based on dehydration or decomposition have not been tested systematically in a school environment. However, the technology is simple and costs can be fairly low. On the other hand, these dry toilets are more easily misused than pit toilets and should be introduced only where sustained competent operation can be expected. The main use for dry-and-reuse technologies is where local conditions rule out any other toilet system: where the ground is too rocky for digging pits; where the ground-water level is too high; where the land is seasonally flooded; or where the environment is so sensitive that any discharges into soil or groundwater would be unacceptable.
The dehydrating toilet. The Vietnamese dehydrating toilet is a box with two chambers built above ground. Urine is collected separately and piped into a jar, where it is stored until used as a fertilizer. Faeces drop into one of the chambers (the other is kept closed). Paper used for anal cleaning is put into a metal bucket and burnt.
After defecating, users sprinkle some ash, lime or soil onto the faeces. When the chamber is nearly full it is topped up with soil and the drop-hole is sealed with mud. The second chamber is then used. When the second chamber is nearly full, the first is opened and emptied. The dehydration process kills the pathogens in the faeces and makes them safe for use as a fertilizer and soil conditioner.(20)
The composting toilet. The composting toilet illustrated below was developed by Greenpeace, an environmental organization, in an attempt to protect the sensitive natural environment of the Pacific islands. It is a single-chamber composting toilet, combined with a greenhouse for evapotranspiration of urine and water. A nylon fishing net hanging from hooks fastened to the chamber walls is used to separate solids from liquids. A mat woven from palm leaves sits in the net to catch solid materials. In some cases, strips of polyester torn from old clothing hang from the net. These enhance evaporation by acting as wicks to draw up liquids into the airflow generated by the large-diameter vent-pipe.(26, 27)
Toilets for temporary use
In times of disaster or emergency, existing toilets may become suddenly unusable. Or special events at a school may require extra temporary toilets for a few days. In dry weather the shallow trench latrine can be used.(28) In wet weather, a bucket toilet with urine separation is a possible option. This is less smelly, easier to handle and requires less frequent emptying than a conventional bucket toilet system (which mixes urine and faeces).
Although toilets are used for urination as well as defecation, there are good reasons for schools to provide urinals. Conventionally, urinals are provided only for boys, but they can also be effectively used by girls. Where urinals are provided, the number of toilets required is reduced. A good urinal can be built and maintained at lower cost than a good toilet. As stated above, odours will be reduced if urine and faeces are dealt with separately.
The compost urinal. The simplest form of urinal is an enclosure around a paved floor, with a shallow pit or trench filled with a mixture of dry organic material (grass, leaves and compost). The pit or trench should be no more than 50-60 cm deep. Once a week the urine-soaked organic material should be removed to a compost heap and the trench refilled with dry organic material. A detailed description of a slightly more elaborate - and odour-free - composting urinal can be found in Patel.(29)
How many toilets and urinals? Many countries have recommendations about how many toilets and urinals should be provided for a given school population. The figures can vary enormously. In Thailand, it is typically 3 toilets per 100 pupils, while in Viet Nam it is 1 toilet for every 100-200 pupils. Reasons for the wide variations include differences in climate, diet, school hours, proximity of the pupils homes and so on. It therefore serves little purpose to specify universal norms.
A primary school needs water for general cleaning purposes, personal hygiene, the operation of WCs and pour-flush toilets, and to water plants. In addition, the school must be able to provide safe drinking-water for students and staff.
Ideally, a school should have its own reliable water-supply system. This may be: piped water from a municipal supply; a gravity-flow system from a natural spring; water drawn from a pond, borehole or well, or collected rainwater. Until such a system is set up, water must be carried to the school, either by vehicle or in bottles and cans by students and staff. The variety of situations and options available is too large to be meaningfully dealt with in this document, but the illustrations show some examples.
Handwashing can be arranged in many ways and at low cost, even where there is no piped supply of water. The illustrations show a number of examples.
© Ministry of Health, Zimbabwe.
In areas where trachoma is a problem, washing facilities should be extended to enable daily face-washing by all students. However, no towels should be provided as this could contribute to the spread of the disease.
Schoolchildren in developing countries sometimes bring their own water bottle to school. Some countries, however, have set minimum standards for the supply of safe drinking-water to pupils. For instance, in Viet Nam, every school is supposed to provide 0.33 litres of boiled water per pupil per day in summer and 0.1 litres in winter.
Some schools boil water to make it safe. Fuel can be saved if this is done on an energy-efficient stove. Examples of stoves are given in Micuta.(30)
© Bellerive Foundation, Switzerland.
Drinking-water can also be disinfected using ultraviolet radiation. In its simplest form the treatment involves filling transparent containers, such as plastic bags with water, then exposing them to sunlight for several hours. Another method is to direct a continuous flow of water through a solar collector. Disinfection is achieved through a combination of ultraviolet radiation and increased temperature.(31)
Drainage. This is an important matter associated with water, its supply and use. All stagnant water around water-supply points should be drained away to flower-beds, trees, banana plants, etc., or to a stone-filled drainage trench.(20)
Solid waste disposal
Schools produce paper, cardboard and plastic waste which has to be collected for disposal. Suitable containers must be provided in classrooms. However, there may not be an organized system of waste collection in the local community. In such instances, paper waste can either be buried in the ground or burnt in an incinerator made from an oil drum. Organic material can be composted, for instance in big cement rings, and used as fertilizer for trees and plants in the school compound. The Ministry of Health in Thailand is currently testing a system of waste separation in schools by providing three containers: for organic waste, non-organic waste and paper.