|Handbook for Emergencies - Second Edition (UNHCR, 1999, 414 p.)|
|17. Environmental sanitation|
· Take immediate action to localize excretia disposal and prevent contamination of the water supply;
· Carefully consider cultural and physical factors and ensure that appropriate anal cleaning materials and hand-washing facilities are available;
· Communal trench latrines may be needed initially, but in most circumstances pit latrines are much better;
· Ensure that latrines can be used at night and are safe for women and children.
21. The priority is to create an efficient barrier against faecal contamination. This can be assured through a sufficient number of sanitary facilities, ensuring that these facilities are properly used and kept clean, and do not become the source of problems such as bad smells and flies, and do not collapse when it rains.
The most common cause of breakdown is inadequate maintenance, even for properly designed and installed systems.
22. The best guarantee of proper maintenance is the individual family allocation of latrines. Breakdown of latrines will lead to contamination of the environment and a high risk of infection and disease. There must be regular inspection and maintenance.
Even when in working order, latrines will not be used unless they are clean. Latrines must be cleaned daily.
23. Individual families will be responsible for their own units, but where communal latrines are unavoidable, special arrangements to keep them clean will be essential. Particular attention must be given to the maintenance and cleanliness of the latrines serving community facilities such as health centres. Refugee workers with proper supervision will be required. It may be necessary to pay or otherwise compensate those who are responsible for keeping communal latrines clean and operational.
24. Disinfectants would prevent the biological degradation of excretia. However the regular addition of soil, ashes or oil, if available, to trench or pit latrines may help control insect breeding and reduce odours.
Disinfectants should not be poured into the pits or tanks of latrines.
25. Two main factors will affect the choice of an excretia disposal system: the traditional sanitation practices of the refugees and the physical characteristics of the area, including the geology, the availability of water, rainfall and drainage. Failure to take proper account of these can easily result in the system itself rapidly becoming a health hazard.
26. The essential starting point is to find out the traditional sanitation practices of the refugees and how these can be modified to reduce health risks in a refugee emergency. The following information will be required:
Previous sanitation system and practices;
Method of anal cleaning;
Preferred position (sitting or squatting);
Need for privacy;
Segregation of sexes and other groups or individuals with whom it is culturally unacceptable to share a latrine;
Cultural practices for children;
Cultural taboos (for example, against contact with anything that may have touched excretia of others);
Social factors, including likelihood of community action to ensure proper use of proposed system;
Need for special orientation (direction) of latrines in some cultures;
Systems used locally in neighbourhood of site.
27. Arrangements must be made to assure the availability of appropriate anal cleaning materials at or near all latrines. This is essential for hygiene.
The latrines must be safe 'for children, and must be able to be used at night.
Pay attention to security for women: for communal units some form of lighting should be provided and it may be necessary to provide guards.
28. Initially the refugees are likely to defecate indiscriminately, contaminating their environment and often the water supply. In consultation with the community leaders, the best first step is to demarcate defecation fields to localize and contain excretia.
29. Designate an area or areas (about 50 m × 50 m each) away from the dwellings and down wind, but sufficiently close to be used. Separate areas for men and women are usually desirable. Within the defecation field, strips of land - roughly 1.5 m wide, 20 m long, on each side of a central access path - will be used, one after the other, beginning with strips farthest from the entrance.
30. Based on a recommended surface area of 0.25 m2 per person per day, exclusive of access paths, defecation fields of the size above would be sufficient for about 250 people during a month, or 500 people during two weeks. Operating defecation fields beyond one month is not advisable.
31. Fence the area(s) and provide privacy by means of partitions and shallow trenches (in the strips) and spades, if possible. Covering excretia with ash, lime or just soil lessens health risks. Locate such areas where the surface water run-off will not cause contamination. Protect the area with cut-off ditches.
32. A publicity campaign will be required to encourage refugees to use these areas and not defecate indiscriminately near dwellings or the water supply. At least one attendant should be assigned to each defecation field. To the extent possible, hand-washing facilities should also be installed nearby.
Selection of a System: Basic Considerations
33. The selection of an excretia disposal system suitable for a particular situation requires consideration of a number of factors. In an emergency, however, time is the critical factor. Pollution of the environment by excretia, with all its attendant risks, cannot be stopped without immediate sanitation measures. Thus the range of choice is always much more limited at the very outset of an emergency.
34. Temporary systems, to meet the most immediate needs, will have to be improved or replaced by others as soon as possible, in order to maintain adequate sanitation standards.
In emergency sanitation, act first and improve later.
35. Figure 1 illustrates some considerations to be taken into account in excretia disposal.
36. The design of sanitary facilities should be governed by cultural factors (discussed above) and by the following physical considerations:
i. Flies and smells: these can be reduced by: installing vent pipes topped with anti-corrosive screens; covering faeces regularly with ash; treating latrines with biological larvicides to control fly larvae; using fly traps, etc.;
ii. Flooded pits or collapsed walls: these can be avoided by ensuring proper construction including having a raised superstructure, well-built base and mound, pit lining, and good drainage. Sometimes these steps are not taken because of, for instance, financial considerations. However, a large number of latrines built quickly and cheaply will not necessarily solve environmental health problems;
iii. Life-span: to dig a pit for excretia is not a very exciting exercise. Normally, the pit should be designed to last two to three years (the capacity of a dry pit should be at least 0.07 cubic meters per person per year). If its dimensions have not been properly calculated, people will have to dig a new pit a short time later. Community members would understandably be reluctant to do this and the site would become covered with pits, some containing unstabilised faecal matter hazardous to human health. In addition, shortage of space limits the number of latrines which can be built;
iv. Cleanliness and privacy: Communal installations are rarely kept clean and become unusable within a very short period of time and encourage transmission of diseases. Therefore family latrines should be preferred whenever possible. Sanitary facilities should preserve users' privacy. Cubicles should be partitioned off within each block. At family and individual level, socio-cultural considerations often make it compulsory to build separated units for men and women. Disregard for these simple criteria might result in misuse and abandonment of facilities;
v. Location: groundwater pollution must be nil or at a minimum. Latrines should be at least 30 m from any groundwater source and the bottom of any latrine at least 1.5 m above the water table. Latrines must be close enough to users' shelters to encourage their use (not more than 50 m). They must be far enough from shelters and other buildings to prevent potential smells and pests from bothering or harming the population (at least 6 m from shelters if possible).
37. There are a number of latrine options: once cultural and physical factors have been taken into account, the key factors to consider are low cost, simplicity of construction and ease of maintenance.
38. Trenches can be used for a few months. If necessary, and where space is available, this solution can continue for longer periods, with new trenches being dug as old ones fill up.
Trench latrines should be dug 1.8 to 2.5 m deep and 75-90 cm wide. Recommended length per 100 persons is 3.5 m.
39. A platform and structure will be needed, providing a seat or squatting hole as appropriate, with lid. When the trench is filled to within 30 cm of the top, it must be covered with soil and compacted. Trench sides must be shored up if there is a danger of collapse.
40. The pit latrine is the most common excretia disposal system used around the world (see figure 2a). It has major advantages over a trench latrine. It consists of four basic components: a pit, a base, a squatting slab (or plate) and a superstructure.
41. If used by only one family these latrines are usually well maintained. Pit latrines can also be used in clusters as communal facilities.
42. Pit latrines are most suitable in conditions of low to medium population density - up to about 300 persons/hectare - but have been used satisfactorily in areas with twice this density. Space is needed not only for the construction of one pit latrine per family, but also for new pits when the old ones are full. This is an important consideration when pit latrines are used as communal facilities.
43. When the pits are three-quarters full, they must be filled with soil and the superstructure and squatting plate moved to a new pit. Applying layers of ashes as the pit fills will speed up the decomposition of excretia and in time the site can be used again.
44. The pit should be about one meter across and over two meters deep. The rim of the pit should be raised about 15 cm off the ground and ditches should be dug around the base to divert surface run off. The pit wall should always be reinforced for one meter below ground level to prevent collapse.
45. The basic variety has both odour and insect problems, but these can be considerably reduced by making the simple improvements of the ventilated improved version (VIP) (see figure 2b), and by adding oil and using lids.
Where pit latrines are used, the ventilated improved version should be built whenever possible.
46. In a VIP latrine the vent pipe should be at least 15 cm in diameter, about 2.5 m high, painted black and placed on the sunny side of the latrine for maximum odour and insect control. Blackening the external surface of the vent pipe only marginally increases the venting velocity, but this factor may be of greater importance under "no wind" conditions. The vent pipe must be fitted with an insect proof gauze screen (so it works as a fly trap). The hole should not be covered by a lid as this impedes the air flow.
47. Bore-hole latrines (figure 3) are dug with a hand auger or mechanical drill and require a smaller slab than a pit. The bore-hole is 35-45 cm in diameter and any depth up to 7 meters. The advantage of the bore-hole latrine is that it can be constructed quickly as a family unit if augers are available. The disadvantages are that the side walls are liable to fouling and fly breeding, they are smellier than vented systems and the risk of ground water contamination is greater because of the depth.
Ventilated Improved Double-Pit (VIDP) Latrine
48. Raised (or built-up) pits can be used where it is not possible to dig deep pits because the water table is high or excavation is difficult (for example in rocky ground).
49. The VIDP latrine (figure 4) (also called alternating-twin pit ventilated latrine) has two shallow pits, both of which are ventilated by separate vent pipes capped with fly screens. It is a good option in crowded areas which may become even more crowded, as it preserves the space needed for replacement latrines.
50. Two pits give more flexibility. A pit fills up in two to three years, and it should then stand for at least one year. This gives enough time for the night soil to dry out and decompose, so that it can be removed more easily and not pose a health hazard. While the full pit is decomposing, the other pit is used. The two pits must not be used at the same time.
Pour-Flush (PF) Latrine
51. Pour-flush latrines (figure 5) are simple in design but need permeable soil for their soak-away. A water seal is made by a U-pipe filled with water below the squatting pan or seat. It is flushed by hand with some 1-3 litres of water into a pit or soak-away. This system is suitable where water is used for anal cleaning and where refugees are used to flushing. It is not suitable where paper, stones, corncobs or other solid materials are used for anal cleaning. Pour-flush latrines will be used properly only if water is readily available. A large container with a 3 litre dipper should be made available close by the latrines.
52. Where liquid effluent has to be disposed of in impermeable soil, stabilization (oxidation) ponds are a simple and cheap solution, particularly in hot climates. Various systems are described in the technical references. If ponds are used they must be securely fenced off.