Sanitation

With food and water supplies, the emphasis is on the prevention of contamination, but with sanitation, it is reducing the source of the contamination. Social habits concerned with excreta disposal are often strongly held and unless these are approached in a sensible manner, any new system will fail. Sanitation is not just the provision of latrines, but a complex and inter-related subject involving people, water supplies and all other aspects of environmental health.

Health factors As shown in Table 3.1, the main impact of sanitation is on groups 2, 3a, 4c and 5c. The installation of sanitation may produce a reduction in the infections shown in Table 3.7.

The provision of sanitation When providing sanitation, there is a sharp contrast with water supplies. Everybody wants a water supply, but nobody wants to change his or her defecation practice. This is quite simple to explain in that substances taken into the body can be understood as a direct cause of illness, whereas excreting something from the body cannot. Defecation is a necessary, but private business and is not a matter for discussion. There are also social reasons that are set by religious, racial or cultural practice. These may dictate where and where not to defecate, will probably separate the sexes and define particular anal-cleansing practices. With all these patterns and customs that have been taught since childhood, any change becomes a long and difficult process. If a family can see the benefits of a latrine, then they will install and look after it; the health authority can then assist in technical specifications and subsidize costs. Any attempt to impose systems or even build them free of charge will cause resentment or non-use.

Like water, sanitation has to be paid for, but here costs are even less accepted by the population. People are only prepared to pay for the minimum possible in getting rid of their excreta. Only in urban areas will it be considered necessary to pay for the removal of excrement; in rural areas, there is sufficient space. A subsidizing scheme then becomes the main way in which sanitation can be improved. For instance, in pit latrine construction, villagers will need to dig their own hole, but might be sold a bag of cement at a reduced price or be provided with a squatting slab free of charge.

Cost is related to convenience, which is why people are prepared to pay for improved systems, their willingness to pay usually having nothing to do with health. A good pit latrine can be as effective in disease control as a conventional water-carried sewage system, the only difference being that the former is outside the house, while the latter carries excreta from within the house. The cost of this convenience is typically ten times that of a pit latrine.

In choosing the most appropriate excreta disposal system, the emphasis should be on simplicity. Only when a simpler method becomes outmoded because of rising standards and expectations will a more sophisticated system become appropriate. A simple incremental process, as illustrated in Fig. 3.8, can be planned. The first stage is to bury excreta, which will lead on to using a pit latrine. If pit latrines are already accepted by the community, then demonstrating the advantages of improved pit latrines will be the next step. The type of facility will also be determined by the availability of water. As mentioned in Section 3.3.3, the provision of water should precede any sanitation programme as

Table 3.7.

The expected improvements from the installation of sanitation.

Possible

Category

Infection

Through reduced contamination of

reduction

1

Trachoma

The environment; flies (group 5c)

+

2

Enteric viruses (including hepatitis A)

Vegetables

+

2

Hymenolepis

Food and water

+

2

Amoebiasis

Vegetables

++

2

Trichuris

Food and water

+

2

Giardia

Food and water

+

2

Shigella

Food and water

++

2

Typhoid

Food and water

++

2

Other Salmonellae

Food and water

++

2

Campylobacter

Food and water

++

2

Non-specific diarrhoeal diseases

Food and water

++

2

Cholera

Food and water

++

3a

Ascaris

Soil

+ + +

3a

Hookworm

Soil

+ + +

3a

Strongyloides

Soil

+ + +

3b

Taenia

Soil

+ + +

4b

Schistosomiasis

Water

+

4c

Fasciolopsis

Water

+

4c

Opisthorchis

Water

+

4c

Paragonimus

Water

+

4c

Diphyllobothrium

Water

+

5

Housefly-transmitted diseases

The environment; flies

±±a

5

Filariasis

Water and Culex quinquefasciatus breeding

+

Sanitation, if not properly built or maintained, can be as responsible for increasing the fly nuisance as well as decreasing it. Refer to footnote of Table 3.2 for the description of+++, ++, + and ±.

Sanitation, if not properly built or maintained, can be as responsible for increasing the fly nuisance as well as decreasing it. Refer to footnote of Table 3.2 for the description of+++, ++, + and ±.

personal hygiene can only be taught if there is water at hand to wash with. The quantity and proximity of this water will then determine the type of sanitary system that can be used. In the second part of Fig. 3.8, the incremental progression of a water-utilizing sanitary system is shown. A pour-flush latrine can be installed where water is obtained from a village standpipe, but with a septic tank or sewerage, a water-flushing system requires in-house water connections.

Siting and contamination The unit must be sited so that it does not contaminate the environment in such a way as to threaten the health of others. With a pit latrine, bacterial pollution can travel downwards for a distance of up to 2 m. If the contamination reaches the water table, it will flow horizontally for up to 10 m. This means that any latrine should be sited at least this distance away from a water supply, such as a well. The latrine should also be placed downhill to the well, although excessive pumping will draw water into the well from all directions, including possibly from a latrine. If a latrine is built less than 10 m from a river or stream, it can pollute it, as the water table will be flowing towards the stream. Latrines in this situation can be potent sources of pollution if the river is used for drinking water. Pollution of the soil is a complex subject and the rough rule of 10 m distance between a latrine and source of drinking water is given as a guide. Contamination is dependent upon the following:

• the velocity of groundwater flow (should be less than 10 m in 10 days);

• the composition of the soil (not fissured, e.g. as in limestone).

Expert advice should be obtained before embarking on a latrine programme.

In a sealed system such as a septic tank or an aquaprivy, contamination of the soil will not take place unless there is a crack in the structure. However, the effluent is highly charged with pathogens and must be disposed of properly. Running it into a storm drain, as often happens, is a bad practice and poses considerable threat of infection. The easiest solution is to lead it into a soakaway, but precautions similar to a latrine need to be taken.

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