Key indicators (to be read in conjunction with the guidance notes)

Guidance notes

1. A sanitary survey is an assessment of conditions and practices that may constitute a public health risk. The assessment should cover possible sources of contamination to water at the source, in transport and in the home, as well as defecation practices, drainage and solid waste management. Community mapping is a particularly effective way of identifying where the public health risks are and thereby involving the community in finding ways to reduce these risks. Note that while animal excreta is not as harmful as human excreta, it can contain cryptosporidium, giardia, salmonella, campylobacter, caliciviruses and some other common causes of human diarrhoea and therefore does present a significant health risk.

2. Microbiological water quality: faecal coliform bacteria (>99% of which are E. coli) are an indicator of the level of human/animal waste contamination in water and the possibility of the presence of harmful pathogens. If any faecal coliforms are present the water should be treated. However, in the initial phase of a disaster, quantity is more important than quality (see Water supply standard 1, guidance note 4).

3. Promotion of protected sources: merely providing protected sources or treated water will have little impact unless people understand the health benefits of this water and therefore use it. People may prefer to use unprotected sources, e.g. rivers, lakes and unprotected wells, for reasons such as taste, proximity and social convenience. In such cases technicians, hygiene promoters and community mobilisers need to understand the rationale for these preferences so that consideration of them can be included in promotional messages and discussions.

4. Post-delivery contamination: water that is safe at the point of delivery can nevertheless present a significant health risk due to re-contamination during collection, storage and drawing. Steps that can be taken to minimise such risk include improved collection and storage practices, distributions of clean and appropriate collection and storage containers (see Water supply standard 3), treatment with a residual disinfectant, or treatment at the point of use. Water should be routinely sampled at the point of use to monitor the extent of any post-delivery contamination.

5. Water disinfection: water should be treated with a residual disinfectant such as chlorine if there is a significant risk of water source or post-delivery contamination. This risk will be determined by conditions in the community, such as population density, excreta disposal arrangements, hygiene practices and the prevalence of diarrhoeal disease. The risk assessment should also include qualitative community data regarding factors such as community perceptions of taste and palatability (see guidance note 6). Piped water supply for any large or concentrated population should be treated with a residual disinfectant and, in the case of a threat or the existence of a diarrhoea epidemic, all drinking water supplies should be treated, either before distribution or in the home. In order for water to be disinfected properly, turbidity must be below 5 NTU.

6. Chemical and radiological contamination: where hydrogeological records or knowledge of industrial or military activity suggest that water supplies may carry chemical or radiological health risks, those risks should be assessed rapidly by carrying out chemical analysis. A decision that balances short-term public health risks and benefits should then be made. A decision about using possibly contaminated water for longer-term supplies should be made on the basis of a more thorough professional assessment and analysis of the health implications.

7. Palatability: although taste is not in itself a direct health problem (e.g. slightly saline water), if the safe water supply does not taste good, users may drink from unsafe sources and put their health at risk. This may also be a risk when chlorinated water is supplied, in which case promotional activities are needed to ensure that only safe supplies are used.

8. Water quality for health centres: all water for hospitals, health centres and feeding centres should be treated with chlorine or another residual disinfectant. In situations where water is likely to be rationed by an interruption of supply, sufficient water storage should be available at the centre to ensure an uninterrupted supply at normal levels of utilisation (see Appendix 2).