Contaminación Del Agua

FINAL REPORT

NICARAGUA

HOUSEHOLD WATER SUPPLY AND TESTING PROJECT

by David H. Manz1, Byron Buzunis2 and Carlos Morales3

December 1993

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Associate Professor, Department of civil Engineering, and Senior Research Associate, Division of International Development of the International Centre of the University of Calgary, Calgary, Alberta, Canada, T2N lN4. T.N.(403) 220-5503. FAX (403)2827026. Graduate student, Department of civil Engineering, University of Calgary, Calgary, Alberta, Canada, T2N lN4. Environmental health consultant, Pan American Health Organization, Nicaragua.

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1.0 Introduction Water suitable for drinking is often very difficult to find or produce in the rural areas of Nicaragua. Though considerable progress has been made to ensure thatpotable water is available to cities and towns, up to 88% of the population outside of major population centres are unable to access safe drinking water. Virtually 100% of farm households have no access to safe drinking water. It is estimated that 48% of the entire population of Nicaragua cannot be adequately served by any existing or proposed potable water supply programs. Cholera epidemics are commonand devastating to the communities in which they occur. (Personal communication with PAHO(Nicaragua), Nicaragua Ministry of Health (MINSA) and Nicaragua Ministry of Water and Sanitation (INAA) staff.) 2.0 Technical Background A serious problem facing those who wish to assist the rural communities in obtaining suitable drinking water is the selection of the technology to be used. The technologychosen must not only perform its intended purpose, it must be affordable, culturally acceptable and very well understood by the people who will be using it. In short, the technology must be appropriate and sustainable. Despite the existence of a vast knowledge base on water supply development and treatment, only a few solutions may be recommended for use in rural communities. Uncontaminated watersupplies may be obtained from borehole wells and springs. However, to be affordable the costs for construction, operation and maintenance need to be shared by an informed and organized community .These water supplies may be contaminated, and frequently are, if they are not operated correctly. In situations where uncontaminated water cannot be found, treatment is the only available solution. Thewater can be boiled but fuel may be expensive or unavailable. Chemicals such as chlorine and iodine, commonly used for water disinfection, may be considered expensive and sometimes undesirable (taste, odour etc.). Simple water filters, such as recommended by the World Health Organization 1987 and common to many peoples of the world, are not intended to and cannot provide the quality of treatmentnecessary to produce pathogen free water . .0" Slow sand filtration, (SSP), has been successfully used for water treatment since the midnineteenth century, Huisman and Wood 1974. It was developed to economically treat large amounts of water which would then be available for distribution. Removal rates of total and faecal bacteria vary between 99 to loo percent, Bellamy et al. 1985a and Bellamy et al.1985b. (It is important to note that the bacteria responsible for cholera, Vibrio Cholerae, is very similar to E. coli bacteria, (faecal coliform bacteria), with respect to its shape, size and how it lives and can be expected to be removed at rates very similar to E. coli.) Removal rates of viruses are reported to vary between 99.9 to 100 percent depending on filter design, Hendricks and Bellamy1991. Removal rates of cysts of Giardia and Cryptosporidium, which are both resistant to disinfection, are reported to be greater than 99.99 percent, Bellamy et al. 1985a and Schuler and Ghosh 1991. Removal of schistosome cercariae, the cause of schistosomiasis, is estimated to be 100 percent, Bernarde and Johnson 1970. Concentration of total or E. coli bacteria measured in terms of number of...