Effectiveness of slow sand filtration for improvement of surface reservoir waters for rural water supply

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In parts of the rural areas of northern Ghana where groundwater is generally inaccessible for exploitation, resort is made to streams, ponds, and constructed surface water reservoirs for drinking water. These sources of water are unprotected and highly susceptible to faecal and agro-chemical contamination. The exposed nature of such waters also creates ample breeding grounds for parasitic disease agents. The potential health risks of such sources are therefore quite substantial. Since a large percentage (about 30%) of common diseases is attributable to ingestion of unsafe water, there is a need to improve drinking water quality especially for community water supplies. The low technology and income status of most rural areas dictate that any intervention must be low-cost and simplified (appropriate technology). Bearing the above considerations in mind it is imperative that research into simplified treatment possibilities be intensified to provide information for the design, construction and operation of full-scale plants. This particular research activity involved the design, construction and operation of a pilot slow sand filter plant to generate data about the actual performance of a simplified slow sand filtration system within the typical rural setting of the selected study area. Samples were taken from the effluents of the different filter components and analysed for concentrations of some selected water quality parameters. The percentage reductions in the concentrations of the selected parameters, due to the actions of the various filter units, were then determined and the effectiveness of the unit operations analysed for the different parameters. The progressive improvement in the quality of the final water was monitored during the period of the filter run to determine the ripening period of the slow sand filter. The final water quality parameters were compared to the stated WHO guideline values for drinking water to determine the acceptability of the final product. A series arrangement was adopted for the roughing filters to enable an estimation of a suitable filter length. Protective measures were incorporated in the design to safeguard the quality of the final water against contamination during the fetching process. Interactions with the members of the user community yielded some interesting information about certain conditions that would compel them to abandon the whole facility. Based on the field experiences and analysis of laboratory tests, recommendations have been proposed for better design and operation of future village-scale plants. Serious attention has also been drawn to the importance of training for sustainable use of the filter system. The conclusion drawn from the analysis of the results of this research is that slow sand filtration is a feasible and appropriate water treatment technology for village-level surface reservoir water improvement in the Northern Region of Ghana.
A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirement for the award of the Degree of Master of Science in Water Supply and Environmental Sanitation, 1999