The assessment of ground water quality for domestic purpose – a site study of Obuasi

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Groundwater is a major source of drinking water to the majority of the people at Obuasi and the surrounding villages. Above all, it provides the base flow for springs, rivers and streams and hence contaminated groundwater may also constitute a hazard to aquatic life and to bathers. Once polluted, it takes a long time to restore to its original purity or state. There is increasing concern that the groundwater reserves in Obuasi are being polluted by pesticides, chemical from the application of fertilizer in farming and industrial effluents, especially mining wastes. The groundwater in Obuasi is suitable for drinking purposes and the natural quality is predominantly controlled by the chemical properties of run-off infiltration, the mineralogy of the soils and aquifer materials, and the residence time in the groundwater system. Human activity especially agriculture and gold mining in the study area, has affected the groundwater quality. Elevated gold mining-related pollutants, arsenic and lead levels are found at Odumasi, Gyimisokakraba, and Kokotenten. The groundwater is generally, characterized by slightly acidic conditions, softness, high alkalinity, low sodium and total dissolved solids levels. The concentration of gold mining-related pollutants is inversely proportional, while suspended solids, turbidity, total dissolved solids and conductivity are directly proportional to distance along the groundwater flow direction. Sampled boreholes showed relatively high levels of turbidity than the wells. Physical, chemical, microbiological, major and trace metals in general were low. The aim of this thesis report is to assess groundwater quality intended for domestic purposes using Obuasi, which is also a mining area as a site study. It involves defining and determining groundwater quality parameters due to domestic effluent discharges, farming and gold mining activity. This analysis incorporates procedures involved in the determination of water quality parameters and comparing to some of the existing World Health Organization (WHO) acceptable water quality standards or guidelines for drinking water. The problem of contaminated groundwater can really be solved only by prevention, which will require the effective enforcement of stricter controls both on the use of agro-chemical pesticides and fertilizers, and also on mining activity and waste discharge both deliberate and accidental.
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, 2001