POLLUTION RISK ASSESSMENT OF GROUNDWATER USING GEOSPATIAL TECHNOLOGY AT KAMKUYWA MARKET CENTER, BUNGOMA

Abstract

Pathogenic contamination of groundwater due to poor sanitation has continuously posed a significant human health risk. Kamkuywa Market Center a peri-urban settlement relies heavily on shallow wells for water supply and use of pit latrines as a means of fecal waste disposal. This increases the risk of groundwater microbial contamination. The objectives of the were to establish the extent of groundwater pollution by coliforms, to determines the relationship between groundwater contamination and selected risk factors, namely: depth to the water table, distance from a shallow well to the nearest pit latrine, pit latrine depth, soil permeability and ground slope for purposes of establishing the optimal well-pit latrine separation distances under different hydro-geological conditions. 531 shallow wells and 1061 pit latrines in the study area were mapped and the separation distances compared to the recommended global and local standards. Water samples in thirty two (32) shallow wells were collected and analyzed for fecal matter content. Regression model was used to determine the relationship between coliform concentration and the selected risk factors such as the separation distances between pit latrines and shallow wells, the depths of pit latrines and shallow wells, and the soil type as well as establish the extent of contamination and optimal distancing. The results indicated that 67.6% of shallow wells did not meet the World Health Organization and the Kenya safe distance criteria. In terms of relationship, pit latrine depth and soil permeability positively correlated with contamination while a negative relationship was established between groundwater contamination and water table depth. There was no relationship established between groundwater contamination and surface slope. Out of 32 shallow wells sampled for fecal coliform analysis, 31 shallow wells tested positive for fecal coliforms. The study also established that over 75% of the study area posted a high risk for groundwater contamination. The predicted optimal distance between wells and pit latrines in the study area ranged between 31m-33m. The study concludes that fecal coliform contamination of groundwater is widespread in Kamkuywa Market Center. The widespread contamination is as a result of extensive groundwater contamination from pit latrines. The study therefore recommended the treatment of domestic water before use, adoption of community septic system and sensitization and awareness on proper siting for pit lines and shallow wells in Kamkuywa Market Center.