Effect of Depth and Distance of the Borehole from the Septic Tank on the Physico-Chemical Quality of Water

Abstract

A study to examine the effect of depth and distance of the boreholes from the septic tank on physico-chemical parameters of the borehole water consumed in Dar Es Salaam, Tanzania was conducted. Samples were collected from 48 boreholes in Ilala, Kinondoni and Temeke districts and subjected to pH, B.O.D (Biological Oxygen Demand), total hardness, copper and lead analyses in relation to safety and quality levels set by WHO and TBS. Analysis by R-statistics indicated that pH and B.O.D significantly (p<0.05) decreased as the depth of borehole increased, whereas total hardness was significantly (p<0.05) higher in very deep boreholes than the other heights. Total hardness and pH were not significantly (p>0.05) affected by distance between septic tank and borehole and the B.O.D levels were significantly higher in the borehole water situated near the septic tank than those which were far. Based on the physico-chemical characteristics of water, 25% of the samples did not comply with WHO and TBS specification limits while 75% complied, most of which had shallow depths and were situated near the septic tank. It may thus be concluded that both the distance and the depth between septic tank and borehole influenced physico-chemical characteristics of water.