Effects of siting boreholes and septic tanks on groundwater quality in Saint Bonaventure Township of Lusaka District

Abstract

The rapid population growth of Lusaka has brought adverse effects on water supply and sewage treatment facilities in the District. Consequently, authorities in Lusaka have allowed use of septic tanks and boreholes in the same area in some Townships. St. Bonaventure located about 7km from Town center to the south in Makeni is one of such areas. Lusaka City is built on a marble which is cut by a network of fissures that are open hollows or filled with soil. This reduces the attenuation of pollutants that would occur through natural filtration. A study on groundwater that was conducted in 2010 in selected areas of Lusaka showed high levels of contamination with bacteria. The general objective of the study was to assess the effect of siting boreholes and septic tanks in the same area on the quality of groundwater in St. Bonaventure Township. Specific objectives were to determine the effect of distance between boreholes and septic tanks on groundwater quality in St. Bonaventure Township and to assess the effect of siting boreholes and septic tanks in relation to direction of groundwater flow on groundwater quality. The study site was purposively selected because all households in the Township used septic tanks and boreholes for human waste treatment and drinking water supply respectively. The study population, therefore, included all the 490 households in the study site. A sample size of 55 households was found at 95% confidence level using EPI INFO version 7 at expected frequency of 20%. The majority (67.27%) of water samples collected from households in St. Bonaventure were satisfactory, while 32.72% were unsatisfactory. The study revealed that only direction of groundwater flow had an association with water quality (total coliform and feacal coliform) at 5% significance level with p-values equal to 0.001 and less than 0.001 respectively. Distance from borehole to soakaway was insignificant in the quality of water. In conclusion, siting boreholes and septic tank systems in the same area was not suitable for St. Bonaventure Township and Lusaka at large because safety of groundwater cannot be guaranteed. Partners in water resource management such as ZEMA, Department of Water Affairs, Geological Department and Lusaka City Council should, therefore, work together each time projects that involve groundwater development and onsite wastewater treatment are to be implemented. LWSC to provide piped water and sewage services to St. Bonaventure.