GEOGENIC CONTAMINANTS IN THE GROUNDWATER IN THE RIFT VALLEY OF TANZANIA- THE CASE OF ARSENIC AND FLUORIDE
Majority of the inhabitants in the large cities and small rural communities in Tanzania depend on rivers, springs, hand-dug and shallow groundwater wells as their main drinking water sources. Hydrogeologically, about 75% of Tanzanian aquifer systems are in crystalline complex rocks with variable composition and age. However, predominantly Precambrian, which form the basement aquifers (e.g. the Pangani and Makutopora basins) and unfortunately this subsurface layer are highly contaminated with arsenic and fluoride. The contamination level of arsenic and fluoride in the soil, sediment, surface water and groundwater are related to the variation of hydrological conditions or geochemical factors (e.g. evaporite dissolution, cation exchange and carbonate weathering, redox potential etc.). Thus there is a huge gap within the primary information about the overall water quality and scarcity information and understanding of the fate and mobility of geogenic contaminants in the groundwater aquifers and surface water supply sources. This information is crucial in exploring aquifers as safe drinking water sources to delineate the associated human health risks of arsenic and fluoride pollution in groundwater sources. On the other hand, the limited studies have been used the locally available materials for developing arsenic and fluoride removal treatment technology for drinking water. These lab scale studies showed the significant potentiality of locally available adsorbent media for innovation and upscaling as water purification technology and develop policy strategies to provide safe drinking water.