Factors affecting distribution of coliforms bacteria in semi-arid groundwater sources- Tanzania

Groundwater sources are highly depended for domestic purposes in semi-arid regions of Tanzania. However, most of them are prone to contamination from natural and anthropogenic sources which affect their quality for drinking purposes and may result in the eruption of water-borne diseases. This study aimed at identifying and quantifying the total coliform (TC), fecal coliform (FC) and Escherichia coli (E. coli) concentrations and establish the possible cause of their distribution in groundwater sources of Singida Urban and Manyoni Districts in Tanzania. A total of 58 randomly selected boreholes and shallow wells were sampled and analyzed using the Membrane Filtration Technique during dry and wet seasons. Overall results showed that the concentrations of all coliforms decreased significantly with an increase in depth (n=58, p≤ 0.05). Increase in temperature and turbidity showed significant increase in FC counts (n=53, AdjR2 = 0.66, p ≤ 0.01). Significant higher microbial contamination was on unpiped wells and those without protective covers in comparison with piped and protected (n =15, p≤ 0.01) and uses buckets (n=14, p≤ 0.01) to withdraw water from the source. Moreover, higher microbial contaminations observed in shallow wells during the wet season could be linked with increased surface runoff from the heap of poultry manure, vegetable farms or livestock feces that infiltrate into groundwater sources situated in the vicinity. Proper covering of wells mouth and use of water pumps to withdraw water instead of buckets are highly recommended to prevent further microbial contamination.