Our study assesses the quality of water in Dar es Salaam city, Tanzania. Borehole water samples collected were analyzed for physicochemical and microbiological characteristics of the underground water. All functional boreholes in the study area were sampled. Pearson correlation coefficient was employed to establish the interaction of the physicochemical characteristics in the underground water. Factor analysis and cluster analysis were employed to determine source apportionment of contaminants in underground water. Results showed that calcium was significantly correlated with electrical conductivity (r=0.624), total dissolved solids (r=0.627), and total hardness (r=0.881) for underground water sources. Calcium concentration is attributed to anthropogenic activities, terrigenous influx in run-off, and/or natural processes within the aquifers. Faecal coliform counts exceeded the World Health Organization maximum permissible limit of 0/100ml at 44ºC at Shauri Moyo and Kigogo Primary School and, therefore, the water was contaminated; the rest of the boreholes were safe. Factor analysis revealed three sources of pollutants in the underground water:
(1) mixed origin of human wastes and soil in runoff
(2) dual origin of turbidity (human wastes and soil/organic matter)
(3) natural/geochemical processes in aquifers.
In conclusion, water hardness is controlled by calcium and faecal contamination is attributed to entry of sewage (human wastes) and organic matter into underground water. There is a need for water to be treated/ filtered and/or boiled before consumption.