Assessment of Spatial Distribution of Excreta Contaminants in Groundwater from Onsite Sanitation Facilities at Kibondemaji Ward, Dar es Salaam

Abstract

The study assessed underground spatial distribution of excreta contaminants from on-site sanitation facilities in terms of groundwater quality at Kibondemaji ward. Twenty (20) water samples from wells were collected. Physicochemical and biological parameters like pH, TDS, electrical conductivity, Nitrate (NO₃), Ammonia (NH₃-N), Phosphate, and Fecal coliform were analyzed. A pollution index was used to determine the gross water quality of the wells. ArcGIS, using Inverse Distance Weighting (IDW), was used to visualize pollutants concentrations and interactions in relation to onsite sanitation facilities. Kibondemaji and surrounding areas’ groundwater exhibited excreta contaminants (FC) exceeding WHO and Tanzania (TZS 789:2008) standards. Kibondemaji B had the highest contamination rate (43.7%) due to large number of shallow wells easily contaminated by onsite sanitation facilities. In some wells, Ammonia and Electrical conductivity were relatively high, suggesting that the water had been contaminated by fresh excreta matter emanating from onsite sanitation facilities. The water quality indices for BH8, BH3, BH6, BH9, BH10, SW5 and SW9 ranged between 0-50 indicating good to excellent water for consumption, whereas the rest (mostly shallow wells) with WQI > 51 were not suitable for consumption due to pollution from the onsite sanitation facilities.