Hydro-geochemistry and health risks assessment of some groundwaters suitability for drinking within the urban region of Unguja Island, Zanzibar

Abstract

Majority of the Island inhabitants depends on groundwaters for drinking therefore the hydrogeochemistry and health risks assessment with respect to WHO standards is absolutely essential for protection policy formulation. The groundwater samples for analyses were collected from selected four wells within each (Chukwani-Mbweni, DarajaMbovu - Amani and Mwanakwerekwe) suburb during the moderate rainy season of January2020.The selection was based on their strategic positions taking into consideration relevant geographical and environmental factors commensurable with this study. Various contaminants and physiochemical parameters were determined using Atomic Absorption spectroscopy, GC/MS, Temp/pH/TDS/EC meter and DR/3900 spectrophotometer. Chemical Oxygen Demand values were also determined. Microbial contamination was determined using the MPN technique. The results shows that these groundwaters are slightly alkaline, microbially contaminated, have high C.O.D. values ranging from 188.5 to 305.7 mg/L indicating the existence of some organic based endocrine disruptive elements, and disparities in water quality parameters with respect to the recommended WHO standards thus ascertaining possible public health risks. The research recommends the need for continuous monitoring, assessment and treatment of these raw groundwaters for drinking at the point of collection rather relying on the old conventional boiling method or drinkingas it is.