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 January 2020. 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 show 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 drinking as it is.
Highlights
Unguja Island of Zanzibar has a current estimated population of 1.8 million with approximately 22% having access to clean water supplied by Zanzibar Water Authority (ZAWA)
Groundwater is regarded as a reliable and resilient water resource for most rural and urban areas of Island of Unguja due to its distributed, subsurface storage and perennial availability as was once reported by [30, 28]. This Island is surrounded by sea with no fresh water body, ground water reserve in Unguja Island is only nourished by seasonal rainfall [8]
The average concentration of calcium was found to be more in M/kwerekwe ground water and above the World Health Organization (WHO) limit incomparable to other zones
Summary
Unguja Island of Zanzibar has a current estimated population of 1.8 million with approximately 22% having access to clean water supplied by Zanzibar Water Authority (ZAWA). Groundwater is regarded as a reliable and resilient water resource for most rural and urban areas of Island of Unguja due to its distributed, subsurface storage and perennial availability as was once reported by [30, 28]. This Island is surrounded by sea with no fresh water body, ground water reserve in Unguja Island is only nourished by seasonal rainfall [8]. It is paramount to have a clear understanding of hydrologic system since it forms the gateway for providing information for the groundwater resource management [55, 83] and source for the natural constituents formulating these groundwaters
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