Levels of Hexavalent Chromium, Copper, and Total Hardness in Springs and Underground Water in Zanzibar Island

Abdul A. J. Mohamed, Ibrahim Abdul Rahman, Sadri A. Said, Lee Hoon Lim, Islam S. Mchenga

Abstract


This study aimed at assessing the level of total hardness and heavy metals (hexavalent chromium and copper) in springs and underground water sources in some areas of tropical Island, Zanzibar. Thirty water samples were analyzed. The Palintest photometer procedures were used to determine the concentrations of hexavalent chromium and copper. The level of total hardness was determined by ethylenediaminetetraacetic acid (EDTA) titration using Eriochrome black-T indicator. Levels of copper, hexavalent chromium and total hardness in the studied samples ranged between 1.38 - 11.0 mg/L, 0.05 - 0.4 mg/L and 32.02 - 1009 (as mg/L CaCO3), respectively. About 77% of all samples have total hardness values higher than the World Health Organization (WHO) guidelines, while the proportion of samples with dangerous concentrations of copper and hexavalent chromium were 70% and 96.6%, respectively. Eighty percent of the water samples fell in the “very hard water” category. The correlation between copper and total hardness, and electrical conductivity and total hardness, were 0.752 and 0.930, respectively. The levels of most of the studied parameters in the drinking water samples exceeded the permissible limits of the WHO drinking water quality guidelines. The results show the urgent need to take immediate mitigation measures and continue the water quality monitoring in Zanzibar, as well as establishing drinking water treatment plants.

 


Keywords


Zanzibar, World Health Organization (WHO), drinking water treatment plants, hexavalent chromium

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References


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