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


  • Abdul A. J. Mohamed Faculty of Science (FOS) Universiti Brunei Darussalam Jalan Tungku,
  • Ibrahim Abdul Rahman
  • Sadri A. Said
  • Lee Hoon Lim
  • Islam S. Mchenga


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


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.



Anawara, H. M., Akaib, J., Mostofac, K.M.G., Safiullahd, S., and Tareq, S.M., Arsenic poisoning in groundwater health risk and geochemical sources in Bangladesh. Environment International, Vol. 27, pp.597-604, 2002.

Moo-Young, H., Johnson, B., Johnson, A., Carson, D., Lew, C., Liu,S. And Hancock, K, Characterization of infiltration rates from landfills: Supporting groundwater modelling efforts’ Environmental Monitoring and Assessment, Vol. 96, pp.283-311, 2004.

Slooff W et al. Integrated criteria document chromium, Bilthoven, Netherlands, National Institute of Public Health and Environmental Protection, Report no.758701002, 1989.

Calder, L.M. Chromium contamination in groundwater. In J.O. Nridgu, & E. Bieboer (Eds.), Chromium in the natural and human environments, New York: Wiley-Interscience, 1998.

International Agency for Research on Cancer. Some metals and metallic compounds. Lyon. IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans, Vol. 23, pp. 205-323, 1980.

United State Environmental Protection Agency (USEPA). Chemical contaminants in drinking water. Technical fast sheet on microbes. EPA 816-03-016, 2003.

Marier, J. R., Cardio- protective contribution of hard waters to magnesium intake. International Reviews of Canadian Biology, 37, pp.115-125, 1978.

National Research Council, Drinking water and health. Washington, DC, National Academy of Sciences. 1977.

Thomas K.S., Sach T.,H. A multicentre randomized controlled trial of ion-exchange water. Softeners for the treatment of eczema in children: protocol for the Softened Water Eczema Trial (SWET) (ISRCTN: 71423189). British Journal of Dermatology, 159, Vol. 3, pp. 561–566, 2000.

WHO. Guidelines for Drinking water quality: Hardness in drinking water. WHO Geneva, WHO/SDE/WSH/03.04/06. 1996.

Anonymous, World Health Organization (WHO) Guidelines for drinking water quality. Vol. 2, pp. 231, 1996.

Suman M., Ravindra, K.,Dahiyaa, R. P., and Chandra, A.. Leachate Characterization and assessment of groundwater pollution near municipal solid waste landfill site. Environmental Monitoring Assessment. Vol. 118, pp. 435-456, 2006.

Grady Hanrahan, Key Concept in Environmental chemistry. Elsevier Inc, Waltham, MA USA, 2012.

Tanzania- Rural Water Supply and Sanitation Programme (T RWSSP) II, 2011-2014.

Mc Gowan W. Water processing: residential, commercial, light-industrial, 3rd ed. Lisle, IL, Water Quality Association. 2000.




How to Cite

Mohamed, A. A. J., Rahman, I. A., Said, S. A., Lim, L. H., & Mchenga, I. S. (2013). Levels of Hexavalent Chromium, Copper, and Total Hardness in Springs and Underground Water in Zanzibar Island. Asian Journal of Applied Sciences, 1(5). Retrieved from https://www.ajouronline.com/index.php/AJAS/article/view/564