Concentration of heavy metals in drinking water of Hawassa Zuria Woreda, Sidama Region, Ethiopia

Abstract

Background: Access to safe drinking water across the globe remains a major public health concern. Hawassa Zuria Woreda faces the same problem of lack of drinking water as other neighboring districts. The main aim of this study was to determine the levels of heavy metals such as Mn, Pb, Zn, Co, Cu, Ni and Fe in drinking water Hawassa Zuria Woreda, Sidama Region, Ethiopia.

Methods: A total of fifteen representative water samples were collected randomly from different sources such as two samples from the source (Bore Hole), five samples from reservoir, and eight samples from taps. Acid cleaned one-liter polyethylene bottles were used to collect samples from the selected water sources, which were then evaluated for seven trace elements (Mn, Pb, Zn, Co, Cu, Ni and Fe).This was determined using Flame Atomic Absorption Spectroscopy (Buck Scientific, Model 210VGP AAS, USA) equipped with deuterium background corrector and used air acetylene flame atomizer.

Results: The results of the physical analysis were in the following range; pH, 6.69 to 7.65; temperature, 20 to 26^oc; electric conductivity, 468.67 to 809.33μS/cm; turbidity, 1.2 to 11.63mg/l; and TDS, 281.2 to 485.60 mg/l. Concentrations of essential trace metal (Cu, Fe, and Zn) were below the guideline values of WHO and Ethiopian standard. Manganese and lead surpassed standard values of WHO and Ethiopian standard in 40% (n=6) in each case. Calculated values of pollution index for Mn, Zn, Fe and Cu were well below 1, which implies that the water samples were not polluted and are safe for drinking, whereas pollution index for Pb (Sample 1, Sample 2, and Sample 11) which was contaminated with lead and for Ni (Sample 4, Sample 8, and Sample 10) which was contaminated with Nickel. Overall six out of the fifteen samples indicated lead and nickel contamination. The mean HPI and HEI were 75.72 and 1.47, respectively. The mean HPI value did not surpass the critical value of 100. The distribution of average metal concentrations in the drinking water was found in the order of Zn>Ni>Co>Cu>Mn>Fe> Pb. One sample t-test revealed that highly significant difference (p<0.01) was observed between the guideline values of WHO and the metals except the lead. Correlation analysis further revealed that the elemental pair Pb/Zn (r =0.524, P < 0.05) is significantly correlated with each other, whereas the rest of elemental pairs show no significant correlation with each other. Element and physicochemical associations show the pair Pb/turbidity(r = 0.715, P < 0.01) is correlated with each other. Similarly, Cu/pH(r = 0.555, P < 0.05) and Cu/Turbidity (r = -0.522, P < 0.01) are significantly correlated with each other. Likewise, EC/turbidity (r = 0.567, P < 0.05) is significantly correlated with each other.

Conclusion: This study strongly suggests that the authorized body pay special attention to physico-chemical approaches for removing nickel and lead from water, such as chemical coagulation, chemical oxidation or reduction, active carbon adsorption, filtration, ion exchange, and membrane technologies.