Heavy metal and drinking water quality on a river system at the Lower Manya Krobo and South Tongu districts, Ghana

Abstract

The water quality examination at the Lower Manya Krobo and South Tongu districts of Ghana was conducted by determining the physico-chemical parameters at 38 sampling sites. The ranges of physico-chemical parameters analysed were 6.45 to 7.26 for pH, -053 to -010 mV for Eh, 26.5 to 30.9^oC for temperature, 61.7 to 83.6 µS/cm for EC, 0 ‰ for salinity, 29.7 to 39.4 mg/L for TDS, 0.63 to 2.28 mg/L for DO, 0 to 4 NTU for turbidity, 0 to 8 mg/L for TSS, 36 to 108 mg/L for total hardness, 0.8 to 5 mg/L for BOD, 23.16 to 46.33 mg/L for HCO₃^-, 2.92 to 23.33 mg/L for Mg²⁺, 7.8 to 11.0 mg/L for Na⁺, 4.0 to 5.9 mg/L for K⁺, 1.99 to 13.99 mg/L for Cl^-, 3.2 to 14.4 mg/L for Ca²⁺, 1.0 to 24.88 mg/L for NO₃^-, 6.55 to 28.11 mg/L for SO₄^2- and 1.33 to 11.66 mg/L for PO₄^3-. While the results for dissolved metals (µg/L ) were 32 to 348 for Fe, 12 to 278 for Mn, 16 to 84 for Cu, 4 to 38 for Pb, 20 to 162 for Ni, 12 to 32 for Cd and 12 to 98 for Cr. Hg, Se, V and Zn were below detection limit. Except Cu which was low, about 37%, 87%, 29%, 33%, 8% and 29%  of the sampling sites had Pb, Ni, Cd, Cr, Fe and Mn values, respectively, above the WHO (2004) standard for drinking water. Therefore, effective water quality management is strongly needed.

Keywords: Lower Manya Krobo, South Tongu, Lower Volta River, physico-chemical parameters, trace elements