Heavy metal contamination and water quality of selected fish ponds at Sunyani, Ghana: A comparison with WHO standards

Selina A. Saah, David Adu-Poku and Nathaniel O. Boadi

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Optimum fish production is greatly dependent on the physical, chemical and biological qualities of water. Hence, successful fish pond management requires an in-depth understanding of water quality. A study to assess heavy metal (Cr, Cd,
Mn, Pb and Zn) contamination and physicochemical parameters of water samples from eight selected fish ponds in Sunyani, Ghana, was conducted. The parameters included temperature, pH, salinity, total hardness, electrical conductivity (EC),
chemical oxygen demand (COD) and biological oxygen demand (BOD). The results revealed detectable Mn and Zn levels in all the selected fish ponds; with Mn levels in three ponds being significantly higher than the World Health Organization (WHO) recommended limit (< 0.500 mg/L). Of the three samples, which showed detectable Cr and Cd levels, concentrations of two exceeded the permissible limits. Pb was below the detection limit in all the samples whilst Cu levels detected in two of the ponds were below the permissible limit. The investigated physicochemical parameters had the following ranges: temperature 26-29 C, pH 5.8-8.2, BOD 0.3-20 mg/L, Total Dissolved Solids (TDS) 37-249 mg/L, EC 73.67-498 µS/cm, total hardness 0.8-5.7 mg/L, salinity 0.03-0.22 psu and COD 2.9-9.7 mg/L. Most of these values were within WHO recommended levels. The findings suggest that regular monitoring of the heavy metal load is necessary to guard against long-term effects of its presence in the water, influencing fish and human uptake.