Assessing the levels of trace metal from two fish species harvested from treated waste water stored in a manmade lake Pretoria, South Africa

Abstract

The persistent problem of water scarcity with the ever increasing demand of water has necessitated the reuse of effluent in agriculture. The present study evaluated the reuse of treated waste water and bioaccumulation properties of two fish species from a manmade lake. Trace metals content of two fish species: Clarias gariepinus and Cyprinus carpio and levels of trace metals from waste water in the lake where the fish species were harvested were determined by inductive couple plasma-optical emission spectrometer (ICP-OES). The trace metal values from fish samples ranged between 0.45 and 4.41 μg/g for Cu, 16.45 and 72.23 μg/g for Zn, 1.92 and 4.71 μg/g for Cr, 2.45 and 5.65 μg/g for Ni, 10.23 and 44.31 μg/g for Mn, 9.67 and 46.59 μg/g for Fe and 0.12 and 0.56 μg/g for Pb. The carp exhibited a significantly higher concentration for the trace metals for all the parts analyzed (p < 0.01). The levels of trace metals concentration in C. carpio was in the order of liver > gill > muscle > bone and metal accumulation was in the order of Zn > Fe > Mn > Cr > Ni > Cu > Pb. The concentration of trace metals such as zinc, iron, chromium and nickel in fish samples were higher than the recommended legal limits for human consumption. The result reveals that properly treated waste water could be used for the purpose of aquaculture.

Key words: Trace metals, waste water, pollution, lake, bioaccumulations inductive couple plasma-optical emission spectrometer (ICP-OES).