Tadesu Hailu, Alemayehu Abebaw and Daniel Minilu
In the present study, the levels of selected heavy metals (Cr, Cd, Mn, Cu, Zn, and Pb) were determined using Flame Atomic Absorption Spectrophotometeric method. The following concentration ranges (mg/L) were recorded in wastewater samples: Cr (2.006-373.005), Cd (0.015-0.051), Mn (1.421-3.049), Cu (0.024-0.906) and Zn (0.105-0.934). Whereas, Pb was found to be blow detection limit (0.04). The concentration of Cr was highest followed by Mn in all sample sites and these values were found to be significantly higher than the maximum permissible limits of WHO, NEQS and FEPA. The levels of Cd, Cu and Zn were within the maximum permissible limits for effluent discharged into rivers. Decreasing in concentrations of heavy metals with distance from point source up to a distance of 40 meters was observed. pH, Temperature (°C), COD, TDS, TSS, SO42- and Cl- (mg/L) were also determined: Temperature (24.65-25.52), pH (8.85-10.31), SO42- (22.74-695.77), TDS (1500.00-4300.00), TSS (1505.00-2498.33), Cl- (235.03-1396.29) and COD (512.39-902.50). Similarly, anion concentration decreased with distance from point source up to a distance of 40 m. The control sample which is 40 m far before the wastewater inter into the Dufa River, recorded the lowest concentrations for all the parameters under studied. A statistical analysis of variance (ANOVA) at 95% confidence level shows that, there is a statistical significance variation of means concentration between the four sampling sites except pH and temperature.
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