Abstract
This research work is focusing on the toxicities of heavy metals of industrial origin to anaerobic digestion of the industrial wastewater. Photobacterium phosphoreum T3S was used as an indicator organism. The acute toxicities of heavy metals on P. phosphoreum T3S were assessed during 15-min half inhibitory concentration (IC50) as indicator at pH 5.5–6. Toxicity assays involved the assessment of multicomponent mixtures using TU and MTI approaches. The results of individual toxicity indicated that the toxicity of Cd, Cu and Pb on P. phosphoreum increased with increasing concentrations and there was a linear correlation. The 15-min IC50 values of Cd, Cu and Pb were 0.537, 1.905 and 1.231 mg/L, respectively, and their toxic order was Cd > Pb > Cu. The combined effects of Cd, Cu and Pb were assayed by equivalent concentration mixing method. The results showed that the combined effects of Cd + Cu, Cd + Pb, Cu + Pb, Cd + Cu + Pb were antagonistic, antagonistic and partly additive. The combined effect of three heavy metals was partly additive.
Highlights
The presence of heavy metals in excess amounts interferes with the beneficial uses of water because of the toxicity of heavy metals and the biomagnification effect brought on by its accumulation on ecology (Chang et al 2006; Altas 2009)
The two combined and joint mixture R2 values were 0.969, 0.9036, 0.9266 and 0.9548, respectively, which showed a linear relationship between the relative luminosity % and heavy metals concentration in a mixture, which is clearly depicted in the Fig. 2
The results suggested that Cd ? Cu and Cd ? Pb effects were antagonistic, as IC50 values are higher than the toxic unit (TU) values (Table 2)
Summary
The presence of heavy metals in excess amounts interferes with the beneficial uses of water because of the toxicity of heavy metals and the biomagnification effect brought on by its accumulation on ecology (Chang et al 2006; Altas 2009). The concentrations of heavy metals beyond threshold values cause inhibition of the anaerobic process, the most suitable method to treat industrial wastewater (Wahaab et al 2010). Inhibitory substances are often found to be the leading cause of anaerobic reactor upset and failure since they are present in substantial concentrations in wastewaters and sludge. There is a need to develop a quick method for assessing the individual and joint toxicity of the pollutants during the anaerobic treatment of industrial wastewater. The present study was conducted to assess the single metal toxicity and acute joint toxicity of Cd, Cu and Pb by P. phosphoreum T3. Two different models were employed to assess the two combined and joint toxicity of the heavy metals in this study
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