Effect of metals on biodegradation kinetics for methyl tert-butyl ether

Many ground waters are polluted with a complex mixture of organic and metal contaminants. Especially, the presence of heavy metals may be of particular concern, since they may be toxic for microorganisms and may interfere with the biodegradation process. A study of methyl tert-butyl ether (MTBE) biodegradation in the presence of heavy metals with the purpose of determining the effects of type and concentration of metals on reaction kinetics was undertaken. The experiments were performed as batch biodegradation experiments, and the kinetic parameters were determined by a nonlinear regression technique. Experimental results showed that the presence of Mn2+ offers a slight stimulating effect on MTBE degradation; however, Cr3+ and Zn2+ resulted in less biodegradation at metal concentrations of 1 mg l−1. The inhibitory effect of adding metals was obvious, with constantly decreasing value of MTBE degradation rate in the following order Cu2+ > Cr3+ > Zn2+ > Mn2+ at metal concentrations 10 mg l−1 and 50 mg l−1. The kinetic parameters of μm were found to be virtually unaffected until a threshold concentration (10 mg l−1) of metal was reached. However, a significant inhibitory effect on bacterial growth, as manifested by a decrease in both Ki values for Cu2+ (at 1 and 10 mg l−1), and both Cr3+ and Zn2+ (at 10 mg l−1).