The highest inhibition coefficient of phenol biodegradation using an acclimated mixed culture

In this study a membrane biological reactor (MBR) was operated at 25 ± 1 °C and pH = 7.5 ± 0.5 to treat synthetic wastewater containing high phenol concentrations. Removal efficiencies of phenol and chemical oxygen demand (COD) were evaluated at four various hydraulic retention times (HRTs) of 24, 12, 8, and 4 hours. The removal rate of phenol (5.51 kg-Phenol kg-VSS(-1) d(-1)), observed at HRT of 4 h, was the highest phenol degradation rate in the literature. According to COD tests, there were no significant organic matter in the effluent, and phenol was degraded completely by mixed culture. Substrate inhibition was calculated from experimental growth parameters using the Haldane, Yano, and Edward equations. The results show that the Haldane equation is fitted to the experimental data in an excellent manner. Kinetic parameters were derived by nonlinear regression with a correlation coefficient (R(2)) of 0.974. The values for Haldane constants μmax, Ks, and Ki were 0.3085 h(-1), 416 mg L(-1) and 1,886 mg L(-1), respectively. The Ki value is the highest value obtained for mixed cultures degrading phenol under batch conditions.