Study On Phenol Biodegradation By Immobilized Candida Tropicalis

Phenol is present in the wastewater of petroleum, chemical engineering, and chemical industries, does harm to biomass for its toxic properties. With the process of economic development, wastewater containing phenol has greatly threatened the environment. As lots of aerobic microorganisms can utilize phenol as sole carbon, biological methods of phenol removal are preferable in wastewater treatment process at a relatively low processing cost and low possibility of secondary pollution.In our study, a strain of Candida tropicalis with high phenol-degrading efficiency was isolated from acclimated activated sludge, and was identified as a member of Candida by the Agricultural Culture Collection of China. Phenol biodegradation intrinsic kinetics was studied under the conditions of optimal growth conditions at temperature of 30℃, pH of 6.0 and excess dissolved oxygen. The kinetics of cell growth of Candida tropicalis was investigated using Haldane's equation with:μmax=0.480 h-1, KS=11.710 mg/L, KI=207.880 mg/L. Phenol consumption kinetics was associated to the cell growth kinetics as: A=0.823, B=0.276 h-1. Furthermore, the phenol biodegradation kinetics at limited dissolved oxygen condition was studied in the fermentor, and the oxygen limitation constant was obtained linearly as: KO=0.826 mg/L.Cells of Candida tropicalis were immobilized onto the polyurethane foams and into the alginate gel beads for batch phenol biodegradation. Corresponding mathematical models were developed to simulate the dynamic behaviors of the batch phenol biodegradation processes by immobilized Candida tropicalis. Model simulated results of the changes of the phenol concentration in the main liquid phase were compared to the experimental results for model validation. Moreover, reasonable predictions of the phenol, cell and dissolved oxygen concentrations within the immobilizing carriers were carried out by the developed models.