Characterization of phenol degradation by high-efficiency binary mixed culture

Two new high phenol-degrading strains, Micrococcus sp. and Alcaligenes faecalis JH 1013, were isolated. The two isolates could grow aerobically in mineral salts medium containing phenol as a sole carbon source at concentration of 3,000 mg L(-1). It was found that the binary mixed culture of the two isolates possessed good potential for phenol removal.

Phenol biodegradation using the binary mixed culture of the two isolates was studied. The optimal conditions were determined to be temperature 32 degrees C, pH 7.0, inoculum size 10.0%, and agitation rate 150 rpm in the synthetic wastewater. In addition, the kinetics of the cell growth and phenol degradation by the binary mixed culture were also investigated using Haldane model over a wide range of initial phenol concentrations from 20 to 2,400 mg L(-1).

The experimental data indicated that the binary mixed culture had pretty high phenol degradation potential, which could thoroughly degrade the phenol in the synthetic wastewater containing phenol 2,400 mg L(-1) within 72 h under aerobic condition. Under the optimal conditions, the phenol concentration was reduced speedily from 1,000 to below 0.28 mg L(-1) in the presence of the binary mixed culture, and the phenol degradation rate reached 99.97% after 16 h. It was well below the standard value 0.28 mg L(-1) as described by Chinese Environmental Protection Agency. It was clear that the Haldane kinetic model adequately described the dynamic behavior of phenol degradation by the binary mixed culture with kinetic constants of q (max) = 0.45 h(-1), K (sq) = 64.28 mg L(-1), and K (iq) = 992.79 mg L(-1). The phenol concentration to avoid substrate inhibition had been inferred theoretically to be 252.62 mg L(-1).

Phenol, as the only carbon source, could be degraded by the binary mixed culture at high initial phenol concentrations. Phenol exhibited inhibitory behavior, and the growth kinetics of the binary mixed culture could be correlated well by the simple Haldane's inhibitory model. The kinetics parameters were invariably required for the design and simulation of batch and continuous bioreactor treating phenolic wastewaters.