Kinetics of phenol biodegradation in high salt solutions

Biological treatment of high-salinity industrial wastewaters using halophilic bacteria can be used to remove organic compounds without first decreasing the salt concentration. While halophilic degradation of phenol and other organics has been investigated, there exists a general absence of kinetic data in current literature to allow evaluation of this treatment alternative. Liquid, soil and sediment samples were collected from three distinct saline environments in the western United States. Samples were enriched in media containing 10% (w/v) NaCl at pH 7.0, with phenol as a substrate. Mixed culture batch experiments were conducted at 30°C with initial phenol concentrations of 50 mg/L. Evaluation of phenol degradation and corresponding cell growth data with Monod and Andrews models indicated that the kinetics were zero-order with respect to phenol. Zero-order specific growth rates ranged from 0.22 to 0.32 h−1, while observed cell yields were 0.18–0.28 mg cell protein/mg phenol for the five cultures. For one of the cultures, phenol degradation rates were also quantified at concentrations of up to 320 mg/L. Under these conditions, specific growth rates ranged from 0.09 to 0.22 h−1, decreasing with increasing initial phenol concentrations. Cell yields at these higher initial phenol concentrations ranged from 0.20 to 0.29 mg cell protein/mg phenol.