Relevance of the Luong model to describe the biodegradation of phenol by mixed culture in a batch reactor

Abstract

The kinetics of phenol biodegradation by mixed culture in a batch reactor was investigated over a wide range of initial phenol concentrations (40–350 mg L-1). The temperature (30°C), the stirring velocity (200 rpm), mineral salt supplementation, namely NaH2PO4 (3 g L-1), KH2PO4 (3 g L-1), MgSO4 (0.1 g L-1), (NH4)2SO4 (1 g L-1), as well as the initial pH (8) were kept constant. All experiments were carried out at a given initial bacterial concentration of 0.08 g L-1 (based on the optical density determination, 0.079). Irrespective of the culture conditions, total phenol degradation was recorded for a culture time ranging from 15.6 to 49.0 h. In addition, the optimal value of the maximum specific growth rate was observed for 125 mg L-1 of phenol. These results show the relevance of the specific microbial consortium used. The Luong equation accurately matched growth kinetics and enabled the relation between the maximum specific growth rates (μ m ) and the initial phenol concentration (S o ) to be described. It could also be used to deduce the substrate saturation coefficient (K s ) and the maximum substrate concentration (S m ) above which growth ceases. The kinetic constants of the Luong equation for phenol were $$ {\mu_m} = {1}.0{4} {{\text{h}}^{ - {1}}},{K_s} = {153}.{2} {\text{mg}} {{\text{L}}^{ - {1}}},{S_m} = {54}0 {\text{mg}} {{\text{L}}^{ - {1}}}\,{\text{and}}\,n = 0.{9} $$ , respectively.