Biodegradation Kinetics of Bi-substrate Solution of Phenol and Resorcinol in an Aerobic Batch Reactor

Abstract

Phenol and resorcinol compounds are found to co-exist in real-life wastewater, especially in petrochemical, coking and coke-oven wastewater. An indigenous mixed microbial culture isolated from effluent treatment plant of a coke oven industry has been employed to investigate for its biodegradation capacity of bi-solute mixture of phenol and resorcinol under aerobic batch reactor operation. A 22 full factorial design with the two substrates at two different levels of initial concentration ranges (high and low) was explored to design the biodegradation experiments. The effect of individual substrate concentrations and their interaction on rate of phenolics biodegradation were also determined. The phenol and resorcinol as substrates were completely utilized after 22 hrs when the solutes are present at low concentrations of 100 mg/L each. But the culture has taken total 58 hrs to biodegrade completely higher initial concentrations i.e., 400 mg/L of each substrate. This study also observed that both specific growth rate of the culture and the specific substrate degradation rate have descended to lower value in presence of phenol and resorcinol as dual substrate in the solution compared to their presence as single substrate, showing the interaction and inhibition by each substrate. Sum kinetic model was used to describe the variation in the specific substrate degradation rates by the mixed culture. From the interaction parameters obtained from this model, it has been observed that resorcinol inhibits specific substrate degradation rate to a higher extent than inhibition caused by phenol (I Resorcinol, Phenol = 0.5, IPhenol, Resorcinol = 0.1, RMSE = 0.04361)