Kinetic modeling and factorial design for co-biodegradation of phenol and m-cresol for aerobic batch reactor system

Abstract

Phenol and cresols co-exist in real-life industrial wastewater, especially in petrochemical, coking and coke-oven industry. An indigenous mixed microbial culture was collected from effluent treatment plant of a coke oven industry. This culture has been employed to biodegrade bi-substrate mixture of phenol and m-cresol under aerobic batch reactor operation. A 2x2 full factorial design with the two phenolic compounds at two different levels of initial concentration (high and low) was explored to design the biodegradation experiments. The variation of the rate of phenolics biodegradation with individual substrate concentration were also determined. The phenol and m-cresol as substrates were completely utilized after 27 hrs when the solutes are present at low concentrations of 100 mg/L each. But the culture has taken total 66 hrs to biodegrade completely higher initial concentrations i.e. 400 mg/L of 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 m-cresol inhibits specific phenol degradation rate to a higher extent than inhibition caused by phenol on m-cresol degradation (I m-cresol, Phenol = 0.966, IPhenol, m-cresol = 0.5, RMSE = 0.0171)