Combined Fenton's oxidation and biodegradation for the treatment of pentachlorophenol -contaminated water

Combinations of chemical and biological degradation processes can be more effective for the treatment of recalcitrant pollutants than either chemical or biological treatment alone. In a laboratory-scale project, pentachlorophenol (PCP) was studied as a model recalcitrant compound for a sequential combined system of Fenton's oxidation and biodegradation. The combined treatment was achieved in a continuous-flow stirred-tank Fenton's reactor and a packed-bed bioreactor.;The goal of this research was to rationally optimize the combined system. Kinetic and stoichiometric data for chemical oxidation and biodegradation were measured in separate studies for both the chemical and the biological processes, and then integrated into a combined reactor model. The model was used to provide an understanding of the combined system and to test two project hypotheses: (i) the combined system can achieve higher mineralization than a single step process, and (ii) recycle of the effluent from the bioreactor back to the chemical reactor can improve the efficiency of the mineralization.;A Fenton's kinetic model for the degradation of PCP was developed and applied to batch and continuous Fenton's reactors. Additionally, kinetic information about the biodegradation process was obtained from the continuous operation of the bioreactor and incorporated into a biodegradation model. The two models were integrated into a model for a continuous combined Fenton's reactor and bioreactor, which also accounted for recycle effects. The model over-predicted the degradation of PCP and TOC in the combined system, but adequately predicted the sensitivity of PCP and TOC degradation achieved by the combined system at different hydrogen peroxide doses and recycle rates. Given these considerations, the model provided information supporting the two project hypotheses.;A suggested reactor operating strategy to improve the system performance was to increase the recycle rate to improve the mineralization of the waste. The model also indicated that the effect of recycle rates was highly dependent on the microbial degradation kinetic parameters.;As opposed to many of the previous empirical or semiempirical studies on combinations of chemical oxidation and biodegradation, the approach followed in this work provides basic understanding of the combined system, and provides an alternative of for process design and optimization.