COMBINED FENTON'S OXIDATION AND BIODEGRADATION FOR THE



COMBINED FENTON'S OXIDATION AND BIODEGRADATION FOR THE

TREATMENT OF PCP-CONTAMINATED WATER

1Julio A. Zimbron and 2Kenneth F. Reardon

1,2Department of Chemical and Bioresource Engineering, Colorado State University, Fort Collins, CO 80523-1370; 1Phone: (970) 491-1123, E-mail: jzimbron@lamar.colostate.edu; 2Phone: (970) 491-6505, 2E-mail: reardon@engr.colostate.edu.

Chlorinated compounds, often found in industrial wastes such as wood treating and paper pulp manufacturing waste, are a common source of water contamination. These compounds are intrinsically recalcitrant to biodegradation, resulting in limited applications of biodegradation to water contaminated from this type of waste. A promising solution to this problem is the combination of chemical oxidation with biological degradation.

Combinations of chemical and biological degradation processes can be more effective and cost-efficient than either chemical or biological treatment alone for the treatment of groundwater, process wastewate,r and drinking water. The goals of this research are (1) to develop a mathematical model for the combination of chemical oxidation using Fenton's reagent (hydrogen peroxide and ferrous ion) and biological degradation of chlorinated phenols, and (2) to use the model to optimize operating conditions and reactor configurations for the combined system.

This presentation includes new data on the mechanisms and rates of Fenton's reaction for PCP in water, as well as new data on the biodegradation rates of chemically oxidized intermediates. The Fenton's degradation rate of PCP was determined by the competitive kinetics method, and compared with the Fenton's degradation rates for other chlorophenols by means of Hammett's equation, a group contribution method. It was found that these degradation rates were inversely proportional to the degree of chlorination of the phenolic ring.

A model aqueous waste consisting of PCP has been treated with a sequential combination of Fenton's reagent (for chemical oxidation) and a packed-bed bioreactor inoculated with activated sludge from a municipal wastewater treatment plant. The PCP concentrations in the feed to the chemical reactor, and the effluent of the chemical reactor and the effluent of the bioreactor were determined. In addition, the amount of protein in the effluent from the bioreactor was measured to estimate the extent of biodegradation of the waste. At a residence time of 1.5 hr in the Fenton's reactor, operating at molar dosage ratios of H2O2/PCP of 3.0 and 7.7, 42% and 63% of the PCP present in the feed was degraded, respectively. PCP was not biodegraded in the following biodegradation stage at a residence time of 5.5 hr. However, the extent of biodegradation achieved by the microbial population on the Fenton's pretreated, PCP-contaminated water was proportional to the extent of the previous Fenton's degradation of PCP.

Key words: mineralization, mixture-based model, advanced oxidation process, biodegradation

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