| Horseradish peroxidase (HRP) enzyme catalyzes the oxidation of aqueous phenols by hydrogen peroxide resulting in the formation and precipitation of polymeric products. The technical feasibility of this enzymatic process for the treatment of industrial wastewaters that contain phenols was investigated. Bench-scale experiments were conducted in which the influences of selected components in the waste matrix on treatment efficiency were assessed.; Experiments with synthetic phenol solutions revealed that the toxicity of HRP-treated phenol solutions declines with time and is dependent on the presence of protective additives, the mode of reagent addition, and the presence of wastewater constituents. Also, many phenolic solutions can be completely detoxified by providing an additional dose of hydrogen peroxide after the completion of the enzymatic reaction. Chitosan was found to be an effective additive for reducing the amount of enzyme required to accomplish phenol transformation in synthetic and actual wastewaters.; HRP was able to accomplish the treatment of phenols in the presence of a wide range of concentrations of suspended solids, salts, metals, and other inorganic and organic species that are frequently present in industrial wastewaters. In certain instances, treatment was more effective in a real waste matrix as compared to the treatment of pure solutions of phenol due to the presence of particular waste components. However, sulfide, manganese(II) and low quantities of cyanide negatively impacted upon the enzymatic transformation of phenol.; It was demonstrated that actual industrial wastewaters collected from pulp and paper production and petroleum refining operations could be treated with HRP and H2O2 to meet regulatory discharge limits for phenol. The enzymatic process can selectively target phenols, which are a major source of toxicity in the wastes, for treatment. Treatment of real wastewaters may require higher than stoichiometric doses of hydrogen peroxide due to the inherent peroxide demand of reduced wastewater constituents or catalytic decomposition of peroxide. HRP-treatment improved wastewater quality as reflected in a significant toxicity reduction. It can also result in a substantial decrease in the biochemical and chemical oxygen demands. |
