Decontamination of wastewater contaminated by polychlorinated biphenyls (PCBs)

Abstract

Wastewater contaminated by PCBs obtained from three different sources was treated at both laboratory and pilot plant scale conditions by ultraviolet oxidation of organics at the presence of hydrogen peroxide after partial adsorption of impurities and PCBs on activated carbon and/or activated bentonite. The procedure was conducted both with and without a Fe(II) catalyst and considerable reduction of PCB concentration was achieved in both cases. In pilot plant scale experiments, activated carbon polishing step followed UV oxidation. The following three types of contaminated waste water were examined: a) aqueous extracts originated in the course of clean-up of contaminated soil by extraction with aqueous solvents. Concentrations of PCBs in extracts were between 1 μg/L to 3,000 μg/L; b) wastewater condensates originated in the process of thermal desorption of PCB from soils. Concentrations of PCBs in condensates were between 300 μg/L and 5,000 μg/L. c) underground water contaminated by PCBs extracted from the sites of old contamination. The content of PCBs was up to 50,000 ng/L. Biodegradation of PCBs with a mixture of indigenous soil bacteria (selected strains of Pseudomonas and Acitenotobacter) was also tested. It was carried out in a reactor with volume of 1.5 m3 by application of the bacteria in a slurry of bentonite with adsorbed PCBs.