Degradation of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans during the UV/ozone treatment of pentachlorophenol-containing water

UV/ozone treatment of seepage water from waste deposits is an upcoming method for water purification to avoid residues contaminated with toxic organic compounds. PCDD and PCDF are components of several seepage waters of special waste deposits. The behaviour of PCDD and PCDF during UV/ozone treatment of aqueous model solutions in a laboratory reactor was examined. The degradation of hepta- and octachlorinated dioxins and the octachlorinated furan follows a first order kinetic. The combination of UV and ozone is more effective than the single application of ozone or UV. The concentrations of the lower chlorinated dioxins and furans reached a maximum after 2 minutes treatment time and decreased rapidly in the further minutes of treatment time. The toxicity equivalent value (TE value) also reached a maximum (36.8 ng/l) after 2 minutes of reaction time. The formation of lower chlorinated PCDD/PCDF as degradation products of the octachlorinated congeneres and their degradation can be explained by a model of successive parallel reactions.