CHLORINATED AROMATICS - OCCURRENCE, USAGE AND METHODS OF DEGRADATION

This paper is summarizing the occurrence, usage and available techniques for dehalogenation of chlorinated aromatics, mainly chlorinated phenols and chlorinated phenoxy- or benzyl- phenols and their homologues, or polychlorinated biphenyls and dibenzodioxins (PCB's and PCDD's). These chemicals are among the most common organic pollutants in the wastewaters from production of pesticides, solvents, paints, pharmaceuticals, wood preserving chemicals, and from pulp and paper industry. Chlorine and other chlorine based oxidants are used for the bleaching of wood pulp accompanied with the formation of toxic organochlorine water pollutants which are polluting the river effluents, its inhabitants and accumulate in the tissues of river biota. These chemicals could be removed (and/or degraded) in many different ways, e.g. there are advanced oxidation processes (AOP's) involving the generation of reactive hydroxyl radicals ((OH)-O-center dot) or hydrodehalogenation processes to effect the destruction of recalcitrant pollutants in water effluents.