The environmental fate of chlorophenolic constituents of bleachery effluents

The essential elements of an environmental hazard assessment are considered. A set of interacting chemical, microbiological and ecotoxicological procedures were developed and applied to chloroguaiacols, chlorocatechols and chlorovanillins present in bleachery effluents. Laboratory studies were carried out on microbiological aspects of biodegradation and biotransformation and conclusions were verified by a critical analysis of selected field material. The procedures involved in laboratory biodegradation and biotransformation studies are discussed. Whether bacterial degradation of chloroguaiacols could occur under natural conditions or only as a result of 'concurrent metabolism' under experimental conditions with high concentrations of a readily degradable 'cosubstrate' is discussed. A study of the O-methylation reaction during the biotransformation of chlorophenols indicated that metabolic transformations could result in the production of compounds no less toxic nor more readily degradable than their precursors. Factors considered were the environmental distribution of relevant bacteria, the role of concurrent metabolism, and the substrate specificity of O-methylation. Verification studies involved spiking experiments using natural sediments without addition either of bacteria or supplementary carbon sources, and analysis of fish samples from areas contaminated with bleachery effluent discharge. The role of oxygen tension was assessed and anaerobic transformations, demethylation and dechlorination processes in sediments was examined. The dilemma of the biodegradation, biotransformation and persistence of chloroguaiacols and chlorocatechols in the environment was discussed and bioavailability studies were advocated. The biological treatment of bleachery effluent is considered and future work suggested, particularly with regard to the binding of compounds to natural matrices. The fate of bleachery treatment sludges is considered. The use of sub-lethal effects, and the metabolic capacities of the organisms should be included in ecotoxicological evaluations together with the acute toxicity tests. There are 43 references.