The failure of conventional waste-treatment methods to solve problems associated with complex industrial wastes, suggests that we must re-examine our approach to this problem. Two distinct types of biodegradation, homogeneous and heterogeneous, have been recognized to occur in the environment and are distinguished according to the solubility or insolubility, respectively, of the compound involved. Unfortunately, many of the most persistent toxic compounds fall into the second or insoluble category, and conventional treatment processes are inefficient in dealing with them.

Our studies have shown that the primary site of the biodegradation of these persistent compounds is at the substance–water interface and that the rate of such biodegradation can be greatly increased if the tested compound can be suspended in an aqueous phase as a fine stable emulsion. Our recent work on PCB biodegradation exemplifies the benefit of a multidisciplinary approach in solving environmental problems, and supports the need to continue fundamental research in such areas of applied environmental science.