Integration of chemical and biological oxidation processes for water treatment: Review and recommendations

The literature of studies which used a combination of chemical and biological degradation (usually oxidative) of organic contaminants in water is reviewed. Beneficial effects of such two-step treatments are commonly reported; these results, primarily for laboratory studies, suggest potential advantages for water treatment via process integration rather than single technology processing. Four wastewater contaminant types are identified which can benefit form combined processes; 1.) recalcitrant compounds 2.) biodegradable wastes with small amounts of recalcitrant compounds 3.) inhibitory compounds and 4.) intermediate dead-end products. The design key for such two-step systems lies in choosing processes that complement each other and lead to a synergistic effect. Predicting this performance outcome requires knowledge of the physical, chemical and biological properties of the major reaction intermediates and their susceptibility to degradation by each process. Economic, physical and technological limitations of the individual processes should be recognized for design of more effective and economical integrated processes. The ultimate treatment goal, whether specific pollutant removal or reduction of a global parameter such as TOC, must be known so that appropriate and complementary processes can be utilized. More work is needed concerning the degradation kinetics within the combined process, form initial attack of the primary compound through dynamics of intermediates and on to total mineralization.