Combined photochemical and biological processes for the treatment of industrial wastewater

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This research proposal deals with modeling, optimization, and the development of combined advanced oxidation technologies and biological processes for the treatment of selected industrial wastewater such as diesel, petrochemical, and pulp and paper wastewater. Due to the limitations of individual chemical, physical, or biological processes in their effectiveness or economical feasibility, almost none is sufficiently applicable on its own. This proposal deals with the question of how best to combine the new applications of Advanced Oxidation Technologies (AOTs) such as photocatalysis, photolysis, and UV/hydrogen peroxide together with biological processes for the purpose of industrial wastewater treatment. In the photochemical oxidation step, the non-biodegradable, bio-refractory, and inhibitory contaminants are converted to biodegradable intermediates, which, in turn, are degraded in the subsequent biological step. To kill toxic microorganisms and deactivate possible viruses from biological effluents, and degrade other low molecular by-products, a further photochemical process will be used after the biological process. The development, optimization, engineering models, studying the dynamics of the systems, and eventually the design of the combined processes are the main objectives of this research proposal. In the first phase of this project, the combination of photocatalysis, photolysis, and UV/hydrogen peroxide will be studied and optimized in terms of economics, contact times, overall efficiency, and the sequence of the processes. Two pilot-plant photoreactors, already designed and constructed, are used to examine the photolytic and photocatalytic processes. In the next phase of this project, the optimized photochemical processes are integrated with the biological process as either pretreatment, post-treatment, or both. The biological treatment of the wastewater is examined in a sequential batch reactor as well as a stirred tank reactor using activated sludge as the source of microorganisms. To optimize these processes, the total cost of the processes, degradation rates, residence time in each reactor, overall efficiency, and the concentrations of the parent and intermediate by-products are analyzed.