ENHANCEMENT OF THE BIODEGRADABILITY OF MODEL WASTE-WATER CONTAINING RECALCITRANT OR INHIBITORY CHEMICAL-COMPOUNDS BY PHOTOCATALYTIC PREOXIDATION

m-Dinitrobenzene, diphenylamine and resorcinol, three aromatic compoun ds found inhibitory or recalcitrant to bio logical treatments, were ch osen as mo del chemicals for this study on the integration of pho to c atalytic-biological treatments. The degradation of each of these compo unds was achieved by ultraviolet photocatalytic oxidation, leading to the formation of intermediate compounds. The photocatalytic treatment was performed in a TiO2 slurry reactor containing an aqueous solution of one of the three chemicals. The biodegradability of model wastewate r treated photocatalytically was measured in terms of BOD1/TOC. Interm ediate compounds that appeared at early stages of the photocatalytic d egradation of m-dinitrobenzene or diphenylamine seemed to be more inhi bitory than the parent compounds but this was not the case for resorci nol. A substantial improvement in BOD1/TOC could be achieved, but it r equired the mineralization of at least 80% of the organic carbon origi nally in the water. Microtox(R) toxicity results confirmed the BOD1/TO C trends for diphenylamine.