Phenolic wastewaters depuration and biodegradability enhancement by ozone over active catalysts

Catalytic and non-catalytic ozonations were investigated in the depuration of simulated phenolic wastewaters. Commercial (N-150: Fe-Mn-O) and laboratory-made (Mn-Ce-O 70/30) catalysts have been used to improve the effluent biodegradability. The N-150 catalytic system followed a free radical pathway detected by means of the application of radical scavengers. After 120 min of reaction, the recovered N-150 catalyst showed low carbon adsorption and negligible leaching behaviour. Moreover, the catalyst remained active after various feed-batch trials. Mn-Ce-O 70/30 led to higher mineralization levels and stronger biodegradable characteristics of the final solution measured by respirometry. Nevertheless, a lower BOD5/COD ratio of the treated effluent as well as a higher ecological impact measured by bio-luminescence techniques was detected. Further application of the N-150 catalyst seems to be preferable to enhance ozone action although its activity can be limited by the presence of radical scavengers in real effluents. (C) 2010 Elsevier B.V. All rights reserved.