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.

Research Highlights
► N-150 (Fe2O3–MnOx) shows to be an active and stable catalyst for catalytic ozonation.
► Toxicity removal and biodegradability enhancement attained after ozonation over N-150.
► Feasible technology as pre-treatment before a biological depuration.
► N-150 activity can be compromised in the presence of radical scavengers.