Catalytic wet peroxide photo-oxidation of phenolic olive oil mill wastewater contaminants: Part II. Degradation and detoxification of low-molecular mass phenolic compounds in model and real effluent

Wet hydrogen peroxide photodegradation, catalyzed by aluminium–iron pillared montmorillonite (Al–Fe)PILC, of a mixture of eight model phenolic compounds present in olive mill wastewater (OMW), has been studied. Important percentages of phenol abatement after the wet hydrogen peroxide photocatalytic oxidation (WHPCO) (86% and 70%) have been achieved after 24 h of the o-diphenolic compounds caffeic acid and hydroxytyrosol, respectively. Monophenolic compounds tyrosol, p-hydroxyphenylacetic acid and p-coumaric acid were the most resistant towards the WHPCO. The apparent rate constant kphenolic molecule decreased with increasing initial pollutant concentration of organic molecule when the other parameters remained unchanged. Almost similar results were obtained with real OMW obtained by ultrafiltration of crude OMW. The toxicity of model and real OMW against the bioluminescent bacteria Vibrio fisheri was significantly decreased by 74% and 68%, respectively after the WHPCO. The subsequent biological treatment using a methanogenic consortium removed the remaining phenolic compounds by more than 70% even with the most recalcitrant compounds.