Treatment of olive mill wastewater using ozonation followed by an encapsulated acclimated biomass

The environmental impacts caused by Olive Mill Wastewater (OMWW) are a concern for both developing and developed countries. In this study, an ozone pretreatment combined with a fixed biomass bio-treatment using the Small Bioreactor Platform (SBP) capsules technology encasing a pure culture of a phenol-degrading OMWW isolate named Delftia EROSY was implemented to reduce phenolic compounds and organic matter in OMWW. Up to 90% of tannic acid (TA), a synthetic phenol model, was removed after the ozonation and biological stages. Ozone pretreatment of TA expedites the biological process by decreasing the time needed for the biodegradation of phenols. Ozonation (ozone dose=765mgL^-1 O₃) of OMWW demonstrated 20% COD and 61% total phenol removal, with an additional 36% increase in COD removal after the biological step (48h). Interestingly, our results also showed that spectral absorbance can be used as a tool for monitoring ozonation followed by bio-treatment of OMWW. Absorbance results clearly demonstrate that bio-treatment is necessary for degrading not only phenolic compounds, but also phenol transformation products and the high organic load of the OMWW, following the ozonation step.