Two-phase olive-oil washing wastewater treatment plus phenolic fraction recovery by novel ion exchange resins process modelling and optimization

Abstract

This research was focused on the modelling and optimization of an environmentally friendly procedure to recover added-value polyphenols (TPhs) from two-phase olive-oil washing wastewaters (OOWW) by ion exchange (IE) resins and simultaneously permit the treatment of this effluent. The reason is the need of olive mills to evolve into a whole environmentally friendly conception to upgrade this ancestral industry, comprising the management of the by-produced effluents. Key operating factors of Dowex 21KXLT® strong-base and Dowex66® weak-base resins were studied, modelled and optimized by statistical multifactorial analysis. Optimal resin amount between 140 and 146 and 114–146 gresin/LOOWW, T from 20 to 25 °C, pH0 between 6.5 and 8.2 and 4.7–7.1 and 60 vs. 25 min contact time were determined for the strong-base and weak-base resins. Final phenols concentration uptake of 60.8% vs. 83.3% plus 55.8% vs. 53.7% COD removal supported major efficacy of the selected weak-base resin. In addition, the process could be directly driven with raw OOWW exiting the mills’ vertical centrifuges upon unmodified pH0 nor T. The high added-value concentrated pool of antioxidant phenols could render feasible the industrial scale-up, and the treated effluent could be now driven to biological treatment given the high removal of TPhs preventing biomass inhibition, or partially discharged.