Ion exchange system for the final purification of olive mill wastewater: Performance of model vs. real effluent treatment

Olive mill wastewater (OMW) is a highly pollutant effluent which can be pretreated through an advanced oxidation process. OMW after this secondary treatment (OMW-2ST) presented high sodium and chloride concentrations, responsible for its high conductivity. In this context, two ion exchange (IE) resins were examined (Dowex Marathon C and Amberlite IRA-67) for final OMW-2ST purification. As this effluent is extremely seasonal and deteriorates within few days, the main parameters affecting IE process were previously optimized with lab-made model OMW-2ST. Then the optimum operating conditions were tested with real OMW-2ST. Evolution of conductivity was evaluated as a function of recirculation time to study the effect of resins disposition and resins dosages and compared with both OMW-2ST. Equilibrium was reached in 10 and 20 min for model and real OMW-2ST, respectively. Furthermore, continuous mode experiments were carried out in to investigate the evolution of conductivity as a function of operating time. Breakthrough time was lower for real versus model OMW-2ST (120 vs. 147.5 min). Minimum 10 g L−1 resin dosage ensured 74% and 78% removal efficiencies, thus fulfilling irrigation water legal requirements and rending the production system cost-effective and environmentally respectful. Finally, model OMW-2ST is confirmed as good simulating media to reproduce IE processes.