Regarding the rejection performance of a polymeric reverse osmosis membrane for the final purification of two-phase olive mill effluents previously treated by an advanced oxidation process

Abstract

In previous works on olive mill wastewater (OMW), secondary advanced oxidation treatment solved the problem related to the presence of phenolic compounds and considerable chemical oxygen demand. However, the effluent presented a significant salinity after this treatment. In this work, an adequate operation of a reverse osmosis (RO) membrane is addressed to ensure constant performance over a long period of time. In this paper, the effect of the operating parameters on the dynamic membrane rejection performance towards the target species was examined and discussed. Rejection efficiencies of all species were observed to follow a similar pattern, which consisted of slight initial improvement that further decreased over time. Rejection of both divalent ions remained constant at over 99% regardless of the operating conditions. Rejections were noticed to follow the order SO42- > Cl- > NO3- and Ca2+ > Mg2+> K+> Na+, as a rule. Divalent species were moderately more highly rejected than monovalent ones, in accordance with their higher charge and molecular size, and sulfate anions were consistently rejected by over 99%. Finally, the RO membrane exiting treated effluent was depleted of the high electro conductivity initially present (above 97% rejection), permitting its re-use as good quality irrigation water (below 1 mS/cm).

Keywords

• effluents reclamation
• olive mill wastewater
• rejection
• reverse osmosis
• wastewater purification