Operation setup of a nanofiltration membrane unit for purification of two-phase olives and olive oil washing wastewaters.

In this research work, the purification of olives and olive oil washing wastewaters from two-phase extraction mills by a novel polymeric NF membrane is addressed. The effluent was previously subjected to a physicochemical secondary-tertiary treatment previously optimized at pilot and industrial scales. Within the adequate operating conditions, suspended solids could be completely removed, and the EC was considerable lowered down to good quality values acceptable for irrigation purposes (1.9-2.0mScm-1), whereas the chemical oxygen demand was reduced below 31.9mgL-1. The standards for discharging in public waterways or reusing the final treated effluent for irrigation with acceptable quality were therefore accomplished. Moreover, the performance of the NF membrane ranged between 2.82 and 6.96Lh-1m-2bar-1, that is, a flux of up to 160Lh-1m-2 at 25bar. Furthermore, the 15-minute acid cleaning plus 15-minute alkaline/detergent cleaning could recover satisfactorily the permeability of the membrane. The necessary overdesign of the membrane operation was estimated as 9.42-17.53%, which meant a maximum required membrane area of 61.82m2. Hence, just 2 membrane modules should be implemented in a medium-sized mill to engineer the operation, boosting the economic feasibility of the proposed process both from operational and capital costs point of views.