Optimization of operating conditions for the valorization of olive mill wastewater using membrane processes.

The main goal of this work was to assess the performance of an integrated membrane system for the treatment and valorization of wastewater generated from an olive mill (OMW) coming from a traditional extraction press. Two different lots of this effluent were firstly processed in an ultrafiltration (UF) pilot unit after a pretreatment by screening. The effect of transmembrane pressure (TMP) and temperature on the chemical oxygen demand (COD) reduction and removal of total phenolic (TPh) content was investigated. Under optimal conditions (TMP = 1.5 bar and T = 20 °C), 20.6 and 26.8% for COD and TPh removal were achieved, respectively. The permeate from UF was then treated by nanofiltration (NF) in order to obtain a retentate enriched in phenolic compounds. The influence of pressure drop (ΔP), temperature, and pH on the removal of COD, TPh, and permeate flow was examined using a 23 full-factorial experimental design. The effect of the independent variables and their interactions on the process performance was analyzed with Pareto charts. Multivariable regression models allowed to built 3D surface plots. The best conditions that maximize the COD abatement (83.3%) and TPh removal (93.1%) were ΔP = 18 bar, T = 20 °C, and a pH 2.7. It can be concluded that the integration of UF and NF processes investigated in this work is a promising strategy for the treatment and valorization of OMW.