Application of membrane distillation technology in the treatment of table olive wastewaters for phenolic compounds concentration and high quality water production

Direct contact membrane distillation process (DCMD) is proposed for the treatment of table olive wastewaters (TOW) for high quality water production and concentration of their phenolic compounds. The main objective was to investigate the effectiveness of DCMD process to concentrate phenolic compounds from TOW that can be reused as a potential source for powerful natural antioxidants. The performance of three commercial membranes, made from polytetrafluoroethylene supported by polypropylene net (TF200, TF450 and TF1000), were tested. The permeate fluxes and polyphenols concentration in both the permeate and retentate have been monitored under different DCMD operating temperatures. It was found that the three membranes exhibit an excellent separation coefficient (greater than 99.5%) even after 4 h of DCMD operation with TOW. High concentration factors were obtained with the membrane TF450 at 70 degrees C, while the membrane TF200 having the lowest pore size was found to be more resistant to fouling phenomenon compared to the other membranes since the reduction of its water permeate flux after TOW treatment did not exceed 2.9%. High quality of the permeate was obtained with phenolic concentration lower than 16 mg of TYE/L. In addition, the values of electrical conductivity of the permeate were lower than 193 mu S/cm for the membranes TF450 and TF200, and lower than 355 mu s/cm for the membrane TF1000. Consequently, DCMD proved to be an effective process for the treatment of TOW for high quality water production and a phenolic-rich concentrate. (C) 2014 Elsevier B.V. All rights reserved.