Fractionation of olive mill wastewaters by membrane separation techniques

► Olive mill wastewaters were fractionated by membrane separation techniques. ► Two ultrafiltration processes followed by a final nanofiltration step were investigated. ► Productivity and fouling index of selected membranes were evaluated. ► Polyphenols, total antioxidant activity and total organic carbon rejections were analyzed. ► A purified fraction enriched in low molecular weight polyphenols was obtained.