Integrated membranes for the recovery and concentration of antioxidant from olive mill wastewater

During olive oil production a great amount of olive mill wastewater (OMW) is produced that is potentially a rich source of bio-phenols with wide array of biological activity. The purpose of the present work is to recover and concentrate the valuable polyphenols from the OMW using integrated membrane systems. Further study was conducted by employing enzymatic hydrolysis using β-glucosidase followed by acid hydrolysis in order to release higher concentration of pure hydroxytyrosol (HT). Meanwhile, efficient treatment of OMW could be achieved for water reuse as well as protecting the environment. The OMW was directly subjected to a microfiltration (MF) where 77.6 and 34.8% reduction of total suspended solids (TSS) and chemical oxygen demand (COD), respectively, were achieved. The Permeate of MF was further subjected to ultra-filtration (UF), where the removal was 44.9% and 100% for the COD and TSS, respectively. Another portion of the MF permeate was also subjected to nano-filtration (NF), where COD was reduced from 33 to 6.9 g/l and 100% TSS removal was achieved. The polyphenols in raw OMW was 2.5 g/l, it was recovered and concentrated in the Retentate of MF, UF and NF to 2.3, 2.0 and 2.4 g/l, respectively. Almost all polyphenols were recovered and concentrated in the NF Retentate solution. By employing the enzymatic hydrolysis using β-glucosidase on NF Retentate followed by acid hydrolysis an amount of 1.3 g/l of pure HT could be released. Based on these results OMW can be used as alternative source of valuable phenolic compound that are useful for industrial and pharmaceutical applications.