Concentration of phenolic compounds from olive washing wastewater by forward osmosis using table olive fermentation brine as draw solution

Abstract

The olive industry has a considerable amount of process water consumption. As a result of the process, a large volume of oil mill wastewater (OMW) and table olive wastewater (TOW), both of them with high concentrations of organic matter, phenolic compounds and conductivity, are released. The appropriate management of these wastewaters is of paramount importance due to their toxic impacts on the environment. In this work, forward osmosis (FO) process is presented as an option to concentrate phenolic compounds for their further recovery. Two membranes, OsmoF2OTM (FTS, USA) and HFFO.6 (Aquaporin, Denmark) were evaluated with NaCl as draw solution (DS) and olive oil washing wastewater (OOWW) filtered at 5μm (5F) as feed solution (FS). Both membranes were able to concentrate the phenolic compounds with acceptable volume reduction (VR) values. The HFFO.6 membrane, which presented the lowest passage of phenolic compounds (TPhC) to the DS, was tested with fermentation brine from table olive processing (FTOP) as DS. As FS the same 5F-OOWW as well as an OOWW ultrafiltration permeate (UF-OOWW) were considered. Interestingly, greater percentages of TPhC concentration were observed compared to the tests with NaCl as DS (74.13–76.93% versus 62.6%, respectively). Although the tests with UF-OOWW presented greater flux, the recovery percentages of TPhC were similar, even slightly lower than those obtained with 5F-OOWW. Therefore, FO appears as a promising option to concentrate TPhC from OOWW and as well as to dilute FTOP. Thus both wastewaters from the olive industry could be treated at the same time.