Fractionation of olive mill wastewaters by membrane separation techniques

This study aims to evaluate the potential of an integrated membrane system in the treatment of olive mill wastewaters (OMWs) to produce a purified fraction enriched in low molecular weight polyphenols, a concentrated fraction of organic substances and a water stream which can be reused in the extractive process of olive oil. In particular, a sequence of two ultrafiltration (UF) processes followed by a final nanofiltration (NF) step was investigated on laboratory scale operating in selected process parameters. The produced fractions were analyzed for their total content of polyphenols, total antioxidant activity (TAA), free low molecular weight polyphenols and total organic carbon (TOC). The performance of selected membranes in terms of productivity, fouling index and selectivity toward compounds of interest was also evaluated and discussed. An integrated membrane process was proposed to achieve high levels of purification of OMWs and a water fraction which can be discharged in aquatic systems or to be reused in the olive oil extraction process.