Impacts of operating conditions on reverse osmosis performance of pretreated olive mill wastewater

Management of the effluent from the olive oil industry is of capital importance nowadays, especially in the Mediterranean countries. Most of the scarce existing studies concerning olive mill wastewater (OMW) treatment by means of membrane processes not only do fix their aims simply on achieving irrigation standards, but lack suitable pretreatments against deleterious fouling issues. With the target of achieving the parametric requirements for public waterways discharge or even for reuse in the production process, a bench-scale study was undertaken to evaluate the feasibility of a thin-film composite reverse osmosis (RO) membrane (polyamide/polysulfone) for the purification of OMW. Previously, OMW was pretreated by means of chemical oxidation based on Fenton’s reagent, flocculation–sedimentation and biosorption through olive stones. Impacts of the main operating parameters on permeate flux and pollutants rejection of the RO process, as well as fouling on the membrane surface, were examined for removing the significant ionic concentration and remaining organic matter load of the pretreated OMW. Combining operating parameters adequately in a semibatch operating regime ensured high and sustainable permeate flux, yielding over 99.4% and 98.5% removal efficiencies for the chemical oxygen demand and ionic content respectively, as well as complete rejection of phenols, iron and suspended solids.

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► Significant ionic and organic load in OMW after physicochemical pretreatment.
► Further depuration of OMW by RO for reuse in process or discharge in sewers.
► Impacts of operation parameters on TFC RO membrane performance are examined.
► Proper operating conditions providing high and stable flux in diafiltration mode.
► Removal efficiencies over 99.36% and 98.45% for COD and ionic content.