Physicochemical analysis and adequation of olive oil mill wastewater after advanced oxidation process for reclamation by pressure-driven membrane technology

Physicochemical characterization of olive mill wastewaters (OMW) was studied after a primary and secondary treatment was implemented in an olive oil factory in Jaén (Spain), comprising natural precipitation, Fenton-like reaction, flocculation–sedimentation and olive stone filtration in series. The application of membrane technology in improving the quality of the secondary-treated OMW (OMW/ST) was examined, to reduce the hazardous electroconductivity (EC) values (2–3mScm−1). Particle size distribution on OMW/ST shows supra-micron colloids and suspended solids as well as sub-micron particles with a mean size below 1.5μm remaining in considerable concentration. The high organic pollutants percentage (31.7%) registered with an average diameter below 3kDa is sensibly relevant for membrane fouling. Mesophilic aerobic bacteria growth warns of possible membrane biofouling formation. The saturation index indicates to work upon recovery factor below 90%. Finally, operating at a pressure equal to 15bar ensured low fouling and high flux production on the selected NF membrane (69.9Lh−1m−2) and significant rejection efficiencies (55.5% and 88.5% for EC and COD). This permits obtaining an effluent with good quality according to the recommendations of the Food and Agricultural Association (FAO) with the goal of reusing the regenerated water for irrigation. •Complete physicochemical characterization of OMW exiting secondary treatment (ST).•Particle size distribution reveals 75.1% particle concentration below 2μm.•31.7% of organic pollutants with size below 3kDa very relevant to membrane fouling•Saturation index warns to work below 90% feedstock recovery factor to avoid scaling.•Quality standards improved to reuse the treated effluent for irrigation.