The effect of permeate recirculation on the depuration of pretreated olive mill wastewater through reverse osmosis membranes

► High ionic and organic pollutants load in OMW after physical-chemical pretreatment. ► Optimal operating conditions found for RO high and stable flux in semibatch mode. ► 20% permeate recirculation fraction or higher ensured high and stable permeate flux. ► 100% s.s., phenols and iron and 99.39% COD and 98.2% conductivity rejections. ► Quality achieved for discharging in sewers or closing loop in olive oil production.