Membrane treatment of biodiesel wash-water: A sustainable solution for water recycling in biodiesel production process

Most biodiesel production processes lead to the generation of large volumes of highly polluted wastewater, namely wash-water effluent. The principal aim of this paper is to show the applicability and effectiveness of the nanofiltration process for treatment of biodiesel wash water effluent and possibility of recycling the treated wastewater. For this purpose, three types of commercial nanofiltration membranes (TW30, NE90 and NE70) have been examined. The effect of two important operating parameters, including operating pressure (6-14 bar) and feed flow-rate (100-250 L/h) on the permeate flux, flux decline, and also separation performances for biological oxygen demand (BOD), chemical oxygen demand (COD), total solids (TS) and total dissolved solids (TDS) were investigated for the TW30 membrane. The obtained results showed that the permeate stream obtained from a feed at a pressure of 12 bar and a flow rate of 250 L/h, through a single stage nanofiltration process have BOD, COD, TDS and TS of 85.6%, 85.8%, 97.3% and 98.8% lower than the initial wash water effluent, respectively. The results of testing the three membranes at 14 bar and 250 L/h showed that TW30 had the lowest fouling tendency and flux decline followed by NE90 and NE70, respectively. The highest rejection for BOD, COD, TDS and TS was also observed for the TW30 membrane which shows this membrane is a good candidate, among the studied membranes, for further consideration and commercial applications.