Feasibility of using an innovative PVDF MF membrane prior to RO for reuse of a secondary municipal effluent

Abstract

The use of microfiltration (MF) or ultrafiltration (UF) prior to reverse osmosis (RO) process for reuse of reclaimed water is becoming increasingly attractive. In this work, a secondary municipal effluent was treated by a pilot-scale continuous filtration system with an innovative polyvinylidene fluoride (PVDF) MF membrane prepared via thermally induced phase separation (TIPS) method. The study showed that the MF system was operated under low normalized trans-membrane pressure (substantially below 40kPa) and high permeate flux (52–60L/m2/h). The MF system was able to treat the secondary effluent of unstable quality with good system stability. The membrane's permeability was easily recovered by chemical enhanced backwash (CEB) at a low effective chorine concentration (300 or 500mg/L). The membrane exhibited excellent mechanical strength and strong chemical resistance throughout the investigation. The treated water from the MF system exhibited stable quality with turbidity less than 0.05NTU, 15-minute silt density index (SDI15) less than 3 and chemical oxygen demand (CODCr) less than 15mg/L. The treated water quality completely met the quality requirement of RO feed water. This work demonstrated the feasibility of using the innovative MF membrane prior to RO for reuse of the secondary municipal effluent.