Microfiltration and ultrafiltration as a pretreatment for nanofiltration of surface water

The efficiency of pretreatment using microfiltration (MF) and ultrafiltration (UF) was investigated in surface water nanofiltration for drinking water production. A series of pretreatments prior to NF were performed to examine their efficiency to improve NF flux. Based on lab-scale nanofiltration experiments, the major foulants appeared to be colloidal particles rather than dissolved organic matter for surface water containing hydrophilic organics. During the NF operations, changes in particle size by MF/UF pretreatment were found to be the reason for different pretreatment efficiencies with the pore size of prefilters. NF flux and pretreatment efficiency were quantitatively interpreted using a theoretical approach based on the particle back-transport model. Considering the energy consumption to produce unit volume of NF permeate, optimum pretreatment conditions were suggested.