Submerged nanofiltration without pre-treatment for direct advanced drinking water treatment

Membrane fouling is a major challenge toward achieving direct nanofiltration (NF) treatment of surface water. This study aimed to evaluate the potential of the novel submerged flat-sheet NF membrane module to achieve low fouling propensity and high separation performance during the direct filtration of surface water. Laboratory-scale NF tests showed that the transmembrane pressure (TMP) increased only by 10 kPa over 24 d during the direct treatment of river and dam water. The NF system showed high (>80%) and stable rejection of color and organics, as well as low and variable conductivity rejection (28–47%). The rejection of negatively charged trace organic chemicals (TOrCs) was >50%, while that of uncharged or positively charged TOrCs was 70%, which was greater than the conventional rapid sand filtration system with powdered activated carbon and intermediate chlorine doses (TOC removal = 20–60%). Overall, this study demonstrated high water quality and stable system operation of the submerged flat-sheet NF system during direct treatment of surface water. [Display omitted] •Efficacy of a novel submerged NF membrane in direct water treatment was evaluated.•Low permeate flux of 4 L/m2h led to a low level membrane fouling.•NF system showed high and stable rejection of color and organics at >80%.•Rejection of ions and many TOrCs was below 50%.