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 <50%. Another NF test that was conducted at a drinking water treatment plant showed negligible membrane fouling with a TMP increase of 3 kPa over 35 d. Separation performance of the NF system remained high: total organic carbon (TOC) removal 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. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

The study demonstrated that the novel submerged flat-sheet NF membrane module has low fouling propensity and high separation performance during the direct filtration of surface water. The NF system showed high rejection of color and organics, with minimal increase in transmembrane pressure. The removal efficiency of total organic carbon was also high.