Hydrolyzed polyacrylonitrile UF-membrane for surface and TAP water treatment: Influence on DBPs formation and removal

Abstract

The integration of pre-treatment methods with low pressure-driven ultrafiltration (UF) has been found effective for reducing the formation of disinfection by-products (DBPs) in drinking water. In this study, a low dose peroxone (H2O2/O3) assisted alkaline hydrolyzed polyacrylonitrile (HPAN) UF-membrane system was explored, to determine its performance efficiency against two dissolved organic matter (DOM) sources and TAP water, specifically focusing the formation and removal of regulated DBPs. Increased hydrophilicity, enhanced incorporation of carboxyl groups, and decreased surface porosity were observed for the PAN membrane as a function of increased hydrolysis time. Filtration experiments involving humic acid (HA) and samples of real DOM sources displayed a high flux recovery (>90%) with the HPAN membrane. The initial flux for the optimized HPAN was found to be twice than that of the NF-3 membrane, irrespective of the DOM source. However, a relatively comparable removal efficiency was observed for both HPAN and NF-3 membranes in terms of organic matter and DBPs formation potential. Additionally, the H2O2/O3-HPAN system significantly reduced the aromatic and fluorescent content of the DOM by upto 70–80%, as represented by the DOC, UV254 and parallel factor analysis (PARAFAC) components. The fluorescence ratio C1/C2 showed a relatively greater reduction for soil-derived organic matter (SOM) as compared to the Olympic Lake (OL) water. Post-chlorination was found highly effective for the degradation of the humic-like DOM component (C1) than that of the fulvic and protein-like components. Moreover, the integration of H2O2/O3 with HPAN was able to remove 80% of the THMs and HAAs formation for both OL and SOM samples, together with a comparable reduction in DBP cytotoxicity. Interestingly, the HPAN membrane by reducing the TAP water DBPs upto 50%, fulfills the criteria of USEPA maximum contaminant level for drinking water.