Removal of haloacetic acids from swimming pool water by reverse osmosis and nanofiltration.
Recent studies report high concentrations of haloacetic acids (HAAs), a prevalent class of toxic disinfection by-products, in swimming pool water (SPW). We investigated the removal of 9 HAAs by four commercial reverse osmosis (RO) and nanofiltration (NF) membranes. Under typical SPW conditions (pH 7.5 and 50 mM ionic strength), HAA rejections were >60% for NF270 with molecular weight cut-off (MWCO) equal to 266 Da and equal or higher than 90% for XLE, NF90 and SB50 with MWCOs of 96, 118 and 152 Da, respectively, as a result of the combined effects of size exclusion and charge repulsion. We further included 7 neutral hydrophilic surrogates as molecular probes to resolve the rejection mechanisms. In the absence of strong electrostatic interaction (e.g., pH 3.5), the rejection data of HAAs and surrogates by various membranes fall onto an identical size-exclusion (SE) curve when plotted against the relative-size parameter, i.e., the ratio of molecular radius over membrane pore radius. The independence of this SE curve on molecular structures and membrane properties reveals that the relative-size parameter is a more fundamental SE descriptor compared to molecular weight. An effective molecular size with the Stokes radius accounting for size exclusion and the Debye length accounting for electrostatic interaction was further used to evaluate the rejection. The current study provides valuable insights on the rejection of trace contaminants by RO/NF membranes.
Interdisciplinary Graduate School, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore; Residues and Resource Reclamation Centre (R3C), Nanyang Environment and Water Research Institute, Nanyang Technological University, 1 Cleantech Loop, CleanTech One, Singapore 637141, Singapore.
Linyan
L
Yang
Singapore Membrane Technology Centre (SMTC), Nanyang Environment and Water Research Institute, Nanyang Technological University, 1 Cleantech Loop, CleanTech One, Singapore 637141, Singapore; School of Chemical and Biomolecular Engineering, The University of Sydney, Sydney, Australia.
Qianhong
Q
She
School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
Man Pun
MP
Wan
Singapore Membrane Technology Centre (SMTC), Nanyang Environment and Water Research Institute, Nanyang Technological University, 1 Cleantech Loop, CleanTech One, Singapore 637141, Singapore; Division of Environmental and Water Resources, School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
Rong
R
Wang
Residues and Resource Reclamation Centre (R3C), Nanyang Environment and Water Research Institute, Nanyang Technological University, 1 Cleantech Loop, CleanTech One, Singapore 637141, Singapore; Division of Environmental and Water Resources, School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore; Department of Civil Engineering, Monash University, VIC 3800, Australia. Electronic address: wcchang@ntu.edu.sg.
Victor W-C
VW
Chang
Department of Civil Engineering, University of Hong Kong, Pokfulam, Hong Kong. Electronic address: tangc@hku.hk.
Chuyang Y
CY
Tang
D005374:Filtration; D057927:Hydrophobic and Hydrophilic Interactions; D008567:Membranes, Artificial; D009995:Osmosis; D013551:Swimming Pools; D014874:Water Pollutants, Chemical / Q000737:chemistry; D018508:Water Purification
D008567:Membranes, Artificial; D014874:Water Pollutants, Chemical
Empirical formula; Haloacetic acids; Nanofiltration; Reverse osmosis; Swimming pool water