title: Evaluating the impacts of membrane type, coating, fouling, chemical properties and water chemistry on reverse osmosis rejection of seven nitrosoalklyamines, including NDMA.
abstract: Reverse osmosis (RO) treatment has been found to be effective for a wide range of organics but generally small, polar, uncharged molecules such as N-nitrosodimethylamine (NDMA) can be poorly rejected. The rejection of seven N-nitrosoalkylamines with molecular masses in the range of 78-158Da, including NDMA, N-nitrosodiethylamine (NDEA), N-nitrosomethylethylamine (NMEA), N-nitrosodipropylamine (NDPA), N-nitrosodibutylamine (NDBA), N-nitrosopyrrolidine (NPyr), N-nitrosopiperidine (NPip) by three commercial brackish-water reverse osmosis membranes was studied in flat-sheet cells under cross-flow conditions. The membranes used were ESPA3 (Hydranautics), LFC3 (Hydranautics) and BW-30 (Dow/Filmtec), commonly used in water reuse applications. The effects of varying ionic strength and pH, dip-coating membranes with PEBAX 1657, a hydrophilic polymer, and artificial fouling with alginate on nitrosamine rejection were quantified. Rejection in deionized (DI) water increased with molecular mass from 56 to 70% for NDMA, to 80-91% for NMEA, 89-97% for NPyr, 92-98% for NDEA, and to beyond the detection limits for NPip, NDPA and NDBA. For the nitrosamines with quantifiable transmission, linear correlations (r(2)>0.97) were found between the number of methyl groups and the log(transmission), with factor 0.35 to 0.55 decreases in transmission per added methyl group. A PEBAX coating lowered the ESPA3 rejection of NDMA by 11% but increased the LFC3 and BW30 rejection by 6% and 15%, respectively. Artificially fouling ESPA3 membrane coupons with 170g/m(2) alginate decreased the rejection of NDMA by 18%. A feed concentration of 100mM NaCl decreased rejection of NDMA by 15% and acidifying the DI water feed to pH=3 decreased the rejection by 5%, whereas increasing the pH to 10 did not have a significant (p<0.05) effect.
authors.affiliation: Department of Civil and Environmental Engineering, Stanford University, Stanford, CA 94305, USA.
authors.forename: Eva
authors.initials: E
authors.lastname: Steinle-Darling
authors.forename: Marco
authors.initials: M
authors.lastname: Zedda
authors.forename: Megan H
authors.initials: MH
authors.lastname: Plumlee
authors.forename: Harry F
authors.initials: HF
authors.lastname: Ridgway
authors.forename: Martin
authors.initials: M
authors.lastname: Reinhard
mesh_terms: D004058:Diffusion; D004128:Dimethylnitrosamine / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008567:Membranes, Artificial; D008970:Molecular Weight; D009602:Nitrosamines / Q000737:chemistry; D009994:Osmolar Concentration; D009995:Osmosis; D010539:Permeability; D011108:Polymers / Q000737:chemistry; D012996:Solutions; D014462:Ultrafiltration / Q000379:methods*; D014867:Water / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*
chemical_list: D008567:Membranes, Artificial; D009602:Nitrosamines; D011108:Polymers; D012996:Solutions; D014867:Water; D004128:Dimethylnitrosamine