title: N-nitrosodimethylamine (NDMA) formation at an indirect potable reuse facility.
abstract: Full-scale experiments to evaluate N-nitrosodimethylamine (NDMA) formation and attenuation were performed within an advanced indirect potable reuse (IPR) treatment system, which includes, sequentially: chloramination for membrane fouling control, microfiltration (MF), reverse osmosis (RO), ultraviolet irradiation with hydrogen peroxide (UV/H₂O₂), final chloramination, and pH stabilization. Results of the study demonstrate that while RO does effectively remove the vast majority of NDMA precursors, RO permeate can still contain significant concentrations of NDMA precursors resulting in additional NDMA formation during chloramination. Thus, it is possible for this advanced treatment system to produce water with NDMA levels higher than regional requirements for potable applications (10 ng/L). The presence of H2O2 during UV oxidation reduced NDMA photolysis efficiency and increased NDMA formation (∼22 ng/L) during the secondary chloramination and lime stabilization. This is likely due to formation of UV/H₂O₂ degradation by-products with higher NDMA formation rate than the parent compounds. However, this effect was diminished with higher UV doses. Bench-scale experiments confirmed an enhanced NDMA formation during chloramination after UV/H2O2 treatment of dimethylformamide, a compound detected in RO permeate and used as model precursor in this study. The effect of pre-ozonation for membrane fouling control on NDMA formation was also evaluated at pilot- (ozone-MF-RO) and bench-scale. Relatively large NDMA formation (117-227 ng/L) occurred through ozone application that was dose dependent, whereas chloramination under typical dosages and contact times of IPR systems resulted in only a relatively small increase of NDMA (∼20 ng/L). Thus, this research shows that NDMA formation within a potable water reuse facility can be challenging and must be carefully evaluated and controlled.
authors.affiliation: Department of Civil Engineering and Architecture, University of Catania, Viale A. Doria 6, 95125 Catania, Italy; Department of Chemical & Environmental Engineering, University of Arizona, 1133 E. James E. Rogers Way, Tucson, AZ 85721, USA.
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Sgroi
authors.affiliation: Department of Civil Engineering and Architecture, University of Catania, Viale A. Doria 6, 95125 Catania, Italy; Department of Chemical & Environmental Engineering, University of Arizona, 1133 E. James E. Rogers Way, Tucson, AZ 85721, USA.
authors.forename: Paolo
authors.initials: P
authors.lastname: Roccaro
authors.affiliation: United Water, Edward C. Little Water Reclamation Facility, 1935 South Hughes Way, El Segundo, CA 90245, USA.
authors.forename: Gregg L
authors.initials: GL
authors.lastname: Oelker
authors.affiliation: Department of Chemical & Environmental Engineering, University of Arizona, 1133 E. James E. Rogers Way, Tucson, AZ 85721, USA; National University of Singapore, NUS Environmental Research Institute (NERI), 5A Engineering Drive 1; T-Lab Building, #02-01, 117411 Singapore, Singapore. Electronic address: snyders2@email.arizona.edu.
authors.forename: Shane A
authors.initials: SA
authors.lastname: Snyder
mesh_terms: D004128:Dimethylnitrosamine / Q000138:chemical synthesis*; D060766:Drinking Water; D006861:Hydrogen Peroxide / Q000737:chemistry; D010126:Ozone / Q000737:chemistry; D014466:Ultraviolet Rays
chemical_list: D060766:Drinking Water; D010126:Ozone; D006861:Hydrogen Peroxide; D004128:Dimethylnitrosamine
keywords: Chloramination; Dimethylformamide; Hydrogen peroxide; Ozone; Reverse osmosis; UV