Use of Pulsed-UV Processes to Destroy NDMA

About five years ago, N-nitrosodimethylamine (NDMA) began to be detected in drinking water sources. Typically an oxidative degradation product of unsymmetrical dimethylhydrazine, NDMA is a component of rocket fuel and is also formed during numerous industrial manufacturing processes as a byproduct of reactions involving chemicals called alkylamines. The US Environmental Protection Agency has identified NDMA as a probable human carcinogen. However, because NDMA had not historically been considered a common drinking water contaminant, no federal or state drinking water standards were established for it until 1998 in California. In addition to its presence in drinking water, it has recently been suggested that NDMA may be present in sewage and reclaimed water after chlorination, as well as surface water processed by conventional drinking water treatment methods. The mechanisms of NDMA formation appear to be associated with the chlorination process. Therefore, an urgent need has developed for technologies that can remediate drinking water sources contaminated by this compound. This need sparked a growing interest in the potential of pulsed-ultraviolet (UV) and pulsed-UV/hydrogen peroxide treatment processes for removing NDMA from drinking water. The authors of this article evaluated the effectiveness of these treatments for NDMA removal. The results showed that NDMA can be reduced with UV light treatment. This finding will help drinking water utilities to better comply with state and federal standards and to more effectively protect public health

191 Chapter 7 Mass Spectrometric Detection of Ozonation Products and Intermediates of Aqueous Aerosol Iodide and/or Sulfite: Implications

The oxidations of sulfite and iodide in the interfacial layers of aqueous droplets exposed for ~ 1 to 10 ms to O3(g) are investigated by online mass spectrometry of electrostatically ejected anions. S(IV) oxidation losses in Na2SO3 microdroplets are proportional to [S(IV)] [O3(g)] up to ~ 90 % conversion. In contrast, although I- is more abundant than HSO3- in the interfacial layers of equimolar (Na2SO3 + NaI) microdroplets and ~ 3 times more reactive than HSO3- toward O3(aq) in bulk solution, it is converted with minimal loss to I3- and IO3-, plus a persistent ISO3- intermediate. These observations reveal unanticipated interfacial gradients, reactivity patterns, and transport phenomena that had not been taken into account in previous treatments of fast gas-liquid reactions and may be of importance for gas-aerosol reactions in the Marine Boundary Layer. 19