| Popis: |
As a result of the implementation of the Stage 2 Disinfectants and Disinfection By-product Rules (DBPRs), many water treatment facilities in the United States began to utilize chloramines as their primary or secondary disinfectant. Although chloramines have been known to have better efficiency for biofilm control than chlorine, our understanding of the reaction, stability, transport and fate of alternative disinfectants in water distribution systems is unfortunately incomplete. In this study, the impact of capsular extracellular polymeric substance (EPS) composition on bacteria disinfection by monochloramine was qualitatively determined using both wild-type and isogenic mutant Pseudomonas strains with different EPS secretion capacity and composition. In order to evaluate their EPS reactivity and contribution to susceptibility to monochloramine, the bacteria disinfection process was investigated using batch experiments with Fourier Transform Infrared Spectroscopy (FTIR) and Matrix-Assisted Laser Desorption/Ionization Time-of-Flight/Time-of-Flight Mass Spectrometry (MALDI-TOF/TOF-MS). Canonical correlation analysis (CCA) and partial least square (PLS) regression modeling were employed to explore the changes that EPS underwent during the monochloramine disinfection process. The analyses results suggested the reactions of peptide fragments of proteins that are associated with previously recognized cellular processes (Glycogen Synthase, D-ribose pyranase, Glycerol-3-phosphate acyltransferase, and Glucose-6-phosphate 1 dehydogenase). In addition, the impact of the protein-based EPS was shown to mitigate the monochloramine efficacy (CT difference of 20.7 mg*min/L) in comparison to the polysaccharide-based EPS (CT difference of 4.7 mg*min/L). This study not only provides fundamental insights into the reactivity of monochloramine with bacterial EPS but it elucidates some of the reactions that occur during the disinfection process. |
