Reactions of Viral Genomes during Disinfection and Advanced Oxidation: Kinetics and Product Identification.

Free chlorine, UV based disinfectants, and advanced oxidation processes are commonly used to inactivate viruses. These disinfectants inactivate viruses by reacting with their biomolecules, including their genomes. Understanding viral genome reaction mechanisms, and identifying the biological and toxicological significance of reaction products, can help us predict the fate of newly emerging viruses during disinfection. However, reaction mechanisms and reaction products of viral genomes with free chlorine and UV used in advanced oxidation are poorly characterized. Further, genome inactivation kinetics have been predominantly measured using polymerase chain reaction (PCR)-based assays, which can underestimate degradation rates, and bias observed reaction kinetics. To address this, we exposed the genome of bacteriophage MS2, a commonly used surrogate for viruses in water treatment scenarios, to free chlorine doses and UV fluence relevant to drinking water treatment and advanced oxidation processes. After exposure, we digested the genome enzymatically into individual nucleosides, and measured decay and product formation using an Orbitrap ion mass analyzer. We found that reaction kinetics of nucleosides incorporated in the MS2 genome differed from those observed for unincorporated nucleosides, and the reaction kinetics of the MS2 genome measured using the Orbitrap ion mass analyzer differed compared to reaction kinetics measured using PCR based assays. We further identified photochemical reaction products, including pyrimidine dimers and hydrates, and chlorination products, including chlorinated nucleosides. The results of this study will help us predict the fate of emerging viruses during disinfection and advanced oxidation, and help us identify the biological and toxicological significance of viral genome disinfection products.