Impact of overlooked halogenating agents on virus disinfection mechanisms

Viruses are a major cause of waterborne illnesses. Water treatment plants use chlorine, one of the most popular disinfectants, to control viruses. However, bromide and chloride are often present at increasing concentrations in drinking water. How these chemicals impact virus disinfection is unclear. This project will investigate their impacts and to optimize viral disinfection in water. Successful completion of this project will benefit society by improving drinking water treatment practices and safety. Increasing levels of halides in water, especially chloride and bromide, are a growing concern for water utilities. When water utilities apply chlorine to control pathogens, reactions between chlorine and halides lead to the formation of halogenating agents (Cl2, Cl2O, BrCl, BrOCl, Br2O) that are orders of magnitude more reactive than chlorine, but are typically overlooked due to their low concentrations. Disinfection guidelines that account for these halogenating agents are needed to apply chlorine effectively. Underdosing chlorine may not sufficiently inactivate pathogens, but overdosing chlorine may exacerbate the formation of toxic byproducts. Simultaneously, there is an urgent need for methods that predict the susceptibility of viruses to disinfectants to be prepared for possible future pandemics caused by waterborne pathogens. Understanding the mechanisms of viral inactivation by disinfectants and how disinfectant species contribute to inactivation is essential for such predictions. This project will determine the impact of increasing chloride and bromide concentrations and the associated halogenating agents on viral inactivation mechanisms. Three tasks are included to accomplish this goal. In task 1, experiments will be conducted to determine the reaction kinetics between halogenating agents and viral biomolecular targets including nucleic acids and amino acids. In task 2, novel mass spectrometry and established molecular techniques will be used to assess the ability of halogenating agents to react with biomolecular targets in model bacteriophages and their impact on bacteriophage function. In task 3, the impact of chloride and bromide on inactivation of representative viruses, and by extension, the impact of chloride and bromide on drinking water disinfection requirements, will be assessed. The results of these tasks will be compared against inactivation rates and mechanisms established for chlorination in waters without halides to determine the relative contribution of overlooked halogenating agents for viral inactivation in halide-containing waters. The project will benefit society by developing guidelines for optimizing disinfection for treatment of halide-containing waters, which will improve water treatment practices and water safety. The project will provide critical information on viral inactivation mechanisms and biomolecule chlorination which will benefit the environmental engineering, chemistry, and biology fields. The results of the project can be extrapolated to other waters that contain halides and are chlorinated to remove pathogens, including wastewaters (for both discharge and reuse), desalination waters, swimming pool waters, and seawater aquaculture systems. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.