Impact of wastewater particles on ultraviolet and chlorine disinfection and public health

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Protecting public health is a primary objective of wastewater treatment facilities, and disinfection is the most important process to control pathogens. Previous research has documented that presence of wastewater particulates affect the disinfection process, and coliform bacteria, the most commonly used indicator microorganism, associated with particles survive typical and much higher doses of disinfection applied in treatment plants. This is troublesome because the survival of particle-associated coliform through a disinfection process may indicate the survival of other more resistant health related microorganisms and may pose a threat to public health. The main objective of this research is to determine to what extent microorganisms are associated with particles, how they are distributed within the floc structure, and how their spatial distribution influences their response to disinfection by chlorine and UV radiation. Another objective is to determine how far into the floc structure UV and chlorine can penetrate and be able to inactivate particle-associated microorganisms. The research will employ a combination of molecular methods, including fluorescence in situ hybridization (FISH), indirect immunofluorescence, and ethidium monoazide (EMA) staining coupled with laser cytometry to provide information on the number, distribution, identity, and viability of particle-associated microorganisms after UV and chlorine disinfection. The study will improve the understanding of the fate and survival of pathogens through a disinfection process in a wastewater treatment plant. The acquired knowledge will benefit regulators, utilities, and consultants, and will help to improve the performance and design of existing and future disinfection processes. This knowledge is useful to provide wastewater facility operators with improved process controls, for consistency in meeting disinfection targets, and is the first step in protecting public health.