Moving Beyond the Silos of Opportunistic Pathogen and Disinfection Byproduct Research to Improve Drinking Water System Management.

Drinking water opportunistic pathogens (OPs) and disinfection byproducts (DBPs) both pose risks to public health, and their variable occurrence from source to tap complicates efforts to control them simultaneously. Management of OPs and DBPs is further hindered by the historical division between microbial and chemical research. This review brings together the current knowledge regarding OPs and DBPs, identifies factors that influence the occurrence of both, and highlights areas where research is needed to better understand their health risks. First, we examine the current understanding of how OPs and DBPs are jointly influenced by physicochemical parameters, source water characteristics, treatment processes including disinfection, and distribution system properties. Temperature, for example, can affect OP and DBP occurrence, where higher temperatures can promote the growth of some OPs, such as , but temperature's effect on DBPs is species-dependent. Methods for quantifying the risks associated with OPs (quantitative microbial risk assessment) and DBPs (chemical risk assessment) are compared, finding that the numerous assumptions and data gaps associated with each method limit comparability across contaminant types. We highlight the urgent need to fill existing data gaps and develop a more unified risk framework so as to move toward holistic assessment of microbial and chemical risks. This review provides suggestions for future research, highlighting ways that researchers might utilize established practices in OP or DBP studies to further our understanding of the other. For example, analysis of source water organic matter composition, which has advanced our understanding of DBP formation, could be utilized to elucidate how source water characteristics influence OPs. This review bridges the gap between the OP and DBP disciplines, arguing that collaboration between the two is needed to address the pressing challenges facing water systems today.