Environmental Science and Engineering Seminar

Microbiological water quality monitoring is critical for managing risk of disease and mortality; currently, regulations rely on the quantification of fecal indicator bacteria using traditional culture-based methods. However, these conventional approaches fall short of distinguishing between planktonic bacteria and bacterial aggregates, which can harbor higher loads of bacteria and associated pathogens and confer them enhanced resilience and infectivity. Due to this limitation, regulatory protocols may be significantly undercounting indicator bacteria and consequently underestimating the actual risk of exposure.

We will show evidence of the widespread and substantial presence of aggregate-bound indicator bacteria across a variety of water matrices and geographies by using size fractionation and an automated rapid method for comprehensive quantification of culturable bacteria. We observe comprehensive bacteria counts far exceeding measurements provided by traditional methods, results being corroborated by direct microscopic and molecular analyses. A specific focus of the presentation will be the analysis of the water quality prior to and during the 2024 Olympics, where several aquatic events (Triathlon, Mixed Relay, Marathon Swimming, Paratriathlon) were held in the Seine river.

Such findings challenge the efficacy of the existing global regulatory frameworks in accurately evaluating waterborne disease risk, by highlighting measurement inconsistencies and variabilities that could explain the persistence of disease outbreaks despite increased regulatory surveillance. Reassessing regulatory protocols to include comprehensive culture-based rapid quantification methods would provide higher-accuracy risk assessments, while automation could enable effective monitoring, including in remote and resource-limited settings.