The flux and impact of wastewater infrastructure microorganisms on human and ecosystem health

[Display omitted] •New pollution indicators improve tracking of urban impacts on water quality.•In the U.S., urban wastewater releases >1021 bacteria per day to water bodies.•Failing water infrastructure may have a big impact on urban water quality.•Urban microorganisms are sources of gene transfer events in aquatic ecosystems.•Urban water infrastructure should be considered an interconnected water microbiome. Wastewater infrastructure is designed, in part, to remove microorganisms. However, many microorganisms are able to colonize infrastructure and resist treatment, resulting in an enormous flux of microorganisms to urban adjacent waters. These urban-associated microorganisms are discharged through three primary routes 1) failing infrastructure, 2) stormwater, and 3) treated wastewater effluent. Bacterial load estimates indicate failing infrastructure should be considered an equivalent source of microbial pollution as the other routes, but overall discharges are not well parameterized. More sophisticated methods, such as machine learning algorithms and microbiome characterization, are now used to track urban-derived microorganisms, including targets beyond fecal indicators, but development of methods to quantify the impact of these microbes/genes on human and ecosystem health is needed.