HUMAN FECAL INDICATOR BACTERIA DEMONSTRATES UBIQUITOUS CONTAMINATION ACROSS MULTIPLE TRANSPORT MECHANISMS IN AN URBAN STORM WATER BASIN IN SOUTHEASTERN WISCONSIN

Human sewage contamination in urban waterbodies poses a significant impairment to water quality and is of major concern with regard to environmental and public health. Discharge of storm water runoff to receiving waters is a known source of human pathogens, however the primary mechanisms by which these pathogens are mobilized into the storm water system are not clearly defined.

The study summarized herein isolates a source specific outfall located in the City of Wauwatosa that has routinely been identified as a major contributor of human fecal bacteria to the Menomonee River. The goal of this research is to evaluate the primary mechanisms by which human fecal indicator bacteria (FIB) enter the storm water system and are delivered to the Milwaukee River watershed and ultimately Lake Michigan by employing molecular based methods using quantitative polymerase chain reaction (qPCR) to identify “hot-spots” of the human Bacteroides genetic marker within the storm water system by: 1) identifying the potential infrastructure mechanisms that contribute to the transport of human FIB, and 2) characterizing the potential physical and/or geographic mechanisms that contribute to the transport of human FIB to the storm water system/or groundwater, and 3) quantifying the human Bacteroides marker under specific conditions to determine the priority mechanism.

A total of 266 storm water samples were collected from 20 select manhole locations within the study storm water basin. Three monitoring wells were also installed within the utility corridors to evaluate the potential for groundwater contamination; to date 45 groundwater samples have been collected from the three monitoring wells. All water samples were analyzed utilizing traditional culture-based methods: fecal coliform (FC), enterococci, and Escherichia coli, as well as molecular methods via qPCR to quantify the presence or absence of the human specific Bacteroides genetic marker.

The results of the study to date suggest that a significant difference was observed in the concentrations of human Bacteroides in the samples collected from within the storm water basin before construction versus after construction. However, ubiquitous contamination was still present throughout the entire storm water shed across multiple transport mechanisms.