Human bacteroides and total coliforms as indicators of recent combined sewer overflows and rain events in urban creeks

Authors: MCGINNIS, SHANNON - Temple University; Spencer, Susan; FIRNSTAHL, AARON - Us Geological Survey (USGS); STOKDYK, JOEL - Us Geological Survey (USGS); Borchardt, Mark; MCCARTHY, DAVID - Monash University; MURPHY, HEATHER - Temple University

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/9/2018
Publication Date: 3/17/2017
Publication URL: http://handle.nal.usda.gov/10113/6018233
Citation: McGinnis, S., Spencer, S.K., Firnstahl, A., Stokdyk, J., Borchardt, M.A., McCarthy, D.T., Murphy, H.M. 2017. Human bacteroides and total coliforms as indicators of recent combined sewer overflows and rain events in urban creeks. Science of the Total Environment. 630:697-976.

Interpretive Summary: Studies on the presence of human pathogens in surface water bodies under the influence of combined sewer overflows are lacking. Combined sewers are designed to transport both sewage and stormwater. When there is heavy rainfall the sewers overflow into lakes and rivers. As more people globally look to improve stormwater infrastructure to reduce overflow events, more baseline data is needed on the presence of pathogens as well as what indicators might be best suited for characterizing human pollution sources. We learned that the concentrations of two groups of bacteria in river water, human Bacteroides and coliforms, were highly correlated with overflow events of combined sewers. On the other hand, other microorganisms often considered to be indicators of pollution, E. coli, pepper mild mottle virus, and human polyomavirus, were not related to the overflow events. These results will help water quality managers identify lakes and rivers affected by combined sewer overflows. Knowing when sewage is present in water, especially water used by people for recreational activities, helps reduce exposures to disease-causing microorganisms.

Technical Abstract: Combined sewer overflows (CSOs) are a known source of human fecal pollution in many urban water bodies. Contact with human fecal pollution can contribute to the spread of human pathogens and represent a significant public health threat. To monitor human fecal contamination in water, bacterial fecal indicator organisms (FIOs) are traditionally used. However, because FIOs are not specific to human sources and do not correlate with the presence of pathogens, alternative fecal indicators, such as human Bacteroides, human polyomavirus (HPoV), and pepper mild mottle virus (PMMoV) detected using qPCR are becoming of interest to policymakers. Despite this, research is lacking on the relationships between these alternative indicators and pollution events, such as CSOs. In order to better understand how traditional and alternative fecal indicators correlate with pollution events, this study measured the relationships between CSOs, rainfall, and concentrations of traditional FIOs, alternative indicators, and human pathogens in two urban creeks. Samples were collected May-July 2016 and were analyzed for concentrations of FIOs (total coliforms and E. coli) using culture-based techniques as well as three alternative fecal indicators and nine human pathogens using qPCR. Among all indicators studied, human Bacteroides and total coliforms were significantly correlated with recent CSO and rainfall events, while E. coli, PMMoV, and HPoV did not show consistent correlations. Results may have implications for future policy or monitoring programs.