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OWML: Current Projects

Project Title: Response of microbial source tracking markers to wet-weather flows in urban, Columbus, Ohio waterways

Project chief:  Christopher M. Kephart

Project support:  Christopher D. Ecker and Donna S. Francy

Cooperators:  City of Columbus and Malcolm Pirnie Arcadis

Project duration:  May 2011 – September 2013

Introduction and problem:
As part of a consent order between the City of Columbus and the State of Ohio, the City is working to reduce combined sewer overflows (CSO)s to nearby waters including the Olentangy and Scioto Rivers. Improvements that have been completed and are operational include wastewater treatment plant (WWTP) expansion and regulator modifications. Future activities include construction of a deep sewer tunnel by 2015 which will increase the capture of wet weather overflows that currently empty into the Scioto River and instead carry the flows to the City’s Jackson Pike and Southerly WWTPs.

The City has contracted with Malcolm Pirnie to monitor water quality in river sites proximal to CSOs during rain events from May through November, 2011. One component of this water-quality monitoring program is to determine concentrations of the fecal indicator bacteria (FIB), E. coli and fecal coliforms. To supplement the pre- and post-construction sampling with information on potential fecal sources, the City has requested that the U.S. Geological Survey (USGS) collect data on microbial source-tracking (MST) markers.

Goals and objectives:
The overall goal of this proposed study is to provide MST host-associated marker data to help understand background levels of select sources of fecal contamination and to characterize the temporal and spatial trends in MST marker data during dry- and wet-weather events. Specific objectives for the study are to:

  1. Determine the concentration of MST markers of fecal contamination in selected river segments in Alum Creek and the Olentangy and Scioto Rivers during dry-weather and over time during wet-weather conditions,
  2. Characterize the presence of each host-associated MST marker with presumed positive source samples and the absence of each marker in presumed negative source samples within the watershed, and
  3. Further the science of MST by testing the use of markers in an urban watershed.

Sample collection and analysis for this study will be done at six river sites along the Olentangy and Scioto Rivers and Alum Creek. At each site, Malcolm Pirnie will collect 12 samples over 72 hours during up to six wet-weather events. Samples will be sent to Pace Analytical Services, Columbus, Ohio, and analyzed for E. coli, fecal coliforms, nutrients, and carbonaceous biochemical oxygen demand (CBOD). A subset of these samples will be analyzed for MST markers at the USGS Ohio Water Microbiology Laboratory (OWML), Columbus, Ohio. Sampling for MST markers will be done at four of the six river sites at 6 time steps (0, 4, 8, 16, 24, and 48 hours) at up to 6 wet-weather events.

Sampling will be done on the four MST river sites (table 1) during three dry weather events—spring, summer, and late summer or early fall. This will provide information on the MST markers and fecal contamination levels during baseline weather conditions.

Fecal samples will be collected from known animal sources throughout the sampling period to verify that the MST markers are present in these sources within this study area.

Samples will be analyzed for the MST markers are listed below.

  • GenBac - general marker of fecal contamination - USEPA, 2010
  • qHF183 - human - Seurnick and others, 2005
  • BoBac - bovine (cattle) - Layton and others, 2006
  • pLA35 - chicken - Weidhaas and others, 2010
  • BacCan - dog - Kildare and others, 2007
  • CGOF1-Bac - Canada goose - Fremaux and others, 2010
  • CGOF2-Bac - Canada goose - Fremaux and others, 2010

Concentrations of MST markers in stream water and collection system samples will be calculated. Summary statistics (average, median, standard deviation) will be used to describe the changes in MST marker concentrations both spatially and temporally. Streamflow data from Malcolm Pirnie and/or nearby USGS stream-gaging stations will be used to estimate instantaneous loads of E. coli and MST markers at river sites, where possible. The relations between fecal indicator bacteria concentrations (E. coli and fecal coliforms) and MST marker concentrations will be examined by use of correlation and/or regression analyses. Results from fecal source samples will be used to test the specificity (correct negatives) and sensitivity (correct positives) of each MST marker.

If agreed to by the City, data on E. coli and fecal-coliform concentrations will be entered into the USGS National Water Information System (NWIS) database for water-quality data (QWDATA). These data are available to the public. Data on MST markers are not entered into NWIS, because standard methods have not been established for these constituents. The results from this project will be published as a pdf-only USGS Scientific Investigations Report (SIR), with Malcolm Pirnie and the City of Columbus as co-authors.