Use of a Genetically Modified Organism To Assess Sewer Line Integrity

When sewer exfiltration leaks into the environment, the entry of fecal bacteria into groundwater and surface water increases health risks. Leaking sewers also are suspected sources of fecal contamination in many surface waters designated for total maximum daily load (TMDL) plans. Development of TMDL plans has been hindered by the lack of a reliable and cost-effective method to identify fecal contamination sources. Current methods of leak detection tend to be relatively inaccurate (dye studies) or very expensive (closed circuit television). Furthermore, detection of a pipe crack does not provide much information about the associated risk, because the risk generally is linked to pathogenic contaminants that cannot be presumed to travel unhindered in liquid flow. BioTrackers proposes to develop a novel method for leak detection and fecal source tracking based on a bacterial tracer that can be dosed to a sewer reach and subsequently sought in surrounding soil, groundwater, and surface water. The organism is a natural isolate of Escherichia coli that has been modified to carry a gfp gene in its chromosome. The gfp expression causes the cell to fluoresce green, so that it can be detected microscopically and by polymerase chain reaction. The U.S. Environmental Protection Agency has granted permission for a pilot study in which the bacterial tracer will be added to two sewer lines suspected of having leaks and to one leak-free line. Soil and water samples from sites adjacent to the sewer lines will be examined for the presence and enumeration of the genetically modified organisms (GMO). The study will be a joint collaboration of the Mecklenburg County Department of Environmental Protection, the North Carolina Department of Natural and Environmental Resources, BioTrackers, and the University of North Carolina¿Charlotte. The goal of this Phase I research project is to test the feasibility of a new method for tracking bacteria in the environment that is inexpensive, quantitative, and unambiguous; allows for a determination of bacterial longevity; identifies both culturable and nonculturable forms of bacteria; and has multiple potential commercial applications, including the sewer leak detection and fecal source tracking that will be tested in this project. This approach would be valuable in any application where the source of fecal coliforms or their fate upon entry into an environment are being investigated. The effectiveness and commercial viability of this approach will be evaluated based on the results of the study. A successful Phase I project will lead to testing of additional commercial applications, creation of additional GMO strains in Phase II, and subsequent commercialization of a bacteria1 tracking service.