Microbial Source Tracking Techniques to Support TMDL Development and Implementation

Srinivasan Rangarajan, Ph.D., P.E. and M. Samadpour

Current policies and regulations have emphasized the use of 'sound science' for development and implementation of Total Maximum Daily Loads (TMDL). Due to aggressive schedules to comply with litigation requirements and the specific water quality issues being dealt with, the development and implementation methodologies used by the states or their designated agencies vary extensively. The development of TMDLs is very dependent on the characterization of the point and non-point sources of pollution, so that the load (LA) and wasteload (WLA) allocations can be made in a technically defensible manner.

The uniqueness and importance of source tracking techniques to support development of pathogen TMDLs is visibly seen from dozens of studies conducted nation-wide. Numerous human pathogens (e.g., Vibrio cholera, Salmonella typhi, Giardia lamblia, Cryptosporidium parvum and Hepatitis A) are spread by fecal contamination of water. Due to difficulties in the detection, identification, and enumeration of specific human pathogens in water samples, indicator organisms are used to assess the potential for the presence of pathogens due to fecal contamination. Fecal coliforms and Escherichia coli are among the commonly used pathogen indicators.

The use of indicator organisms is limited by its inability to track organisms associated with fecal contamination to their potential sources. Microbial source tracking techniques, on the other hand, can be used to assess the impact of suspected sources of microbial pollution in rivers, lakes, and water reservoirs. Once the sources of microbial pollution (e.g., human, pets, mammalian livestock, avian livestock, mammalian wildlife and avian wildlife) are identified, their pollution loadings can appropriately be included in the TMDL development process and control measures can be devised to reduce or eliminate their impact.

Determination of the sources of microbial pollution requires establishing a large collection of bacterial isolates of a specific species from the impacted waterbody that is representative of the genetic diversity of that bacterial species in the watershed. Identification of the microbial pollution sources is then achieved by subtyping the water isolates and matching the subtypes to a collection of bacterial isolates of the same species from known sources, which include humans and various animal species.

The purpose of this workshop is to introduce different microbial source tracking techniques developed by leading research and academic institutions in the country, and their real-world applications. In particular, this workshop is organized into the following two parts to provide wealth of information to engineers and scientists: 1) comparison of different MST techniques and their percent effectiveness in identifying the various human and animal non-point sources; 2) wide-range of case studies to demonstrate the application of these techniques in the TMDL development and implementation process.

This workshop will include distinguished speakers from academia, federal government, research institutions and consulting community who develop and/ or adopt MST techniques for watershed management projects. The intended goal is to provide the engineers and scientists (with no background in microbiology, but more interested in source tracking applications) with solid introduction to these techniques highlighting their strengths and limitations, and demonstrate their application in the TMDL development and implementation process.

To be Presented at:

November 13-16, 2002
National TMDL Science and Policy Conference
Hosted by the Water Environment Federation
Phoenix, Arizona