Date of Award
Doctor of Philosophy
Dr. Joseph G. Engemann
Dr. Elwood Ehrle
Dr. Robert Poel
The focus of this study is to assess the efficacy of fecal coliform bacteria as a microbiological water quality indicator. The scientific and educational context of fecal coliform bacteria is explored through analysis of large sets of water quality data, focused field monitoring projects, and review of commonly used resources for school-based and volunteer water-related studies. Analyzed data sets include long term sampling (10 years), multiple sites, daily samples, storm event samples, and other parameters monitored in parallel with bacteria. Special attention is given to data sets from Kent County, Michigan. A background reference site in Michigan unimpacted by humans was monitored for two years. Field comparisons of membrane filtration with other bacteriological methods for Escherichia coli were performed.
Results of exploratory data analysis of long-term monitoring data established station profiles (box plots) for expected fluctuations in levels of bacteria. Typically, stations on the main reaches of Michigan rivers exceed fecal coliform bacterial levels of 200 colonies per 100 mL between 30 and 60% of the time. Tributary stations vary from 30 to 80% exceedance, and drains are in a range of 70 to 97% exceedance. The "background" site had significant levels of fecal coliform bacteria, E. coli, and total coliforms throughout the year that were not associated with humans. The direct inoculation of a water sample onto a plastic film with gel (Petrifilm™) had satisfactory performance and could be effectively used as an alternative method to membrane filtration for student monitoring.
Neither fecal coliform bacteria nor E. coli appears to meet all of the basic criteria for a credible water quality indicator, especially for Michigan. Additionally, misconceptions about indicator bacteria are commonly found in educational materials. Further analysis of the efficacy of federal and Michigan water quality standards for the protection of human health in recreational areas is needed. Collection of additional epidemiological evidence and consideration of site-specific standards that correlate with precipitation events should be part of this analysis. Extensive knowledge about the watershed is a key to interpretation of microbiological monitoring results as they relate to human health considerations.
Vail, Janet Heyl, "An Analysis of Fecal Coliform Bacteria as a Water Quality Indicator" (1998). Dissertations. 1594.