a USDA-ARS, 230 Bennett Lane, Bowling Green,
KY 42104
b Department of Chemical and Environmental Engineering, University
of California, Riverside, B355 Bourns Hall, Riverside, CA 92521
* Corresponding author (cbolster@ars.usda.gov )
Received for publication June 4, 2005. Due to the difficulties in testing for specific pathogens, water samples are tested for the presence of nonpathogenic indicator organisms to determine whether a water supply has been contaminated by fecal material. An implicit assumption in this approach is that where pathogenic microorganisms are present fecal indicator organisms are present as well; yet surprisingly few studies have been conducted that directly compare the transport of indicator organisms with pathogenic organisms in ground water environments. In this study we compared the cell properties and transport of Escherichia coli, a commonly used indicator organism, and Campylobacter jejuni, an important enteropathogen commonly found in agricultural wastes, through saturated porous media. Differences in cell properties were determined by measuring cell geometry, hydrophobicity, and electrophoretic mobility. Transport differences were determined by conducting miscible displacement experiments in laboratory columns. Under the experimental conditions tested, C. jejuni was much more negatively charged and more hydrophobic than E. coli. In addition, C. jejuni cells were slightly longer, narrower, and less spherical than E. coli. The variations in cell properties, primarily surface charge, resulted in significant differences in transport between these two microorganisms, with the transport of C. jejuni exceeding that of E. coli when conditions favored low attachment rates, thus calling into question the usefulness of using E. coli as an indicator organism for this important pathogen.
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Published online 31 May 2006
Published in J Environ Qual 35:1088-1100 (2006)
DOI: 10.2134/jeq2005.0380
© 2006 American
Society of Agronomy, Crop Science Society of America, and Soil Science
Society of America
677 S. Segoe Rd., Madison, WI 53711 USA
Demonstration of Methods to Reduce E. coli Runoff from Dairy Manure Application Sites Donald W. Mealsa,* and David C. Braunb a Ice.Nine Environmental Consulting, 84 Caroline
Street, Burlington, VT 05401 * Corresponding author (dmeals@adelphia.net ) Received for publication October 4, 2005. Contamination by bacteria is a leading cause of impairment in U.S. waters, particularly in areas of livestock agriculture. We evaluated the effectiveness of several practices in reducing Escherichia coli levels in runoff from fields receiving liquid dairy (Bos taurus) manure. Runoff trials were conducted on replicated hay and silage corn (Zea mays L.) plots using simulated rainfall. Levels of E. coli in runoff were 104 to 106 organisms per 100 mL, representing a significant pollution potential. Practices tested were: manure storage, delay between manure application and rainfall, manure incorporation by tillage, and increased hayland vegetation height. Storage of manure for 30 d or more consistently and dramatically lowered E. coli counts in our experiments, with longer storage providing greater reductions. Manure E. coli declined by >99% after 90 d of storage. On average, levels of E. coli in runoff were 97% lower from plots receiving 30-d-old and >99% lower from plots receiving 90-d-old manure than from plots where fresh manure was applied. Runoff from hayland and cornland plots where manure was applied 3 d before rainfall contained 50% fewer E. coli than did runoff from plots that received manure 1 d before rainfall. Hayland vegetation height alone did not significantly affect E. coli levels in runoff, but interactions with rainfall delay and manure age were observed. Manure incorporation alone did not significantly affect E. coli levels in cornland plot runoff, but incorporation could reduce bacteria export by reducing field runoff and interaction with rainfall delay was observed. Extended storage that avoids additions of fresh manure, combined with application several days before runoff, incorporation on tilled land, and higher vegetation on hayland at application could substantially reduce microorganism loading from agricultural land. --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |