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ARS Home » Plains Area » Temple, Texas » Grassland Soil and Water Research Laboratory » Research » Publications at this Location » Publication #323644
Title: Effects of field storage method on E. coli concentrations measured in storm water runoff

Author
item Harmel, Daren
item WAGNER, KEVIN - Texas Water Resources Institute
item MARTIN, EMILY - Texas A&M University
item Smith, Douglas
item WANJUGI, PAULINE - Texas A&M University
item GENTRY, TERRY - Texas A&M University
item GREGORY, LUCAS - Texas Water Resources Institute
item HENDON, TINA - Tarrant Regional Water District

Submitted to: Environmental Monitoring and Assessment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/10/2016
Publication Date: 2/16/2016
Publication URL: http://handle.nal.usda.gov/10113/62160
Citation: Harmel, R.D., Wagner, K., Martin, E., Smith, D.R., Wanjugi, P., Gentry, T., Gregory, L., Hendon, T. 2016. Effects of field storage method on E. coli concentrations measured in storm water runoff. Environmental Monitoring and Assessment. 188:170. doi:10.1007/S10661-016-5183-9.

Interpretive Summary: Storm water runoff is increasingly assessed for fecal indicator organisms (e.g., Escherichia coli, E. coli) and its impact on contact recreation. These bacteria indicate the potential for stomach illnesses from swimming in contaminated waters. Concurrently, use of automatic samplers along with logistic, economic, technical, and personnel barriers are challenging conventional protocols for sample holding times and storage conditions in the field. A common holding time limit for E. coli is 8 hr with a 10 C storage temperature, but several research studies support longer hold time thresholds. The use of autosamplers to collect E. coli water samples has received little field research attention; thus, this study was implemented to compare refrigerated and unrefrigerated autosamplers and evaluate potential E. coli concentration differences due to field storage temperature (storms with holding times 24 hr). Data from 85 runoff events on four diverse watersheds showed that field storage times and temperatures had little impact on average E. coli concentrations. Graphs and error values did, however, indicate a weak tendency for higher concentrations at the refrigerated samplers. These results do not provide overwhelming evidence to support or refute the requirements for refrigerated autosamplers and the 24 hr holding time. They do, however, cast some doubt on conventional protocols for field holding time and storage temperature and emphasize the need to adequately consider practical constraints related to logistics, funding, travel time, and autosampler use.

Technical Abstract: Storm water runoff is increasingly assessed for fecal indicator organisms (e.g., Escherichia coli, E. coli) and its impact on contact recreation. Concurrently, use of autosamplers along with logistic, economic, technical, and personnel barriers are challenging conventional protocols for sample holding times and storage conditions in the field. A common holding time limit for E. coli is 8 hr with a 10 C storage temperature, but several research studies support longer hold time thresholds. The use of autosamplers to collect E. coli water samples has received little field research attention; thus, this study was implemented to compare refrigerated and unrefrigerated autosamplers and evaluate potential E. coli concentration differences due to field storage temperature (storms with holding times 24 hr). Data from 85 runoff events on four diverse watersheds showed that field storage times and temperatures had little statistically significant impact on mean and median E. coli concentrations. Graphs and error values did, however, indicate a weak tendency for higher concentrations at the refrigerated samplers, but it is unknown to what extent differing die-off and/or regrowth rates, heterogeneity in concentrations within samples, and lab analysis uncertainty contributed to the results. These results do not provide overwhelming evidence to support or refute the requirements for refrigerated autosamplers and the 24 hr holding time. They do, however, cast some doubt on conventional protocols for field holding time and storage temperature and emphasize the need to adequately consider practical constraints related to logistics, funding, travel time, and autosampler use.