E. coli as an indicator of beach water quality

Transcription

1 E. coli as an indicator of beach water quality Meredith B. Nevers U.S. Geological Survey Porter, Indiana U.S. Department of the Interior U.S. Geological Survey

2 Indicators of Water Quality for Great Lakes Beaches E. coli enterococci Present in gastrointestinal tract of humans Used as an indicator that human sewage is present in beach water, originating from combined sewer overflows, leaking septic systems, etc.

3 Development of Recreational Water Quality Standards: Fecal Indicator Bacteria Vast majority of E. coli is harmless to humans (>99.9%) E. coli O157:H7 is one of the pathogenic strains Coliform bacteria Fecal coliform bacteria E. coli Pathogenic E. coli

4 Human Pathogens Potentially Present in Raw Domestic Wastewater Organism Disease Symptoms Bacteria E. coli (enteropathogenic) Salmonella typhi Other Salmonella spp. Vibrio cholerae Protozoa Cryptosporidium Entamoeba histolytica Giardia lamblia Viruses Adenovirus Enteroviruses Norwalk agent Rotavirus Gastroenteritis Typhoid fever Salmonellosis Cholera Cryptosporidiosis Amebiasis Giardiasis Respiratory disease Gastroenteritis Gastroenteritis Gastroenteritis Diarrhea High fever, diarrhea Food poisoning Severe diarrhea and dehydration Diarrhea Prolonged diarrhea Mild to severe diarrhea Diarrhea, vomiting

5 Challenges of E. coli as an indicator for recreational water Culture assay takes hours E. coli are present in natural environments

6 E. coli concentrations in water can change quickly Day 2 E. coli (CFU/100 ml) R 2 = Mean E. coli (CFU/100 ml) EPA limit 235 E.coli CFU (100 ml) Day 1 E. coli (CFU/100 ml) Day 1 Day 2 Indiana Dunes National Lakeshore beaches Beach visitors swam on day one when E. coli exceeded the EPA standard, but the beach was under advisory/closure on day two when E. coli was low

7 E. coli and enterococci naturally occur and may grow under common conditions

8 E. coli and enterococci are present in recreational beach sand E. coli and enterococci persisted in sub- surface sand year-long at two Indiana beaches summer sampling winter sampling Sand along with associated fecal indicator bacteria is re-suspended into beach water through wave action

9 Sources of fecal indicator bacteria Determine the Relative Risk of Swimming-Related Illnesses Sources Relative risk Human feces/sewage High Non-human (e.g., animal feces) Moderate Environmental (e.g., plants, soil & sediments, sand) Low (unknown?)

10 Potential Solutions Modeling Rapid Testing Refined Source Identification Sanitary Survey Quantitative Microbial Risk Assessment

11 Modeling E. coli for the beaches west of the Burns Ditch Outfall LS MQ WS WB OD

12 4 North Wind, Currently Used Method 4.00 North Wind, USGS Predictive Modeling Log E. coli 2 1 year 4 5 Predicted vs. actual E. coli counts at Indiana Beaches in 2004 and 2005 Log E. coli year R Sq Linear = R Sq Linear = Predicted Value Predicted Value 0.4 R sq. USGS Predictive Modeling R sq. Currently Used Method Mean Prediction accuracy USGS Predictive Modeling and Currently Used Method (EPA) at Indiana Beaches in 2004 and Year

13 Predictive model (S.A.F.E.) used for beach management U.S. Department of the Interior U.S. Geological Survey

14 QPCR: a promising rapid method Comparison study at Burns Ditch, Wells Street, and Lake Street Beaches Log enterococci Log enterococci R=0.797** Log E. coli R=0.682** 0.0 R=0.650** Log CCE E. coli and enterococci counts were correlated in beach water Culturable enterococci counts were correlated with cell equivalents (QPCR) in beach water Shively, D. A., R. L. Whitman, and M. N. Byappanahalli (2008). A Comparison of Quantitative PCR and Membrane Filtration Methods for Assessing Recreational Water Quality Using Enterococci as Indicators. A report to the Indiana Department of Environmental Management

15 Next steps Improve and expand predictive models Field-test rapid methods New epidemiology studies on rapid methods and at additional beaches Expand source tracking and sanitary surveys

16 Meredith B. Nevers US Geological Survey, Lake Michigan Ecological Research Station 1100 N. Mineral Springs Rd. Porter, Indiana ext. 425 U.S. Department of the Interior U.S. Geological Survey Link