Finding sources of fecal coliform bacteria in stormwater runoff

Transcription

1 Finding sources of fecal coliform bacteria in stormwater runoff David Tomasko, Ph.D. May 12, 2016

2 Why the concern over bacteria? Cholera Tens of millions killed over the centuries > 100,000 Americans 11 th President, James Polk Typhoid fever Jamestown Colony More deaths than from battle in Civil War Modes of transmission of typhoid (Anonymous 1939)

3 John Snow and the founding of modern epidemiology Located ca. 10 from abandoned cess pit

4 Two main types of bacteria Cocci (from Greek for seed) Round Single Chains More complex arrangements Bacilli (from Latin for stick) Rod-shaped Single Chains More complex

5 Total coliform bacteria Subset of rod or stick-shaped bacteria Pathogenic (disease-causing) Non-pathogenic Why such a broad category? Inability of historical monitoring programs to detect specific pathogenic bacteria (National Research Council [NRC] 2004) Vibrio cholerae cholera Salmonella typhii typhoid fever Problems? Lack of specificity Lots of false positives Need for a more refined technique

6 Fecal coliform bacteria Testing using techniques hopefully more similar to human gastrointestinal tract Higher incubation temperature Replicating warm blooded organisms Bile salts Produced by liver Original derivation of 200 colony forming units (cfu) / 100 ml 18% of total coliform bacteria from Ohio River would test positive (NRC 2004) Prior standard for total colform bacteria (U.S. Federal Water Pollution Control Administration) of 1,000 cfu / 100 ml 0.18 x 1,000 = 180 Rounded up to 200 cfu / 100 ml

7 Fecal coliform standard (FAC ) Class III - monthly average less than of 200 cfu / 100 ml Based on minimum of 10 samples over 30 days Nor exceed 400 cfu / 100 ml in 10% of the samples Nor exceed 800 cfu / 100 ml on any one day Question if monthly sampling, and value of 205? Not in excess of % of samples, but less than 400 Not enough samples for 200 not impaired Question if monthly sampling, and value of 405? Not in excess of % of samples, and higher than impaired

8 341 WBIDs impaired for fecal coliform bacteria 179 WBIDs with TMDLs for fecal coliform bacteria

9 Important considerations Fecal coliform bacteria are indicators of contamination by pathogenic organisms Bacteria such as Salmonella sp. (typhoid), E. coli (gastroenteritis), Vibrio sp. (cholera) Viruses such as enteroviruses, Hepatitis A Parasites such as Giardia sp., Cryptosporidium sp. Used for decades as more precise indicator of threat of contamination than total coliform bacteria

10 However Fecal coliform bacteria can survive and multiply in sediments to numbers far higher than in original dosage from sewage (LaLiberte and Grimes 1982, Ksoll et al. 2007) Klebsiella pneumoniae Normal constituent of human intestines But also a natural constituent of soils (Caplenas and Kanarek 1984) Fecal coliform bacteria do not have to come from feces, whether human or animal (Roll and Fujioka 1997)

11 Fecal coliform bacteria in the Miami River watershed Potential sources can include non-human fecal material, decay of vegetation (both native and non-native) and naturally occurring soil bacteria. (Wagner Creek TMDL; FDEP 2006)

12 Situation in Sunshine Lake Hypereutrophic lake in Charlotte County Massive algal bloom of benthic-associated cyanobacteria Public demand to do something led to dredging of lake Concurrent and ongoing work to determine the source(s) of nutrients that enabled the algal bloom to form Ambient water Groundwater sampling Bottom seepage Surface water runoff Nutrient species (nitrogen and phosphorous) Bacteria as potential indicator of sewage

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14 Hypothesis and Findings If fertilizer a source Elevated nitrogen and phosphorous, moderate bacteria If sewage a source Elevated nitrogen and phosphorous, high bacteria If combination both nutrients elevated, bacteria moderate to high What was found - Extremely high levels of phosphorous Average to below average levels of nitrogen Very high levels of fecal coliform bacteria (> 1 million cfu / 100 ml) How to explain findings?

15 Interpretation of findings Elevated phosphorous from influence of phosphorous-rich soils (adjacent to Bone Valley Formation) Low nitrogen indicates lack of sewage and/or fertilizer influences But what about elevated bacteria? Source Molecular Laboratories (Miami) Used in FC TMDL for Wagner Creek (FDEP 2006) 3 locations sampled twice ESP gene of Bacteroidetes bacteria for humans Maximum frequencies for humans and dogs (combined) of less than 1% So where did those bacteria come from, if not from humans or dogs??

16 Follow up steps Consistent with guidance from FDEP (2011) Work with Utilities to determine possibility of wastewater problems Walk the WBID Some evidence of dog feces Locations with bare soils LOTS of grass clippings

17 Experimental design Four treatments with three replicates each 50 grams of dog feces 50 grams of bare soil 100 grams of grass clippings Controls 12 five-gallon buckets held in an abandoned trailer with no AC or fans Ambient lake water with added materials Project done from June to July 2015 Fecal coliform bacteria sampled (APHA standard methods by NELAC-certified laboratory) on days 0, 2, 4, 8, 16 and 30

18 Overall set up

19 Dog feces Soil

20 Grass clippings Controls

21 So, what did we find??

22 Interpretation Elevated fecal coliform bacteria sources Not from sewage Not from soils Less so from dogs Microbial source testing and Walk the WBID Although can be a source, obviously Mostly from grass clippings Not fecally-contaminated grass clippings

23 Implications for Charlotte County Sewage not the source of bacteria No need to fix the sewage collection system Dogs could be a source Public education Soils not likely a source Grass clippings likely a source Public education Consistent with existing literature

24 Broader Implications > 150 TMDLs for fecal coliform bacteria in Florida > 300 WBIDs impaired for fecal coliform bacteria But Fecal coliform bacteria not specific to humans Not specific to mammals Not specific to animals, even

25 How much of an issue is non-human sources? 150,000 to 290,000 cfu / 100 ml in two events from White Ibis in Clam Bay, Collier County (Atkins 2012) Based on average, one bird could cause 120,000 gallons of water to exceed shellfish harvesting limit of 43 cfu / 100 ml 850 birds could produce enough fecal coliform bacteria (every day) to impair the 150 million gallons of Class II waters of Clam Bay On a larger scale.

26 Number of birds observed Fecal coliform bacteria load (billion / day) Bird-related fecal coliform bacteria loads to Malibu Lagoon, CA (Malibu Creek TMDL; US EPA) 2, , ,

27 Draft revised criteria from FDEP (10/2013) Class II Based on 5 samples per month Geometric mean not to exceed 35 Enterococci cfu / 100 ml No more than 10% to exceed 130 Enterococci cfu / 100 ml Supplements Fecal Coliform Bacteria standard Class III freshwater Based on 5 samples per month Geometric mean not to exceed 126 E. coli cfu / 100 ml No more than 10% to exceed 410 E. coli cfu / 100 ml Replaces Fecal Coliform Bacteria standard Class III marine Based on 5 samples per month Geometric mean not to exceed 35 Enterococci cfu / 100 ml No more than 10% to exceed 130 Enterococci cfu / 100 ml Replaces Fecal Coliform Bacteria standard

28 Have we solved the false positive problem? More on this later But these indicators can also survive and grow associated with decomposing vegetation (like fecal coliform bacteria) (Byappanahalli et al. 2003, Whitman et al. 2003) Has anyone already switched to these new standards? What did they find??

29 Summary from Moore et al. (2007) Epidemiology studies in 70 s and 80 s show good correlation between enterococcus concentration and bather illness in sewage-impacted water Partly in response EPA recommends (1986) enterococcus be used as salt water indicator In 1999, California required testing recreational waters for Enterococcus (in addition to Fecal Coliform bacteria) So, fewer false positives??

30 Moore et al. (2007) What??

31 While sewage is dominated by fecal Enteroccci

32 Urban stormwater runoff is equally influenced from decomposing vegetation

33 Even split in oceanic waters

34 Experience in Southern California Shift to use of Enterococci as primary indicator of bacterial impairment in 1990s Resultant 5-fold increase in impairment determinations 60% of which were exceedances of Enterococci, not Fecal Coliform bacteria Sewage is itself associated with Enterococci species that are 90% associated with fecal input Urban runoff can be equally dominated by Enterococci species that are associated with decomposing vegetation Oceanic bathing waters were influenced equally by fecal material and decomposing vegetation Even if fecal sources not proof from humans

35 Potential implications in Florida Class II waters potential increased frequency of impairment Class III freshwater likely a decreased frequency of impairment Class III marine potential increased frequency of impairment How to respond to impairment? Don t MODEL it not enough real data Walk the WBID look for potential sources Where appropriate, source identification Don t just assume it s from humans Doesn t have to be from humans to be a problem

36 Questions?