finding sources of fecal coliform bacteria in stormwater ... webinar presenter...finding sources of...
TRANSCRIPT
Finding sources of fecal
coliform bacteria in
stormwater runoff
David Tomasko, Ph.D.
May 12, 2016
Why the concern over bacteria?
• Cholera
– Tens of millions killed over the centuries
– > 100,000 Americans
• 11th President, James Polk
• Typhoid fever
– Jamestown Colony
– More deaths than from battle in Civil War
Modes of transmission of typhoid (Anonymous 1939)
John Snow and the founding of
modern epidemiology
Located ca. 10’ from
abandoned cess pit
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
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
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
Fecal coliform standard (FAC 62-302)
• 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 800
– 100 % 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 800
– 100 % of samples, and higher than 400 - impaired
341 WBIDs
impaired for
fecal coliform
bacteria
179 WBIDs
with TMDLs
for fecal
coliform
bacteria
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
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)
“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)
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
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?
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??
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
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
Overall set up
Dog feces Soil
Grass clippings Controls
So, what did we find??
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
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
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
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….
Bird-related fecal coliform bacteria loads to
Malibu Lagoon, CA (Malibu Creek TMDL; US EPA)
0
400
800
1,200
1,600
2,000
Nu
mb
er o
f b
ird
s o
bse
rved
0
50
100
150
200
250
300
350
400
Feca
l co
lifo
rm b
acte
ria
load
(b
illio
n /
day
)
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
Have we solved the “false positive”
problem?
• 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??
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??
Moore et al. (2007)
What??
While sewage is dominated by “fecal” Enteroccci
Urban stormwater runoff is equally influenced
from decomposing vegetation
Even split in oceanic waters
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
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
