Transcript Enterococci as indicators of raw sewage in the Hudson River

Enterococci in the Hudson River
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What is it?
What does it tell us?
How does it get in the river?
How do we test for it?
What can we do about it?
PPT adapted from the summer 2007 research of
Suzanne Young, Barnard graduate. Project funded by The
Hudson River Foundation through a Polgar Fellowship.
(adapted by M. Turrin for Snapshot Day website)
What is Enterococci bacteria?
• A bacteria correlated with many of the human
pathogens found in raw sewage.
• It replaced ‘fecal coliform’ as the federal
standard for water quality in public beaches in
brackish/estuarine waters.
• Enterococci strongly correlates with swimmer
illness so it is useful for testing in areas where
the water carries a ‘recreational use’
classification*
*It is a goal of the Hudson River Estuary Program Action Plan that
much of the river will fall under this classification.
What are Potential Sources of
Sewage in the Hudson?
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Combined sewer outfalls*
Malfunctioning wastewater treatment facilities
Malfunctioning septic tanks
Runoff from streets and banks of waterways
Waste from boats and swimmers
* where sewage and storm drains are connected - as in NYC and - rainfall can
cause the system to overload, bypassing the treatment facility
NYCDEP
How do CSOs work?
CSO Facts for New York City
• 70% of NYC’s sewers are combined
• More than 494 outfalls in NYC
• Overflow can occur with 1/10th inch of rainfall
due to all the pavement and other impervious
surfaces!
Take a look at a ruler and see what a little amount of rain 1/10th inch is!
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Individual outfalls release sewage 50-80 times
per year
That equates to once every 4.5 to 7 days, or the equivalent of one to two
times a week!
• 27 billion gallons/year is released in NYC
In this study Enterococci is studied as
indicators of raw sewage in the Hudson
River focusing on two locations
125th street in West
Harlem
Piermont Pier in
Rockland County
125th Street: Future Harlem Piers
Piermont Pier
Suzanne collecting a
water sample
Tested using EPA Method 1600, which does
not distinguish sources of the bacteria, only
presence & rate of presence
The EPA standard for a single sample maximum is 104 Colony Forming
Units (104) per 100ml of sample water.
Presence - shows
entero colonies to be
counted
Absence - Clean
agar plate with no
growth
EPA Method 1600: Membrane
Filtration
• The Procedure
– Collect samples
– Dilute samples
– Filter diluted samples
– Incubate on mEI agar
plates
– Count colony growth
Filtration
Incubation at 41°C
Colony Count
(As viewed through a
microscope)
3000
West Harlem Results
Enterococci concentration reported as Colony Forming Units
(CFU) forming per 100 ml - charted with Rainfall events
2.5
CFUs
rainfa
ll
2500
2000
1.5
1500
1
Precipitation (in.)
ENT conc. (CFUs/100ml)
2
1000
0.5
500
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X axis represents dates June-Aug 2007
Look at this graph - Do you see a correlation between Enterococci (ENT) concentrations &
rainfall? How often do ENT counts go higher than 104 CFUs/000ml?
Combined
sewage
outfall
>1500 CFUs/100ml
3ml dilution
>1500
CFUs/100ml
Second Site - Piermont Pier - sampled in 2 places in Sparkill Creek and 3 spots
around the pier
Piermont Sampling Sites
North Side of Pier
End of Pier
South Side of Pier
Sparkill Creek: Below Dam
Sparkill Creek: Above Dam
Piermont: Enterococci and Rainfall for a
2 week period July 16-30th
700
1.4
CFUs
Rainfall
ENT (CFUs/100ml)
600
1.2
500
1
400
0.8
300
0.6
200
0.4
100
0.2
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Precipitation (in.)
If you are
comparing
this graph
to the
Harlem
River Site
graph be
careful to
note that
the Y axis
here is in
much lower
increments,
so overall
rates of
entero
would be
lower for
this site.
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Date
Rainfall does not seem to be a main source of enterococci in the Sparkill
- there is a consistent loading from another source…let’s see if we can
tell what might be a contributor…
Piermont: North and South of Pier
400
338
350
CFUs/100ml (average)
300
250
200
150
100
50
19
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North Side
South Side
North
P-value= .007
P-value <.05
South
6/25/2007
2.5
135
7/2/2007
20
77.5
7/9/2007
32.5
1500
7/18/2007
150
445
7/24/2007
10
630
*geo mean
19
338
Here is the data from
sampling both sides of the
pier. It seems the south side
has a regular contribution.
*See next slide for discussion of geometric mean
Geometric mean & water quality
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Many wastewater dischargers, or regulators who monitor swimming beaches and shellfish areas,
must test for and report bacteria concentrations. Often, the data must be summarized as a
"geometric mean" (a type of average) of all the test results obtained during a reporting period.
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WHY? A geometric mean, unlike an arithmetic mean, tends to reduce the effect of very high or
low values, which might bias the mean if a straight average (arithmetic mean) were calculated.
This is helpful when analyzing bacteria concentrations, because levels may vary anywhere from
10 to 10,000 fold over a given period. In our sample on the previous page the range was from 10
to 1500, still a large span.
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Very generally the geometric mean is really a log-transformation of data to enable meaningful
statistical evaluations. Practical definition: The average of the logarithmic values of a data set,
converted back to a base 10 number.
North Side
South Side
On the South side
of the pier is the
Sparkill Creek and
an outfall pipe.
Look at the next
slides to see if you
can tell how much
each might have
contributed to the
ENT counts.
Outfall Pipe
Sparkill Creek
900
853
800
CFUs/100ml (average)
700
606
600
500
400
300
200
100
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Sparkill
Sparkill UP
Sparkill
P-value= .18
Sparkill UP
7/2/2007
190
410
7/9/2007
315
575
7/18/2007
1500
1500
7/24/2007
1500
1500
606
853
geo mean
Both the upper &
lower Sparkill
sites seem to be
regular
contributors
Outfall and Mid-Channel Comparison
90
outfall
82
80
CFUs/100ml (geo.mean)
70
60
50
9/26/2006
13.0
2
10/18/2006
1500.0
2
11/10/2006
350.0
193.3333
4/18/2007
624.0
272
4/25/2007
1500
102.5
5/21/2007
220.0
5
6/18/2007
25.0
5
6/20/2007
2.5
2.5
7/12/2007
12.5
5
7/16/2007
3.333333
5
8/23/2007
324
2.5
82.3
9.8
geo mean
40
mid-channel
P-value= .055
30
20
10
10
Sampling at the
outfall varies
considerably with
just over half the
samples exceeding
standards.
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Piermont Outfall (from boat)
Tappan Zee Mid-channel
Tappan Zee Bridge
Mid-Channel
sampling site
from boat
Piermont Pier
Outfall sampling
site from boat
Could you argue that the Sparkill Creek also contributes to the Outfall
sampling site? Would the tidal cycle at sampling time have any impact on
contributions found from the Sparkill or the Outfall?
Previous Studies have
considered other items like:
• Salinity - found salinity negatively correlates
with ENT
• Grazing Communities - will affect
bacteria mortality & inactivity
• UV light - affects bacteria mortality &
inactivity
• Sediment - Like many other contaminants,
bacteria can be retained & resuspended in
sediments. Tidal resuspension of sediments is a
factor to consider.
Conclusions
– Rainfall strongly correlates with ENT
concentrations
– Tidal action may influence persistence of ENT
or disturb sediment and resuspend
– Some wastewater treatment plants are not
up-to-date with effective treatment processes
– There is a need for holistic approaches,
ecologically sound practices such as those
suggested in the following slides…
Current CSO Legislation legislation attempts to control the
problem through laws/legal remedies
• Clean Water Act - enacted 1977
• EPA CSO Control Policy
– Long Term Control Plans (submitted
6/30/07)
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Tank construction
Floatables controls
Wet weather capacity upgrades
Sewer system improvements
No discussion of BMPs (best
management practices) to reduce
stormwater volume
We need to switch from
thinking of stormwater as a
WASTE to be treated (costing
the city more money and
energy) to looking at it as a
RESOURCE to be used.
• Yes, capturing more stormwater so that
less volume actually reaches the rivers or
sewers and treatment plants
One small way - encouraging Green
Roofs/Rooftop Gardens
• Capture and absorb
stormwater
• Create wildlife
habitat
• Counteract “urban
heat island” effect
• Aesthetic benefits
• Costs ~$8-10/sq.ft.
more than reg.
Incentives
Chicago leads U.S. in sq.ft. of green roofs
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first municipal green roof in country atop city hall
Provides grants and stormwater “credits”
Density bonus in central business district
Expedited permit process, fee waivers
PLANYC
In 2007, property tax abatement to
offset 35% of the installation cost of
green roofs
What Other Ideas Can you
Think Of?
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1.More street trees
2.Rain barrels
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4.
5.
Suzanne’s research was supported
with help from:
Peter Bower
Greg O’Mullan
Sarah McGrath
John Lipscomb and Riverkeeper
Lamont Doherty Earth Observatory
Hudson River Foundation
Natural Resources Defense Council