Enterococci in the Hudson River

• 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?

• 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

NYCDEPHow 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!

• Individual outfalls release sewage 50-80 times per year

• 27 billion gallons/year is released in NYC

Take a look at a ruler and see what a little amount of rain 1/10th inch is!

That equates to once every 4.5 to 7 days, or the equivalent of one to two times a week!

In this study Enterococci is studied as indicators of raw sewage in the Hudson

River focusing on two locations

Piermont Pier in Rockland County

125th street in West Harlem

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

Absence - Clean agar plate with no growth

Presence - shows entero colonies to be counted

The EPA standard for a single sample maximum is 104 Colony Forming Units (104) per 100ml of sample water.

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)

West Harlem Results Enterococci concentration reported as Colony Forming Units

(CFU) forming per 100 ml - charted with Rainfall events

0

500

1000

1500

2000

2500

3000

ENT conc. (CFUs/100ml)

0

0.5

1

1.5

2

2.5

Precipitation (in.)

CFUs

rainfall

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?

X axis represents dates June-Aug 2007

>1500 CFUs/100ml

Combined sewage outfall

>1500 CFUs/100ml

3ml dilution

Piermont Sampling SitesNorth Side of Pier

Sparkill Creek: Below Dam

South Side of Pier

End of Pier

Sparkill Creek: Above Dam

Second Site - Piermont Pier - sampled in 2 places in Sparkill Creek and 3 spots around the pier

0

100

200

300

400

500

600

700

Date

ENT (CFUs/100ml)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

Precipitation (in.)

CFUs

Rainfall

Piermont: Enterococci and Rainfall for a 2 week period July 16-30th

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…

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.

19

338

0

50

100

150

200

250

300

350

400

North Side South Side

CFUs/100ml (average)

Piermont: North and South of Pier

  North 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

P-value= .007

P-value <.05

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• 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.

• 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.

• 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.

Outfall Pipe

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.

606

853

0

100

200

300

400

500

600

700

800

900

Sparkill Sparkill UP

CFUs/100ml (average)

Sparkill Creek

  Sparkill Sparkill UP

7/2/2007 190 410

7/9/2007 315 575

7/18/2007 1500 1500

7/24/2007 1500 1500

geo mean 606 853

P-value= .18 Both the upper & lower Sparkill sites seem to be regular contributors

82

10

0

10

20

30

40

50

60

70

80

90

CFUs/100ml (geo.mean)

outfall mid-channel

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

geo mean 82.3 9.8

P-value= .055

Outfall and Mid-Channel Comparison

Piermont Outfall (from boat) Tappan Zee Mid-channel

Sampling at the outfall varies considerably with just over half the samples exceeding standards.

Piermont Pier Outfall sampling site from boat

Mid-Channel sampling site

from boat

Tappan Zee Bridge

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)

• 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.

• 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

Incentives

Chicago leads U.S. in sq.ft. of green roofs

PLANYCIn 2007, property tax abatement to offset 35% of the installation cost of

green roofs

What Other Ideas Can you Think Of?

• 1.More street trees

• 2.Rain barrels

• 3.

• 4.

• 5.

Suzanne’s research was supported with help from:

Peter BowerGreg O’MullanSarah McGrath

John Lipscomb and RiverkeeperLamont Doherty Earth Observatory

Hudson River FoundationNatural Resources Defense Council