Low and Mixed Dose Jar Test Study to Evaluate Alum Treatment at Maximum Flow

on the Catskill Aqueduct

By Nicholas Prokopowicz

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Presentation Overview

• Background of NYC Water Supply System

• Summary of Water for the Future Project

• History of Alum Treatment

• Overview of Study

• Conclusion

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NYC water travels up to 125 miles from its upstate

watershed source before reaching the faucets of 9

million downstate consumers.

NYC Water Supply System

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Visit www.nyc.gov/waterforthefuture for further details.

Water for the Future Project

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• Supplies average water demand of 1,100 MGD (Million Gallons per Day)

• 3 Systems

• Croton

• Catskill

• Delaware

• Supplies average water demand of 1,100 MGD

• 3 Systems

• Croton• Multiple contributing

reservoirs. Circa 1906

• Filtration Plant – 2015

• 290 MGD

• Catskill

• Delaware

NYC Water Supply System

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• Supplies average water demand of 1,100 MGD

• 3 Systems

• Croton

• Catskill

• Delaware• Pepacton, Neversink,

Cannonsville and Rondout Reservoirs. Circa 1944

• 820 MGD

NYC Water Supply System

Rondout-West Branch (RWB) Tunnel

• Losing 15-35 MGD• Bypass repairs slated

for 2021• 5-8 months shutdown

for connection6

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• Supplies average water demand of 1,100 MGD

• 3 Systems

• Croton

• Catskill

• Ashokan and Schoharie Reservoirs. Circa 1915

• 590 MGD

• Delaware

NYC Water Supply System

↑  640 MGD

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Ashokan Reservoir

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Tropical Storm Tammy 2005

October 7-8, 2005 during Tropical Storm Tammy

• >6 inches of precipitation fell

• 32 NTU water spilled at the Dividing Weir

• 18 NTU water entered the Aqueduct

• Alum treatment began on October 13, 2005

• Treatment was administered for 180 days

• Treatment continued until May 24, 2006

Retrieved from – Alum Post-Treatment Report Water Quality and System Operations Catskill Water Supply, September 2006

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Tropical Storms Irene and Lee 2011

August 28, 2011 Hurricane Irene weakened to a tropical storm and passed over New York City

• Path passed directly over the NYC Water Supply watersheds

• Catastrophic flooding damage occurred to many watershed communities

• Resulting turbidity reached 75 NTU entering the aqueduct

• Alum treatment began August 29, 2011

Retrieved from – Alum Treatment After Action Report, July 2012

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Tropical Storms Irene and Lee 2011

Retrieved from – Alum Treatment After Action Report, July 2012

10 days later Tropical Storm Lee hit the region

• Turbidity entering the aqueduct peaked at 240 NTU

• Turbidity in the West Basin exceeded 3,000 NTU

• Treatment was administered for 260 days

• Treatment continued until May 15, 2012

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Catskill Alum Plant

19172014

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Previous Jar Test Results

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0 5 10 15

% R

educt

ion in T

urb

idity

Alum added (mg/L)

2005-2006 % Change

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% R

educt

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idity

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2011-2012 % Change

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Previous Jar Test Results

0.0

2.0

4.0

6.0

8.0

10.0

≤6.5 6.51-6.60 6.61-6.70 6.71-6.80 6.81-6.90 6.90<

Fin

al T

urbi

dity

(NT

U)

Final pH Range

2005 & 2011 Event Jar Tests Combined

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Previous Aqueduct Data

Pretreatment vs. Post Treatment

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*Outliers reach 180 NTU

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Previous Aqueduct Data

Pretreatment vs. Post Treatment

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2005-2006 Descriptive StatisticsAlum dose (mg/L)

Mean 6Standard Error 0.20

Median 7.5Mode 8

Standard Deviation 3.05Sample Variance 9.27

Skewness -1.47Range 11

Minimum 0Maximum 11

Count 234

2011-2012 Descriptive StatisticsAlum dose (mg/L)

Mean 11Standard Error 0.28

Median 10Mode 7

Standard Deviation 4.60Sample Variance 21.12

Skewness 0.36Range 23

Minimum 0Maximum 23

Count 261

*Outliers reach 180 NTU

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CATALUM

• 5BRK

Leaving the reservoir

Image is not to scale

Currently Offline

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What is the purpose and goals of the study?

The maximum flow of the Catskill Aqueduct will be restored to >600 MGD.

Can DEP effectively treat high turbidity at 600 MGD?

• Maximum amount of dry alum approx. 31,000 lbs/day.

• Currently limits operations to a 6.0 mg/L dosage.

• What would be the effectiveness of 6.0 mg/L?

• What is the effectiveness of using a mixture of dry and liquid alum?

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Low and Mixed Dose Alum Study

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Low Dose Alum Study

6.0 mg/L of Alum addedTurbidity (NTU) Starting Turbidity 5 8 12 20 *50 *100

30 min settling 2.0 1.3 2.4 3.1 *6.5 *11.5

1 hour settling 1.7 1.6 1.4 2.2 *5.2 *10.2

2 hours settling 0.8 0.9 1.2 1.5 *3.9 *7.7

24 hours settling 0.5 0.6 0.9 0.8 *2.6 *3.5

32 hours settling 0.5 0.5 0.7 0.6 *2.3 *3.1* Values calculated from average of 4 replicates.

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Settling Time (Hours)

Starting Turbidity *100ntu6.0 mg/L of Alum added

Low Dose Alum Study

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Settling Time (Hours)

Starting turbidity *50ntu6.0 mg/L of Alum added

*Values calculated from average of 4 replicates

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Kenscio Laboratory staff tested:

Samples of water at 50 NTU

• Adding powder alum at a dosage of 6.0 mg/L with enough liquid alum to attain the final desired dosage

• Testing a range from 7.0 mg/L to 16.0 mg/L

• Dosages of 8.0 mg/L & 9.0 mg/L were replicated

Samples of water at 100 NTU

• Adding powder alum at a dosage of 6.0 mg/L with enough liquid alum to attain the final desired dosage

• Testing a range from 7.0 mg/L to 16.0 mg/L

• Dosages of 10 mg/L & 12 mg/L were replicated

Mix Dose Alum Study

What if 6.0 mg/L of dry alum is augmented by liquid alum?

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Mix Dose Alum Study

Starting turbidity at 50 NTU

Alum (mg/L) 7 8 9 10 11 12 13 14 15 16

10min Settling (NTU) 6.1 5.2 7.7 5.0 3.8 4.7 3.7 6.5 6.5 6.4

20min Settling (NTU) 4.4 3.4 5.2 3.8 5.0 5.1 4.1 4.5 5.2 6.2

30min Settling (NTU) 3.4 3.1 2.6 3.5 2.6 4.7 4.4 4.1 5.1 5.9

60min Settling (NTU) 6.9 5.0 2.7 3.1 3.8 4.1 3.3 4.4 5.2 5.7

Final pH 6.65 6.67 6.74 6.53 6.55 6.58 6.45 6.38 6.30 6.28

Starting Turbidity at 100 NTU

Alum (mg/L) 7 8 9 10 11 12 13 14 15 16

10 min Settling (NTU) 8.6 6.3 6.2 4.9 4.5 4.8 4.6 3.7 7.0 11.9

20 min Settling (NTU) 6.9 6.8 4.8 3.2 4.2 4.2 4.3 5.0 6.8 9.2

30 min Settling (NTU) 6.8 5.8 3.4 3.3 4.0 3.2 3.1 4.3 6.7 10.7

1 hour Settling (NTU) 7.7 5.6 3.7 2.9 4.0 2.8 3.1 4.3 6.1 9.8

Final pH 6.68 6.65 6.81 6.75 6.73 6.75 6.65 6.56 6.49 6.43

Starting Turbidity at 50 NTU

Alum (mg/L) 7 8 9 10 11 12 13 14 15 16

10min Settling (NTU) 6.1 5.2 7.7 5.0 3.8 4.7 3.7 6.5 6.5 6.4

20min Settling (NTU) 4.4 3.4 5.2 3.8 5.0 5.1 4.1 4.5 5.2 6.2

30min Settling (NTU) 3.4 3.1 2.6 3.5 2.6 4.7 4.4 4.1 5.1 5.9

60min Settling (NTU) 6.9 5.0 2.7 3.1 3.8 4.1 3.3 4.4 5.2 5.7

Final pH 6.65 6.67 6.74 6.53 6.55 6.58 6.45 6.38 6.30 6.28

Starting Turbidity at 100 NTU

Alum (mg/L) 7 8 9 10 11 12 13 14 15 16

10 min Settling (NTU) 8.6 6.3 6.2 4.9 4.5 4.8 4.6 3.7 7.0 11.9

20 min Settling (NTU) 6.9 6.8 4.8 3.2 4.2 4.2 4.3 5.0 6.8 9.2

30 min Settling (NTU) 6.8 5.8 3.4 3.3 4.0 3.2 3.1 4.3 6.7 10.7

1 hour Settling (NTU) 7.7 5.6 3.7 2.9 4.0 2.8 3.1 4.3 6.1 9.8

Final pH 6.68 6.65 6.81 6.75 6.73 6.75 6.65 6.56 6.49 6.43

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Time (minutes)

50 NTU Sample with 9 mg/L Alum

94% Reduction in

Turbidity

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Time (minutes)

50 NTU Sample with 8 mg/L Alum

92% Reduction in

Turbidity

Mix Dose Alum Study

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100 NTU Sample with 10 mg/L Alum

96% Reduction in

Turbidity

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Time (minutes)

100 NTU Sample with 12mg/L Alum

95% Reduction in

Turbidity

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Mix Dose Alum Study

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Under optimal conditions• A sample of Catskill Aqueduct water

with turbidity that is ≤20 NTU can be mitigated with 6.0 mg/L of dry alum.

• For samples of Catskill Aqueduct water that have a turbidity of 50 and 100 NTU, a mixture of 6.0 mg/L of dry alum augmented with liquid alum will be needed to adequately reduce the turbidity.

Final Statement

Conclusion

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Citations• New York City Department of Environmental Protection Alum Post-Treatment

Report Water Quality and System Operations Catskill Water Supply – Volumes 1 and 2, September 2006

• New York City Department of Environmental Protection Alum Treatment After Action Report, July 2012

• NYC Environmental Protections Strategy 2011-2014 retrieved from: http://www.nyc.gov/html/dep/pdf/strategic_plan/dep_strategy_2011.pdf

• Operational Control of Coagulation and Filtration Processes, Manual M37; 1st

American Water Works Association. Denver, CO. 1992

• United States Environmental Protection Drinking Water Treatability Database: Conventional Treatment – 2014 retrieved from: http://iaspub.epa.gov/tdb/pages/treatment/treatmentOverview.do?treatmentProcessId=1934681921

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