Vasyl Kravchyk, EIT, PMP – NYC DEPMarc Santos, PE – Hazen and Sawyer

2

NYC Water Supply System

Supplies average water

demand of 1,100 MGD

3 Systems:• Croton

• Catskill

• Delaware

3

74 miles, Ashokan to KensicoCatskill Aqueduct

1913-1916: Aqueduct construction

Historical tests for max capacity ~660mgd

1925: Max capacity

at ~630mgd

2015: Current max flow ~591mgd

4

Maximize Catskill Aqueduct hydraulic capacity to augment supply available during Rondout-West Branch Tunnel outage

• Identify and assess capacity improvement options

Catskill Optimization Program Scope

5

Restoring Capacity in Catskill Aqueduct

5

Capacity reduction attributed to wall deposits (biofilm)

Capacity improvement options:

• cleaning and/or lining

• chemical addition

6

Historical Applications in Restoring Pipeline Capacity

50

10 days 20 days

Indian Brook Siphon, East Pipe, NY (1947)

Hartford, CT (1954)

San Diego Aqueduct, CA (1953)

Wichita, KS (1945)

Little Rock, AR (1951)

Indian Brook Siphon, Central Pipe, NY (1947)

Hetch Hetchy Aqueduct, CA (1938)(plus 0.2 to 0.4 mg/L ammonia)

Duration of Treatment

Co

nce

ntr

atio

n o

f C

hlo

rin

e (

mg/

L)

6 months 1 year 2 years

7

Biofilm is dark brown and slimy consistency• Large organic component and high levels of iron and manganese

• Filamentous manganese oxidizing bacteria - adapt to low nutrient conditions

• Filamentous biofilm morphology may contribute to adverse hydraulic effects

Aqueduct Biofilm Wall Analysis

Catskill Aqueduct April 20101/4 inch thick at Rondout Uptake Chamber

Catskill Aqueduct June 2013Biofilm Sample Collection from Aqueduct

8

Aqueduct Sampling

9

Primary Objective (ATL Study)1. Hydraulic Benefit from chemical addition for:

a) Mitigation of new biofilm growth

b) Reduction of existing biofilm

c) Type of chemical

Secondary Objectives

2. Turbidity impacts of adding chemicals

3. Decay Rates of oxidants along the length of the aqueduct

4. DBP formation in varying seasons

Ashokan Test Loop Study Objectives

10

Phase I: Biofilm growth to establish population

Phase II: Chemical addition to Treat biofilm

• Raw Water (control)

• Sodium Hypochlorite

• Chloramines

• Chlorine Dioxide

Phase III: Chemical addition and dechlorination(investigate oxidation effects)

Primary Objective Test Plan

11

Raw water supply from Ashokan Reservoir

3/8-inch ID flexible tubing

• Configured as 50 to 100 ft long loops

• Sized and operated to produce flow velocities comparable to flow velocity in aqueduct

Replicate Aqueduct Conditions

12

Chemical addition systems • Chlorine (sodium hypochlorite)

• Chloramines (sodium hypochlorite + ammonium hydroxide)

• Chlorine dioxide (CDG 3000 solution)

ATL Pilot Systems

13

Headloss/Hydraulics → Flow and Pressure

Chemical Dose → Chemical Residuals

Water Quality → pH, Temp, DO, Turb, ORP

Metals → Dissolved/total Fe and Mn

DBPs → Chlorite and Chlorate

ATL: Pilot Operations and Sampling

Test Loop in basement of Ashokan Lower Gate Chamber

14

Design/Space Constraints

15

ATL: Overview of Test Runs

Dose (mg/L)

LOW INTERMEDIATE HIGH

|

0.25

|

0.5|

2.0

|

4.0

|

1.0|

1.5|

3.0

CDG 3000

Sodium Hypochlorite

Chloramines

16

ATL: Phase I, Biofilm Growth

New Loops

Fouled Loops

(60 Days)

17

Raw Water Loops

18

Low Dose, New Loops

19

Low Dose, Fouled Loops

20

High Dose, Fouled Loops

21

Intermediate Dose, Fouled Loops

22

Objective 1a: Prevention of new biofilm growth

• Low doses maintained hydraulic performance on new loops

Objective 1b: Reduction of headloss with established biofilm

• Low doses maintained hydraulic performance on fouled loops

• High and intermediate doses improved hydraulic performance of fouled loops

Objective 1c: Comparison of hydraulic benefit by oxidant

• Clear difference between hydraulic performance of raw water loops and treated chemical loops

• All chemicals provided equal treatment performance in test loops

• Chlorine dioxide performed equally to sodium hypochlorite and chloramines without a residual

Summary of Treatment Phases

23

• Visual changes observed between raw water and chemically treated loops

Biofilm Samples from Raw Water and Treated Loops

Visual Inspection

Chlorine

Chlorine Dioxide

Chloramines

Raw Water

24

Testing Methods

Heterotrophic Plate Counts

16S rRNA

Deep 16S Analysis

Metagenomic analysis

Microbial Analysis

25

Unforeseeable Challenges

Air

intrusionAlewifeBiofilm clogging

rotameters/valve strainers

CDG3000 solution degradation of feed tubing FREQUENT REPLACEMENT

Fouling of rotameters and strainers REGULAR CLEANING

Varying head in the aqueduct INSTALLED BOOSTER PUMP

Alewife fish (sawbellies) intrusion STRAINER

Air intrusion scouring biofilm AT END OF TESTING PHASE

Booster

Pump

Peristaltic

Pumps

26

• Full-scale design of chemical addition and dechlorination systems

• Chlorine – Sodium hypochlorite

• Chlorine dioxide – PurateTM

• Dechlorination – Sodium bisulfite

Next Steps – Full-Scale

Ashokan Screen Chamber

27

Acknowledgements

27

Joint Venture

Project Team NYC DEP Pilot Operators

Tom McEnerney

Julie Herzner

Bill Becker

Ben Stanford

UMass Amherst

Cornell University

Vasyl Kravchyk

Wendy Sperduto

John Hoffman

Dan Michaud

Todd West

Mike Giuliano

Kevin McNiff

Marc Santos

Vasyl Kravchyk

Patty Heegle

Paul Brandt

Rahul Raina

Linda Fang

Deb Dryer

Diane Sheppard

Questions?

Vasyl Kravchyk, EIT, PMPVasylK@dep.nyc.gov718-595-7512

Julie Herzner, PEJherzner@hazenandsawyer.com212-539-7256