Bob Ardizzone, P.E.Charlie He, P.E., LEED AP

Treatment and Operational Strategy forRemoval of PFOA and PFOS: A Case Study

at an Arizona Wellfield

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Presentation Outline• Project Background and Scope

• Three Tools Beneficial for Water Utilities

• Take Home Messages

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PFOS and PFOA Were Recently Detected in Several Drinking Water Wells• PFOA concentrations ranged from

5 to 200 ng/L

• PFOS concentrations ranged from6 to 50 ng/L

• 2 wells have PFOA and PFOS that exceed EPA’s new HA

• Wells are critical water supply during summer and therefore required an immediate response

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Carollo Performed the Following Tasks in Developing a Plan to Remove PFOS and PFOA• Interim (short term) Treatment Strategy Plan

− GAC can effectively remove PFOS and PFOA

− Equipment available and can be implemented immediately

− Easy to operate, does not require chemicals or power

− GAC waste disposal manageable

• Interim GAC Facilities Operational Assistance

• Bench Scale Testing

• Long Term Treatment & Operational Strategy Plan

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Carollo Performed the Following Tasks in Developing a Plan to Remove PFOS and PFOA

Interim (Short‐Term)Treatment Strategy

Bench Testing 

Projection Model

Full Scale Monitoring

Well Head vs Centralized

Alternative Evaluation

O&M Costs Conceptual Design

Long Term Ops Strategy

Well Field Modeling

Capital Costs

Long Term Treatment and Operation Strategy Plan

PFOS and PFOADetected in Well Field

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Several Tools Could Benefit Other Water Utilities on PFAS Treatment Evaluation

OperationModel

BenchTesting

Full ScaleMonitoring &

Testing

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Follow Sampling Protocols to Monitor Spatial and Temporal Variations in PFOA and PFOS• Sampling Protocol

− Change over time− Across the wellfield

− Raw vs. Treated− Lead vs. Lag − PFOS + PFOA

− Long chain + short chain−WQ parameters for IX and

RO assessment

−Other

ND = Non-detect

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2AL Inf 4AL Inf 9AL Inf 5AL Inf 10AL Inf

PFOA (ng/L) PFOS (ng/L)

EPA Health Advisory Level for PFOA + PFOS: 70 ng/L

80% of HA Levels: PFOA + PFOS: 56 ng/L

ND ND

Well A Well B Well C Well D Well E

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e 4PF

OS

+ P

FOA

Conc

entr

atio

ns (n

g/L)

• Flow records or bed volume

• Analytical methods and costs

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What Does Estimated Carbon Capacity X µg/g Mean?• Theoretical carbon capacity• Equivalent to Y months full scale operation

ONLY IF carbon capacity can be fully utilized • Insufficient info for estimating full scale carbon

change-out time

Two Types of Bench Testing Are Typically Conducted for IX and GAC

Types of Bench Testing Apparatus Purposes Efforts

Isotherm (Jar Testing)

• Assess theoretical total capacity

• Compare different carbon or media relative to each other

• Cannot correlate with full scale operation

• Static and less sophisticated

• Fast and cost effective• Easier to conduct

• 5+ gal sample• Can perform in

hours to days

RSSCT (Column Testing)

• Correlates better with full scale operation

• Answers adsorption rates• Instrumental for operation

model calibration • Can be used to estimate

change-out frequency

• Dynamic and more sophisticated

• Need special training• More difficult to

conduct• 50+ gal sample• Can perform in

days to weeks

Note: RSSCT = Rapid Small Scale Column Testing

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Carbon Preparation for Column Testing Considers Scale-up Hydraulic Conditions and Pore Structure

TACTIC Analysis  = Total Adsorption Capacity with Temperature Influence Correction

Original Carbon  Crushed  Carbon

Testing Column

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Carbon Preparation for Column Testing Considers Scale-up Hydraulic Conditions and Diffusivity

Full Scale Small Column 1 (1.1 cm) Small Column 2 (0.5 cm)

Value Units Constant Diffusivity

Proportional Diffusivity Units Constant

DiffusivityProportional

Diffusivity Units

Column Diameter 12 ft 1.1 1.1 cm 0.5 0.5 cmMesh Size 12 x 30 - 100 x 120 100 x 120 - 140 x 170 140 x 170 -Particle Diameter 1.0 mm 0.15 0.15 mm 0.10 0.10 mmEmpty Bed Contact Time per Vessel (EBCT) 4.6 min 0.10 0.69 min 0.04 0.44 min

Flow Rate 1100 gpm 183 28 ml/min 46 4 ml/minLoading Rate 23.8 m/h 115.9 17.4 m/h 7.5 13.6 m/hMedia Depth 4.9 ft 20 20 cm 10 10 cmBed Volume 678 cf 19 19 mL 2 2 mLReynold's Number (R) 7 - 5.4 0.8 - 0.2 0.4 -Schmidt's Number (S) 1581 - 1581 1581 - 1581 1581 -Run time until breakthrough 10 months 4.1 – 6.8 27.2 - 45.3 days 1.7 - 2.8 17.4 - 29 days

Sample Volume Needed - - 285 - 475 285 - 475 gal 30 - 50 30 - 50 gal

Note: Highlighted in green is the column design utilized in this testing.

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Breakthrough is Defined as the Point at Which Treated Water is No Longer Meeting Treatment Goal

Treatment Intent Treatment Goal

Maximum Use of Carbon 90% of raw concentration

Treat to < HA with a safety factor (e.g., 80% of HA Level)

56 ng/L (for example)

Maximum Removal Non Detect

0

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1

0 10,000 20,000 30,000 40,000 50,000 60,000 70,000 80,000

Nor

mal

ized

PFO

A+P

FOS

(C/C

0)

Number of Bed Volumes Treated

Non Detect

Treatment Target

Maximum Useof Carbon

C

AA2

B B2

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Two Sets of Tests Were Conducted for Carbon 1 on Well A Water

0.000

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Nor

mal

ized

PFO

A+P

FOS

(C/C

0)

Number of Bed Volume Treated

Test 1Raw waterPFOA = 45 ng/LPFOS = 180 ng/L

Test 2Raw waterPFOA = 43 ng/LPFOS = 170 ng/L

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Column Tests Established Basis for Performance Projection Model to Guide Design and Operation

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PFOS and PFOA Module Is Being Added into Friendly Groundwater Treatment App

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Model Establishes Carbon Change-Out Frequency and Warning Levels to Guide Operation

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0 20,000 40,000 60,000 80,000 100,000 120,000 140,000 160,000

PFO

A+P

FOS

Con

cent

ratio

n (n

g/L)

Number of Bed Volumes Treated

Vessel 1Vessel 2Final Effluent

80% of HealthAdvisory Level:56 ng/L

Non-Detect

Modeled PFOA + PFOS

Conservative “3-week” Warning Level: Y ng/L

Conservative “5-week” Warning Level: Z ng/L

Estimated Media Replacement Frequency: ~ X months

Well A Water, Carbon 1, Two in Series; Treatment Goal: 56 ng/L

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Full Scale Operation Data Matched Modeled Results Well, Serving as a Great Calibration

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80

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180

0 20,000 40,000 60,000 80,000 100,000 120,000 140,000 160,000

PFO

A+P

FOS

Con

cent

ratio

n (n

g/L)

Number of Bed Volumes Treated

Vessel 1Vessel 2Final Effluent

80% of HealthAdvisory Level:56 ng/L

Non-Detect

Modeled PFOA + PFOS

Measured PFOA + PFOS (Lead Vessel Product)Measured PFOA + PFOS (Lag Vessel Product)

Well A Water, Carbon 1, Two in Series; Treatment Goal: 56 ng/L

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To Treat to Non-Detect with Two Vessels in Series, Carbon May Need to Be Changed Out Monthly

Modeled PFOA + PFOS

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180

0 20,000 40,000 60,000 80,000 100,000 120,000 140,000 160,000

PFO

A+P

FOS

Con

cent

ratio

n (n

g/L)

Number of Bed Volumes Treated

Non-Detect

Estimated Media Replacement Frequency: 1 month

Well A Water, Carbon 1, Two in Series; Treatment Goal: Non-Detect

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0

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140

0 20,000 40,000 60,000 80,000 100,000 120,000 140,000 160,000 180,000

PFO

A+P

FOS

Con

cent

ratio

n (n

g/L)

Number of Bed Volumes Treated

Vessel 1Vessel 2Vessel 3Vessel 4Final Effluent

Non-Detect

Estimated Media Replacement Frequency: X’ months

Modeled PFOA + PFOS

Conservative “3-week” Warning Level

Conservative “5-week” Warning Level

To Treat to Non-Detect and Use Carbon More Efficiently, Consider Four Vessels in SeriesWell A Water, Carbon 1, Four in Series; Treatment Goal: Non-Detect

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A Second Carbon Product Demonstrated Better Removal of PFOS and PFOA

0 1 2 3 4 5 6 7 8 9

0%

5%

10%

15%

20%

25%

30%

0 10,000 20,000 30,000 40,000 50,000 60,000 70,000 80,000 90,000

Estimated Operation Time (Months)

PFO

A+P

FOS

(C/C

0)

# of Bed Volumes

Raw waterPFOA = 44.5 ng/LPFOS = 195 ng/LPFOA + PFOS = 239.5

56 ng/L

Well A Water, Carbon 2, Two in Series

Non-Detect

Testing lasted m bed vol.or > n months equivalent

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A Second Carbon Product Demonstrated Better Removal of PFOS and PFOA

0 2 4 6 8 10 12 14

0%

10%

20%

30%

40%

50%

60%

0 20,000 40,000 60,000 80,000 100,000 120,000 140,000 160,000

Estimated Operation Time (Months)

PFO

A+P

FOS

(C/C

0)

# of Bed Volumes

Raw waterPFOA = 29 ng/LPFOS = 85 ng/LPFOA + PFOS = 114

56 ng/L

Well B Water, Carbon 2, Two in Series

Non-Detect

Lead vessel product remained non-detect for m

bed vol. or > n months equivalent

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Other Testing and Analysis Results May Also Be Relevant to Your Water• Carbon 1 removed more organics at the beginning but

Carbon 2’s removal is more sustainable

• Depending on level of DOC and PFOA + PFOS, use of DOC and UV254 as operation guide may NOT be feasible.

• Evaluate interference of other organic contaminants and impacts of peroxidation

• Evaluate centralized vs. individual wellhead treatment

• Reserve footprint for future water quality changes

• Consider treatment of other contaminants (Arsenic, Nitrate, Fluoride, Cr VI, etc.)

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Completed and Ongoing Testing Identifies Potential O&M Savings

Annual O&M Costs

20 Year O&M Saving: $X M 20 Year O&M

Saving: ~$Y M

No Testing Completed Testing Ongoing Testing

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Take Home Messages

• Media (Carbon or Resin) selection may be site specific

• Several tools help utilities develop customized solutions and capture savings

• GAC could be a great interim option for emergency response to PFOS and PFOA

• Long term cost-effectiveness must be evaluated through testing

• RSSCT and modeling provides first hand, scalable, and valuable insights to guide design and operation

Questions?Bob Ardizzone, P.E., BArdizzone@carollo.com

Charlie He, P.E., LEED AP, CHE@carollo.com

602-263-9500, Carollo Engineers