xvEPA

EPA Document No.
815R24011

Best Available Technologies and Small System
Compliance Technologies for Per- and Polyfluoroalkyl
Substances (PFAS) in Drinking Water


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Best Available Technologies and Small System Compliance Technologies for
Per- and Polyfluoroalkyl Substances (PFAS) in Drinking Water

Prepared by:

U.S. Environmental Protection Agency
Office of Water
Office of Groundwater and Drinking Water
Standards and Risk Management Division
Washington, DC 20460

EPA Document Number: 815R24011

March 2024


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Best Available Technologies and Small System Compliance Technologies for PFAS in Drinking Water
815R24011	March 2024

Disclaimer

Mention of trade names or commercial products does not constitute endorsement or
recommendation for use.


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Best Available Technologies and Small System Compliance Technologies for PFAS in Drinking Water
815R24011	March 2024

Contents

1.0 Introduction	2

1.1 PFAS Background	4

2.0 Best Available Technology Evaluation for GAC	8

2.1	High Removal Efficiency	9

2.1.1	Have high removal efficiencies that achieve potential MCLs been
documented?	9

2.1.2	Are the effects of water quality parameters on treatment effectiveness and
reliability well-known?	11

2.1.3	Is the technology reliable enough to continuously meet a drinking water
MCL?	11

2.1.4	Is additional research needed?	12

2.2	History of Full-Scale Operation	12

2.2.1	Do existing studies include full-scale operations at drinking water treatment
facilities?	12

2.2.2	Are there studies of full-scale treatment of residuals that fully characterize
residual waste streams and disposal options?	14

2.2.3	Can the bench or pilot studies be scaled up to represent full-scale treatment,
including residuals generation and handling?	15

2.2.4	Is additional research needed?	15

2.3	General Geographic Applicability	15

2.3.1	What regions do the existing research studies represent?	15

2.3.2	Is it known that regional water quality variations will limit treatment
effectiveness or reliability in some areas?	15

2.3.3	Are there any regional issues with respect to residuals handling or water
resource use?	15

2.3.4	Is additional research needed?	15

2.4	Compatibility with Other Treatment Processes	16

2.4.1	Have the effects (adverse or beneficial) of the treatment process on other
processes likely to be present at existing plants been evaluated?	16

2.4.2	Will additional pre- or post-treatment be required for integration into an
existing (or planned) treatment train?	16

2.4.3	Is additional research needed?	16

2.5	Ability to Bring All of the Water System into Compliance	16

2.5.1 Will the treatment process adversely affect the distribution system or water

resource decisions?	16

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2.5.2	Might the treatment process, residuals handling, or pre- or post-treatment
requirements raise new environmental quality concerns?	16

2.5.3	Is additional research needed?	16

2.6 Reasonable Cost Basis for Large and Medium Systems	17

2.6.1	Is the technology currently used by medium and large systems (including uses
for other treatment purposes)?	17

2.6.2	Do the treatment studies provide sufficient information on design assumptions
to allow cost modeling?	17

2.6.3	Is additional research needed?	17

3.0 Best Available Technology Evaluation for IX	18

3.1	High Removal Efficiency	19

3.1.1	Have high removal efficiencies that achieve potential MCLs been
documented?	19

3.1.2	Are the effects of water quality parameters on treatment effectiveness and
reliability well-known?	20

3.1.3	Is the technology reliable enough to continuously meet a drinking water
MCL?	21

3.1.4	Is additional research needed?	21

3.2	History of Full-Scale Operation	21

3.2.1	Do existing studies include full-scale operations at drinking water treatment
facilities?	21

3.2.2	Are there studies of full-scale treatment of residuals that fully characterize
residual waste streams and disposal options?	22

3.2.3	Can the bench or pilot studies be scaled up to represent full-scale treatment,
including residuals generation and handling?	22

3.2.4	Is additional research needed?	22

3.3	General Geographic Applicability	22

3.3.1	What regions do the existing research studies represent?	22

3.3.2	Is it known that regional water quality variations will limit treatment
effectiveness or reliability in some areas?	22

3.3.3	Are there any regional issues with respect to residuals handling or water
resource use?	23

3.3.4	Is additional research needed?	23

3.4	Compatibility with Other Treatment Processes	23

3.4.1 Have the effects (adverse or beneficial) of the treatment process on other

processes likely to be present at existing plants been evaluated?	23


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3.4.2	Will additional pre- or post-treatment be required for integration into an
existing (or planned) treatment train?	23

3.4.3	Is additional research needed?	23

3.5	Ability to Bring All of the Water System into Compliance	23

3.5.1	Will the treatment process adversely affect the distribution system or water
resource decisions?	23

3.5.2	Might the treatment process, residuals handling, or pre- or post-treatment
requirements raise new environmental quality concerns?	24

3.5.3	Is additional research needed?	24

3.6	Reasonable Cost Basis for Large and Medium Systems	24

3.6.1	Is the technology currently used by medium and large systems (including uses
for other treatment purposes)?	24

3.6.2	Do the treatment studies provide sufficient information on design assumptions
to allow cost modeling?	24

3.6.3	Is additional research needed?	24

4.0 Best Available Technology Evaluation for RO/NF	25

4.1	High Removal Efficiency	26

4.1.1	Have high removal efficiencies that achieve potential MCLs been
documented?	26

4.1.2	Are the effects of water quality parameters on treatment effectiveness and
reliability well-known?	28

4.1.3	Is the technology reliable enough to continuously meet a drinking water
MCL?	28

4.1.4	Is additional research needed?	28

4.2	History of Full-Scale Operation	28

4.2.1	Do existing studies include full-scale operations at drinking water treatment
facilities?	28

4.2.2	Are there studies of full-scale treatment of residuals that fully characterize
residual waste streams and disposal options?	28

4.2.3	Can the bench or pilot studies be scaled up to represent full-scale treatment,
including residuals generation and handling?	29

4.2.4	Is additional research needed?	29

4.3	General Geographic Applicability	29

4.3.1	What regions do the existing research studies represent?	29

4.3.2	Is it known that regional water quality variations will limit treatment
effectiveness or reliability in some areas?	30

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4.3.3	Are there any regional issues with respect to residuals handling or water
resource use?	30

4.3.4	Is additional research needed?	30

4.4	Compatibility with Other Treatment Processes	30

4.4.1	Have the effects (adverse or beneficial) of the treatment process on other
processes likely to be present at existing plants been evaluated?	30

4.4.2	Will additional pre- or post-treatment be required for integration into an
existing (or planned) treatment train?	30

4.4.3	Is additional research needed?	30

4.5	Ability to Bring All of the Water System into Compliance	31

4.5.1	Will the treatment process adversely affect the distribution system or water
resource decisions?	31

4.5.2	Might the treatment process, residuals handling, or pre- or post-treatment
requirements raise new environmental quality concerns?	31

4.5.3	Is additional research needed?	31

4.6	Reasonable Cost Basis for Large and Medium Systems	31

4.6.1	Is the technology currently used by medium and large systems (including uses
for other treatment purposes)?	31

4.6.2	Do the treatment studies provide sufficient information on design assumptions
to allow cost modeling?	31

4.6.3	Is additional research needed?	32

5.0 Summary of Best Available Technology Evaluation	33

6.0 Small System Compliance Technology Evaluation	35

6.1	SSCT Analysis Method	35

6.2	Results	37

6.3	Small System Affordability Analysis with Potential Additional Expenditure

Margins and when Accounting for Financial Assistance	39

7.0 References	41

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Figures

Figure 1. Chemical Structure of PFOA and PFOS	6

Figure 2. Conceptual Diagram of the GAC Treatment Process	9

Figure 3. Conceptual Diagram of the IX Treatment Process	18

Figure 4. Conceptual Diagram of the RO Treatment Process	25

Tables

Table 1. BAT Criteria for PFAS Technologies Evaluation	3

Table 2. PFAS with Treatability Data	5

Table 3. PFAS Classified by Functional Group and Chain Length	6

Table 4. Studies of GAC Treatment for Carboxylate PFAS	10

Table 5. Studies of GAC Treatment for Sulfonate PFAS	10

Table 6. Studies of GAC Treatment for Other PFAS	11

Table 7. Full-scale GAC Systems Removing PFAS from Drinking Water	12

Table 8. Studies of IX Treatment for Carboxylate PFAS	19

Table 9. Studies of IX Treatment for Sulfonate PFAS	19

Table 10. Studies of IX Treatment for Other PFAS	20

Table 11. Full-scale IX Systems Removing PFAS from Drinking Water	21

Table 12. Studies of RO/NF Treatment for Carboxylate PFAS	26

Table 13. Studies of RO/NF Treatment for Sulfonate PFAS	27

Table 14. Studies of RO/NF Treatment for Other PFAS	27

Table 15. PFAS Removal Technologies Evaluated Against BAT Criteria	34

Table 16. Expenditure Margins for SSCT Affordability Analysis	35

Table 17. Design and Average Flow Estimates and Service Estimates for the 50th

Percentile or Median System	36

Table 18. Total Annual Cost per Household for Candidate Technologies	37

Table 19. Total Annual Cost per Household Assuming Hazardous Waste Disposal for

Spent GAC and Resin	38

Table 20. SSCT Affordability Analysis Results - Technologies that Meet Effectiveness and

Affordability Criteria	39

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Acronyms and Abbreviations

ANSI

American National Standards Institute

BAT

best available technology

EBCT

empty bed contact time

EPA

Environmental Protection Agency

GAC

granular activated carbon

IX

ion exchange

MCL

maximum contaminant level

MHI

median household income

MGD

million gallons per day

mg/L

milligrams per liter

NF

nanofiltration

ng/L

nanograms per liter

NSF

NSF International, The Public Health and Safety Company

O&M

operating and maintenance

PFAS

per- and polyfluoroalkyl substances

POU

point-of-use

RCRA

Resource Conservation and Recovery Act

RO

reverse osmosis

RSSCT

rapid small-scale column test

SDWA

Safe Drinking Water Act

SSCT

small system compliance technology

TOC

total organic carbon

WBS

Work Breakdown Structure

See also Table 2 for abbreviations for individual PFAS compounds.

1 Formerly National Sanitation Foundation

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1.0 Introduction

The U.S. Environmental Protection Agency (EPA) finalized a regulation for certain per- and
polyfluoroalkyl substances (PFAS) under the Safe Drinking Water Act (SDWA). This document
addresses treatment technologies that drinking water systems could use to meet the requirements
of the regulation. Specifically, it provides an evaluation of several technologies against
predefined criteria to determine whether they might be considered best available technologies
(BATs). In addition, it provides an evaluation of technologies for small systems against criteria
to determine whether they can be designated small system compliance technologies (SSCT).

The three technologies included in the BAT evaluation are: granular activated carbon (GAC),
PFAS-selective ion exchange (IX), and reverse osmosis (RO) or nanofiltration (NF). Table 1
provides a list of the six major criteria considered for the BAT evaluation, along with specific
evaluation questions. Sections 2.0 through 4.0 provide a discussion of the extent to which each
technology meets the BAT criteria. Section 5.0 provides a summary of the BAT evaluation
results. The detailed discussion is based primarily on literature search information and technical
analysis conducted during development of the document, Technologies and Costs for Removing
Per- and Polyfluoroalkyl Substances fi'om Drinking Water (USEPA, 2024a). That document
contains a more complete description of each technology and the state of science regarding their
use for PFAS treatment.

The SDWA, as amended in 1996, requires that EPA list technologies for small systems [Section
1412(b)(4)(E)(ii)]:

The Administrator shall include in the list any technology, treatment technique, or other
means that is affordable, as determined by the Administrator in consultation with the
States, for small public water systems serving -

(I)	a population of 10,000 or fewer but more than 3,300;

(II)	a population of 3,300 or fewer but more than 500; and

(III)	a population of 500 or fewer but more than 25;

and that achieves compliance with the maximum contaminant level (MCL) or treatment
technique, including packaged or modular systems and point-of-entry or point-of-use
treatment units (POU).

Section 6.0 of this document provides EPA's analysis to identify SSCTs for the rule.
Specifically, it evaluates the three technologies against the affordability and compliance
effectiveness criteria for SSCTs. It also presents preliminary results on the affordability of POU
devices. POU devices are not currently listed as a compliance option because the rule requires
treatment to concentrations below the current NSF International2/American National Standards
Institute (NSF/ANSI) certification standard for POU device removal of PFAS. However, POU
treatments are reasonably anticipated to become a compliance option for small systems in the
future if NSF/ANSI develop a new certification standard that mirrors or is more stringent than
the regulatory standard. As of the writing of this document, NSF/ANSI is considering lowering
its current standard to the regulatory standard. Based on efficacy of reverse osmosis technology,
RO POU devices can be reasonably anticipated to remove the majority of PFAS when they are

2 Formerly National Sanitation Foundation

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properly designed and maintained. Other POU devices (e.g., activated carbon) may also meet
EPA PFAS regulatory limits. These devices would also need third-party testing and certification
against the regulatory limits.

EPA's affordability criterion uses an affordability threshold of 2.5 percent of the median
household income (MHI) of the median water system (as ranked by MHI) in each small system
size category (i.e., systems serving populations of (1) 25 - 500; (2) 501 - 3,300; and (3) 3,301 -
10,000 people). As long as the sum of baseline expenditures on water (i.e., current costs
excluding PFAS treatment costs) and the incremental expenditures associated with a particular
PFAS treatment technology do not exceed 2.5 percent of MHI, then that technology meets the
affordability criterion.

Table 1. BAT Criteria for PFAS Technologies Evaluation

CRITERION

1. High Removal Efficiency

1.1.	Have high removal efficiencies that achieve potential MCLs been documented?

1.2.	Are the effects of water quality parameters on treatment effectiveness and reliability well-known?

1.3.	Is the technology reliable enough to continuously meet a drinking water MCL?

1.4.	Is additional research needed?	

2. History of Full-Scale Operation

2.1.	Do existing studies include full-scale operations at drinking water treatment facilities?

2.2.	Are there studies of full-scale treatment of residuals that fully characterize residual waste streams and
disposal options?

2.3.	Can the bench or pilot studies be scaled up to represent full-scale treatment, including residuals generation
and handling?

2.4.	Is additional research needed?	

3. General Geographic Applicability

3.1.	What regions do the existing research studies represent?

3.2.	Is it known that regional water quality variations will limit treatment effectiveness or reliability in some
areas?

3.3.	Are there any regional issues with respect to residuals handling or water resource use?

3.4.	Is additional research needed?	

4. Compatibility with Other Treatment Processes

4.1.	Have the effects (adverse or beneficial) of the treatment process on other processes likely to be present at
existing plants been evaluated?

4.2.	Will additional pre- or post-treatment be required for integration into an existing (or planned) treatment
train?

4.3.	Is additional research needed?	

5. Ability to Bring All of the Water System into Compliance

5.1.	Will the treatment process adversely affect the distribution system or water resource decisions?

5.2.	Might the treatment process, residuals handling, or pre- or post-treatment requirements raise new
environmental quality concerns?

5.3.	Is additional research needed?	

6. Reasonable Cost Basis for Large and Medium Systems

6.1.	Is the technology currently used by medium and large systems (including uses for other treatment purposes)?

6.2.	Do the treatment studies provide sufficient information on design assumptions to allow cost modeling?

6.3.	Is additional research needed?

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1.1 PFAS Background

Per- and polyfluoroalkyl substances (PFAS) are abroad class of approximately 10,000 synthetic
chemicals (Rogers et al., 2021; Weaver, 2020; USEPA, 2021d). As a result of their water-
resistant, stain-resistant, and non-stick properties, they are incorporated in or used as coatings for
many products. Household and industrial PFAS applications include use in carpeting, clothing,
cookware, cosmetics, electronics, fire-fighting foam, glass, and packaging. The manufacture of
PFAS and PFAS-containing products, along with the use and disposal of these products, have
resulted in releases to air, soil, and water (ATSDR, 2021; Rogers et al., 2021; Weaver, 2020).
The same properties that make PFAS useful in industry and commerce also make them stable
and persistent in the environment (ATSDR, 2021).

Table 2 lists PFAS for which treatability data are available in the literature included in EPA's
Drinking Water Treatability Database (USEPA, 2021a; 2021b; 2021c). The two most frequently
studied PFAS are PFOA, which refers to perfluorooctanoic acid or perfluorooctane carboxylate,
and PFOS, which refers to perfluorooctane sulfonic acid or perfluorooctane sulfonate.3 Figure 1
shows the chemical structure of these two PFAS. Both molecules incorporate a chain of fully
fluorinated (perfluorinated) carbon atoms but differ in the functional group attached at the end of
the chain. In PFOA, the terminal functional group is carboxylic acid (CO2H) or carboxylate
(CO2") in the anionic form. In PFOS, the terminal functional group is sulfonic acid (SO3H) or
sulfonate (SO3") in the anionic form.

Both PFOA and PFOS include a total of eight carbon atoms in their molecular chain. Other
perfluorinated PFAS incorporate the same terminal functional groups but have a different
number of carbon atoms in the chain. For example, PFHxA refers to a perfluorinated six-carbon
compound with a carboxylic acid or carboxylate functional group. PFHxS refers to a
perfluorinated six-carbon compound with a sulfonic acid or sulfonate functional group. In
general, degree of fluorination, functional group, and chain length provide a means of classifying
PFAS compounds, as shown in Table 3. Buck et al. (2011) and ITRC (2020) provide a more
detailed and nuanced categorization of PFAS, but for purposes of discussing treatment
technologies and costs this simplified categorization is useful.

3 Although different sources within the literature may use the names for the acid and anion forms of PFOA, PFOS, and other
perfluorinated PFAS interchangeably, they most frequently occur in the environment in their anion form (ITRC, 2020).

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Table 2. PFAS with Treatability Data

Abbreviation

Full Name

Chemical Abstract Service (CAS)
Number

ADONA

Ammonium 4,8-dioxa-3H-perfluorononanoate

958445-44-8 or 919005-14-4 (as acid)

F-53B
FtS 4:2

A combination of 9-chlorohexadecafluoro-3-
oxanone-1-sulfonic acid and 11-chloroeicosafluoro-
3-oxaundecane-1-sulfonic acid
Fluorotelomer sulfonate 4:2

756426-58-1 and 763051-92-9
(respectively)

414911-30-1

FtS 6:2

Fluorotelomer sulfonate 6:2

27619-97-2

FtS 8:2

Fluorotelomer sulfonate 8:2

39108-34-4

HFPO-DA*
Nafion BP2
N-EtFOSAA

Ammonium perfluoro-2-methyl-3 -oxahexanoate,
Perfluoro(2-methyl-3 -oxahexanoic) acid
Perfluoro-2-{[perfluoro-3-(perfluoroethoxy)-2-
propanyl]oxy}ethanesulfonic acid
2-(N-Ethyl-perfluorooctanesulfonamido)acetate

62037-80-3 (as ammonium salt), 13252-

13-6 (as acid)

749836-20-2

2991-50-6

N-MeFOSAA

2-(N-Methylperfluorooctanesulfonamido)acetate

909405-48-7 or 2355-31-9 (as acid)

PFBA

Perfluorobutanoic acid

375-22-4

PFBS

Perfluorobutyl sulfonic acid

375-73-5

PFBSA

Perfluorobutylsulfonamide

30334-69-1

PFDA

Perfluorodecanoic acid

335-76-2

PFDoA

Perfluorododecanoic acid

307-55-1

PFDS

Perfluorodecyl sulfonic acid

335-77-3

PFECHS

Perfluoro-4-(perfluoroethyl)cyclohexylsulfonate

80988-54-1

PFHpA

Perfluoroheptanoic acid

375-85-9

PFHpS

Perfluoroheptyl sulfonic acid

375-92-8

PFHxA

Perfluorohexanoic acid

307-24-4

PFHxS

Perfluorohexyl sulfonic acid

355-46-4

PFHxSA

Perfluorohexanesulfonamide

41997-13-1

PFMOAA
PFMOBA

Difluoro(perfluoromethoxy)acetic acid, also known
as perfluoro-2-methoxyacetic acid
Perfluoro-4-methoxybutanoic acid

674-13-5
863090-89-5

PFMOPrA

Perfluoro-3-methoxypropanoic acid

377-73-1

PFNA

Perfluorononanoic acid

375-95-1

PFNS

Perfluorononane sulfonic acid

68259-12-1

PF02HxA

Perfluoro-3,5-dioxahexanoic acid

39492-88-1

PF030A

Perfluoro-3,5,7-trioxaoctanoic acid

39492-89-2

PF04DA

Perfluoro-3,5,7,9-butaoxadecanoic acid

39492-90-5

PFOA

Perfluorooctanoic acid

335-67-1

PFOS

Perfluorooctane sulfonic acid

1763-23-1

PFOSA

Perfluorooctanesulfonamide

754-91-6

PFPeA

Perfluoropentanoic acid

2706-90-3

PFPrS

Perfluoropropane sulfonate

110676-15-8

PFTriA

Perfluorotridecanoic acid

72629-94-8

PFUnA

Perfluoroundecanoic acid

2058-94-8

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* HFPO-DA is used in a processing aid technology developed by DuPont to make fluoropolymers without using PFOA. The
chemicals associated with this process are commonly known as GenX Chemicals and the term is often used interchangeably for
HFPO-DA along with its ammonium salt.

Sources: USEPA, 2021a; 2021b; 2021c

PerfluorooctanoicAcid (PFOA)

Perfluorooctane Sulfonic Acid
(PFOS)

Figure 1. Chemical Structure of PFOA and PFOS

Sources: NCBI, 2021a; 2021b

Table 3. PFAS Classified by Functional Group and Chain Length

Number of
Carbons

Perfluorinated
Carboxylic
Acids/Carboxylates

Perfluorinated

Sulfonic
Acids/Sulfonates

Other
Perfluorinated

Polyfluorinated

3



PFPrS



PFMOAA

4

PFBA

PFBS

PFBS A

FtS 4:2, PF02HxA,
PFMOPrA

5

PFPeA

PFPeS



PF030A,
PFMOBA

6

PFHxA

PFHxS

HFPO-DA,
PFHxSA

FtS 6:2, PF04DA

7

PFHpA

PFHpS



ADONA, Nafion
BP2

8

PFOA

PFOS

PFOS A PFECHS

FtS 8:2, 9C1-
PF30NS

9

PFNA

PFNS





10

PFDA

PFDS



llCl-PF30UdS

11

PFUnA

PFUnS



N-MeFOSAA

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Number of
Carbons

Perfluorinated

Perfluorinated

Other
Perfluorinated



Carboxylic
Acids/Carboxylates

Sulfonic
Acids/Sulfonates

Polyfluorinated

12

PFDoA

PFDoS



N-EtFOSAA

13

PFTriA

PFTriS





Sources: ITRC, 2020; USEPA, 2021a; 2021b; 2021c

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2.0 Best Available Technology Evaluation for GAC

GAC is a porous adsorptive media with extremely high internal surface area. GAC is
manufactured from a variety of raw materials with porous structures including bituminous coal,
lignite coal, peat, wood, coconut shells, and others. Physical and/or chemical manufacturing
processes are applied to these raw materials to create and/or enlarge pores, resulting in a porous
structure with a large surface area per unit mass.

When water is treated with GAC, it passes through treatment columns or beds containing GAC.
The process separates dissolved contaminants from the water through adsorption to the surfaces
in the pores of the GAC. In the case of PFAS, the literature suggests that the primary
mechanisms of adsorption include both hydrophobic and electrostatic interactions (Ateia et al.,
2019). In addition to removing PFAS, GAC can remove contaminants including taste and odor
compounds, natural organic matter, volatile organic compounds, synthetic organic compounds,
disinfection byproduct precursors, and radon. Organic compounds with high molecular weights
are also readily adsorbable.

The contaminants are adsorbed by GAC until the carbon is no longer able to adsorb additional
molecules at the influent feed concentration. At this point, the result is reduced removal of the
contaminant, referred to as "breakthrough." Figure 2 is a conceptual diagram of the GAC
treatment process, from initial adsorption to breakthrough. Once the contaminant concentration
in the treated water reaches an unacceptable level, the carbon is considered "spent" and must be
replaced by virgin or reactivated GAC. The length of time between GAC replacement events is
known as "bed life" and is often quantified in "bed volumes," which are a measure of
throughput. Reactivation4 is a process that removes organic compounds from adsorption sites on
GAC so that it can be reused. Although different methods are available for GAC reactivation, the
process most commonly involves high temperature thermal treatment in a specialized facility
such as a multiple hearth furnace or rotary kiln (Matthis and Carr, 2018; USEPA, 2022b).

4 The terms "reactivation" and "regeneration" are sometimes used interchangeably in the drinking water industry. GAC vendors,
however, make a distinction between the two processes. The appropriate term for the process used on spent GAC containing
adsorbed PFAS is reactivation (Matthis and Carr, 2018).

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Initial adsorption

At breakthrough

Influent
water

Influent
water

I—N

Treated
water

Treated
water



GAC

Spent GAC

• PFAS

Figure 2. Conceptual Diagram of the GAC Treatment Process

2.1 High Removal Efficiency

2.1.1 Have high removal efficiencies that achieve potential
MCLs been documented?

Yes. EPA's Drinking Water Treatability Database (USEPA, 2021a; 2021b; 2021c) includes
extensive data from the literature on PFAS removal by GAC. Results are available from studies
conducted in the laboratory, in the field at pilot scale, and in full-scale application, as shown in
Table 4, Table 5, and Table 6. The literature demonstrates PFAS removal efficiencies for many
PFAS compounds in the high 90 percent range and to levels below analytical detection limits.
For PFOA and PFOS, maximum removal efficiencies are greater than 99 percent, also to below
analytical detection limits5 and lower than the regulatory thresholds currently under
consideration.

5 The analytical detection limit is the lowest amount of a substance whose presence or absence can be determined; this is strictly
lower than the quantification limit which is the lowest concentration that can be determined with acceptable precision and
accuracy. These are also different than the minimum reporting limit which is a combination minimum quantification limits from
different EPA validated laboratories.

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Table 4. Studies of GAC Treatment for Carboxylate PFAS

PFAS
Compound

Number
of

Carbons

Number of
Bench Studies

Number of
Pilot
Studies

Number of
Full-scale
Studies

Maximum
Removal
Efficiency

Source(s) for Maximum
Removal Efficiency

PFBA

4

8

5

5

99.5

Westreich et al. 2018

PFPeA

5

7

5

5

90

Appleman et al. 2013;
McCleaf et al. 2017; Park
et al. 2017; Lombardo et
al. 2018; Kempisty et al.
2019; Liu etal. 2019;
Park et al. 2020

PFHxA

6

12

6

6

99.5

Westreich et al. 2019

PFHpA

7

9

5

7

>99

Zeng et al 2020

PFOA

8

23

9

17

>99.8

Forrester and Bostardi
2019

PFNA

9

6

3

8

>99

Zeng et al 2020

PFDA

10

6

1

4

97

Appleman et al. 2013

PFUnA

11

1

0

1

90

McCleaf etal. 2017

PFDoA

12

3

0

0

90

McCleaf et al. 2017; Park
etal. 2017

PFTriA

13

1

0

0

90

McCleaf etal. 2017

Sources: USEPA, 2021a; 2021c











Table 5. Studies of GAC Treatment for Sulfonate PFAS





PFAS
Compound

Number
of

Carbons

Number of
Bench Studies

Number of
Pilot
Studies

Number of
Full-scale
Studies

Maximum
Removal
Efficiency

Source for Maximum
Removal Efficiency

PFPrS

3

0

1

0

90

Liu et al. 2019

PFBS

4

13

7

8

99.5

Westreich et al. 2018

PFPeS

5

2

2

0

90

Liu et al. 2019

PFHxS

6

13

7

11

99.5

Westreich et al. 2018

PFHpS

7

2

4

1

>99

Belkouteb et al. 2020

PFOS

8

24

10

15

99.7

Woodard et al. 2017

PFNS

9

1

0

0

95.82

Wang et al. 2020

Sources: USEPA, 2021b; 2021c

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Table 6. Studies of GAC Treatment for Other PFAS

PFAS

Number

Number of

Number of

Number of

Maximum

Source for Maximum

of

Carbons

Pilot
Studies

Full-scale
Studies

Removal
Efficiency

Compound

Bench Studies

Removal Efficiency

PFMOAA

3

0

0

1

70

Hopkins et al. 2018

FtS 4:2

4

0

1

0

Not reported



PFBSA

4

1

0

0

56

Yan et al. 2020

PF02HxA

4

0

0

1

90

Hopkins et al. 2018

PF030A

5

0

0

1

90

Hopkins et al. 2018

FtS 6:2

6

1

3

0

88

Casey et al. 2018

HFPO-DA

6

1

1

1

93

Hopkins et al. 2018

PFHxSA

6

1

1

0

80

Rodowa et al. 2020

PF04DA

6

0

0

1

90

Hopkins et al. 2018

Nafion BP2

7

0

1

1

>99

Hopkins et al. 2018

FtS 8:2

8

1

3

0

88

Woodard et al. 2017

PFOSA

8

3

1

0

95

Kothawala et al. 2017

PFECHS

8

1

0

0

65

Yan et al. 2020

Source: USEPA, 2021c

2.1.2	Are the effects of water quality parameters on treatment
effectiveness and reliability well-known?

Yes. Natural organic matter, often measured as dissolved organic carbon or total organic carbon
(TOC), can interfere with GAC's capacity to adsorb PFAS (Appleman et al., 2013; Ateia et al.,
2019; Berretta et al., 2021; Gagliano et al., 2020; Kothawala et al., 2017). The significance of
this interference may depend on the specific type of natural organic matter present (Gagliano et
al., 2020; Kothawala et al., 2017). However, in general, it does not necessarily reduce the
maximum removal effectiveness of GAC. Instead, it shortens the time to breakthrough, meaning
more frequent GAC replacement can be required at higher TOC concentrations, all other factors
being equal. Therefore, it should be possible to reliably manage the impact of natural organic
matter through piloting, selection of design parameters, and operational monitoring.

2.1.3	Is the technology reliable enough to continuously meet a
drinking water MCL?

Yes. Numerous full-scale drinking water facilities are using GAC to meet current state drinking
water requirements for PFAS (see Question 2.2.1, below). In general, GAC is an established,
reliable technology that has been used successfully to meet other MCLs.

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2.1.4 Is additional research needed?

No. Additional research is not required.

2.2 History of Full-Scale Operation

2.2.1 Do existing studies include full-scale operations at
drinking water treatment facilities?

Yes. As indicated under Question 2.1.1, there are numerous studies of GAC performance for
PFAS removal at full-scale facilities. These effectiveness studies include results for GAC
facilities designed specifically to target PFAS, in addition to facilities originally designed for
other contaminants. In total, the literature identifies 34 full-scale GAC facilities removing PFAS
from drinking water, as listed in Table 7.

Table 7. Full-scale GAC Systems Removing PFAS from Drinking Water

Location

Moose Creek, Fairbanks North Star
Borough, Alaska

Gustavus, Alaska

Airline/Lambert Water Treatment Campus,
Marana, Pima County, Arizona

Picture Rocks Water Treatment Campus,
Marana, Pima County, Arizona

Municipal Services Commission of the
City of New Castle, New Castle, Delaware

Emerald Coast Utilities Authority,
Pensacola, Escambia County, Florida

Kennebunk, Kennebunkport & Wells
Water District, Kennebunk, Maine

Mary Dunn Water Supply Wells, Hyannis
& Town of Barnstable, Massachusetts

City of Westfield Department of Public
Works, Westfield, Massachusetts

Plainfield Township, Kent County,
Michigan

Ann Arbor Water Treatment Plant, Ann
Arbor, Michigan

Oakdale Public Works, Oakdale,
Minnesota

Flow

rate
(MGD)

2.2

Not
reported

Not
reported

Not
reported

0.50

1.44

2.90

1.44

Not
reported

50

3.6

Groundwater Year of
or Surface Startup
Water

Sources

Groundwater
Groundwater
Groundwater
Groundwater
Groundwater
Groundwater
Groundwater
Groundwater
Groundwater

2016

2018-
2019

Not
reported

Not
reported

Alaska Community Action on
Toxics 2019; Forrester 2019

Alaska Community Action on
Toxics 2019

Marana Water 2019

Marana Water 2019

2015 Mordock 2016; Forrester 2019

2017	Robinson 2018; Forrester
2019

2020 Berretta et al. 2021; Business
Wire 2018

2015 Gallagher 2017; Forrester
2019

2018	Westfield 2019

Groundwater 2018 Biolchini 2018

Surface Water 2018 Stanton 2019; Page 2020

Groundwater 2006 MDH 2010; ATSDR 2008

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Location

Flow
rate
(MGD)

Groundwater
or Surface
Water

Year of
Startup

Sources

Merrimack Village District Water Works,
Merrimack, Hillsborough County, New
Hampshire

Not
reported

Groundwater

2020

Cronin 2020

Pease International Tradeport Drinking
Water System, Portsmouth, New
Hampshire

0.72

Groundwater

2019

City of Portsmouth 2020;
Forrester 2019

Town of Petersburgh Water District,
Petersburgh/Rensselaer County, New York

0.07

Not reported

2017

Forrester 2019; NYS DEC
2020a

Hampton Bays Water District, Suffolk
County, New York

9

Groundwater

2018

Gordon 2018

Wright-Patterson Air Force Base, Dayton,
Ohio

2.74

Groundwater

2017

Barber 2017; Forrester 2019

Horsham Water and Sewer Authority,
Horsham, Montgomery County,
Pennsylvania

1.44

Groundwater

2017

Boodoo et al. 2019;
Montgomery News 2017;
Forrester 2019

Village of Hoosick Falls, New York

1.01

Groundwater

Not
reported

Forrester 2019; NYS DEC
2021

City of El Campo Water Department, El
Campo, Texas

Not
reported

Groundwater

2017

Sullivan 2018

Issaquah, Washington

4.32

Groundwater

2016

Issaquah 2020; Mende 2019;
Kwan and York 2017

Airway Heights Water System, City of
Airway Heights, Washington

Not
reported

Groundwater

2018

ATSDR 2020

Joint Base Lewis-McChord, Washington

Not
reported

Groundwater

Not
reported

Sullivan 2018

Little Hocking Water Association, Little
Hocking, Ohio

Not
reported

Groundwater

2007

Cummings et al 2015

Former Naval Air Station, Brunswick,
Maine

Not
reported

Not reported

2011

Danko 2018

Washington Lake Filtration Plant,
Newburgh, New York

8.86

Groundwater

2017

Forrester 2019; NYS DEC
2020b

Liberty Utilities, Litchfield Park, Arizona

1.58

Groundwater

2017

ADEQ 2021; Forrester 2019

Passaic Valley Water Commission,
Garfield, New Jersey

0.5

Groundwater

Not
reported

Forrester 2019; Sobko 2021

Aqua Pennsylvania, Chalfont Borough,
Pennsylvania

0.58

Groundwater

Not
reported

Forrester 2019; Chalfont
Borough 2021

Montclair Water Bureau, Montclair, New
Jersey

0.72

Groundwater

Not
reported

Forrester 2019; PFAS Project
Lab 2021

Warrington Township Water and Sewer
Department, Warrington, Pennsylvania

0.58

Groundwater

Not
reported

Forrester 2019; Warrington
Township 2017

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Location

Flow Groundwater Year of
rate or Surface Startup
(MGD) Water

Sources

Rome Water and Sewer Division Rome,
Georgia

9 Groundwater Not Forrester 2019; City of Rome
reported 2019

Sweeny Water Treatment Plant, Cape Fear
Public Utilities Authority, North Carolina

44 Surface Water 2022 Vandenneyden and Hagerty

2020

Parkersburg Utility Board, Parkersburg,
West Virginia

Not Not reported
reported

reported

Not USEPA 2009

MGD = million gallons per day

2.2.2 Are there studies of full-scale treatment of residuals that
fully characterize residual waste streams and disposal
options?

The most likely management option for spent GAC containing adsorbed PFAS is reactivation.
There are a number GAC vendor-operated reactivation facilities available, including some that
hold Resource Conservation and Recovery Act (RCRA) permits to treat spent GAC that is
classified as hazardous waste (USEPA, 2020; Matthis and Carr, 2021). Matthis and Carr (2021)
report results from leaching tests on GAC used to remove PFAS from drinking water at full-scale
after reactivation, also in a full-scale facility. They found that 15 of the 16 PFAS compounds
analyzed were below analytical limits in the leachate. PFBA was present, but only at 1.9 parts
per trillion. These results suggest that reactivated GAC should be suitable for reuse.

The full-scale study in Mathis and Carr (2021), however, did not fully address the fate of PFAS
in the GAC reactivation process. There are a limited number of smaller scale studies that
examine whether PFAS compounds are transformed, volatilized, or destroyed/defluorinated
during the process (e.g., Watanabe et al., 2016; Watanabe et al., 2018; Xiao, 2020). These studies
suggest that the fate of PFAS in GAC reactivation depends on factors including PFAS chain
length, reactivation temperature, and combustion atmosphere (Baghirzade et al., 2021).

DiStefano et al., (2022) showed >99.99 percent destruction of PFAS at a full-scale commercial
reactivation facility with a large percentage of the PFAS destruction occurring in the furnace.
The fluoride mass balance was reported to be 61.4 percent. In the future, additional full-scale
research might be needed to better understand and manage PFAS air emissions from GAC
reactivation facilities. The results of this research might necessitate changes to spent GAC
management practices. Approximately 10-30 percent of GAC may be lost during the reactivation
process and new GAC must be added to replace the lost GAC. There are also circumstances
when reactivating spent GAC may not make economic sense. In these circumstances, GAC may
be disposed of after use, such as in a landfill, and then replaced with completely new GAC.
Future RCRA hazardous waste regulations could also limit the available management options.

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2.2.3	Can the bench or pilot studies be scaled up to represent
full-scale treatment, including residuals generation and
handling?

For PFAS removal, there is no consensus in the literature regarding methods to scale up GAC
from bench-scale tests, specifically rapid small-scale column tests (RSSCTs), to full-scale
(Hopkins, 2021; Kempisty et al., 2019; Meng et al., 2021; Redding et al., 2019). However, as a
mature and established technology, the scale-up of GAC from pilot- to full-scale is well
understood and has been implemented at full-scale facilities treating PFAS (e.g., Vandermeyden
and Hagerty, 2019).

2.2.4	Is additional research needed?

In general, additional research is not required. However, in the future, additional full-scale
research might be needed to better understand and manage PFAS air emissions from GAC
reactivation facilities.

2.3 General Geographic Applicability

2.3.1	What regions do the existing research studies represent?

EPA's Drinking Water Treatability Database (USEPA, 2021a; 2021b; 2021c) includes
effectiveness data for PFAS removal by GAC in waters from 12 geographically dispersed U.S.
states (Arizona, Colorado, Illinois, Maine, Michigan, Minnesota, New Hampshire, New Jersey,
North Carolina, Ohio, Pennsylvania, Washington, and West Virginia), as well as from countries
overseas. The full-scale facilities listed under Question 2.2.1 are distributed across the U.S. from
Alaska to Florida and Maine to Arizona.

2.3.2	Is it known that regional water quality variations will
limit treatment effectiveness or reliability in some areas?

No. Although there may be regional variations in natural organic matter, these variations are
likely to be less significant than variation among individual water sources within a region.
Furthermore, as discussed under Question 2.1.2, it should be possible to reliably manage the
impact of water quality variations through piloting, design parameter selection, and operational
monitoring.

2.3.3	Are there any regional issues with respect to residuals
handling or water resource use?

Under current state regulations, there no known regional barriers with respect to spent GAC
reactivation or disposal.

2.3.4	Is additional research needed?

No. Additional research is not required.

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2.4	Compatibility with Other Treatment Processes

2.4.1	Have the effects (adverse or beneficial) of the treatment
process on other processes likely to be present at existing
plants been evaluated?

Yes. GAC can have a beneficial effect by removing natural organic matter (see Question 2.1.2)
and trace contaminants other than PFAS (e.g., volatile organic compounds) from treated water.
Removal of natural organic matter (as measured by total organic carbon) results in meaningful
co-benefits, including reducing disinfection byproduct formation. In general, GAC does not have
significant negative effects on other treatment processes.

2.4.2	Will additional pre- or post-treatment be required for
integration into an existing (or planned) treatment train?

No. In general, GAC integrates easily with traditional treatment trains.

2.4.3	Is additional research needed?

No. Additional research is not required.

2.5	Ability to Bring All of the Water System into Compliance

2.5.1	Will the treatment process adversely affect the
distribution system or water resource decisions?

No. Although there can in some cases be temporary water chemistry changes immediately
following GAC changeout, these effects are readily managed by diverting the first few bed
volumes of treated water to waste. In general, GAC does not have adverse distribution system or
water resource effects.

2.5.2	Might the treatment process, residuals handling, or pre-
or post-treatment requirements raise new environmental
quality concerns?

Possibly. As discussed under Question 2.2.2, uncertainty exists about the fate of PFAS in GAC
reactivation. For example, unregulated air emissions from reactivation may result in secondary
environmental impacts.

2.5.3	Is additional research needed?

Additional research might be needed to better understand and manage PFAS emissions from
GAC reactivation facilities.

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2.6 Reasonable Cost Basis for Large and Medium Systems

2.6.1	Is the technology currently used by medium and large
systems (including uses for other treatment purposes)?

Yes. The 34 full-scale PFAS GAC systems identified in the literature include medium and large
systems: 16 are larger than 1 million gallons per day (MGD) and two are larger than 10 MGD,
with the largest being 50 MGD.

2.6.2	Do the treatment studies provide sufficient information
on design assumptions to allow cost modeling?

Detailed data are available from the treatment studies for all the relevant design parameters,
including:

•	Vessel configuration (i.e., number of vessels in series)

•	Empty bed contact time (EBCT)

•	GAC bed life

•	Loading rate

•	Residuals management options.

2.6.3	Is additional research needed?

No. Additional research is not required.

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3.0 Best Available Technology Evaluation for IX

IX is a physical/chemical separation process in which ions such as per- and polyfluoroalkyl
substances (PFAS) in the feed water are exchanged for an ion (typically chloride) on a resin
generally made of synthetic beads or gel. In application, feed water passes through a bed of resin
in a vessel or column. For PFAS compounds, vendors generally recommend using PFAS-
selective resins (Boodoo, 2018a; Boodoo et al., 2019; Lombardo et al., 2018; Woodard et al.,
2017).

The IX process continues until the resin does not have sufficient exchange sites available for the
target PFAS compounds. At this point, the result is reduced removal of the contaminant, referred
to as "breakthrough." Figure 3 is a conceptual diagram of the IX treatment process, from initial
adsorption to breakthrough. Once the contaminant concentration in the treated water reaches an
unacceptable level, the resin is considered "spent." In IX processes removing more traditional
contaminants (e.g., nitrate), the capacity of the spent resin is often restored by rinsing the media
with a concentrated chloride solution. However, conventional regeneration solutions are not
effective for restoring the capacity of PFAS-selective resins (Liu and Sun, 2021). Regeneration
of selective resins may be possible using organic solvents (Boodoo, 2018a; Zaggia et al., 2016)
or proprietary methods (Woodard et al., 2017). These alternative regeneration practices are
generally practical or cost-effective only with very high influent concentrations, such as in
remediation settings. Therefore, in drinking water applications using PFAS-selective resin,
vendors recommend a single-use approach where the spent resin is disposed and replaced with
fresh resin (Boodoo, 2018a; Lombardo et al., 2018). The length of time between resin
replacement events is known as "bed life" and is often quantified in "bed volumes," which are a
measure of throughput.

Initially

At breakthrough

Influent
water

Resin

Spent Resin • PFAS •Chloride

Figure 3. Conceptual Diagram of the IX Treatment Process

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3.1 High Removal Efficiency

3.1.1 Have high removal efficiencies that achieve potential
MCLs been documented?

Yes. EPA's Drinking Water Treatability Database (USEPA, 2021a; 2021b; 2021c) includes
extensive data from the literature on PFAS removal by IX. Results are available from studies
conducted in the laboratory, in the field at pilot scale, and in full-scale application, as shown in
Table 7, Table 8, and Table 9. The literature demonstrates PFAS removal efficiencies for many
PFAS compounds in the high 90 percent range and to levels below analytical detection limits.
For PFOA and PFOS, maximum removal efficiencies are greater than 99 percent, also to below
analytical detection limits and lower than the regulatory thresholds currently under consideration.

Table 8. Studies of IX Treatment for Carboxylate PFAS

PFAS
Compound

Number
of

Carbons

Number of
Bench Studies

Number of
Pilot
Studies

Number of
Full-scale
Studies

Maximum
Removal
Efficiency

Source(s) for Maximum
Removal Efficiency

PFBA

4

11

5

2

99.3

Dixit et al. 2020; Dixit et
al. 2021

PFPeA

5

7

3

2

95.5

Schaefer et al. 2019

PFHxA

6

11

4

3

>97

Liu 2017

PFHpA

7

9

6

4

>99

Zeng et al. 2020

PFOA

8

15

7

4

99.3

Dixit et al. 2019; Dixit et
al. 2020; Dixit et al. 2021

PFNA

9

6

3

2

>99

Zeng et al. 2020;
Kumarasamy et al. 2020

PFDA

10

7

0

0

>99

Kumarasamy et al. 2020

PFUnA

11

1

0

0

90

McCleaf et al. 2017

PFDoA

12

2

0

0

99.3

Dixit et al. 2021

PFTriA

13

1

0

0

90

McCleaf etal. 2017

Sources: USEPA, 2021a; 2021c











Table 9. Studies of IX Treatment for Sulfonate PFAS





PFAS
Compound

Number
of

Carbons

Number of
Bench Studies

Number of
Pilot
Studies

Number of
Full-scale
Studies

Maximum
Removal
Efficiency

Source(s) for Maximum
Removal Efficiency

PFBS

4

12

8

4

99.3

Dixit et al. 2020; Dixit et
al. 2021

PFPeS

5

2

0

0

74

Yan et al. 2020

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PFAS

Number of

Number

Compound „	Bench Studies

Carbons

Number of Number of Maximum
Pilot	Full-scale Removal

Studies

PFHxS

PFHpS

PFOS

PFNS

11

2
16
1

Studies

7

Efficiency

>99

93
99.7
54.9

Source(s) for Maximum
Removal Efficiency

Zeng et al. 2020; Boodoo
2018a; Arevalo et al.
2014; Kumarasamy et al.
2020

Yan et al. 2020
Woodard et al. 2017
Wang et al. 2020

Sources: USEPA, 2021b; 2021c

Table 10. Studies of IX Treatment for Other PFAS

PFAS
Compound

PFBSA
PFMOPrA
PFMOBA
FtS 6:2
HFPO-DA

PFHxSA
FtS 8:2
PFOSA
PFECHS

Number
of

Carbons

4

4

5

6
6

Number of
Bench Studies

1
1

1

2
4

1

2

3
1

Number of
Pilot
Studies

0

0

0
2

1

0

2
0
0

Number of
Full-scale
Studies

0

0

0

0

0

0

0

1
0

Maximum
Removal
Efficiency

98
99.3
99.3
99.3
99.3

99
99.3

98
97

Source(s) for Maximum
Removal Efficiency

Yan et al. 2020

Dixit et al. 2021

Dixit et al. 2021

Dixit et al. 2021

Dixit et al. 2020; Dixit et
al. 2021

Yan et al. 2020
Dixit et al. 2021
Yan et al. 2020
Yan et al. 2020

Source: USEPA, 2021c

3.1.2 Are the effects of water quality parameters on treatment
effectiveness and reliability well-known?

Yes. PFAS-selective resins are designed to have higher affinity for PFAS than other anions, such
as nitrate, sulfate, bicarbonate, and chloride. However, these anions can be present in drinking
water at concentrations many orders of magnitude higher than PFAS. Therefore, they can
compete with PFAS for available exchange sites on the resin (Ateia et al., 2019; Berretta et al.,
2021; Boodoo, 2021). Data are not available to precisely quantify the effect of competing anions
under a wide range of water quality conditions. However, in general, competition does not
necessarily reduce the maximum removal effectiveness of the resin for PFAS. Instead, it shortens
the time to breakthrough, meaning more frequent resin replacement may be required in the

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presence of competing anions, all other factors being equal. Therefore, it should be possible to
reliably manage the impact of competition through piloting, selection of design parameters, and
operational monitoring.

3.1.3	Is the technology reliable enough to continuously meet a
drinking water MCL?

Yes. Several full-scale drinking water facilities are using IX to meet current state drinking water
requirements for PFAS (see Question 2.2.1, below). In general, IX is an established, reliable
technology that has been used successfully to meet other MCLs.

3.1.4	Is additional research needed?

No. Additional research is not needed.

3.2 History of Full-Scale Operation

3.2.1 Do existing studies include full-scale operations at
drinking water treatment facilities?

Yes. The first full-scale system treating drinking water using PFAS-selective IX commenced
operation in 2017 (WWSD, 2018). Since that time, several additional full-scale facilities have
begun using the technology, as listed in Table 11. The effectiveness studies enumerated under
Question 3.1.1 include results for some of these facilities.

Table 11. Full-scale IX Systems Removing PFAS from Drinking Water



Flow rate
(MGD)

Groundwater

Year of
Startup



Location

or Surface
Water

Sources

Pease International Tradeport Drinking
Water System, Portsmouth, New
Hampshire

Not
reported

Groundwater

2019

City of Portsmouth

2020

Horsham Water and Sewer Authority,
Horsham, Montgomery County,
Pennsylvania

0.14

Groundwater

2021

Boodoo 2018a;
Boodoo et al. 2019;
HWSA 2021

Security Water and Sanitation Districts,
Security, Colorado

9

Groundwater

2019

Jent 2020

Stratmoor Hills Water District, Stratmoor

1

Groundwater

Not

Berretta et al. 2021

Hills, El Paso County, Colorado

reported

City of Stuart, Florida

4

Groundwater

2018

Aqueous Vets 2019

Warminster Municipal Authority,
Warminster, Pennsylvania

Not
reported

Not reported

Not
reported

Boodoo 2018a;
Boodoo 2018b

Widefield Water and Sanitation District,

Not

Groundwater

2017

WWSD 2018

Widefield, Colorado

reported

MGD = million gallons per day

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3.2.2	Are there studies of full-scale treatment of residuals that
fully characterize residual waste streams and disposal
options?

There are no known full-scale studies of spent resin from IX facilities specifically for the
removal of PFAS. In general, however, the characteristics and quantities of spent resin are
predictable. This waste stream contains the PFAS compounds and other anions removed from the
treated water. The generation rate is a function of bed volume and replacement frequency.

Under current regulations, spent resin is typically incinerated (Boodoo, 2018b). The literature is
inconclusive regarding the fate of PFAS during incineration in general (USEPA, 2020) and there
are no studies specific to incineration of IX resin. Additional full-scale research might be needed
to better understand and manage PFAS air emissions from incineration facilities. The results of
this research might necessitate changes to spent resin management practices. Similar to GAC, IX
resins may also be landfilled. Future RCRA hazardous waste regulations could also limit the
available management options.

3.2.3	Can the bench or pilot studies be scaled up to represent
full-scale treatment, including residuals generation and
handling?

The use of RSSCTs to predict IX performance for PFAS removal is a recent development (Najm
et al., 2021; Schaefer et al., 2019; Zeng et al., 2020), so there are no validated methods to scale
up from these bench-scale results. However, as a mature and established technology, the scale-up
of IX from pilot- to full-scale is well understood and has been implemented at full-scale facilities
treating PFAS (e.g., WWSD, 2018).

3.2.4	Is additional research needed?

In general, additional research is not required. However, additional full-scale research might be
needed to better understand and manage PFAS air emissions from incineration facilities.

3.3 General Geographic Applicability

3.3.1	What regions do the existing research studies represent?

EPA's Drinking Water Treatability Database (USEPA, 2021a; 2021b; 2021c) includes
effectiveness data for PFAS removal by IX in waters from four geographically dispersed U.S.
states (Alabama, Colorado, New Jersey, and Pennsylvania). The full-scale facilities listed under
Question 3.2.1 are located in Colorado, New Hampshire, and Pennsylvania.

3.3.2	Is it known that regional water quality variations will
limit treatment effectiveness or reliability in some areas?

No. Although there may be regional variations in competing anions, these variations are likely to
be less significant than variation among individual water sources within a region. Furthermore,
as discussed under Question 3.1.2, it should be possible to reliably manage the impact of water
quality variations through piloting, selection of design parameters, and operational monitoring.

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Best Available Technologies and Small System Compliance Technologies for PFAS in Drinking Water
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3.3.3	Are there any regional issues with respect to residuals
handling or water resource use?

Under current state regulations, there no known regional barriers with respect to spent resin
disposal.

3.3.4	Is additional research needed?

No. Additional research is not required.

3.4	Compatibility with Other Treatment Processes

3.4.1	Have the effects (adverse or beneficial) of the treatment
process on other processes likely to be present at existing
plants been evaluated?

Yes. In general, IX can have an adverse effect on treated water chemistry by increasing
corrosivity. One vendor suggests this issue may be limited in the case of PFAS-selective resin
(Boodoo, 2018b, see Question 3.5.1). In cases where this impact does occur, it can be managed
through post-treatment corrosion control or alterations to existing corrosion control. The
technology can also have a beneficial effect by removing other undesirable anions from the
treated water (e.g., nitrate, sulfate), even when using PFAS-selective resin (see Question 3.1.2).

3.4.2	Will additional pre- or post-treatment be required for
integration into an existing (or planned) treatment train?

Possibly. The treated water chemistry changes resulting from IX might require post-treatment
corrosion control or alterations to existing corrosion control.

3.4.3	Is additional research needed?

No. Additional research is not required.

3.5	Ability to Bring All of the Water System into Compliance

3.5.1 Will the treatment process adversely affect the
distribution system or water resource decisions?

In general, IX treatment can increase treated water corrosivity because of chloride ion addition
and/or carbonate along with bicarbonate removal. For example, Berlien (2003) reported
increased corrosivity with a full-scale application of IX for perchlorate treatment. One vendor of
PFAS-selected resin reports that this effect is limited to the first 200 bed volumes of treatment
for their product. During this initial period, pH in treated water will decrease by 1 to 1.5 units;
then the alkalinity and pH of the treated water returns to normal (Boodoo, 2018b). In cases where
increased corrosivity occurs, distribution system effects can be managed by adjusting corrosion
control programs.

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3.5.2	Might the treatment process, residuals handling, or pre-
or post-treatment requirements raise new environmental
quality concerns?

Possibly. As discussed under Question 3.2.2, uncertainty exists about the fate of PFAS during the
incineration of spent resin. For example, unregulated air emissions from reactivation may result
in secondary environmental impacts. In addition, the corrosivity impacts discussed above under
Question 3.5.1, if not adequately managed through post-treatment, could create new
environmental quality concerns in the distribution system.

3.5.3	Is additional research needed?

Additional research might be needed to better understand and manage address PFAS air
emissions from incineration facilities.

3.6 Reasonable Cost Basis for Large and Medium Systems

3.6.1	Is the technology currently used by medium and large
systems (including uses for other treatment purposes)?

Yes. The full-scale PFAS IX facilities identified in the literature include two medium systems
(larger than 1 MGD). There are many medium and large systems that use selective IX for other
contaminants (e.g., perchlorate).

3.6.2	Do the treatment studies provide sufficient information
on design assumptions to allow cost modeling?

Detailed data are available from the treatment studies for all the relevant design parameters,
including:

•	Vessel configuration (i.e., number of vessels in series)

•	EBCT

•	Resin bed life

•	Loading rate

•	Residuals management options.

3.6.3	Is additional research needed?

No. Additional research is not required.

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4.0 Best Available Technology Evaluation for
RO/NF

RO and NF are membrane separation processes that physically remove contaminants from
drinking water. These processes separate solutes such as PFAS compounds from solution by
forcing the solvent to flow through a membrane at a pressure greater than the normal osmotic
pressure. In drinking water treatment, these membranes are most often used in a spiral-wound
configuration that consists of several membrane envelopes, layered with feed spacers and rolled
together in around a central collection tube.

The membrane is semi-permeable, transporting different molecular species at different rates. The
application of pressure splits the influent water passing over the membrane into two streams:

•	Treated water or "permeate" that passes through the membrane layers along with solutes of
lower molecular weight into the central collection tube

•	Water containing higher molecular weight solutes that remains outside the membrane layers,
called "reject," "concentrate," or "brine."

"Recovery rate" and "rejection rate" are the percentages of influent water that are recovered as
permeate and lost as reject, respectively.6 Figure 4 is a conceptual diagram of this process as
applied to water containing PFAS. Specific membranes differ in terms of the size of dissolved
contaminants they can remove. Membranes that remove smaller contaminants require higher
feed pressure. Feed pressures for NF membranes are typically in the range of 50 to 150 pounds
per square inch (psi). Feed pressures for RO membranes are in the range of 125 to 300 psi in low
pressure applications (such as PFAS removal) but can be as high as 1,200 psi in applications
such as seawater desalination (USEPA, 2022c). As discussed under Question 4.1.1, both RO and
NF membranes have the capacity to remove PFAS.

Figure 4. Conceptual Diagram of the RO Treatment Process

0 Note that recovery and rejection rates are not directly related to removal efficiency, which is the percentage of influent PFAS
removed from the treated water.

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4.1 High Removal Efficiency

4.1.1 Have high removal efficiencies that achieve potential
MCLs been documented?

Yes. EPA's Drinking Water Treatability Database (USEPA, 2021a; 2021b; 2021c) includes
extensive data from the literature on PFAS removal by RO and NF. Results are available from
studies conducted in the laboratory, in the field at pilot scale, and in full-scale application, as
shown in Table 10, Table 11, and Table 12. The literature demonstrates PFAS removal
efficiencies for many PFAS compounds in the high 90 percent range and to levels below
analytical detection limits. For PFOA and PFOS, maximum removal efficiencies are greater than
99 percent, also to below analytical detection limits and lower than the regulatory thresholds
currently under consideration.

Table 12. Studies of RO/NF Treatment for Carboxylate PFAS

PFAS
Compound

Number
of

Carbons

Number
of Bench
Studies

Number
of Pilot
Studies

Number
of Full-

scale
Studies

Maximum

NF
Removal
Efficiency

Maximum
RO

Removal
Efficiency

Source(s) for Maximum
Removal Efficiency

PFBA

4

2

1

2

99

99.9

Lipp et al. 2010

PFPeA

5

2

3

2

>99

>99

Horst et al. 2018; Liu et
al. 2021; Dickenson and
Higgins 2016

PFHxA

6

3

4

4

>98

99.2

Liu et al. 2021

PFHpA

7

1

2

3

99

>99

Steinle-Darling et al.
2008; Liu et al. 2021

PFOA

8

4

4

5

99.9

99.9

Boonya-Atichart et al.
2016; Lipp et al. 2010

PFNA

9

2

1

4

99

>98

Steinle-Darling et al.
2008; Dickenson and
Higgins 2016; Appleman
etal. 2014

PFDA

10

2

0

4

99

>99

Steinle-Darling et al.
2008; Dickenson and
Higgins 2016; Appleman
etal. 2014

PFUnA

11

1

0

2

99

>77

Steinle-Darling et al.
2008; Dickenson and
Higgins 2016; Appleman
etal. 2014

PFDoA

12

0

0

2



>87

Dickenson and Higgins
2016; Appleman et al.
2014

- = no data; NF = nanofiltration; RO = reverse osmosis
Sources: USEPA, 2021a; 2021c

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Table 13. Studies of RO/NF Treatment for Sulfonate PFAS

PFAS
Compound

Number
of

Carbons

Number
of Bench
Studies

Number
of Pilot
Studies

Number
of Full-

scale
Studies

Maximum

NF
Removal
Efficiency

Maximum

RO
Removal
Efficiency

Source(s) for Maximum
Removal Efficiency

PFPrS

3

0

1

0

>98

>99

Liu et al. 2021

PFBS

4

3

4

3

99.8

99.8

Lipp et al. 2010

PFPeS

5

0

1

0

>98

>99

Liu et al. 2021

PFHxS

6

2

4

4

>99

>99

Appleman et al. 2013;
Thompson et al. 2011;
Liu et al. 2021

PFHpS

7

0

1

0

>98

>99

Liu et al. 2021

PFOS

8

6

4

5

>99.9

99.9

Lipp et al. 2010; 2163

PFDS

10

1

0

0

99

-

Steinle-Darling et al. 2008

- = no data; NF = nanofiltration; RO = reverse osmosis
Sources: USEPA, 2021b; 2021c









Table 14. Studies of RO/NF Treatment for Other PFAS





PFAS
Compound

Number
of

Carbons

Number
of Bench
Studies

Number
of Pilot
Studies

Number
of Full-

scale
Studies

Maximum

NF
Removal
Efficiency

Maximum

RO
Removal
Efficiency

Source(s) for Maximum
Removal Efficiency

PFMOAA

3

0

1

0

-

>98.5

CDM Smith 2018

PF02HxA

4

0

1

0

-

>80.8

CDM Smith 2018

PF030A

5

0

1

0

-

>67.2

CDM Smith 2018

FtS 6:2

6

1

2

1

99.5

>65.5

Steinle-Darling et al.
2008; CDM Smith 2018

HFPO-DA

6

0

1

0

-

>64.2

CDM Smith 2018

PFOSA

8

2

0

1

98.5

>13

Steinle-Darling et al.
2008; Dickenson and
Higgins 2016

N-

MeFOSAA

11

0

0

2

-

>84

Dickenson and Higgins
2016

N-EtFOSAA

12

0

0

2

-

>58

Dickenson and Higgins
2016

- = no data; NF = nanofiltration; RO = reverse osmosis
Source: USEPA, 2021c

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4.1.2	Are the effects of water quality parameters on treatment
effectiveness and reliability well-known?

Yes. In general, water quality affects the design (e.g., concentrate volume, cleaning frequency,
antiscalant selection) of RO and NF systems, but not removal efficiency. The literature
specifically for PFAS removal by membranes supports this conclusion. For example, Appleman
et al. (2013) found that the effectiveness of NF for PFAS removal was not impaired by the
presence of humic acid. Similarly, Steinle-Darling and Reinhard (2008) found that ionic strength
did not have a significant effect on removal performance. Although these authors noted a
significant effect from pH, this effect was observed at pH 2.8, substantially lower than typical
drinking water influent. Boonya-Atichart et al. (2016) found no significant effect within a more
typical range of pH (5.5 to 10). Although they observed a slight decrease in effectiveness with
increasing total dissolved solids, this effect was not significant.

4.1.3	Is the technology reliable enough to continuously meet a
drinking water MCL?

Yes. In general, RO and NF are established, reliable technology that has been used successfully
to meet other MCLs. As discussed under Question 4.2.1, full-scale plants recently began
operation using low-pressure RO designed to meet state drinking water requirements for PFAS.

4.1.4	Is additional research needed?

No. Additional research is not needed.

4.2 History of Full-Scale Operation

4.2.1	Do existing studies include full-scale operations at
drinking water treatment facilities?

Yes. Two drinking water systems, in North Carolina (Dowbiggin et al., 2021) and Alabama
(Wetzel, 2021; WHNT News, 2019), recently constructed full-scale treatment plants using low-
pressure RO. These are the first two treatment plants utilizing membrane technology specifically
targeted at PFAS removal from drinking water. Although performance data are not yet available
from these facilities, the effectiveness studies enumerated under Question 4.1.1 include results
from full-scale facilities using membrane separation to treat other contaminants.

4.2.2	Are there studies of full-scale treatment of residuals that
fully characterize residual waste streams and disposal
options?

There are no full-scale studies of residuals from RO or NF facilities specifically for the removal
of PFAS. In general, however, the characteristics of membrane concentrates are predictable and
handling and treatment options are well understood. This waste stream contains the PFAS
compounds and other dissolved solids removed from the treated water. The two full-scale
facilities identified under Question 4.2.1 are designed for recovery rates of 85 to 92 percent
(Dowbiggin et al., 2021; Wetzel, 2021; WHNT News, 2019), which means that concentrate

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flows at these facilities would account for 8 to 15 percent of influent (i.e., 100 percent minus the
recovery rate). Assuming these facilities achieve 95 percent removal efficiency, PFAS
concentrations in this waste stream would be approximately 6 to 12 times the concentration in
influent water.7

For disposal of membrane concentrate, most systems use surface water discharge or discharge to
sanitary sewer. Deep well injection is common in Florida. A small percentage of systems use
land application, evaporation ponds, or recycling (Mickley, 2018). The large volume of residuals
is a well-known obstacle to adoption of membrane separation technology, in general. In the case
of PFAS removal, the high PFAS concentration in the residuals might limit the disposal options
or require additional treatment prior to disposal, depending on state and local discharge
regulations. Concentrate treatment is not common in other applications (Mickley, 2018). Studies
specific to treatment of concentrate containing PFAS currently are limited to lab- or pilot-scale
(Tow et al., 2021). The Alabama facility identified under Question 4.2.1 initially planned to treat
membrane concentrate through its existing granular activated carbon (GAC) filters prior to
discharge (WHNT News, 2019). More recent reports (Wetzel, 2021) do not address concentrate
treatment at this facility. The North Carolina facility includes the construction of a discharge
pipeline to a point "several miles" away, downstream of any drinking water intakes (Dowbiggin
et al., 2021).

4.2.3	Can the bench or pilot studies be scaled up to represent
full-scole treatment, including residuals generation and
handling?

Yes. As a mature and established technology, the scale-up of RO, in general, from bench- to
pilot- to full-scale is well understood and has been implemented at full-scale facilities treating
PFAS (e.g., Dowbiggin et al., 2021).

4.2.4	Is additional research needed?

In general, additional research is not required. In cases where regional or system-specific
conditions associated with PFAS-bearing residuals management present a significant barrier,
however, additional research on residuals treatment prior to disposal would be useful.

4.3 General Geographic Applicability

4.3.1 What regions do the existing research studies represent?

EPA's Drinking Water Treatability Database (USEPA, 2021a; 2021b; 2021c) includes
effectiveness data for PFAS removal by membrane separation in waters from three
geographically dispersed U.S. states (California, Illinois, and North Carolina), as well as from
countries overseas. The full-scale facilities listed under Question 4.2.1 are located in Alabama
and North Carolina.

7 The concentration in the reject stream can be calculated as the concentration in influent times the removal efficiency, divided by
the rejection rate. In this example, 0.95 / 0.15 = 6.33 and 0.95 / 0.08 = 11.88.

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4.3.2	Is it known that regional water quality variations will
limit treatment effectiveness or reliability in some areas?

No. There are no data indicating that regional water quality variations will limit effectiveness or
reliability. As discussed under Question 4.1.2 water quality affects the design (e.g., concentrate
volume, cleaning frequency, antiscalant selection, temperature) of a RO and NF systems, but not
their effectiveness or reliability.

4.3.3	Are there any regional issues with respect to residuals
handling or water resource use?

The large volume of reject water "lost" from membrane separation can be an issue in regions
where water scarcity is a concern. The Small Business Advocacy Review Panel (1999) pointed
out that a water rejection rate of 20 to 25 percent can present a problem where water is scarce,
such as in the western states. The availability of discharge options for residuals is also a region-
and system-specific issue, depending on location, climate, and state and local regulations. The
technology is more likely to be feasible when ocean or estuarine discharge is an option.

4.3.4	Is additional research needed?

No. Additional research is not required.

4.4 Compatibility with Other Treatment Processes

4.4.1	Have the effects (adverse or beneficial) of the treatment
process on other processes likely to be present at existing
plants been evaluated?

Yes. Adverse effects are unlikely. Membrane separation might have some effect on treated water
chemistry (see Question 4.5.1), which might alter corrosion control or blending requirements.
Generally, however, these effluent chemistry changes should not require significant adjustments
to downstream treatment processes. Regarding beneficial effects, RO and NF membranes can
remove a wide range of contaminants, including inorganic ions, total dissolved solids, nitrate,
radionuclides, some disinfection byproduct precursors, and synthetic organic chemicals. Since
membrane permeate has a reduced chlorine demand, its finished water requires a low dose of
disinfectant.

4.4.2	Will additional pre- or post-treatment be required for
integration into an existing (or planned) treatment train?

Possibly. Post-treatment can be required to control corrosion impacts (Lipp et al., 2010),
particularly in instances where blending is not possible (see Question 4.5.1).

4.4.3	Is additional research needed?

No. Additional research is not required.

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4.5	Ability to Bring All of the Water System into Compliance

4.5.1	Will the treatment process adversely affect the
distribution system or water resource decisions?

Yes, if not properly managed. The permeate from RO and, in some cases, NF can be corrosive.
The extent of this impact is site-specific (Bergman et al., 2012). In other drinking water
treatment applications, the permeate is often blended with untreated water to produce a less
corrosive finished water (Mickley, 2018). If the source water has a sufficiently low concentration
of PFAS and other contaminants, blending may reduce post-treatment requirements. Thus,
distribution system effects can be managed by adjusting corrosion control programs or blending
practices.

As discussed under Question 4.3.3, the large volume of membrane concentrate might have an
impact on water resource decisions in regions where water scarcity is a concern.

4.5.2	Might the treatment process, residuals handling, or pre-
or post-treatment requirements raise new environmental
quality concerns?

Yes. The disposal of large membrane concentrate volumes, containing high PFAS
concentrations, could create an environmental quality concern. As discussed under Question
4.3.3, discharge concerns are region- and system-specific. In addition, the corrosivity impacts
discussed above under Question 4.5.1, if not adequately managed through post-treatment, could
create new environmental quality concerns.

4.5.3	Is additional research needed?

No. Additional research is not required.

4.6	Reasonable Cost Basis for Large and Medium Systems

4.6.1	Is the technology currently used by medium and large
systems (including uses for other treatment purposes)?

Yes. Both full-scale PFAS RO facilities identified in the literature are large (10 and 48 MGD).
There are many medium and large systems that use RO or NF for other contaminants.

4.6.2	Do the treatment studies provide sufficient information
on design assumptions to allow cost modeling?

Detailed data are available from the treatment studies for the following design parameters:

•	Membrane type

•	Flux rate

•	Recovery rate

•	Residuals management options.

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Assumptions about pretreatment requirements and cleaning procedures, in general, are
determined based on major water quality parameters, such as hardness parameters, chloride,
sulfate, silica, pH, silt density index, and total dissolved solids. They typically are not affected by
trace contaminant influent concentrations or removal requirements. There is nothing unique
about PFAS removal by membrane separation that suggests a different relationship between the
major water quality parameters and typical pretreatment and cleaning requirements.

4.6.3 Is additional research needed?

No. Additional research is not required.

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5.0 Summary of Best Available Technology
Evaluation

Table 15 provides a summary of the evaluation results for the three technologies against each of

the criteria. Based on this evaluation, the overall conclusions are:

•	GAC is a potential BAT. It has been shown to achieve high removal efficiency for PFAS. It
is a mature and established technology in general and has been used for full-scale treatment
of PFAS at many facilities. Changes in air quality regulations might necessitate changes to
spent GAC management practices. Research on the fate of PFAS during GAC reactivation
would provide additional clarity on the significance of this issue. Future RCRA hazardous
waste regulations could also limit the available management options.

•	IX is a potential BAT. PFAS-selective resin has been shown to achieve high removal
efficiency for PFAS. IX is a mature and established technology in general and PFAS-
selective resin has been used for full-scale treatment at several facilities. Changes in air
quality regulations might necessitate changes to typical spent resin management practices.
Research on the fate of PFAS during spent resin incineration would provide additional clarity
on the significance of this issue. Future RCRA hazardous waste regulations could also limit
the available management options.

•	Membrane separation using RO or NF is a potential BAT. It has been shown to achieve high
removal efficiency for PFAS, including at full-scale facilities designed for other
contaminants. Two drinking water systems recently constructed full-scale treatment plants
specifically targeting PFAS using low-pressure RO. Large volumes of residual concentrate,
however, will likely restrict the technology's applicability on a system-specific basis.
Additional research on treatment of PFAS-bearing membrane concentration could help
mitigate this issue in some cases.

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Table 15. PFAS Removal Technologies Evaluated Against BAT Criteria

Criterion

GAC

IX

RO/NF

1. High Removal Efficiency







1.1. Have high removal efficiencies that achieve potential MCLs

Yes

Yes

Yes

been documented?







1.2. Are the effects of water quality parameters on treatment

Yes

Yes

Yes

effectiveness and reliability well-known?







1.3. Is the technology reliable enough to continuously meet a

Yes

Yes

Yes

drinking water MCL?







1.4. Is additional research needed?

No

No

No

2. History of Full-Scale Operation







2.1. Do existing studies include full-scale operations at drinking

Yes

Yes

Yes

water treatment facilities?







2.2. Are there studies of full-scale treatment of residuals that

Yes (given

Yes (for

Yes (for

fully characterize residual waste streams and disposal options?

current

other

other



regulations)

treatment

treatment





purposes)

purposes)

2.3. Can the bench or pilot studies be scaled up to represent full-

Yes

Yes

Yes

scale treatment, including residuals generation and handling?







2.4. Is additional research needed?

Maybe

Maybe

Maybe

3. General Geographic Applicability







3.1. What regions do the existing research studies represent?

Nationwide

Nationwide

Nationwide

3.2. Is it known that regional water quality variations will limit

No

No

No

treatment effectiveness or reliability in some areas?







3.3. Are there any regional issues with respect to residuals

Not currently

Not currently

Yes

handling or water resource use?







3.4. Is additional research needed?

No

No

No

4. Compatibility with Other Treatment Processes







4.1. Have the effects (adverse or beneficial) of the treatment

Yes

Yes

Yes

process on other processes likely to be present at existing plants







been evaluated?







4.2. Will additional pre- or post-treatment be required for

No

Possibly

Possibly

integration into an existing (or planned) treatment train?







4.3. Is additional research needed?

No

No

No

5. Ability to Bring All of the Water System into Compliance







5.1. Will the treatment process adversely affect the distribution

No

Possibly

Possibly

system or water resource decisions?







5.2. Might the treatment process, residuals handling, or pre- or

Possibly

Possibly

Yes

post-treatment requirements raise new environmental quality







concerns?







5.3. Is additional research needed?

Maybe

Maybe

No

6. Reasonable Cost Basis for Large and Medium Systems







6.1. Is the technology currently used by medium and large

Yes

Yes

Yes

systems (including uses for other treatment purposes)?







6.2. Do the treatment studies provide sufficient information on

Yes

Yes

Yes

design assumptions to allow cost modeling?







6.3. Is additional research needed?	No	No	No

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6.0	Small System Compliance Technology
Evaluation

6.1	SSCT Analysis Method

A technology must be both effective and affordable to be designated as an SSCT. Technologies
that meet the effectiveness criterion include those designated as BATs for the rule: GAC, PFAS-
selective IX, and RO. This section also presents preliminary affordability results for POU RO.
POU RO is not currently a compliance option because the regulatory options under consideration
require treatment to concentrations below 70 ng/L total of PFOA and PFOS, the current
certification standard for POU devices. However, POU treatment is reasonably anticipated to
become a compliance option for small systems in the future should NSF/ANSI develop a new
certification standard that mirrors EPA's regulatory standard.

To evaluate affordability, EPA compared incremental costs per household for each technology
against an expenditure margin. Table 16 shows the expenditure margins for each system size
category. It also shows how EPA derived the expenditure margins, beginning with estimates of
MHI, which vary by system size category. The annual affordability threshold for household
expenditures on drinking water is 2.5 percent of MHI. EPA deducted estimates of baseline or
current water bills from the affordability threshold to obtain the expenditure margin estimates.

Table 16. Expenditure Margins for SSCT Affordability Analysis

System Size
(Population
Served)

Median Household
Income1

Affordability
Threshold2

Baseline Water
Cost3

Expenditure
Margin



A

B = 2.5% x A

C

D = B - C

25-500

$62,950

$1,574

$551

$1,022

501-3,300

$60,926

$1,523

$638

$885

3,301-10,000

$66,746

$1,669

$666

$1,002

Notes:

1	MHI based on U.S. Census 2010 American Community Survey 5-year estimates (U.S. Census Bureau, 2010) stated in 2010
dollars, adjusted to 2022 dollars using the CPI (for all items) for areas under 2.5 million persons.

2	Affordability threshold equals 2.5 percent of MHI.

3	Household water costs derived from 2006 Community Water System Survey (USEPA, 2009), based on residential revenue per
connection within each size category, adjusted to 2020 dollars based on the Consumer Price Index (for all items) for areas under
2.5 million persons.

The cost per household varies by technology and by system size category. EPA used the
following method to estimate per-household costs using EPA's work breakdown structure
(WBS) drinking water treatment cost models:

•	Estimate system-level daily design and average flow based on median population

•	Estimate entry point design and average flow by dividing system-level flow by the average
number of entry points8

8 Except for POU RO. The analysis here assumes POU devices must be installed at all households regardless of entry point.
Therefore, costs are estimated based on the total system-level flow.

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•	Estimate capital costs using a technology-specific WBS cost curve and design flow

•	Estimate O&M costs using a technology-specific WBS cost curve and average flow

•	Annualize capital costs at 7 percent over the expected useful life of the treatment process

•	Calculate total annual costs (annualized capital costs plus O&M costs)

•	Multiply total annual costs by the average number of entry points,9 conservatively assuming
systems must install treatment at all entry points (erring on the side of higher costs)

•	Divide total annual costs by the median number of households served

•	Assess affordability by comparing these values with the expenditure margins.

Table 17 shows median population served, number of households, number of entry points, and
resulting design and average flows used in these calculations. EPA generated costs assuming
systems must meet MCLs for PFOA and PFOS of 4 nanograms per liter (ng/L) each, with initial
influent concentrations of 70 ng/L and 264 ng/L, respectively. These influent concentrations
correspond to the 90th percentile for each contaminant, considering detected values only.

Table 17. Design and Average Flow Estimates and Service Estimates for the 50th Percentile
or Median System

System Size (Population Served)

rarameier



25-500

501-3,300

3,301-10,000

System Population1

A

110

1,140

5,476

System Households2

B = A/2.53

43

451

2,164







Groundwater



System Design Flow3 (MGD)

C

0.049

0.458

2.051

System Average Flow3 (MGD)

D

0.012

0.147

0.776

Entry Points4

E

1

2

2

Entry Point Design Flow (MGD)

F = C/E

0.049

0.229

1.025

Entry Point Average Flow (MGD)

G = D/E

0.012

0.074

0.388







Surface Water



System Design Flow3 (MGD)

H

0.050

0.459

2.026

System Average Flow3 (MGD)

I

0.015

0.156

0.748

Entry Points4

J

1

1

1

Entry Point Design Flow (MGD)

K = H/J

0.050

0.459

2.026

Entry Point Average Flow (MGD)

L = I/J

0.015

0.156

0.748

Notes:

1	Median system populations are from USEPA Safe Drinking Water Information System Federal (SDWIS/Fed) fourth quarter
2021 "frozen" dataset that contains information reported through January 14, 2022

2	Median system household estimates equal median populations divided by 2.53 persons per household, based on 2020 Census
data (Table AVG1. Average Number of People per Household, by Race and Hispanic Origin/1, Marital Status, Age, and
Education of Householder: 2020).

3	Flow estimates are based on regression equations that relate population and design or average flows, derived in USEPA (2000).

4	Entry point data from 2006 Community Water System Survey (USEPA, 2009), Table 13, values rounded to nearest whole
number.

9 Except for POU RO, as discussed in the previous footnote.

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EPA generated costs for each system size category for 22 treatment technology scenarios. There
are eight scenarios for GAC comprising all combinations of two source waters (ground and
surface), two cost levels (low and high), and two bed life scenarios. The bed life scenarios reflect
results from linear equations derived as described in USEPA (2024a) and correspond to a range
of influent TOC from 0.5 mg/L and 2 mg/L (discussed further in Section 6.2). There are eight
scenarios for IX that are combinations of two source waters, two cost levels, and two bed life
scenarios. The bed life scenarios for IX also result from equations presented in USEPA (2024a).
For IX, they correspond to a range of total influent PFAS from 334 ng/L to approximately 7,000
ng/L (discussed further in Section 6.2). There are four scenarios for RO to account for two
source waters, and two cost levels. There are two scenarios for POU RO to account for two
source waters. Costs for POU RO do not vary by cost level input (high, mid, low). USEPA
(2024a) contains the cost curve parameters for all the treatment technology scenarios. There are
separate parameter sets for capital costs and O&M costs and for small, medium, and large entry
point sizes (corresponding to design flow ranges of less than 1 MGD, 1 MGD to less than 10
MGD, and greater than or equal to 10 MGD).

6.2 Results

Table 18 provides ranges of per-household costs for each technology and system size category.
The ranges indicate minimum and maximum costs across the scenarios noted in the previous
section.

Table 18. Total Annual Cost per Household for Candidate Technologies

System Size

GAC

IX

RO

POU1

(Population Served)

25-500

$607 to $1,241

$563 to $990

$4,332 to $5,224

$345 to $357

501-3,300

$203 to $484

$171 to$351

$721 to $1,324

$327 to $327

3,301-10,000

$178 to $417

$145 to $284

$388 to $544

Unavailable2

Notes:

1.	POU is not currently a compliance option because the regulatory options under consideration require treatment to
concentrations below the current certification standard for POU devices. However, POU treatment is anticipated to become a
compliance option for small systems in the future should NSF/ANSI develop a new certification standard that mirrors (or is
demonstrated to treat to concentrations lower than) EPA's regulatory standard. The affordability conclusions presented here
should be considered preliminary estimates because they reflect the costs of devices certified under the current testing standard,
not a future standard.

2.	For evaluating costs for the PFAS rulemaking, EPA's WBS model for POU treatment does not cover systems larger than 3,300
people (greater than 1 MGD design flow).

For each system size category, the per-household cost range for GAC is lower than the
corresponding expenditure margin in Table 16. The lower end of the cost range reflects a bed life
corresponding to an influent TOC of 0.5 mg/L, which is a typical detection limit for TOC. The
upper end of the range corresponds to an influent TOC of 2 mg/L, which is approximately the
median for surface water systems and the 85th percentile for groundwater systems.

Based on the linear equations from USEPA (2024a), TOC influent concentrations above 3.2
mg/L may sufficiently reduce GAC bed life such that regulated utilities may choose other
treatment options. The maximum influent TOC value of 3.2 mg/L used in this analysis should
not be regarded as a strict limit on the practicality or affordability of GAC. EPA is aware that
systems may use GAC with TOC influent concentrations above 3.2 mg/L. The bed life equations

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are based on pooled data from a limited number of studies and reflect central tendency results
under varying water quality conditions. They should not be used in lieu of site-specific
engineering analyses or pilot studies to estimate bed life or treatment costs for specific individual
treatment systems. Individual systems might achieve longer GAC bed lives and lower treatment
costs at higher influent TOC concentrations, particularly if their influent concentrations of PFAS
are lower than the 90th percentile values used in this analysis.

For IX, the per-household cost range for each system size category also is lower than the
corresponding expenditure margin in Table 16. The lower end of the cost range reflects a bed life
corresponding to a total influent PFAS concentration of 334 ng/L, the sum of the initial influent
concentrations of PFOS and PFOA, assuming that no other PFAS compounds are present. The
upper end of the range assumes additional PFAS compounds are present such that total influent
PFAS is approximately 7,000 ng/L. Data are not available to estimate bed life for higher influent
concentrations using the linear equations from USEPA (2024a). IX costs are uncertain beyond
this value, but it should not be regarded as a strict limit on the feasibility or affordability of the
technology.

For RO, the results are mixed. The cost range is lower than the expenditure margin for the largest
size category but higher than the margin for the smallest size category. The upper bound of the
cost range is also higher than the margin for the middle size category. Therefore, RO meets the
SSCT criteria only for the largest system size category.

Table 18 includes preliminary results for POU RO. As discussed above, POU RO is not a
compliance option under current certification standards but is expected to become an option in
the future should NSF/ANSI develop a new certification standard that mirrors or is more
stringent than EPA's regulatory standard. The results for POU RO reflect the costs of devices
certified under the current testing standard, which might differ from the costs of devices certified
under a future standard. Therefore, the POU RO costs should be considered preliminary
estimates. Based on the preliminary estimates, POU RO would meet the affordability criteria for
the two smaller size categories. For evaluating costs for the PFAS rulemaking, EPA's WBS
model for POU treatment does not cover systems serving greater than 3,300 people (greater than
1 MGD design flow).

The results discussed above assume management of spent GAC and spent IX resin using current
typical management practices (reactivation for GAC and incineration for resin) and do not
acknowledge all possible management scenarios such as landfilling which may be more
appropriate for select entities. Future changes to regulations might result in classification of spent
GAC or spent IX resin as hazardous waste. Table 19 shows the resulting cost per household if
systems are required to dispose of these residuals as hazardous waste. Although costs increase in
this scenario, the increases are not significant enough to change the conclusions about
affordability.

Table 19. Total Annual Cost per Household Assuming Hazardous Waste Disposal for Spent
GAC and Resin

System Size (Population Served)	GAC	IX

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Best Available Technologies and Small System Compliance Technologies for PFAS in Drinking Water
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25-500

501-3,300

3,301-10,000

$630 to $1,369
$211 to $520
$185 to $438

$586 to $1,027
$176 to $360
$148 to $289

Table 20 provides a summary of which technologies meet SSCT criteria for the three system size
categories. As discussed above, the affordability conclusions do not change under hazardous
waste regulations.

Table 20. SSCT Affordability Analysis Results - Technologies that Meet Effectiveness and
Affordability Criteria

System Size (Population Served)

GAC

Ion Exchange

RO

POU1

25-500

In some cases2

Yes

No

Yes

501-3,300

Yes

Yes

No

Yes

3,301-10,000

Yes

Yes

Yes

Unavailable3

Notes:

1.	POU is not currently a compliance option because the regulatory options under consideration require treatment to
concentrations below the current certification standard for POU devices. However, POU treatment is anticipated to become a
compliance option for small systems in the future should NSF/ANSI develop a new certification standard that mirrors (or is
demonstrated to treat to concentrations lower than) EPA's regulatory standard. The affordability conclusions presented here
should be considered preliminary estimates because they reflect the costs of devices certified under the current testing standard,
not a future standard.

2.	Upper bound estimated annual household treatment costs exceed expenditure margin. Lower bound estimated annual
household treatment costs do not exceed the expenditure margin. This exceedance is primarily driven by capital costs and
attributable to the use of high-cost materials (e.g., stainless steel) in the upper bound estimates. Systems using low-cost
materials, but with source water characteristics otherwise set to the upper bound (e.g., influent PFAS at approximately 7,000
ng/L, influent TOC at 2 mg/L), would fall below the expenditure margin.

3.	For evaluating costs for the PFAS rulemaking, EPA's WBS model for POU treatment does not cover systems larger than 3,300
people (greater than 1 MOD design flow.

6.3 Small System Affordability Analysis with Potential

Additional Expenditure Margins and when Accounting for
Financial Assistance

As part of EPA's consideration of potential additional annual expenditure margins to improve
the assessment of affordability impacts to low income and disadvantaged communities, EPA
considered two incremental cost analyses are conducted utilizing alternative potential
expenditure margins. The first expenditure margin threshold is based on 1.0 percent of annual
MHI based on a recommendation from EPA's National Drinking Water Advisory Council
(NDWAC). The second expenditure margin threshold is set equal to 2.5 percent of the lowest
quintile of annual household income and is based on an AWWA 2021 expert panel report. These
expenditure margins are estimated for each of the small system size categories: 25 to 500, 501 to
3,300, and 3,301 to 10,000 people served. Additionally, EPA's Science Advisory Board (SAB)
and the NDWAC recommended to EPA that the national level affordability analysis should
include the impact of financial assistance if the financial support is generally available to all

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Best Available Technologies and Small System Compliance Technologies for PFAS in Drinking Water
815R24011	March 2024

systems (nationwide). EPA is also considering including this recommendation in the national
affordability calculations. For further discussion, please see section 9.13.2 of EPA's Economic
Analysis for the Per- and Polyfluoroalkyl Substances National Primary Drinking Water
Regulation (EPA, 2024b).

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7.0 References

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Dixit, F., Barbeau, B., Mostafavi, S.G., and Madjid, M. 2020. Removal of legacy PFAS and
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Jent, H. 2020. Crews near completion on new ion-exchange treatment plant to purify water in
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