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INNOVATIVE RESEARCH FOR A SUSTAINABLE FUTURE

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PERFLUOROALKYL AND POLYFLUOROAKLY SUBSTANCES (PFAS)

Technologies for Reducing PFAS in Drinking Water

PFAS in the Environment

Per- and polyfluoroalkyl substances (PFAS) are a
very large class of man-made chemicals that includes
PFOA, PFOS and GenX chemicals. Since the 1940s,
PFAS have been manufactured and used in a variety
of industries in the United States and around the
globe. PFAS are found in everyday items such as
food packaging and non-stick, stain repellent, and
waterproof products, including clothes and other
products used by outdoor enthusiasts. PFAS are also
widely used in industrial applications and for
firefighting. PFAS can enter the environment through
production or waste streams and can be very
persistent in the environment and the human body.
There is toxicological evidence that some PFAS can
potentially cause adverse health effects in animals
and humans.

EPA researchers have been studying a variety of
technologies at bench-, pilot-, and full-scale levels to
determine which methods work best to remove PFAS
from drinking water. Some PFAS are soluble in
water, and left unchecked, can make their way into
our drinking water. Because of the chemical
properties of PFAS, researchers have found that
certain technologies are better able to remove some
PFAS from drinking water than others, specifically
perfluorooctanoic acid (PFOA) and
perfluorooctanesulfonic acid (PFOS), which are the
most studied of these chemicals. Other PFAS, like
Gen-X chemicals, can also be removed but to varying
degrees.

Effective technologies include activated carbon
adsorption, ion exchange resins, and high-pressure
membranes, such as nanofiltration or reverse
osmosis. These technologies can be used in drinking
water treatment facilities, in water systems in
hospitals or individual buildings, or even in homes at
the point-of-entry, where water enters the home, or at
a point-of-use, such as a kitchen sink or a shower.

Activated Carbon Treatment

U.S. Environmental Protection Agency

HI Office of Research and Development

Activated carbon treatment is the most studied
treatment for PFAS removal. Activated carbon is
commonly used to adsorb organic compounds in
drinking water treatment systems. Adsorption is a
process of accumulating a substance, such as PFAS,
at the interface between liquid and solid phases.
Activated carbon is an effective adsorbent because it
is a highly porous material and provides a large
surface area to which contaminants may adsorb.
Activated carbon is made from organic materials with
high carbon contents such as wood, lignite, and coal;
and is often used in granular form called granular
activated carbon (GAC).

GAC has been shown to effectively remove PFAS
from drinking water when it is used in a flow-through
filter mode after particulates have already been
removed from the water via conventional sand
filtration, or a similar process. According to the
research, GAC can be 100 percent effective for a
period of time, depending on the specific PFAS that
needs to be removed, the type of carbon used, the
depth of the bed of carbon, flow rate of the water,
temperature, and the degree and type of organic
matter as well as the presence of other contaminants,
or constituents, in the water.

For example, GAC works well on longer-chain PFAS
like PFOA and PFOS, but shorter chain PFAS like
perfluorobutanesulfonic acid (PFBS) and
perfluorobutyrate (PFBA) do not adsorb as well
resulting in earlier breakthrough, making GAC a
more expensive treatment because it would need to
be replaced, or reactivated, more often to have high
efficiency. In addition, disposal of the PFAS removed
during reactivation of the GAC must also be
considered.

Another type of activated carbon treatment is
powdered activated carbon (PAC) which is the same
material as GAC, but it is smaller in size. Because of
the small particle size, PAC cannot be used in a flow
through bed, but can be added directly to the water

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and then removed through filtration or in a
clarification stage. Used in this way, PAC is not as
efficient or economical as GAC at removing PFAS.
Research finds that even at very high PAC doses with
the very best carbon, it is unlikely to remove a high
percentage PFAS; however, it can be used for modest
percent removals. If PAC is used, the drinking water
treatment plant will need to determine what disposal
options are appropriate for the resulting sludge that
contains adsorbed PFAS.

Ion Exchange Treatment

Another treatment option is anion exchange
treatment, or resins. Ion exchange resins are made up
of highly porous, insoluble polymeric material. The
resin beads that are used in a filtration mode are
made from hydrocarbons. There are two broad
categories of ion exchange resins: cationic and
anionic. The negatively-charged cationic exchange
resins (CER) are effective for removing positively-
charged contaminants, and positively-charged anion
exchange resins (AER) are effective for removing
negatively-charged contaminants, like PFAS. Ion
exchange resins are like tiny powerful magnets that
attract and hold the contaminated materials from
passing through the water system. Negatively
charged ions of PFAS are attracted to the positively
charged anion exchange resins. AER has shown to
have a high removal capacity for many PFAS;
however, it is typically more expensive than GAC.
Of the different types of AER resins, perhaps the
most promising are the PFAS-selective class of AER
in a single use mode. Because this treatment
technology does not need resin regeneration, there is
no liquid contaminant waste stream from the
regeneration process to consider, but the spent resin
will need to be managed by either disposal or
incineration.

Like GAC, AER removes 100 percent of the PFAS
for a time that is dictated by the type of PFAS that
needs to be removed, the choice of resin, bed depth,
flow rate, and the degree and type of background
organic matter and other contaminants or
constituents.

membranes are tighter than nanofiltration
membranes, and have higher percent removals.

Research shows that these types of membranes are
typically more than 90 percent effective at removing
a wide range of PFAS, including shorter chain
PFAS. With both high-pressure membrane types,
approximately 80 percent of the feed water (the water
coming into the membrane) passes through the
membrane to the effluent (the treated water).
Approximately 20 percent of the feedwater is
retained as a high-strength concentrated waste. A
high-strength waste stream can be difficult to treat or
dispose, especially for a contaminant such as
PFAS. This technology may be best suited as a point-
of-use technology for a homeowner, since the volume
of water being treated is much smaller and the waste
stream could be disposed of down the drain with less
cause for concern. Use of high-pressure membranes
used at the point-of-entry to a home or building may
have a waste disposal problem because it is treating
all the water used in that building and the waste
stream will have a similarly higher flow rate. Also,
high pressure membranes produce a treated water that
is corrosive, and care must be taken (as is done at
water utilities) to make sure this doesn't result in
metal (lead and copper) corrosion of the building's
premise plumbing and fixtures.

CONTACT

Thomas Speth, PhD, P.E. (Ohio)
speth.thomas(a)epa.gov

For more information about drinking water
technologies available for removing PFAS, please
visit EPA's Drinking Water Treatability Database.

This interactive literature review database contains
more than 65 regulated and unregulated
contaminants and covers 34 processes commonly
employed or known to be effective. Users can search
by contaminant or technology.

High-Pressure Membranes

High-pressure membranes, such as nanofiltration or
reverse osmosis, have been extremely effective at
removing PFAS. Of the two, reverse osmosis

VS U.S. Environmental Protection Agency

H9 Office of Research and Development

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