WC138 SeptOct 2024 - Flipbook - Page 25
Table 1- comparing approach between ground filtration system (Ion exchange resin) and in situ permeable sorption barrier (colloidal activated carbon)
Treatment approach
Above ground treatment vessel
(Ion exchange resin media)
Design Parameters
• 3 Drinking water wells
• Total flow: 12,000 liters/min
• PFAS concentration between 207 and 291 ng/l *
Treatment objective
Removal of 95% PFAS in the influent
(18 compounds) and below 30 ng/L at all times at exit
Treatment scenario
3 separate above ground installations plus vessels
and IX media supplies for 4 years.
• Barriers dimensions: 75 m long x 2 m thick x 5 m high,
• Barrier volume= 750 m3 @ 30% porosity (sandy aquifer)
• Pore volume = 225 m3
Total cost
$11,400,000 CDN
$800,000 CDN
in two of the four municipal wells as well as for two samples of
water distributed by aqueduct.
As a result, the need for affected municipalities to change
their supply sources entails costs and a reduction in supply
capacity and flexibility, as well as affecting public confidence in
municipal infrastructures. Remediation of PFAS-contaminated
solid and aqueous media is extremely challenging due to their
high chemical and thermal stability in the environment, their
unique physicochemical properties (both hydrophobic and
oleophobic behaviors), and their extremely persistent nature
(limited or no biodegradable).
The costs associated with standard above-ground filtration
systems to address the problem can be very expensive. For a
temporary treatment solution, the City of Saguenay awarded an
$11.4-million contract for the installation of ion exchange resin
filters at the network point of entry to reduce PFAS present
in large quantities in the aqueduct network that serves the
Grande-Baie and Port-Alfred sector. These filters will be used
until a new water source is found.
An innovative in situ solution
Although various methods have been reported for removing
PFAS compounds from contaminated soils, the immobilization method has been an important solution for remediating
PFAS-contaminated soils, although its long-term effectiveness is
still being investigated.
This article examines an in-situ immobilization technology for PFAS in soil and/or groundwater via the application
of colloidal activated carbon (CAC) for which structure was
modified specifically for PFAS sorption. The thermal treatment
of this activated carbon under reducing conditions removes
acids, creates basic surface centers and significantly increases the
sorption capacity of anionic PFAS. The influence of dissolved
humic substances on PFAS adsorption to this activated carbon
was found to be very low. This technology was developed by a
WAT E R C A N A D A . N E T
In situ permeable sorption barrier
(colloidal activated carbon “Intraplex® B")
German company and implemented at several European sites to
limit the progression of PFAS contamination via groundwater
movement, and thus protect sensitive receptors.
The CAC is injected into the contaminated zone via well
screens or targeted injection points. With a particle size of one
to two microns, the suspension is optimally distributed within
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WATER C AN ADA • SEP TEMBER/OCTOBER 2024
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