On March 14, 2023, EPA announced the proposed National Primary Drinking Water Regulation (NPDWR) for six Per- and Polyfluoroalkyl Substances (PFAS) including perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorononanoic acid (PFNA), hexafluoropropylene oxide dimer acid (HFPO-DA, commonly known as GenX Chemicals), perfluorohexane sulfonic acid (PFHxS), and perfluorobutane sulfonic acid (PFBS). When finalized, the proposed regulation will require public water systems to monitor for these chemicals.
In anticipation of the regulations, Fairfax Water hired an
independent lab to test their water using current EPA-approved methods that can
detect PFAS at much lower concentrations than previous methods. Fairfax Water
also participated in the Virginia Department of Health (VDH) Occurrence Study
that was completed in 2021. However, the practical quantitative limit was
4 ppt just at the proposed regulatory limit. Fairfax Water found that some of
the results for the Occoquan Reservoir for PFOS and PFAS were above the MRL and
the regulatory limit. Since that time the Occoquan Watershed Laboratory has
upgraded their analytical equipment.
PFAS dissolves in water and combined with their chemical
properties means that traditional drinking water treatment technologies used at
water treatment plants are not designed to remove them, it is believed though,
that carbon filtration does remove some. Activated carbon adsorption, ion
exchange resins, and high-pressure membranes have been found to remove PFAS
from drinking water, especially PFOA and PFOS, which have been the most studied
of these chemicals and the PFAS substances with the lowest promulgated drinking
water limit . Testing these technologies at the new regulatory limits is
underway, but even if effective it could cost millions up to a billion dollars
to remove PFAS from the Occoquan Reservoir, then the problem is how to dispose
of the PFAS removed from the water. This would bring a whole new liability to
the water utility.
The best strategy is to look for the sources of PFAS in the
Occoquan watershed and prevent those from reaching the reservoir rather than
removal by Fairfax Water. Source water protection is the best solution if it can be done.
With that in mind both Fairfax Water and the EPA have developed an
analytic framework which provides information about PFAS across the
environment. Now Fairfax Water has begun testing in the watershed to identify
the sources of PFAS.
Armed with $750,000 in new equipment for the purpose, the
Occoquan Watershed Laboratory has begun to test samples from throughout the
Occoquan watershed to determine where the PFAS in the reservoir is coming from.
To start with there are several potential known sources: the reclaimed water
from UOSA, accidental releases from Manassas airport, and the old Vint Hill army base where the
Fauquier Times reported that for the past several years, the U.S. Department of
Defense has been monitoring PFAS contamination at Vint Hill that is believed to
be tied to a former burn pit where soldiers practiced putting out fires with
firefighting foam containing PFAS chemicals, which then leached into the soil
and the groundwater.
There is no longer enough water in the rivers in the
Occoquan watershed to consistently meet the demand during dry periods, so the Upper Occoquan Service Authority,
UOSA, the waste water treatment plant also delivers 40 million/day of recycled
water that originated in the Potomac River to the Occoquan Reservoir.
Supplementing the supply. According to Fairfax Water diet is responsible for
66%-72% of exposures to PFOA and PFOS (the two chemicals that have been most
widely studied). In some cases, they have also leached into both surface and
groundwater. Water is responsible for 22%-25% of exposures. Keeping PFAS
out of the source water the real challenge when PFAS is in our diet and
wastewater is reused in our drinking water supplies. To stay within the
regulatory limit, Fairfax Water will have to identify the PFAS content in the
various source of water and can mix them to minimize exposure or remove them.
Another way PFAS could have reached the Occoquan Reservoir
was from accidental release from Manassas Airport. The Manassas Airport is
upstream from the Occoquan Reservoir along Cannon Branch which flows into Long
Branch, and accidents do happen. In February 2020, a malfunction
released a large spill of PFAS-based firefighting foam from a
hangar at Manassas Regional Airport, in the Occoquan River basin. Aqueous
film-forming foam, which is known as AFFF, is a firefighting foam
widely used in the aviation industry because it quickly extinguishes fuel fires
by spreading across the surface, depriving the fire of oxygen. This also makes
a spill hard to control. The spill was not entirely contained. The foam
contains chemicals known as per- and polyfluoroalkyl substances (PFAS). There
are likely to have been other spills over the years. So, soils and groundwater
in that part of the watershed may be contaminated.
The Fauquier Times has reported that the area near Vint Hill
army base gets its drinking water from Buckland Water and Sanitation, a private
company, and that the water is
distributed by the Fauquier County Water and Sanitation Authority.
Buckland apparently has been testing
Vint Hill wells for PFAS for years but failed to disclose it since it was
not covered under the safe drinking water act. The level of contamination at
the site was reported by the Fauquier Times and the Prince William Times was
hundreds of times higher than the proposed drinking water standard.
There are other potential sites in the Occoquan Watershed to
be studied and tested for PFAS. The old Atlantic Richfield superfund site
recently acquired by Microsoft was never tested for PFAS though the groundwater
has been monitored for solvents for years. There are likely to be other sites
to test.
Related Reading and sources:
https://www.sciencedirect.com/science/article/pii/S0160412023003069?via%3Dihub
No comments:
Post a Comment