GRA's Ninth Symposium in the Series on Groundwater Contaminants
focused on 1,4-dioxane and Other Solvent Stabilizer Compounds
in the Environment. The December 10th Symposium, held at
the San Jose Doubletree Hotel, attracted more than 100 participants
from ten states. The event was held in cooperation with
the International Association of Hydrogeologists, and was
sponsored by Applied Process Technology Inc. We present
here an abbreviated synopsis of some of the presentations.
The author and symposium chair, Tom Mohr, presented his
research on the occurrence of solvent stabilizers in chlorinated
degreasing and dry cleaning solvents. His research was supported
in part by his employer, the Santa Clara Valley Water
District, and is the subject of an upcoming book by
CRC Press. Solvent stabilizers are chemicals added to chlorinated
solvents such as trichloroethylene (TCE), methyl chloroform
(TCA), and perchloroethylene (PCE). These additives serve
to inhibit reactions that otherwise lead to the deterioration
and ultimate breakdown of the solvent, diminishing or preventing
solvent performance in the intended industrial application.
These solvent stabilizers have been empirically developed
and refined over the last 50 years to include a wide variety
of chemical additives.
Identification of these solvent stabilizer compounds may
be useful in forensic investigations for deconvoluting commingled
plumes. Stabilizers and other wastes associated with degreasing
may also alter the properties of DNAPL, potentially affecting
DNAPL subsurface behavior. Addition of DDT to PCE for combined
dry cleaning and moth protection would increase the toxicity
of releases from dry cleaners where this practice was used.
Due to its physical and chemical properties, 1,4-dioxane
is extremely mobile, moving far ahead of the VOC plumes
in which it is found. In addition, it has attracted the
greatest interest among the many solvent stabilizers commonly
added to chlorinated solvents because of its classification
as a probable human carcinogen. The severity of impacts
from 1,4-dioxane is open to debate due to uncertainties
regarding the toxicological studies used to derive the cancer
slope factor. Until such issues are resolved, 1,4-dioxane
can certainly create problems for remedial project managers
and water utility operators alike.
Vince Christian of the San Francisco Bay Regional
Water Quality Control Board presented his work on a
survey of sites at which 1,4-dioxane has been detected in
the San Francisco Bay Area. After discovering 1,4-dioxane
in groundwater at more than 250,000 ppb at a San Jose solvent
recycling facility in 1998, SFBRWQCB requested testing for
1,4-dioxane at 15 sites, primarily electronics manufacturing
plants comprising some of Silicon Valley's leading semiconductor
manufacturers. The survey confirmed that 1,4-dioxane is
present at the majority of TCA release sites. Mr. Christian
highlighted his agency's interim policy for establishing
cleanup levels for 1,4-dioxane contamination of soil and
groundwater. The groundwater Environmental Screening Level
(ESL) for current or potential drinking water sources is
the provisional Action Level established by California's
Department of Health Services, 3 ppb. For non-drinking water
sources, the ESL is 50 ppm. For soil above drinking water
sources, the 1,4-dioxane ESL is 1.8 ug/kg, and above non-drinking
water source waters, 30 mg/kg. For full details on the derivation
and application of SFBRWQCB's ESLs, see http://www.swrcb.ca.gov/rwqcb2/esl.htm.
A detailed case history of the Pall-Gelman Sciences site
in Washtenaw County Michigan was presented by Farsad
Fotouhi of Pall Corporation and Jim Brode
of Fishbeck Thompson Carr and Huber Inc. Large quantities
of 1,4-dioxane were released from a holding pond and through
a waste injection well at the Gelman Sciences plant beginning
in the 1960's. 1,4-dioxane was used as a solvent for cellulose
acetate, a component of micro-porous filters. Fotouhi and
Brode pioneered analytical and remedial solutions to deal
with this challenging contaminant. Because 1,4-dioxane is
not easily removed by air stripping or carbon adsorption,
and relatively immune to biodegradation, Pall initially
developed ultraviolet light solutions for this contaminant.
Ms. Dellilah Sabba of the Stanford Linear Accelerator
Center (SLAC) profiled several occurrences of 1,4-dioxane
at the SLAC site in Menlo Park, California. Ms. Sabba noted
that 1,4-dioxane occurrence at the SLAC site is closely
associated with TCA and its abiotic degradation product,
1,1-DCE. In some locations, 1,4-dioxane was found with 1,1,-DCE
where no TCA was detected. 1,4-dioxane was found in groundwater
at a maximum concentration of 7,300 ppb. The existing remedial
solution, granular activated carbon, was found to remove
1,4-dioxane, in spite of expectations to the contrary, based
on 1,4-dioxane's low KOC value. Low influent concentrations,
very low flow rates, and possible biodegradation of 1,4-dioxane
on carbon surfaces may explain this unexpected but encouraging
result.
Dr. Julie Stickney of Arcadis G&M Inc's Portland
Maine office presented her paper entitled "An Updated Evaluation
of the Carcinogenic Potential of 1,4-dioxane". Dr. Stickney
and six colleagues collaborated to complete a comprehensive
review and critique of the toxicological literature and
the basis for the cancer slope factor now in use for 1,4-dioxane.
Two studies applying physiologically based pharmacokinetic
(PBPK) modeling suggests that the current cancer slope factor
used by EPA significantly overestimates the potential cancer
risk, and Dr. Stickney concludes that a formal reevaluation
of the carcinogenic potency of 1,4-dioxane is warranted
to account for available information on the pharmacokinetics
and mode of action. To facilitate the proposed reevaluation,
Arcadis G&M is convening a Risk Management Consortium workshop
in Washington D.C. to address toxicology and risk assessment
issues for 1,4-dioxane on February 11th, 2004. The Consortium
is sponsored by the Synthetic Organic Chemical Manufacturers
Association (SOCMA).
Tim Shangraw of EMSI (Arvada, Colorado) presented his
work on fixed film biological processes for 1,4-dioxane
removal from groundwater at the Lowry Landfill Superfund
Site near Denver, Colorado. Mr. Shangraw's team evaluated
numerous remedial technologies for 1,4-dioxane removal,
including UV-oxidation, activated carbon, and advanced oxidation
processes. After diagnostic bench tests, Shangraw's team
is now deploying a full-scale, fixed film moving bed biological
treatment system to reduce 1,4-dioxane from site groundwater.
Fortuitously, the contaminant tetrahydrofuran, which is
a critical requirement of 1,4-dioxane degradation, is also
present in site groundwater.
Paul Abrams, M.D., J.D. of Global BioSciences
Inc. (North Attleborough, Massachusetts) presented his
firm's work on 1,4-dioxnae degradation using Butane Biostimulation.
A groundwater sample containing 1,4-dioxane was incubated
under a butane-air mixture for four weeks at 10°C. Butane
consumption and 1,4-dioxane rates were evaluated, and 1,4-dioxane
concentrations as high as 7.7 mg/L were degraded to sub-ppb
concentrations within 48 hours. Previous studies estimate
that the aqueous aerobic half-life of 1,4-dioxane is between
672 and 4320 hours. Dr. Abrams pointed out that bacteria
grown on butane rapidly produce the required enzymes, and
butane is highly soluble, allowing it to be administered
over a larger subsurface area. A field study of butane biostimulation
for in situ remediation of 1,4-dioxane has not yet been
conducted, though the presenter was optimistic that butane
biostimulation will be effective.
Mr. Marco Odah of Accelerated Remediation Technologies
(Kansas City) presented the In-Well Air Stripping concept
for 1,4-dioxane removal using subsurface circulation. Mr.
Odah acknowledged that 1,4-dioxane has a very low Henry's
Law Constant (4.88 x 10-6 atm.m3/mole), leading to only
~30% removal by conventional air stripping. The recirculation
feature of the in-well air stripping approach, may iteratively
reduce 1,4-dioxane concentrations to target compliance concentrations
with enough effort. Mr. Odah estimated that recirculating
1,4-dioxane contaminated groundwater could achieve a 99.9%
reduction in 12 passes. The technology has not yet been
field-tested for 1,4-dioxane sites, but has been successful
for remediation of MtBE and chlorinated solvents.
Dr. Fred Payne presented a paper prepared with Dr.
Suthan Suthersan, Barry Molnaa, and Scott Davis of Arcadis
G&M's Michigan and Richmond, California offices on Developing
In Situ Reactive Zone Strategies for 1,4-dioxane. Dr. Payne
described a concept for the source mass distribution of
hydrophilic compounds like 1,4-dioxane (fully miscible in
water) that suggests such compounds may provide a very persistent
source zone. In a dual porosity framework divided into 'static'
pore space and 'migratory' pore space, high concentrations
of hydrophilic compounds may invade the static spaces, and
diffuse back out after the center of mass has left the migratory
spaces. This leads to long tailing of contaminant concentration
curves over time, with a significant amount of the overall
contaminant mass in the aquifer residing in the static pore
space. Consequently, many volumes of pore flushing would
be required to address a 1,4-dioxane release using pump
and treat technology. Dr. Payne therefore proposes in situ
reactive zones as a conceivable solution for 1,4-dioxane
releases (the concept has not yet been tested for 1,4-dioxane
sites). Two potential in situ reactive technologies are
suggested, one using redox manipulation for biodegradation,
the second using ozone sparging. Research to date has documented
aerobic degradation of 1,4-dioxane. Dr. Payne suggests anaerobic
degradation may also be possible, and trials of these approaches
are underway in the eastern U.S. and Midwest.
Dr. Reid Bowman of Applied Process Technology (San
Francisco) presented his paper, "Ozone-Peroxide Advanced
Oxidation Water Treatment of 1,4-dioxane and Chlorinated
Solvents." Dr. Bowman profiled several successful applications
of line pressure advanced oxidation process, packaged as
the HiPox™ system, for removal of 1,4-dioxane from groundwater.
The HiPox™ system utilizes a static mixer to prolong contact
time with injected hydrogen peroxide and ozone. Remedial
Feasibility using this particular brand of advanced oxidation
is confirmed through pilot testing using a mobile unit to
obtain design data for scale up. In a 1,000 gpm full scale
application with 4.6 ppb influent, the system consistently
reduces concentrations to below 1 ppb. This technology is
also effective for removal of chlorinated solvents, MtBE,
and other contaminants. Dr. Bowman has developed a computer
process model that has been shown to accurately predict
system performance.
Neil Blandford of D.B. Stephens & Associates (Albuquerque,
New Mexico) and his colleague Dr. Nicole Sweetland presented
a paper, "Rethinking Traditional Approaches to Hydraulic
Capture in Preparation for the Next Series of Emerging Chemicals
of Concern in Groundwater". Mr. Blanford focused on the
issue of reinjection of treated groundwater, from which
some contaminants that eluded detection by conventional
analyses may not have been removed. Blanford proposes a
new paradigm for hydraulic capture to account for the possible
future discovery of additional contaminants requiring remediation.
The alternative approach seeks to contain all water extracted
and treated. This approach requires more intensive monitoring
and may result in source area disturbance, but reduces the
overall risk over the long term by ensuring that contaminants
not currently identified or removed by treatment systems
are not redistributed.
The symposium closed with a lively and thought-provoking
talk by Brian Haughton, an environmental lawyer and
a partner at Barg Coffin Lewis & Trapp, LLP in San
Francisco. Mr. Haughton compared the issue of 1,4-dioxane
at solvent release sites to the steroids scandal involving
baseball great Barry Bonds (analytical advances permitted
identification of a new variety of steroids not previously
detected in routine testing for performance enhancing drugs).
Emerging contaminants can be characterized as emergent due
to new knowledge, new toxicology, new analytical capabilities,
and new understanding of the significance of chemicals in
the environment. How should society react to emerging contaminants?
Mr. Haughton framed society's choice as being of two aphorisms:
"better safe than sorry", and, "measure twice, cut once".
In the first case, we should immediately cease all use of
the chemical, test everywhere on the property without regard
to cost and clean like hell, and eliminate all evidence
of human impact on the environment. In the second case,
take no action until there is unanimity and certainty that
the subject chemical indisputably causes cancer, and even
then don't ban the chemical, and there's no need to test
until there's evidence that the dose from exposure to the
chemical at the site is in fact lethal. Where between these
two extremes should our actions lie? Do RPs care only about
costs? Do regulators care only about the environment? As
actors on the contamination stage, we stand together in
a pond full of alligators. We each tend to respond most
to the nearest alligator. Together, we have a common interest
in reducing the alligator population!
Mr. Haughton called attention to our duty to deal with unintended
consequences, including those that are directly negative,
such as MtBE in gasoline and groundwater, and PDBEs in kids'
pajamas. We also have a duty to attend to the indirect unintended
consequences, as we live in a world of limited resources.
Water purveyors and RPs alike have limited budgets. Haughton
profiled a series of water quality regulation requirements,
and contrasted these with the cost benefit analysis approach.
Haughton noted that Governor Schwarzenegger's second Executive
Order calls upon each state agency to track down all conceivable
underground regulation and conduct cost benefit analysis.
The Governor's goal is to prohibit enforcement of underground
regulation, requiring instead that formal rule-making with
Notice and Comment be completed first. As an example of
underground regulation, Haughton pointed to advisory drinking
water Action Levels promulgated by DHS - these look like,
walk like, and talk like rules - they are rules. The challenge
with the Rule Making process is that attorneys tend to hammer
every problem that looks like a nail.
The Groundwater Resources Association extends its appreciation
to the speakers, the symposium sponsor, Applied Process
Technologies, the exhibitors, and the attendees for making
this event successful.
Tom Mohr is GRA's Vice President and Seminar Chair, and
the author of the Solvent Stabilizers White Paper. Mohr
is a hydrogeologist with the Santa Clara Valley Water District.
He organized the 1,4-dioxane symposium calling on contacts
from his continuing research on 1,4-dioxane and other solvent
stabilizers. tmohr@valleywater.org
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