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Distinguishing Natural from
Anthropogenic Perchlorate
Paul B. Hatzinger, Shaw Environmental, Inc.,
Lawrenceville, NJ
Column Studies on Perchlorate
Reduction by Autotrophic Bacteria in the Presence of
Zero-Valent
Iron
Mark R. Matsumoto, University of California, Riverside,
Riverside, CA
Perchlorate Reduction in a Packed
Bed Bioreactor Using Elemental Sulfur
Ashish K. Sahu, University of Massachusetts, Amherst,
MA
Demonstration of Active and
Semi-Passive Approaches to In Situ Bioremediation of
Perchlorate in Groundwater
Thomas Krug, GeoSyntec Consultants, Guelph, ON, Canada
Removal of Perchlorate from Drinking
Water and Ion Exchange Regenerate Brines
Brian Dougherty, Electrochemical Design Associates,
Inc., Emeryville, CA
Lessons Learned for Future Designs
from Thermal Treatment of Perchlorate in Soil
Shouvik Gangopadhyay, ECC, Camp Edwards, MA
Distinguishing
Natural from Anthropogenic Perchlorate
Paul B. Hatzinger, Ph.D., Shaw Environmental, Inc.,
17 Princess Road, Lawrenceville, NJ
08648, Tel: 609-895-5356, Fax: 609-895-1858, Email:
paul.hatzinger@shawgrp.com
Neil C. Sturchio, Ph.D., University of Illinois at
Chicago, 845 West Taylor Street, Chicago, IL 60607, Tel:
(12-355-1182, Fax: 312-413-2279, Email: sturchio@uic.edu
J. K. Böhlke, Ph.D., US Geological Survey, 431 National
Center, 12201 Sunrise Valley Drive, Reston, VA 20192, Tel:
703-648-6325, Email: JKbohlke@usgs.gov
W. Andrew Jackson, Ph.D., Texas Tech University, Lubbock,
TX 79409, Tel: 806-742-2801 (230), Fax: 806-742-3449,
E-mail: Andrew.jackson@ttu.edu
Baohua Gu, Ph.D., Oak Ridge National Laboratory, P. O. Box
2008, Oak Ridge, TN 37831, Tel: (65-574-7286, Fax:
(65-576-8543, gub1@ornl.gov
Until recently, it was assumed that
all of the reported groundwater impacts from perchlorate
resulted from
historical disposal practices by the military, the
aerospace and ordnance industries, and perchlorate
manufacturers. However,
new evidence suggests that Chilean nitrate fertilizer and
natural mineral sources in the United States may also
contribute to groundwater and drinking water
contamination. The
overall extent to which natural
sources add to groundwater pollution is unknown,
but there are numerous perchlorate plumes for which
military or industrial sources are unlikely, and natural
sources are suspected.
Stable isotope ratio analysis has been widely used
to document the origin and geochemical behavior of both
organic and inorganic pollutants.
Recently, isotopic methodologies have also been
developed for perchlorate, and these techniques have been
used to analyze a wide variety of man-made and natural
perchlorate sources.
The isotopic signatures of chlorine (37Cl:
35Cl ) and oxygen (18O: 16O)
in these materials have been observed to differ
significantly between naturally-occurring and
anthropogenic perchlorate.
In addition, the natural perchlorate analyzed to
date is characterized by a positive D17O, which
is not observed for any of the man-made material.
A sampling procedure utilizing custom ion exchange
columns has been developed to collect adequate quantities
of perchlorate for isotopic analysis (i.e., 5 - 10 mg)
from dilute groundwater plumes.
Sampling is currently underway at several locations
for which perchlorate origin is unknown. In combination with other key hydrogeological and geochemical
parameters, stable isotope analysis is expected to provide
critical evidence for perchlorate origin in groundwater.
An overview of stable isotope analysis and its application
for perchlorate forensics will be provided.
Column
Studies on Perchlorate Reduction by Autotrophic Bacteria
in the Presence of Zero-Valent Iron
Xueyuan Yu, Dept. of Chemical and Environmental
Engineering, University of California, Riverside,
Riverside, CA 92521, Tel: 951-827-2956, Fax: 951-827-5969,
Email: xyu@engr.ucr.edu
Christopher Amrhein, Dept. of Environmental Sciences,
University of California, Riverside, Riverside, CA 92521,
Tel: 951-827-5196, Fax: 951-827-5196, Email:
christopher.amrhein@ucr.edu
Marc A. Deshusses, Dept. of Chemical and Environmental
Engineering, University of California, Riverside,
Riverside, CA 92521, Tel: 951-827-2477, Fax: 951-827-5696,
Email: mdeshuss@engr.ucr.edu
Mark R. Matsumoto, Dept. of Chemical and
Environmental Engineering, University of California,
Riverside, Riverside, CA 92521, Tel: 951-827-3197, Fax:
951-827-5696, Email: matsumot@engr.ucr.edu
Recently, the presence of perchlorate contaminated ground
water has been a rising concern in the USA.
To treat perchlorate contaminated ground water,
bioremediation is the preferred strategy as ClO4-
is converted to chloride and eliminated from the
environment. H2
is the favored energy source for the perchlorate reducing
microorganisms (PRMs) as it does not result in excess
biomass growth and can be more cost-effective than organic
compounds. As
an alternative to supplying external H2 gas,
zero-valent iron (ZVI) can serve as the ultimate electron
donor by supplying H2 in-situ
to PRMs via the iron corrosion process.
In primary batch experiments of this research,
combined ZVI-Dechloromonas
sp. HZ successively reduced perchlorate at increasing
degradation rates when perchlorate was added in successive
cycles. Effects
of pH, nitrate, cell density, and iron activity on the
performance of ZVI-PRMs were also evaluated.
As a follow-up to that study, flow-through column
experiments were conducted to evaluate basic operation
variables such as influent composition, flow rate,
perchlorate concentration, nitrate concentration and cell
density on the reduction process.
In the first column experiment, ZVI (570 g, 18/25 mesh) was
packed into a glass column (2.5 cm ID. x 50 cm) and
inoculated with a relatively small amount of biomass (OD600=0.015).
This was operated at a fixed flow rate of 3.6 mL/hr
(Velocity=0.17 m/d, EBCT=63 hours) to simulate the
movement of ground water in a field scale iron wall.
At the influent concentration of 500 ppb,
perchlorate removal (>99%) was achieved and maintained
for both reagent-grade solution and perchlorate-amended
tap water.
In the second experiment, ZVI-filled columns (3.8 cm ID. x 60
cm) were run at relatively high flow rates up to 4.5 L/hr
(Velocity = 95 m/d, HRT = 9 min).
Two columns were inoculated with relatively large
amounts of biomass (OD600=1 and 3,
respectively). In
a third column, soil obtained from a rapid infiltration
wastewater treatment plant (Colton, CA) was placed in the
first 20 cm of the column and followed by 30 cm of ZVI
with no other bacterial amendment.
The final column operated as a control containing
only ZVI with no bacterial addition.
Perchlorate degradation profiles along the flow
path were monitored with time.
At the influent concentration of 500 ppb, complete
(RE >99%) perchlorate removal was observed in both of
the bacterial-amended ZVI columns at flow rates ranging
from 7 to 50 mL/min (HRT=14 to 98 min). In the soil
amended column, no reduction of perchlorate was observed
in the soil layer; however, reduction through the iron
layer was observed with complete removal of perchlorate at
flow rates ranging from 7 to 30 mL/min (HRT=15 to 65 min).
Minimal perchlorate reduction was observed in the
control column, confirming that the reduction of
perchlorate was biological rather than chemical.
When influent perchlorate concentration was varied
between 30 and 1000 ppb, the best overall results were
achieved in the soil-amended column.
At an influent perchlorate concentration of 30 ppb,
perchlorate breakthrough (> 6 ppb) was observed only
when the molar ratio of nitrate to perchlorate was greater
than 1000:1 in the soil-amended column.
These studies demonstrate the feasibility of using
biologically active ZVI for large-scale treatment of
perchlorate-contaminated water.
Perchlorate
Reduction in a Packed Bed Bioreactor Using Elemental
Sulfur
Student
Presenter
Ashish K
Sahu, University of Massachusetts, 18 Marston Hall, Department of Civil and
Environmental Engineering, Amherst, MA, 01003, Tel:
413-577-3229, Fax: 413-545-2202, Email: aksahu@acad.umass.edu
Sarina J. Ergas, University of
Massachusetts, 18 Marston Hall, Department of Civil and
Environmental Engineering, Amherst, MA, 01003, Tel:
413-545-3224, Fax: 413-545-2202, Email: ergas@ecs.umass.edu
Perchlorate release in groundwater
has affected water supplies to approximately 15 million
people in the US and has primarily occurred in association
with manufacturing of missiles, rockets, fireworks and
industrial processes. Presently, perchlorate contamination
has been recorded in drinking water in 38 US states. The
Commonwealth of Massachusetts has proposed limits on
perchlorate of 1 mg/L because of adverse effects to the
thyroid. Although perchlorate is on the EPA contaminant
list, no standards have been set so far.
Various researchers and have found
that perchlorate can be used as an electron acceptor in
anaerobic microbial metabolism. A variety of electron
donors including H2, ethanol, acetate and sugar
derivatives have been investigated for perchlorate removal
using both mixed and pure cultures.
This study investigated a novel
process for treatment of perchlorate contaminated water
using elemental sulfur as an electron donor.
A microbial culture capable of coupling sulfur
oxidation with perchlorate reduction was enriched from a
denitrifying wastewater inoculum under anaerobic
conditions. Microbial biomass was added to flasks
containing elemental sulfur, crushed oyster shell and 5
mg/L ClO4- . An initial
acclimatization period of approximately 15 days was
observed, after which perchlorate was reduced to below
detection limits (500ppb).
Subsequently, the cultures were
inoculated into an upflow bioreactor packed with elemental
sulfur and crushed oyster shell media. Groundwater
containing ~5 mg/L of ClO4- was
continuously fed to the column at an initial hydraulic
retention time (HRT) of 53 hours. HRT was optimized to 13
hour over the first three months of operation.
Intermittent recirculation resulted in faster degradation
of perchlorate, possibly due to more uniform distribution
of the biomass through the column. The column is presently
being operated with low levels of perchlorate (100 ppb)
and with other co-contaminants, which shall be discussed
at the meeting.
Demonstration
of Active and Semi-Passive Approaches to In
Situ Bioremediation of Perchlorate in Groundwater
Thomas Krug, GeoSyntec Consultants, 130
Research Lane, Guelph, Ontario, Canada, N1G 5G3, Tel:
519-822-2230, Fax: 519-822-3151, Email: tkrug@geosyntec.com
Evan E. Cox, GeoSyntec Consultants, 130 Research Lane, Guelph,
Ontario, Canada, N1G 5G3, Tel: 519-822-2230, Fax:
519-822-3151
David M. Bertrand, GeoSyntec Consultants, 130 Research
Lane, Guelph, Ontario, Canada, N1G 5G3, Tel: 519-822-2230,
Fax: 519-822-3151
John D. Coates, Department of Plant and Microbial Biology,
University of California, Berkeley, Berkeley, CA 94720,
Tel: 510-643-8455, Email: jcoates@nature.berkeley.edu
Bryan Harre, Navel Facilities Engineering Service Center,
1100 23rd Ave, Code 441
, Port Hueneme, CA 93043,
Tel: 805-982-1795, Email: harrebl@nfesc.navy.mil
In situ bioremediation is increasingly being used to treat
perchlorate-impacted soils and groundwater.
Groundwater bioremediation demonstrations have
routinely reduced perchlorate from starting concentrations
ranging from 250 to 500,000 µg/L to less than the
practical quantitation limit (PQL) of 4 µg/L using a
variety of electron donors and varying delivery
configurations. Provided that electron donor addition is balanced with the
electron acceptor demand, perchlorate biodegradation can
be accomplished without unduly impacting groundwater redox
and quality, maintaining the groundwater as a valuable
resource. Approaches
that inject large batches of soluble or slow-release
electron donors (e.g., molasses, edible oils, HRC) tend to
adversely impact groundwater quality by producing
significant methane and sulfide, and by mobilizing metals
such as manganese and iron making these approaches
unsuitable for many sites.
GeoSyntec has received funding from ESTCP (Project CU-0219)
to demonstrate semi-passive and active in situ
bioremediation approaches for perchlorate-impacted
groundwater. The
semi-passive approach has been demonstrated at the
Longhorn Army Ammunitions Plant (LHAAP) in northeast
Texas. The
data from the demonstration show that significant
reductions in perchlorate concentrations can be achieved
using the semi-passive biobarrier system for in situ
bioremediation of perchlorate without having significant
impacts on secondary water quality characteristics.
The active approach is being demonstrated at the Naval
Industrial Reserve Ordnance Plant (NIROP) facility in West
Valley City, Utah. Extraction
and re-injection wells have been installed at the site in
a line perpendicular to the direction of groundwater flow.
Groundwater is being extracted, amended with
electron donor and reinjected on a continuous basis.
The concentration of electron donor is being
limited to provide just enough electron donor for
perchlorate degradation but not enough to have significant
impacts on secondary water quality characteristics.
Results from both demonstrations will be presented.
Removal
of Perchlorate from Drinking Water and Ion Exchange
Regenerant Brines
Brian Dougherty, Electrochemical Design
Associates Inc. 5705 Hollis Street, Emeryville CA 94608, Tel:
510-463-0233, Fax: 510-217-6826, Email: brian-d@e-d-a.com
Stephen Harrison. Electrochemical Design Associates Inc.
5705 Hollis Street, Emeryville, CA 94608, Tel:
510-463-0231, Fax: 510-217-6826, Email Stephen-h@e-d-a.com
Chulheung Bae, Electrochemical Design Associates, 5705
Hollis Street, Emeryville, CA 94608, Tel: 510-463-0340,
Fax: 510-217-6826, Email: chul-b@e-d-a.com
Perchlorate
ions from rocket fuel, flare and munitions manufacture and
use have escaped into groundwater in several states in the
USA. Perchlorate
causes alarm because it mimics iodine physiologically and
is adsorbed by the thyroid gland, subsequently interfering
with the endocrine systems of the brain. Removal of
perchlorate to very low ppb is difficult on two fronts:
competing ions such as nitrate, sulfate, carbonate
etc. are often present at 1000 times higher concentration
than perchlorate, and perchlorate is surprisingly stable
considering its reputation as a rocket fuel oxidant.
Direct electrochemical reduction of perchlorate in the
parts per billion range is too slow and expensive to be
viable. Ion exchange produces a troublesome disposal
problem: either a perchlorate laden ion exchange resin; or
a brine stream containing high concentrations of
perchlorate, nitrate, sulfate and bicarbonate.
Electrochemical redox
reduction of perchlorate, coupled to ion exchange
capture and concentration is an economic and elegant
method of dealing with both nitrate and perchlorate,
particularly if the kinetics of the reduction process are
fast. Perchlorate is surprisingly stable to reduction at a
reducing cathode and with common reducing redox ions such
as Cr2+ and Fe2+.
The reduction of perchlorate with Ti3+
is well documented in the literature, but the kinetics are
slow in common solutions.
In our latest study, we have discovered that the
reaction of perchlorate with titanium ions in
methanesulfonic acid is very fast.
We describe the laboratory experiments and pilot
plant field trials in California that demonstrate the
utility of this method for removing perchlorate and
nitrate directly from drinking water and from regenerant
brines from ion exchange systems.
Lessons
Learned for Future Designs from Thermal Treatment of
Perchlorate in Soil
Shouvik Gangopadhyay, ECC, PB 519 Gaffney Road, Camp
Edwards, MA 02542, Tel: 508-563-9767x135, Fax:
508-563-7659, Email: sgangopadhyay@ecc.net
Paul Nixon, Impact Area Groundwater Study Program, 1803
West Outer Road, Camp Edwards, MA 02542-5003, Tel:
508-968-5620, Fax: 508-968-5286, Email: paul.nixon@us.army.mil
Scott Michalak, United States Army Corps of Engineers, 696
Virginia Road, Concord MA 01742-2751, Tel: 978-318-8350,
Fax: 978-318-8663, Email: Scott.C.Michalak@nae02.usace.army.mil
A soil remediation project, using ex-situ thermal treatment
to remove explosives, was modified at the latter stages of
planning to include treatment of perchlorate. The
design-build approach consisted of a bench scale study,
and pilot testing. The bench-scale study verified
treatability of perchlorate via thermal destruction and
established baseline treatment conditions. Pilot scale
studies, conducted with soil spiked with known
concentrations of perchlorate, allowed confirmation of
laboratory results and defined the process parameters for
successful full-scale treatment.
The project specific treatment goal for perchlorate was 4
ppb. The pilot tests results revealed a reduction in
treatment effectiveness at elevated perchlorate
concentrations in the feed soil. During initial
full-scale operations, a high rate of treatment failures
was experienced. Analytical results of samples collected
from various stages along the treatment train indicated a
potential for a portion of the perchlorate-contamination
to by-pass the primary treatment process. This potential
would likely be higher with greater concentration of
perchlorate in the feed soil, explaining the reduction in
treatment efficiency. Slower feed rates and higher
operating temperature did not show any conclusive positive
impact on treatment efficiency. Recycling the particulates
from the air pollution control equipment back into the
feed soil was initially considered, but was deemed
infeasible with the current equipment design. A
cost-effective solution was achieved by reducing the size
of the treated soil sample batch volume to analyze for
perchlorate more frequently, thereby reducing the amount
of soil requiring re-treatment. The initial re-treatment
rate of 30% dropped to 1.33%
after the process was modified, resulting in an overall
11% re-treatment rate for the entire project. Future
plant designs intended for treatment of perchlorate to
very low concentrations goals potentially improve
destruction efficiency by recycling particulates to the
beginning of the process instead of the treated soil
discharge.
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