3
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/A newsletter about soil, sediment, and ground-water characterization and remediation technologies
January 2005
Issue 16
Recentdiscoveries ofpreviously undetected but potentially hazardous chemical compounds in environmental media
havefocusedattentionontheneedforbetterunderstandingofthese ''emergingcontaminants.''Increasedidentification
of emergent contaminants in soil, sediment, and ground water isdueingreatpartto the development ofnew analytical
methods, as well as increased field testing. The high persistence and ground-water mobility of many emergent
contaminants often require the use ofex-situ cleanup technologies. This issue o/Technology News and Trends
highlights new analytical methods and innovative cleanup technologiesfortwo emergent contaminants, perchlorate
and1,4-dioxane.
Recent Developments in Analytical Methods for Emerging Contaminants
Development trends in analytical methods for
emerging contaminants were reviewed last year by
the U.S. EPA's National Exposure Research
Laboratory (NERL). In addition to methods for more
widely recognized contaminants such as perchlorate
and methyl terf-butyl ether (MTBE), tools were
examined for new high-priority compounds, such as
perfluorooctanoic acid (PFOA), polybrominated
diphenyl ethers (PBDEs), Pharmaceuticals, and
endocrine disrupting compounds (EDCs).
Mass spectrometry (MS) plays an increasing role in
contaminant identification and measurement and has
been enhanced through lower detection limits,
improved analytical instrumentation, and new
derivization procedures. The use of low-pressure gas
chromatography (GC) with GC/MS, for example,
proved to be a simple but important improvement to
traditional GC/MS analysis that allows for much
shorter analysis times. Other analytical techniques
that are used increasingly are:
> time-of-flight, quadrupole-ion trap, and Fourier
transform MS;
> chiral separations, usually with chiral GC or liq-
uid chromatography (LC) columns or with cap-
illary electrophoresis;
> on-line coupling of extraction with separation/
detection such as solid-phase extraction (SPE)
or solid-phase microextraction (SPME) coupled
withLC/MS;
> LC/MS/MSandGC/MS/MS;
> coupling of LC and ion chromatography (1C)
with inductively coupled plasma (ICP)-MS for
inorganics; and
> matrix-assisted laser desorption ionization
(MALDI)-MS and electrospray ionization
(ESI)-MS for microorganism/pathogen identi-
fication.
Some of the more significant research results in
emerging contaminants identified during the NERL
review included:
> Sensitive analytical techniques now allow for
more routine detection of perchlorate. 1C with
ESI-MS is emerging as an important tool for
analyzing perchlorate and other ionic contami-
nants in water due to its ability to provide high
specificity/sensitivity and sub-ppb detection
limits in different environmental matrices. Per-
chlorate in both water and soil can be detected
to levels of 0.05 ng/L and 0.5 ng/kg, respec-
tively, using newLC/ESI-MS/MS methods.
> Early research on the fluorochemicals, PFOA
and perfluorooctane sulfonate (PFOS), reveals
that both compounds display unexpected tox-
icity, persistence, and bioaccumulative ability.
LC/ESI-MS/MS commonly is used to obtain
ppb- to ppt-level measurements in environmen-
tal and biological samples. Little information is
available, however, on fluorochemical exposure
pathways, environmental occurrence, environ-
mental fate, or optimal cleanup technologies.
> PBDEs, which are commonly used as flame re-
tardants, also emerged due to their environmen-
tal persistence and potential adverse develop-
mental effects. While PBDEs are not regulated
in the U. S., Europe has established a directive
for control of their emissions. GC with EI-MS
and negative ion chemical ionization (CI) cur-
rently are used to detect PBDEs in biological
samples at low pg/g levels.
[continued on page 2]
Contents
Recent Developments
in Analytical Methods
for Emerging
Contaminants page 1
Fluidized Bed Reactor
and Ion Exchange
Systems Added for
Perchlorate Removal page 2
Ultraviolet and
Hydrogen Peroxide
Treatment Removes
1,4-Dioxane from
MultipleAquifers page 3
Containerized Wetland
Bioreactor Evaluated for
Perchlorate and Nitrate
Degradation page 5
CLU-IN Resources
The CLU-IN Contaminant Focus
area (http://vwvw.cluin.org/
contaminantfocus/) bundles
information associated with
cleanup of individual contami-
nants and contaminant groups,
which currently include
1,4-dioxane, chromium VI,
MTBE, perchlorate, PCBs, and
trichloroethene. Information is
presented on policy and
guidance, chemistry and
behavior, environmental
occurrence, toxicology, detection
and site characterization,
treatment technologies, and
conferences/seminars.
Recycled/Recyclable
Printed with Soy/Canola Ink or paper that
contains at least 50% recycled fiber
-------
[continuedfrom page 1]
I Newly-discovered EDC s, for which EPA is
required to develop screening and testing
strategies, were the subject of increased stud-
ies. Researchers are testing new GC/MS and
LC/MS/MS methods, as well as integrated
methods employing both biological and chemi-
cal procedures, for measuring EDCs in envi-
ronmental samples.
> Increased discovery of Pharmaceuticals in
surface water and ground water has led to
intensive study of their potential estrogenic
effects on humans and wildlife. Technologi-
cal improvements now allow field staff to
measure the occurrence of Pharmaceuticals
in surface and ground water and to examine
their fate in wastewater, where a few have
been found to be resistant to treatment. The
high polarity of Pharmaceuticals requires the
use of LC/MS and LC/MS/MS or an effi-
cient derivatization procedure combined with
GC/MS and GC/MS/MS for analysis at low
ng/L levels in environmental samples.
> Improved analytical tools were developed for
herbicide and pesticide degradation products,
which can exist in the environment at greater
concentrations and higher frequencies than their
parent compounds. The development of chiral
chromatography nowprovides for analysis of
individual isomers indicating the occurrence,
degradation, and environmental fate of chiral
pesticides. A new SPE-LC/ESI-MS method
also was developed to measure acetanilide her-
bicide (e.g., alachlor) degradation products in
ground water. For soil, an ion trap-LC/MS/
MS method was developed to identify addi-
tional metabolites of trifluralin, a complex pes-
ticide. Analytical instrumentation advanced
significantly through development of a super-
sonic GC/MS technique providing enhanced
molecular ions and rapid measurement of pes-
ticides in complex matrices.
Recent discoveries of emerging disinfection
byproducts (DBFs) such as nitrosodi-
methylamine (NDMA), halonitromethanes,
and iodinated DBFs (including iodo-acids)
were made in drinking water. NDMA also has
been found as a contaminant in ground water.
Analytical techniques for these emerging DBFs
involve derivatization with GC-ECD, SPE-
GC/MS, andpurge-and-trap-GC/MS. Ahighly
sensitive method for NDMA involves the use
of GC/CI-MS/MS, which allows low ng/L
U.S. EPA Websites
www.epa.gov
www.epa.gov/OGWDC/ccl/clfs.html
www.epa.gov/ogwdw/methods/methods.html
www.epa.gov/athens/publications/EPA 600 R02 068.pdf
www.epa.gov/safewater/mdbp/mdbp.html
www.epa/gov/mtbe
www.epa.gov/OGWDW/mtbe.html
www.epa.gov/safewater/arsenic. html
www.epa.aov/endocrine/
Topic
Agency-wide site, with searchable link
contaminant candidate list
analytical methods on drinking water
results of nationwide DBP occurrence study
EPAs microbial and DBP rules
MTBE
MTBE in drinking water
arsenic
EDCs
(ppt) detection. Exploration of LC/MS meth-
ods continues in efforts to identify highly
polar DBFs potentially missed in traditional
GC/MS methods.
> National security issues have generated ad-
vancements in methods for rapid detection
of chemical and biological warfare agents.
New developments include an automated
SPME-GC/MS method for measuring
2-chlorovinylarsonous acid in humans; a
packed capillary LC/ESI-MS method for iden-
tifying chemical warfare agents, their degra-
dation products, and related compounds in
soil samples; andMALDI-MS and LC/ESI-
MS methods for identifying botulinum tox-
ins.
As part of this review, NERL identified websites
containing related information on emergent
contaminants (Figure 1). Complete results of the
re view are available in the January 15,2004,issue
of Analytical Chemistry (Richardson, S.D.,Anal.
Chem. 2004, 76(12), 3337-3364).
Contributed by Susan D. Richardson, Ph.D.,
EPA/NERL (706-3 55-8304 or
richardson.susan(q)epa.gov)
This article has been reviewed in accordance
•with the U.S. EPAs peer and administrative
review policies and approved for publication.
Figure 1. New information on emergent
chemical-specific analytical methods,
regulations/standards, and technical studies is
continuously added to online resources.
Additional Website
www.dhs.ca.gov/ps/ddwem/chemicals/NDMA/NDMAindex.htm CA Department of Health Services, NDMA
Fluidized Bed Reactor and Ion Exchange Systems Added for Perchlorate Removal
Ground water beneath the GenCorp Aerojet
facility in Rancho Cordova, CA, is actively treated
by multiple-technology, ex-situ treatment systems,
three of which are designed to remove commingled
perchlorate andtrichloroethene (TCE). Perchlorate
removal is achieved through use of either a fluidized
bed reactor (FBR) or an ion exchange unit. The
first perchlorate-specific technology to be
implemented was the FBR, which was added to
an existing ground-water extraction and treatment
system in 1998 shortly after perchlorate was
discovered in the western portion of the site. In
2002, the ion exchange unit was added to a separate
treatment system to address perchlorate in another
TCE plume located in the northern portion of the
site. Both perchlorate treatment components
consistently have achieved perchlorate
concentrations below the 4 ug/L detection limit in
post-treatment effluent.
An FBR is a columnar reactor that optimizes
biological treatment of ground water through use of
activated carbon or sand serving as a medium for
biological growth. Water flows upward through
the reactor at a sufficient velocity to expand and
fluidize the bed. The design allows for a large
inventory of biomass to be maintained within the
reactor while maximizing contact between
microorganisms and contaminants. Additional
components of the system include continuous sand
filters to remove solids (primarily waste biomass)
and equipment to handle solids.
[continued on page 3]
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[continuedfrom page 2]
At Rancho Cordova, ground water extracted
through 21 wells is diverted to a system employing
four 14-foot-diameter, 22-foot-high bioreactors
operating in parallel (Figure 2). Each reactor
contains 44,000 pounds of carbon substrate to
which ethanol is added as an electron donor. The
FBRs are equipped with a bed-cleaning eductor
system that typically adjusts the reactor bed height
once each day. Retention time within each reactor
averages 12 minutes. The system has shown
capability to treat up to 5,400 gpm and currently
operates at arate of approximately 5,000 gpm.
Following FBR treatment, ground water is treated
in a UV/oxidation system to destroy NDMA and
an air stripping system to remove VOCs. Final
treated effluent is released onsite to surface water.
Approximately 90,000 gallons of wastewater
(0.5% solids) generated in the FBR process each
week are discharged to the sanitary sewer under an
existing permit. The FBR process completely
destroys perchlorate, without the need for offsite
waste disposal. To date, the FBR system has
removed 60 tons of perchlorate mass while treating
8.7 billion gallons of ground water. Operation and
maintenance of the system is estimated at
$0.15/1,000 gallons of treated water.
Supplied by 22 ground-water extraction wells, the
ion exchange unit operates in a separate area of the
facility. Prior to ion exchange treatment, ground
water is exposed to a dual/parallel air stripping
system for VOC removal, adjusted for pH by
adding carbon dioxide, and filtered through
5-micron bags for particulate removal.
Ground water then is routed to twelve 48-inch-
diameter ion exchange vessels arranged in two parallel
banks of six (Figure 3), which allows for operation
of a two-stage "lead/lag" treatment process operating
at a rate of 980 gpm. Each vessel contains 60 ft3 of
a "once-through" gel anion resin targeting
perchlorate removal. The lead stage removes the
bulk of perchlorate from ground water in the first
bank of vessels. Lag-stage operations in the second
bank continuously polish lead-stage effluent to
achieve a perchlorate concentration below 4 ug/L.
Final effluent from the ion exchange system returns
to the subsurface through six onsite recharge wells.
Once the lead-stage vessels are exhausted, reaching
their pre-set level of perchlorate breakthrough (30%),
they are removed from the system. The lead vessels
then are replaced with ones containing fresh resin
and switched to a lag-stage position through valve
changes. Spent resin is removed from the vessels
and disposed at an approved landfill as non-
hazardous waste.
Design of the ion exchange system allows for future
addition of ion exchange modules to accommodate
higher process flow if more recovery wells are
required. Use of a lead/lag design optimizes
expenditure of the ion exchange resin by allowing
higher perchlorate breakthrough concentrations in
effluent from the lead vessel, while still reaching
target concentrations of perchlorate in the lag-stage
effluent. On average, resin replenishment in each
vessel is required every 45 days. A total of
2,500 ft3 of resin was expended at an estimated
cost of $625,000 (including labor and disposal)
over the two years of operation. Use of the ion
exchange system has resulted in removal of
1,480 pounds of perchlorate mass while treating
850 million gallons.
Aerojet estimates that operation and maintenance
costs forthe combined treatment system average
$0.24/1,000 gallons. The FBR and ion exchange
systems are anticipated to operate indefinitely.
As an active member of the national Perchlorate
Study Group, Aerojet continues to evaluate
additional technologies that may accelerate ground-
water cleanup. Preliminary data from current pilot
tests on the use of in-situbioremediation to remove
perchlorate in soil and ground water show
promising results.
Contributed by Chris Fennessy, GenCorp
Aerojet (916-355-3341 or
christopherfennessy(q}qeroiet.com). Alex
MacDonald, California Regional Water Quality
Control Board (916-464-4625 or
amacdonald(Swaterboards.ca.gov). Bill
Guarini, Shaw Environmental (609-895-5384
or •william.guarini(S)shawgrp.com). and Tim
Peschman, USFilter (651-638-1325 or
veschm 'ter.com)
Ultraviolet and Hydrogen Peroxide Treatment Removes 14-Dioxane from Multiple Aquifers
Pall Life Sciences (PLS) operates a full-scale UV7
hydrogen peroxide (H202) system at its facility
near Ann Arbor, MI, to remediate ground water
containing high concentrations of
1,4-dioxane. Over 60,000 pounds of 1,4-dioxane
have been extracted from the ground water using
this combined technology since treatment began
in 1997. The Michigan Department of
[continued on page 4]
-------
[continuedfrom page 3]
Environmental Quality (DEQ) is overseeing
cleanup of the PLS site.
As former owners of the property, Gelman
Sciences Inc. used large quantities of 1,4-dioxane
from 1966-1986 for the production of
microporous filters. Onsite wastewater disposal
resulted in the release of 1,4-dioxane to ground
water, where multiple plumes developed. When
1,4-dioxane contamination was identified in the
mid- 1980s, ground-water concentrations were as
high as 221,000 ug/L, and several local drinking
water wells were affected. As defined by the State
ofMichigan residential drinking water criterion of
85 |xg/L, the plumes collectively encompass an
area of approximately 0.6 mi2.
Ground water is generally shallow, averaging 15
feetbelowgroundsurface. The subsurface consists
of glacial deposits that are up to 300-feet thick
and overlie the Mississippian-aged Coldwater
Formation (primarily shale), which serves as the
lower boundary of contamination. At least two
primary sand/gravel aquifers with differing ground-
water flow directions and rates exist within the
area's clay-rich deposits. 1,4-Dioxane has migrated
through these aquifers at least 8,000 feet from the
source areas.
Figure 1 portrays the general scheme of the PLS
treatment system. Eighteen purge wells, including
a 4,479-ft long horizontal well, are used to extract
and divert ground water to the PLS site, hi alined
pretreatment pond known as "the Red Pond,"
purged water is mixed with sulfuric acid
(93% solution by volume) in order to lower the
pH to 3.8, which earlier studies showed optimal
forUV/H202 chemical reactions.
hi the first step of treatment, a 50% FL^ solution
is inj ected into the treatment line and mixed with
ground water by a static mixer. Water then passes
through a multiple-chamber UV system
consisting of 22 lamps, where it is exposed to UV
radiation for approximately 5 seconds. After
UV/FF^ treatment, the pH of the treated water
is raised to approximately 6.9 by adding sodium
hydroxide (40% by volume) in order to meet
surface water discharge requirements of 6.5-9.0.
Sodium bisulfate also is added to remove excess
FLO prior to discharge onsite to a holding pond
known as "the Green Pond." The discharge is
monitored daily to ensure compliance with state
requirements. Under its NPDES permit, PLS can
extract, treat, and discharge up to 1,300 gpm. The
discharge is monitored daily to ensure compliance
with State requirements prior to its release into an
unnamed tributary of Honey Creek, which flows
into the Huron River.
Ground water is monitored routinely at 50-100
locations. Although treatment has only slightly
reduced the plumes' areal extent, 1,4-dioxane
concentrations within the plumes have decreased
significantly due to mass removal. A nearly
100-fold reduction in 1,4-dioxane concentrations has
been observed in some areas. Maximum 1,4-dioxane
concentrations in the plume are now less than
10,000 ng/L.
Large volumes of reactive chemicals are required for
treating ground water using the current UV/FL^
treatment system. The electrical demand also is high,
averaging approximately 660 kW/hr/day at a cost of
approximately $850/day. The overall treatment cost
using the UV/H20, treatment system is
approximately $3.50 71,000 gallons. PLS plans to
convert the UV/FFp2 system to an ozone/FL^-based
technology in 2005 in order to reduce H202
consumption by 50% and eliminate the need for
sulfuric acid and sodium hydroxide.
In the new system, which PLS is in the final stage of
designing, water from the extraction wells will be
transferred to a pre-treatment pond to settle non-
soluble iron. Following
settlement, water will be
transferred to a central
environmental building for
introduction of H£>2 through
injector quills. The water then
will be transferred to separate
units where ozone will be
administered through a series
of venturi injectors. The treated
water will be transferred back
to the environmental building
Figured The Pall Life Sciences
facility employs a dual technology
approach for treating 1,4-dioxane-
contaminated ground -water extracted
from a complex aquifer system.
for addition of post-treatment chemicals, if
necessary, and allowed to settle in a second pond
priorto surface water discharge. The new system
will reduce 1,4-dioxane concentrations at a rate
similar to UV/FL^ treatment while minimizing
production of bromate (a common byproduct of
ozone treatment of ground water containing
bromide). Treatment costs using the ozone/LL^-
based technology are anticipated to be
approximately $1.50/1,000 gallons.
Evaluation of alternative cleanup remedies capable
of removing contaminant mass from the aquifers
while maintaining hydraulic conditions is
underway. Last year, PLS conducted an in-situ
chemical oxidation (ISCO) pilot test involving
injection of FL^ and Fenton's reagent (iron
catalyst) into one of the confined aquifers, but a
minimal reduction of 1,4-dioxane concentrations
was achieved. Additional field testing of ISCO
using ozone resulted in a slightly higher rate of
removal, but bromate formation exceeded the
10 |og/L maximum contaminant level. Use of the
current pump-and-treat method is anticipated to
continueuntilthe 1,4-dioxanetargetcleanupcriteria
are reached.
Contributed by Jim Erode, Fishbeck Thompson
CarrandHuber (269-375-3824 or
iwbrode(a)FTCH.com). FarsadFotouhi, Pall
Corporation (734-913-6130 or
farsad_fotouhi(S)pall.com). and Sybil Kolon,
MichiganDEQ (517-780-7937 or
kolons(a)michizan. sov)
Topsoil & mix
Sand & silt
Clay
Sand & Gravel
Clay
Sand & Gravel
-------
Containerized Wetland Bioreactor Evaluated for Perchlorate and Nitrate Degradation
The U.S. Department of Energy (DOE) and
Lawrence Livermore National Laboratory (LLNL)
designedandconstructedan innovative containerized
wetland (bioreactor) system that began operationin
November 2000 to biologically degrade perchlorate
and nitrate under relatively low-flow conditions at a
remote location at Site 300 known as Building 854.
Since initial start-up, the system has processed over
3,463,000 liters of ground water and removed over
38 grams of perchlorate and 148 kilograms ofnitrate.
Site 300 is operated by the University of California
as a high-explosives and materials testing facility
supporting nuclear weapons research. The
11 -square-mile site located in northern California
was added to the NPL in 1990, primarily due to the
presence of elevated concentrations of VOCs in
ground water. At the urging of the regulatory
agencies, perchlorate was looked for and detected
in the ground water in 1999. VOCs, nitrate, and
perchlorate were released into the soil and ground
water in the Building 854 area as the result of
accidental leaks during stability testing of weapon
components or from waste discharge practices that
are no longer permitted at Site 300.
Design of the wetland bioreactors was based on
earlier studies showing that indigenous chlorate-
respiring bacteria could effectively degrade
perchlorate into nontoxic concentrations of
chlorate, chlorite, oxygen, and chloride. Studies also
showed that the addition of organic carbon would
enhance microbial denitrification. Early onsite
testing showed acetic acid to be a more effective
carbon source than dried leaf matter, dried algae, or
milk replacement starter (a nutrient and carbon
source used in a Department of Defense
phytoremediation demonstration).
Using solar energy, ground water is pumped into
granular activated carbon canisters to remove VOCs
(Figure 5). Following removal of VOCs, the
effluent, which contains approximately 46 mg/L
ofnitrate and 13 ug/L of perchlorate, is gravity-fed
continuously into two parallel series of two 1,900-
L tank bioreactors. Each bioreactor contains coarse,
aquarium-grade gravel and locally obtained plant
species such as cattails (Typha spp.), sedges
(Cyperus spp.), and indigenous denitrifing
microorganisms. No inocula were added to the
system. Ground water initially was allowed to
circulate through the bioreactor for three weeks to
acclimate the wetland plants and to build a biofilm
from indigenous flora. Sodium acetate is added to
the first bioreactor in each of the two series to
promote growth and metabolic activity of rhizome
microorganisms. The split flow from each series is
combined and flows through two back-up ion
exchange columns to assure complete perchlorate
removal. Effluent from the ground-water treatment
system ismonitored and discharged to an infiltration
trench in accordance with the Substantive
Requirements for Waste Discharge issued by the
California Regional Water Quality Control Board.
The solar-powered facility operates 10-15 hr/day,
depending on cloud cover, hours of sunlight, and
battery storage capacity. An active flow rate of
3.8 L/min is set to provide a minimum reactor
hydraulic retention time (HRT) of 17 to 20 hours.
As plants mature, the HRT requirement will increase
due to accumulation of organic debris and rootlets,
which decrease the available pore water space in
the tank. Test data showed that degradation of
perchlorate and nitrate, without an added carbon
source, required HRTs of four days and 20 hours,
respectively. In the presence of a 0.25 g/L solution
of sodium acetate, the HRT decreased to 0.5 days.
Treatment system samples are collected quarterly
from the influent and monthly from the effluent and
analyzed in a laboratory for VOCs, nitrate, and
perchlorate. Laboratory analysis for perchlorate in
influent and effluent ground water uses ion
chromatography in accordance with EPA methods
300.0 and314.0. Analytical results indicate that the
contained wetland reduces perchlorate
concentrations from 14-27 ug/L to Iessthan4 ug/L,
which is the analytical reporting limit. The State's
current public health goal is 6 ug/L. hi addition,
nitrate concentrations are decreased from 48 mg/L
to belowthe45mg/Ldischargerequirement Portable
field instruments are used to collect and analyze
samples for pH, electrical conductivity, and
temperature. In addition, treatment-system
optimization samples are collected quarterly from
the solar unit effluent and the bioreactor effluent for
analysis of VOCs, nitrate, perchlorate, and dissolved
oxygen. Over the course of operation, perchlorate
has been periodically detected in the bioreactor
effluent. Initial breakthroughs coincided with acetic
acid injection system problems, which were
corrected by replacing a venturi-type pump with
a peristaltic pump. More recent breakthroughs
were corrected by removing plant material from
the bioreactor.
Operation of the wetland bioreactor for more than
four years resulted in a stable ecosystem of
indigenous microorganisms. Dominant organisms
were identified through use of gradient gel
electrophoresis conducted on sediment samples
taken from noncontinuous, vertical coring of the
bioreactor. The bacteria species identified from
reactor gravel closely affiliated with species
commonly distributed in soils, mud layers, and
fresh water. Most of the bacteria (Pseudomonas,
Aanetobactet;Halomonas,andNitmspira)respye
aerobically or anaerobically with nitrate as the
terminal electron acceptor. Severalidentifiedgenera
[continued on page 6]
Contact Us
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-------
Solid Waste and
Emergency Response
(5102G)
EPA 542-N-05-001
January 2005
Issue No. 16
United States
Environmental Protection Agency
National Service Center for Environmental Publications
P.O. Box 42419
Cincinnati, OH 45242
Presorted Standard
Postage and Fees Paid
EPA
Permit No. G-35
Official Business
Penalty for Private Use $300
[continuedfrom page 5]
(Rhizobium, Acinetobacter, etcAXanthomonas) are
capable of fixing atmospheric nitrogen into a
combined form (ammonia) utilizable by host
plants. Isolates from the Proteobacteria class,
known for its ability to reduce perchlorate, also
were identified.
Environmental conditions in the wetland bioreactor
fluctuated with seasonal changes, even in
California's temperate climate. Seasonal average
ambient air temperature ranged between 7 to 11 °C
during the cold season, and between 17 and 26°C
during the warm season. Depending on the time
of day, wetland plants moderated water temperature
variations from 1 to 5°C. The influent water pH was
about 7.5, and the effluentwas about7.1, well within
regulatory discharge limits (6.5 to 8.5). The pH was
potentially moderated during the growing season by
biological carbon dioxide consumption (aquatic
photosynthesis). Bioreactor redox potential ranged
from -100 to -150 mV within a few weeks of
operation and establishment of the microbial
community and native plants. Measurements show
that active bacterial growth is consuming oxygen
within the bioreactor, generally causing redox values
to be in an anaerobic range (<0.5 mg/L for dissolved
W-854-03
Extraction
5% :
sodium
acetate
Solar
treatment
photovoltaic
array
VOC treatment
Volatile organic compound removal
Wetland bioreactors
Nitrate and perchlorate removal
oxygen). Dissolved oxygen in the effluent water
fluctuates with seasonal effects of the plant growth
cycle, metabolic activity in the bioreactor, and
acetic acid inj ection rate.
Results demonstrate that the wetland bioreactor
system can successfully remove commingled
perchlorate and nitrate from ground water in a
relatively short time (hours versus days) when
continuously provided with a carbon source. In
addition, the bioreactor degrades nitrate and
perchorate to non-toxic byproducts, eliminating
the need for costly waste disposal of ion-exchange
resin. Above-ground containerized wetlands are
easy to maintain and can be moved when cleanup
is complete without impacting the natural habitat.
Contributed by Valerie Dibley and Paula
Krauter,LLNL, (925-422-9777or
dibleymM.gov. and 925-422-0429 or
kmuter2(a)llnl.zov)
Figure 5. Constructed ecosystems at Site 300
employ sun, -wetlandplants, gravel,
microorganisms, and -water to trap and degrade
perchlorate and nitrate in ground -water.
EPA is publishing this newsletter as a means of disseminating useful information regarding innovative and alternative treatment techniques and
technologies. The Agency does not endorse specific technology vendors.
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