Transcript remediation of nitrate-contaminated groundwater using a - CLU-IN

USE OF A UNIQUE BIOBARRIER TO REMEDIATE
NITRATE AND PERCHLORATE IN GROUNDWATER
Presented by Betty A. Strietelmeier
Los Alamos National laboratory
To 2001 International Containment and Remediation
Conference
Orlando, FL
June 10-13, 2001
Co-authors: M.L. Espinosa, J.D. Adams, P.A. Leonard, and
E.M. Hodge
Nitrate as a Contaminant
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Nitrate is a highly soluble anion that readily transports in
groundwater resulting in contamination of large subsurface areas
Many sites are affected by nitrate contamination
Large number of activities contribute to the problem:
– Farming, fertilization, animal feedlots, dairy
– Manufacturing of explosives, chemicals
– Nuclear industry, large amounts of nitric acid used to dissolve
metals and actinides
– Mining industry
Nitrate health effects can be severe
– “Blue baby syndrome” from oxygen depletion in bloodstream
– Increased rates of gastric cancer in susceptible adults
Biobarrier Concept
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Cost-effective solution to shallow groundwater
plumes
– Uses waste material, solves waste disposal
problem simultaneously
– Simple to use, just place in trench in path of
plume
– Material is durable, replacement not necessary
for many years, if at all
Biobarrier Concept, cont’d.
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Can be used with other barrier materials to
remediate multiple contaminants
– LANL Multi-Barrier system (4 different
sections)
– Multi-Barrier system removes colloids,
actinides and metals, nitrate, perchlorate and
other biodegradable organic compounds,
strontium and cesium
– Potential for use with high explosives,
petroleum hydrocarbons and halogenated
organic compounds
Biobarrier and Biofilms
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Biobarrier is carbon-based, biofilm forms on surface,
utilizes carbon for microbial growth, destroys nitrate
Porous material used to prevent plugging of biobarrier
Biofilm growth is not excessive, carbon released
slowly, provides for growth control
Development of biofilm takes time, only indigenous
organisms naturally present are used
Growth of selected population is based on
contaminants present, i.e. nitrate enhances growth of
denitrifiers
Nitrate Reduction Enzymes
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Assimilatory nitrate reductases
– Convert nitrate to ammonium compounds
– Provide nitrogen to cell for synthesis of amino acids,
other amino-based cellular constituents
– Not oxygen-sensitive, present in all microbial species
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Dissimilatory nitrate reductases
– Nitrate respiration, acts in place of oxygen as electron
acceptor in respiration, usually is oxygen sensitive
– Second to aerobic respiration in amount of energy
derived by microbial cell
– Reduction occurs at higher redox potential than for
redox-active metals and radionuclides
Dissimilatory Nitrate Reduction
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Two types of DNR, only one is true “denitrification”
First is carried out by many facultative anaerobes
– Nitrate reduced to nitrite and excreted
– Nitrite also can be reduced via hydroxylamine to ammonia
(nitrate ammonification process)
Second, true “denitrification” is carried out by denitrifiers
– Nitrate is sequentially reduced to nitrite, nitric oxide, nitrous
oxide and nitrogen gas
– A reductase enzyme carries out each reduction step
– Last three products are gases and can be lost to the atmosphere
Third type recently found in a bacterial species, single
denitrification enzyme present: nitrous oxide reductase which
converts N2O to N2, does not use nitrate or nitrite as substrate
Denitrification
(1)
(2)
(3)
(4)
NO3- ---> NO2- ---> [NO] ---> N2O ---> N2
+5
(1)
(2)
(3)
(4)
+3
+2
Nitrate reductase
Nitrite reductase
Nitric oxide reductase
Nitrous oxide reductase
+1
0
Biobarrier Laboratory Study
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Objectives of Study
– Determine effectiveness of carbon-based
material in supporting growth of a biofilm (i.e.
by providing carbon nutrient), and in nitrate
destruction (determine denitrification rates)
– Determine limits for nitrate levels degraded
– Quantify denitrifying microbial populations
– Determine the amounts of nitrite and ammonia
produced by system with time
– Determine if perchlorate reduction occurs
– Determine the pH in the biobarrier with time
Biobarrier Laboratory Study, cont’d.
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Investigated two biobarrier support
(nutrient) materials
– Pecan shells
– Pecan shells and dog food
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Mortandad Canyon groundwater used in
batch degradation studies
– Nitrate at natural concentrations (~25 mg/L or
0.5 mM)
– Nitrate spiked up to 600 mg/L (9.7 mM) nitrate
Biobarrier Laboratory Study, cont’d.
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Experimental set-up, 3 controls, 1 test
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1A/B - Water and support material are sterile
2A/B - Support material sterile, water non-sterile
3A/B - Water sterile, support material non-sterile
4A/B - Both water and support material non-sterile
5A/B - Sample of water used in experiment
Nitrate Concentration Range
– Background (~30 ppm) to 600 ppm nitrate
Biobarrier Laboratory Study, cont’d.
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Studies conducted in batch mode
– Ratio of 10 ml water to 1 g solid
– Ratio of 1 g pecan shells to 0.1 g dog food
Two sizes of containers, 20 ml or 100 ml
 Incubation at room temperature for up to 21
days
 Sampled periodically and analyzed for
nitrate, nitrite, ammonia, perchlorate and pH
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Analytical Methods
Nitrate, nitrite, ammonia and perchlorate Ion Chromatography (IC)
 Microbial cell counts - Most Probable
Number (MPN) technique with denitrifying
medium
 pH - hydrogen ion electrode
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Results of Study 9.7 mM (600 ppm)
Nitrate with Pecan shells
Results of Study, 9.7 mM (600 ppm) Nitrate
with Pecan shells and Dog Food
Nitrate Degradation Rates, Sterile Control with
Pecan Shells, Background to 600 ppm Nitrate
Nitrate Degradation, Non-Sterile Test with
Pecan Shells, Background to 600 ppm Nitrate
Nitrate Degradation, Sterile Control with Pecan Shells
and Dog Food, Background to 600 ppm Nitrate
Nitrate Degradation, Non-Sterile Test with Pecan
Shells and Dog Food, Background to 600 ppm Nitrate
Accumulation of Nitrate
Degradation Products
Pecan shell biobarrier system
Pecan Shell – 9.7 mM nitrate in MCO-5 Water
Day
Nitrate (mM) Nitrite (mM)
Ammonia (µM)
1
9.20
0
11
2
9.10
0
11
7
4.10
1.3
100
14
3.00
0.7
133
21
1.50
1.3
106
Accumulation of Nitrate
Degradation Products
Pecan shell/dog food biobarrier
system
Pecan Shell and Dog Food – 9.7 mM nitrate in MCO-5 Water
Day
1
2
7
14
Nitrate (mM)
6.22
2.58
0.01
0.02
Nitrite (mM)
2.3
4.1
0.9
1.5
Ammonia (µM)
156
217
778
794
21
0.02
1.9
806
Perchlorate Biodegradation
Microbial Quantitation (MPNs)
Denitrifying Most Probable Number (MPN) cell counts (cells/mL) in
MCO-5 water unamended with nitrate (i.e. ~30 ppm)
Sample Identification
1A-Sterile Control
1B-Sterile Control
2A-PS Sterile, H2O not
2B-PS Sterile, H2O not
3A-H2O Sterile, PS not
3B-H2O Sterile, PS not
4A-PS + H2O Unsterile
4B-PS + H2O Unsterile
Day 1
9.3E+04
9.0E+03
1.1E+04
3.4E+04
>1.1E+06
>1.1E+06
>1.1E+06
>1.1E+06
Day 7
9.3E+04
0.0E+00
>1.1E+07
>1.1E+07
>1.1E+07
>1.1E+07
>1.1E+07
>1.1E+07
Day 14
2.4E+05
0.0E+00
>1.1E+07
>1.1E+07
>1.1E+07
>1.1E+07
>1.1E+07
>1.1E+07
Day 21
1.1E+08
4.6E+07
>1.1E+08
>1.1E+08
>1.1E+08
>1.1E+08
>1.1E+08
>1.1E+08
pH Measurements
The pH of the Sterile Control (1A/B) and the Unsterile
Cultures (4A/B), pecan shells and pecan shell/dog food
systems in MCO-5 water, 9.7 mM nitrate (600 ppm)
Pecan Shells
Day
pH – 1A/B
1
5.7
2
5.4
7
7.3
14
7.4
21
7.2
nd = not determined
not determined
Pecan Shell + Dog Food
pH – 4A/B
pH –1A/B
pH – 4A/B
7.3
7.4
8.0
8.4
8.2
5.7
5.6
5.5
5.5
7.1
nd
6.1
5.8
5.3
5.6
Conclusions
Either biobarrier material will effectively
degrade nitrate up to 9.7 mM (600 mg/L) in
under two weeks
 Addition of dog food enhances the rate of
nitrate destruction, but increases production
of ammonia
 Healthy microbial population is present by
day 7 (>108 cells/ml)
 Perchlorate is reduced in biobarrier, but more
investigation of interferences is needed
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Future Work
Investigate more fully the effectiveness of
biobarrier in reduction of perchlorate
 Determine perchlorate concentration range over
which biobarrier is effective
 Investigate effectiveness of biobarrier in
destruction of other biodegradable organics such
as petroleum hydrocarbons, high explosives,
chlorinated hydrocarbons and PAHs
 Investigate microbial populations and community
structure using molecular tools
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