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Soil clean-up by bioremediation. Prof. dr. ir. W. Verstraete Dr. ir. N. Boon ir. W. Ossieur ([email protected]) Laboratory of Microbial Ecology and Technology (LabMET) Faculty of Bioengineering Ghent University LabMET.Ugent.be. Topics of discussion. General considerations - PowerPoint PPT Presentation
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1 Laboratory of Microbial Ecology and Technology
Soil clean-up by Soil clean-up by bioremediationbioremediation
Prof. dr. ir. W. VerstraeteDr. ir. N. Boonir. W. Ossieur
Laboratory of Microbial Ecology and Technology (LabMET)
Faculty of BioengineeringGhent UniversityLabMET.Ugent.be
2 Laboratory of Microbial Ecology and Technology
Topics of discussionTopics of discussion
General considerations
Ex situ clean-up by micro-organisms
In situ clean-up by micro-organisms
Future perspectives
3 Laboratory of Microbial Ecology and Technology
Topics of discussionTopics of discussion
General considerations
Ex situ clean-up by micro-organisms
In situ clean-up by micro-organisms
Future perspectives
4 Laboratory of Microbial Ecology and Technology
1.1. General ConsiderationsGeneral Considerations The 33 synthetic organic contaminants reported to be
most frequently found in drinking water wells (Rittman et al.,
1994)
Tetrachloroethene (PCE) Dichloromethane Benzene
Trichloroethene (TCE) Chloromethane Ethyl benzene
1,1-Dichloroethene (DCE) Bromoform Isopropyl benzene
1,2-Dichloroethene Ethylene dibromide Toluene
Vinyl Chloride Dibromochloropropane Xylene
1,1,1-Trichloroethane Dibromochloromethane Cyclohexane
1,1,2-Trichloroethane Trifluorotrichloroethane Acetone
1,2-Dichloroethane Gamma-BHC (lindane) Dioxane
1,1-Dichloroethane Alpha-BHC Di-n-butyl-phtalate
Carbon tetracloride Delta-BHC Butyl-benzyl-phtalate
Chloroform Parathion Bis-(2-ethylhexyl)-phtalate
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Many of these toxic compounds serve as food to some types of microbes.
Microbes can eliminate or neutralize many toxic
compounds in the environment
1.1. General considerationsGeneral considerations
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1.1. General considerationsGeneral considerations
The application of micro-organisms to clean-up contaminated sites is considered to be a sustainable solution because it is based on:
• the natural degradation capacity of the environment
• a minimal impact on the environment Firms and environmental consulting are the
interested parties for this application
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1.1. General ConsiderationsGeneral Considerations
The application of micro-organisms to realize the clean-up of contaminated soils can be done by 3 strategies:
– Natural Attenuation
– Biostimulation
– Bioaugmentation
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1.1. General ConsiderationsGeneral Considerations
Monitored Natural Attenuation (MNA):– In situ degradation by ‘indigenous’ bacteria under
natural conditions without intervention of human actions
– Actions: Monitoring of the degradation products produced by the indigenous populations
– Example:Perchloroethylene ethene, Dover (VS), Dehalobacter and Desulfitobacterium, Davis et al. (2002) Journal of Contaminant Hydrology, 57, 41-59.
Cl
Cl
Cl
Cl
Cl
Cl
H
Cl
H
Cl
H
Cl
H
Cl
H
HPCE TCE cis-DCE VC ethene
9 Laboratory of Microbial Ecology and Technology
1.1. General ConsiderationsGeneral Considerations
Principal criteria for the use of MNA– There must be solid indications that clean-up
can be achieved in a reasonable time-span (< 30 years);
– The processes must be aimed at the protection of the site and its surroundings;
– There must be transparent agreements on financial responsibilities over long-term periods, also if certain goals are not reached or unforeseen events occur;
– There must be proper geohydrological monitoring
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1.1. General ConsiderationsGeneral Considerations
Biostimulation:– Accelerated natural attenuation by human
intervention– Actions: in situ supplementation of
nutrients to the soil + monitoring of the degradation products produced by the stimulated indigenous population
– Example:Oil, Houston (VS), + inorganic nutrients and alternative electron acceptor, Mills et al. (2004) Marine Pollution Bulletin, 49, 425-435
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1.1. General ConsiderationsGeneral ConsiderationsBioaugmentation:
– The inoculation of bacteria into the soil to improve the specific biological activity
– If the degradation by indigenous populations delivers harmful products ordemands too much time
– Actions: in situ supplementation of bacteria and nutrients in the soil + monitoring of the degradation products of the inoculated and stimulated indigenous bacteria
– Example:Tetrachloromethane, Schoolcraft (VS), Pseudomonas stutzeri KC + acetate and nutrients, Dybas et al., (2002) Environmental Science and Technology, 36, 3635-3644.
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Topics of discussionTopics of discussion
General considerations
Ex situ clean-up by micro-organisms
In situ clean-up by micro-organisms
Future perspectives
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2.2. EEx situx situ clean-up by m.o. clean-up by m.o.
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2.2. EEx situx situ clean-up by m.o. clean-up by m.o.
Griftpark (Utrecht, 1996)– 10 ha, surrounded by bentonite clay wall
down to 50m into the clay layer– Time scale : 1-3 centuries!– Pump 10 m3/h water (~netto precipitation) to
1) Activated sludge
2) Decantor
3) Sandfilters
4) Activated carbon filter
+ biofilter
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2.2. EEx situx situ clean-up by m.o. clean-up by m.o.Griftpark (Utrecht, 1996)
– Time scale : 1-3 centuries!– Price :
• Investment: 150 x 106 EUR or 15 x 106 EUR/ha• Operation: 0,5 EUR/M3 water or 4000 EUR/ha.yr
In (µg/L) Out
COD 120 000
90-95% removal
CN 50
Phenols 250
BTEX 8 000
PAKs 5
Oil 14 000
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2.2. EEx situx situ clean-up by m.o. clean-up by m.o.
Membrane-aerated biofilm reactor– No undesired coagulation of iron oxides– No stripping of 1,2 dichloroethane (DCA)
(Hage et al., AMB 64, 718-725, 2004)
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2.2. EEx situx situ clean-up by m.o. clean-up by m.o.
Example: Pd-PCB
Biopalladium byBiopalladium byShewanella oneidensisShewanella oneidensis MR-1 MR-1
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2.2. EEx situx situ clean-up by m.o. clean-up by m.o.
Catalytic activity in solution?
PCB 21
IntermediatesBiphen
yl
ClCl
Cl
Cl
ClCl
ClCl
Cl
Cl Cl
Cl Cl
PCB 173
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-200
0
200
400
600
800
1000
0 50 100 150 200 250 300 350
-200
0
200
400
600
800
1000
0 50 100 150 200 250 300 350
-100
0
100
200
300
400
500
600
0 50 100 150 200 250 300
time (min)
Co
nc
en
tra
tio
n
(µg/
L)
0
50
100
150
200
250
300
350
400
0 100 200 3000
100
200
300
400
0 100 200 300
ClCl
Cl
ClCl
Cl
ClCl ClCl
ClCl
2.2. EEx situx situ clean-up by m.o. clean-up by m.o.
Catalytic activity in solution
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2.2. EEx situx situ clean-up by m.o. clean-up by m.o. Example: Budelco Groundwater containing:
several mg Zn2+/Lup to 1g SO4
2-/L
Groundwater to discharge
Biopaq – UASB reactor
Aerobic reactor with limited oxygen supply
SO42- S2-
Zn2+ + S2- ZnS To re-use
Excess of S2- S0 To re-use
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Topics of discussionTopics of discussion
General considerations
Ex situ clean-up by micro-organisms
In situ clean-up by micro-organisms
Future perspectives
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3.3. IIn situn situ clean-up by m.o. clean-up by m.o. Several in situ bioremediation strategies (MNA,
biostimulation, bioaugmentation), and several concepts to reach clean-up goals
None of them will be the solution for the total clean-up of a contaminated site (source versus plume)
None of them is the only answer for the problem
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Cl
ClCl
Cl ClCl ClCl
Cl
Cl
Cl
ClCl ClCl
ClCl
+ll
VCcis-1,2-DCETCE etheen
1,1,2-TCA 1,2-DCA
propeen1,2-DCP
Ethenes
Ethanes
Propanes
+l 0 -1/2 -l -3/2 -llOx. Degree C
resistance against reductive degradation
FAST DEGRADATION
UNDER ANAEROBIC CONDITIONS
PCE
SLOW DEGRADATION UDNER ANAEROBIC
CONDITIONS
3.3. IIn situn situ clean-up by m.o. clean-up by m.o.
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3.3. IIn situn situ clean-up by m.o. clean-up by m.o. Challenges for the anaerobic remediation of
chlorinated ethenes in groundwater– DNAPL formation (inaccessibility)– Microbial degradation mechanism:
reductive dehydrochlorination, but– Accumulation of recalcitrant and carcinogenic
intermediates: cis-DCE and VC due to:• Oxidation degree of the intermediates• Competition for hydrogen
– Complete degradation from PCE to ethene seems to be attainable if Dehalococcoides species are present, but it is not a guarantee!
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3.3. IIn situn situ clean-up by m.o. clean-up by m.o. Challenges for the anaerobic remediation of
chlorinated ethenes in groundwater (competition for H2) (required hydrogen pressure)
Complexfermententable
substrates
Simplefermententable
substrates
H2
PCE
TCE
TCE
cis-DCE
cis-DCE
VC
VC
C2H4
CO2 CH4 SO42- HS-
0,6-0,9 0,1-2,5
2-24
5-100 1-10
FBFB
DHB DHB MB SRB
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3.3. IIn situn situ clean-up by m.o. clean-up by m.o. The biodegradation of 1,2-dichloroethane by the
anaerobic halorespiring bacteria:Desulfitobacterium dichloroeliminans strain DCA1
The anaerobic strain respires 1,2-DCA and this process delivers energy!
Complete and fast degradationof high concentrations
No toxic intermediates like VC
1 mCl
Cl
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3.3. IIn situn situ clean-up by m.o. clean-up by m.o.In situ pilot test in contaminated aquifer
inoculum
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inoculuminoculum
Wolk Stam
DCA1
Wolk Stam
DCA1
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3.3. IIn situn situ clean-up by m.o. clean-up by m.o.In situ pilot test in contaminated aquifer
Injectionwell
0
200
400
600
800
1000
1200
1400
0 9 14 21 28 35
Time (day)
Co
nce
ntr
atio
n (
µm
ol/L
)
1,2-dichloorethaneEthene
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3.3. IIn situ n situ clean-up by m.o.clean-up by m.o. Intensive monitoring of:
• Physico-chemical parameters:pH, T, redox potential, D.O., conductivity
• Chemical parameters:decrease 1,2-DCA and increase etheneno detection of VC and CH4
• Molecular parameters:concentration strain DCA1 through specific molecular techniques
Goal: in situ biodegradation and to obtain data for the simulation of the transport and the activity of strain DCA1 with MOCBAC-3D
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3.3. IIn situ n situ clean-up by m.o.clean-up by m.o. Molecular confirmation of the transport of
strain DCA1 from the injection well towards the monitoring well
Activity of the robust strain DCA1 in the injection well and monitoring well confirmed by:– Strong decrease in the 1,2-DCA concentration (e.g. from
1142 to 1µM in a time interval of 36 days)– Increase ETHENE concentration– NO production of vinyl chloride and CH4
Excellent biodegradation capacity of strain DCA1 in reduced groundwater conditions
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3.3. IIn situ n situ clean-up by m.o.clean-up by m.o. The degradation of carbon tetrachloride
(CT): field evaluation of a full-scale bioaugmentation technique in a CT- and nitrate impacted aquifer (MI)
Inoculation of Pseudomonas stutzeri KC, a denitrifying bacterium that co-metabolically degrades CT without producing chloroform (CF)
Goal: to establish and maintain a “biocurtain” for CT degradation through– the intermittent addition of base to create
favorable pH conditions;
– inoculation strain KC;
– weekly addition of acetate (electron donor), alkali, and phosphorus.
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3.3. IIn situ n situ clean-up by m.o.clean-up by m.o.
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3.3. IIn situ n situ clean-up by m.o.clean-up by m.o. The degradation of CT:
– High CT removal efficiencies (median of 98-99.9%)
– Uniform removal efficiencies over a significant vertical depth (15 m), despite significant variability in hydraulic conductivity
– Similar levels of strain KC colonization(>105 strain KC/g)
– Sustained and efficient (98%) removal of CT has been observed over 4 yr
– Low levels of CF (<20 ppb) and H2S (<2 ppm)
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3.3. IIn situ n situ clean-up by m.o.clean-up by m.o. Approximately 18,600 m3
of contaminated groundwater was treated during the project
Closely spaced wells and intermittent substrate addition were effective means of delivering organisms and substrates to subsurface environments.
Dybas et al. (2002) Environ. Sci. Technol. 3635-3644
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3.3. IIn situn situ clean-up by m.o. clean-up by m.o.
Exxon Valdez (March 1989): spill of33.000 tons of crude oil in Alaska
3500-5500 sea otters out of a total population in the region of approximately 35.000
300000-675000 seabirds perished
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3.3. IIn situn situ clean-up by m.o. clean-up by m.o.
Oil degraders:– A lot of bacteria can degrade
environmental pollutants such as oil– Three modes of microbial uptake:
• Utilization of solubilized organic compound• Direct contact of cells (e.g. fimbrae)• Direct contact with fine substrate droplets
– Enhanced uptake by the production of biosurfactans
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3.3. IIn situn situ clean-up by m.o. clean-up by m.o.No biosurfactans => cells do not clump and do not stick to oil droplets
oil
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Biosurfactans cells stick to oil droplets
3.3. IIn situn situ clean-up by m.o. clean-up by m.o.
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Topics of discussionTopics of discussion
General considerations
Ex situ clean-up by micro-organisms
In situ clean-up by micro-organisms
Future perspectives
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4.4. Future PerspectivesFuture Perspectives A wide variety of bioremediation strategies can be
offered, based on the great diversity of ‘genetic capacity’ and ‘biological know-how’ present in the microbial ecosystem in the soil
These sustainable techniques can and will be applied in the future if:– They are proven to be safe– They are proven to offer protection to the
environment over a long-term periods (monitoring)– They are studied by interdisciplinary research– They are integrated with other clean-up strategies
to achieve a complete answer to the problem
42 Laboratory of Microbial Ecology and Technology
Take-home messageTake-home message
Microbial communities bring about a wide variety of powerfull processes.
We are able to use a number of these processes for soil clean-up purposes and to develop sustainabale and safe biotechnology-techniques.