Ian Ross Ph.D, Mike Mueller and Philip Block Ph.D. (FMC Environmental Solutions)
Introduction
In Situ Chemical Oxidation ad Bioremediation
The application of in-situ chemical oxidation (ISCO) technologies, which are based on the delivery of oxidising
agents to contaminated source zones in order to oxidise contaminants into harmless end products within the soil
mass, is a promising method for remediation of multiple contaminants. Typical oxidants used traditionally have
included potassium permanganate, hydrogen peroxide (Fenton’s reagent) and ozone. Each of these oxidants has
it’s limitations (e.g. persistence, reactivity etc.) within a soil matrix. Klozur® persulfate (Na2S2O8) is a more recent
addition to the list of possible oxidants for use within ISCO applications and possesses multiple advantages as
compared to more traditional oxidants.
The application of in-situ chemical oxidation (ISCO) will cause destruction of organic compounds, so it will also cause
some micro-organisms to be killed in locations where the oxidant is distributed. However, the oxidant does not
distribute throughout he whole aquifer formation, groundwater containing micro-organisms will flow back in to the
oxidised zone and microbial populations are very resilient as they are often present as biofilms and encapsulated in
exopolysaccharides, glycoprotein and glycolipids. Thus microbial growth in aquifers following application of ISCO is
commonplace and there is usually a bacterial recolonisation event following oxidation which occurs as subsurface
conditions are more favourable as a results of an increase of terminal electron acceptors, such s oxygen, sulfate, ferric
iron etc.
1. Direct Oxidation:
Impact of ISCO on Sulfate Reducing Bacteria (SRBs)
After ISCO the residual sulfate and oxygen from persulfate can be used by aerobic or sulphate reducing bacteria to
continue to biodegrade any residual hydrocarbons . The addition of both oxygen and/or sulfate as remedies for
petroleum hydrocarbon impacted soil and groundwater are well know technologies, so the benefits of theses terminal
electron acceptors following oxidation can be exploited to allow further contaminant destruction. With this in mind
FMC evolved a novel product where activation of persulfate is promoted using Permeox Plus which comprises calcium
peroxide to promote high pH activation and also releases oxygen to promote aerobic biodegradation. The product is
called Klozur CR (combined remedy) which comes as a solid which can de dissolved in water and injected into the
subsurface.
S2O8-2 + 2H+ + 2e-  2HSO4-1
persulfate anion
A stoichiometric equation can be derived e.g. for PCE
2S2O8-2 + C2Cl4 + 4 H2O  2CO2 + 4Cl- + 4H+ + 4HSO4-1
3 kg / kg
2. Radical Formation
“Klozur CR (Combined Remedy)”
S2O8-2 + activator  SO4•- + (SO4•- or SO4-2)
Klozur ® Persulfate
NaOH
Heat
Kinetically Fast (Reaction Kinetics with Contaminant)
Capable of Destroying Wide Range of Contaminants
Increases solubility of contaminants in water
Temperature Range: 35 – 45º C
H2O2
Iron
Hydrogen Peroxide
Chelated Iron
Slower Reaction Kinetics (Extends
Persulfate Lifetime in Subsurface)
Capable of Destroying: Chlorinated
Ethenes, BTEX,
PAHs, MTBE
Target in Groundwater: 75 – 100
ppm soluble Fe
Kinetically Fast (Reaction Kinetics with Contaminant)
Capable of Destroying Wide Range of Organics
Benefit of two powerful radical species.
Typical Concentration Ratio: 5:1, moles peroxide : mole persulfate
+
for up to one year
• stimulate aerobic
bioremediation
CaO2 + 2 H2O → H2O2 + Ca(OH)2
S2O82- → SO4·- , OH·-
2 H2O2 → O2 + 2 H2O
W. Michigan Lab Study -Prof. Dan Cassidy
• contaminated sediments from Kalamazoo River
• initial contaminant loadings
• 7720 mg/kg PCB
• 9063 mg/kg PAHs
• 175 ug/kg total Hg
• study incorporated 3 dosages
• 4 g Klozur / kg sediment
• 10 g Klozur / kg sediment
• 20 g Klozur / kg sediment
A study of the ability of Klozur persulfate to degrade
recalcitrant organic compounds including PCB’s and
PAH’s in addition to methyl mercury (MeHg), was
performed using contaminated sediments in a stirred
tank reactor (pictured above). The higher dose of
persulfate caused significant contaminant destruction.
However, following treatment the microbial
population in the reactor was monitored and
sulphate reducing bacteria were seem to recolonise
the reaction vessel. The sulphide produced from
biological activity also complexed the mercury,
removing it from solution.
groundwater
ISCO
• Provides the strength of “Fenton’s Chemistry” but with extended subsurface lifetime (3 – 4 months) and little to
log MPN/g soil
• Activated Persulfate is a strong oxidant used for in situ and ex situ destruction of contaminants in soil and
Bioremediation
no heat or gas evolution
•
Applicable across a broad range of organic contaminants
• Effective activation method is based on contaminant, site lithology, and hydrogeology
Klozur® persulfate can destroy all organic compounds dissolved in water, however the kinetics of this reaction
can be controlled using differing activators. Examples of differing organic contaminants that Klozur ®
persulfate can mineralise are presented below, however further compounds such BTEX, TCA, TCE, PCE,
pharmaceuticals and pesticides can also be mineralised.
Examples of Contaminants Destroyed by Klozur Persulfate
Freons
Phenols
phenol
Pentachlorophenol
nitrophenol
PAHs
Anthracene
Benzopyrene
Styrene
Naphthalene
Pyrene
Chrysene
trimethylbenzene
Oxygenates
MTBE
TBA
FMC, Klozur, EHC, ISGS, DARAMEND, TERRAMEND, and PermeOx are registered trademarks
of the FMC Corporation. Copyright ©2012 FMC Corporation. All rights reserved. 21-01-EIT-DL
Chlorobenzenes
Chlorobenzene
Dichlorobenzene
trichlorobenzene
TPH
BTEX
GRO
DRO
ORO
creosote
Pesticides
DDT
Chlordane
Heptachlor
Lindane
Toxaphene
MCPA
Bromoxynil
Others
Carbon disulfide
PFOS / PFOA
Aniline
PVA
TNT / DNT
Properties
• formulated as a slurry
•
pH ~ 11
Single Product to add
to water and inject,
provides both ISCO
and Bioremediation
• Activation produces a radical which is powerful and kinetically fast
Chlorinated Solvents
PCE, TCE, DCE
TCA, DCA
Vinyl chloride
Carbon tetrachloride
Chloroform
Chloroethane
Chloromethane
Dichloropropane
Trichloropropane
Methylene chloride
% reductions from control
Dose
MeHg1
(%)
PCB2
(%)
PAH2
(%)
NOM
(%)
Dose 1
>99.96
31
27
22
Dose 2
>99.96
59
61
37
Dose 3
>99.96
91
88
43
1
time= 5-10 days
2
time= 4-8 weeks
MPN of Sulfate Reducing Bacteria (SRB)
Typical Application
• Direct push injection
• Emplacement (excavations, barrier walls)
Source Zone
ISCO applied first in
source zone
Injection well
Down gradient
plume
Bio applied in plume
groundwater flow
monitoring well
• Activated persulfate will not sterilize soil /
groundwater
• 20 – 30% initial drop in microbial
population observed for both aerobic and
anaerobic species
• Rebound of microbial species observed,
sometimes greater than initial concentrations
• Cell utilization of contaminant substrate will be
influenced but not halted
• Calcium peroxide – activated persulfate is
effective on TPH / BTEX compounds
• SRB’s can be stimulated by residual sulfate
Dose 1
Dose 2
Dose 3
2
4
6
8 10 12 14 16 18 20 22 24 26 28 30
Time (weeks)
HgS formation after 30 weeks
Sulfide Production
400.0
Dose
Control
Conclusions
Control
0
Target Compounds
•
TPH, BTEX, MTBE, PAHs
•
Chlorobenzene, Phenols etc.
Treatment Train Approach
8
7.5
7
6.5
6
5.5
5
4.5
4
3.5
3
Dose 1
Dose 2
[HgS] (μg/kg)*
22.5
104.7
135.2
% total Hg
11.1
51.6
66.6
Sulfide Conc. (mg/L as S)
High pH
Heat
PermeOx® Plus
• slow release of oxygen
• ISCO for 2 – 3 months
• self-activating high pH persulfate
• residual sulfate to stimulate
anaerobic bioremediation of
hydrocarbons
Kinetically Fast (Reaction Kinetics with Contaminant)
Capable of Destroying Wide Range of Organics
pH between 10.5 – 12 (maintained while the Klozur
is present)
Pre-treatment titration is needed to determine the
soil’s buffering capacity
[email protected] +44 7855745531
350.0
300.0
Control
250.0
Dose 1
200.0
Dose 2
150.0
Dose 3
100.0
50.0
0.0
Dose 3
169.7
83.5
0 2 4 6
8 10 12 14 16 18 20 22 24 26 28 30
Time (weeks)
*[HgS]=203 μg/kg if all Hg precipitated as cinnabar.
Conclusions
•
•
•
•
No MeHg producedKlozur® CR oxidized all contaminants in a sediment high in NOM (>14%)
Native SRB survived the highest dose (20 g/kg) and thrived soon afterwards
SRB produced sulfide within weeks
>80% of Hg precipitated as HgS after 30 weeks
FMC Chemicals Ltd  Wirral International Business Park, Commercial Road, Bromborough, Wirral, CH62 3NL  Tel: +44 1514827356  www.environmental.fmc.com