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ISCR vs. ISCO?
THE CHOICE IS
USUALLY CLEAR
________________________________________________________
Many
chlorinated hydrocarbon compounds (CHCs) can be degraded via oxidative
or reductive processes (http://umbbd.ahc.umn.edu).
Accordingly, various in situ chemical oxidation (ISCO)
technologies using oxidizing agents such as Fenton’s chemistry,
permanganate and persulfate have been developed to remediate impacted
environments. Each of these oxidants and their activators offer
seemingly unique features and they can be very effective on a varying
range of CHCs (ISBS technology described at
http://www.adventus.us/isbs.htm). However, a potentially more
effective remedial strategy may entail in situ chemical
reduction (ISCR) using EHCTM (www.AdventusGroup.com
)
or granular iron (zero-valent metal) (www.eti.ca)
as the reductant.
So
– which technology is more appropriate for a given site?
In general, if the
targeted environment is hypoxic (low Eh; oxygen limited), it seems
intuitive to employ an ISCR strategy using EHCTM or ZVI
technology. Conversely, an ISCO strategy would likely be more effective
in an oxic environment. Iron permeable reactive barriers (PRBs) are
extremely robust and can be deployed in both anoxic and oxic
environments.
A number of other
important factors should be considered when selecting between an ISCR or
ISCO approach for a specific site. As summarized in the following
table, these include: targeted treatment area (source removal, plume
control or both), contaminant characteristics, presence of free product,
residuals or phase-separated hydrocarbons (e.g., NAPL), desired
clean-up time, chemical recalcitrance and degradation kinetics,
longevity of the added reagents in the subsurface, environmental impacts
(secondary plumes) and health & safety issues.
Contact us at
toll-free at 888 295-8661, or online at
www.AdventusGroup.com for a free situation analysis and independent
assessment of various ISCO, ISBS or ISCR remedial alternatives.
COMPARATIVE
ANALYSIS OF ISCR vs. ISCO REMEDIAL TECHNOLOGIES
|
Factor |
ISCR
(EHCTM)
|
Granular
Iron
(Zero-Valent
Iron)
|
ISCO
(Fenton’s,
Peroxide, Persulfate, Permanganates) |
|
Existing
redox conditions |
More
appropriate for reduced environments (ORP < 0 mV; DO < 2 mg/L).
|
Can be
applied in any Eh condition. |
More
appropriate for oxidized environments (ORP > 0; DO > 2 mg/L). |
|
Material
handling safety |
Non-hazardous; Minor dust consideration.
|
Environmentally friendly materials.
|
Some require
significant health and safety precautions during installation.
|
|
Treatable
Constituents of Interest (COI) |
Active
towards a wide range of COIs, including ethenes and ethanes.
Can reduce and immobilize / adsorb certain metals; Ineffective
on BTEX and other refined petroleum hydrocarbons.
|
Active
towards a wide range of COIs, including chlorinated and
non-chlorinated compounds; Reactivity sometimes variable and
dependent upon activators; Active on BTEX and related COIs.
|
|
PRB
applicability |
Very
applicable to PRBs for plume control - estimated lifetime of 3
to 5 years for EHC. |
Very
applicable to PRBs for plume control - estimated lifetime of 20+
years for iron PRBs. |
Not
applicable for PRBs due to liquid
nature of products; Usually too expensive for treatment of
larger plumes or situations where the source cannot be treated. |
|
NAPL
applicability |
Not widely
considered applicable for NAPL situations.
|
Iron or iron/
clay can be mixed into NAPL zones. |
Some
technologies have shown success on NAPL; ISBS technology
demonstrated for flux reduction. |
|
Non-NAPL
source applicability |
Potentially
applicable to non-NAPL sources, if reagents are appropriately
distributed and source is accurately delineated. |
|
COI
concentrations in groundwater plumes |
More cost
efficient at lower COI concentrations.
|
Particularly
effective at reducing large concentrations in a short period of
time. |
Effective at
various COI concentrations. |
|
Organic
content of soils |
Applicable to
soils of high or low organic content.
|
Application
independent of soil organic content. |
Best suited
to oxic soils with low organic content due to increased reagent
loading requirements for soils high in organic content. |
|
Other factors
influencing application rate
|
High
concentrations of competing electron acceptors such as oxygen,
sulfate and nitrate will increase EHC loading requirements.
|
Nitrate will
increase rate of iron passivation. |
Usually
difficult to accurately assess Total Oxidant Demand (TOD); May
need to repeat applications.
|
|
Field
performance highly dependent upon effective construction
techniques; Field performance usually adheres
to engineered variables.
|
Predictable
performance. |
Field
performance highly dependent upon effective construction
techniques; Field performance does not always adhere to
engineered variables. |
The Adventus
Group exclusively offers EHCTM and ZVI technologies along
with ISBS in situ stabilization technology. Other ISCO
technologies available from various vendors and suppliers.
Please contact us
for more information on any of these technologies at:
Michael Mueller
Director of Marketing
The Adventus Group
Direct: (+01) 860-841-9138
Toll-free: (+01) 888-295-8661
Fax: (+01) 866-890-0765
Email:
mmueller@adventus.us
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