Adventus Americas Outlines In Situ Chemical Reduction (ISCR) Advantages; Remediation biotechnology firm clarifies differences between ISCR and In Situ Chemical Oxidation (ISCO) technologies.

FREEPORT, Ill. -- Adventus Americas, Inc., an international remediation biotechnology firm, recently outlined topical decision-making criteria for remediation engineers and environmental professionals.

The Potential Significance of ISCR

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. However, an equally or perhaps more effective remedial strategy, especially for plume treatment, entails in situ chemical reduction (ISCR) using EHC(TM)or granular iron (zero-valent metal) as the reductant.

Dr. Richard Brown, Director of Remedial Technologies at Environmental Resource Management, Inc. (ERM - Ewing, NJ) is the inventor of various ISCO technologies and approaches, in particular the use of activated persulfate, and has helped pioneer the use of ISCR technologies in the remedial industry. Considering the potential use of ISCR for remedial applications, Dr. Brown stated: "The next generation of remedial solutions seems focused around our established ability to effectively manage in situ redox potentials, particularly reducing conditions. ISCO was the first body of technology to show the importance of redox conditions. ISCR is an extension of this fundamental approach. Combining elements from our experiences with natural attenuation processes, enhanced reductive dechlorination, and mechanisms of abiotic chemical destruction, these innovative ISCR technologies promise to yield safe, rapid and effective remedial solutions to some of our more challenging environmental situations".

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 EHC 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.

About Adventus

The Adventus Group provides an intriguing portfolio of innovative remediation technologies, comprised of patented offerings from Adventus Americas Inc. and EnviroMetal Technologies Inc. Our business model is to support site owners, environmental engineers, and diverse consulting professionals by providing unbiased design and selection of the most cost-effective remedial strategies.

The Adventus Group exclusively offers EHC and ZVI technologies along with ISBS in situ stabilization technology. Other ISCO technologies are available from various other vendors and suppliers.

Since inception in 2003, Adventus has been continually expanding industry visibility. The Adventus Group has operated at over at over 300 field sites throughout North America, Europe, Japan and Australia. The Adventus family of companies has offices in Colorado, Connecticut, Illinois, New Jersey, and Ontario, Canada. For more information on Adventus, visit the company's Web sites at www.adventus.us or www.eti.ca

COMPARATIVE ANALYSIS OF ISCR vs. ISCO REMEDIAL TECHNOLOGIES


                                                           ISCO
                             ISCR       Granular Iron   (Fenton's,
   Factor                 (EHC(TM))     (Zero-Valent     Peroxide,
                                            Iron)       Persulfate,
                                                       Permanganates)
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Existing redox         More appropriate               More appropriate
 conditions             for reduced                    for oxidized
                        environments   Can be applied  environments
                        (ORP less than  in any Eh      (ORP greater
                        0 mV; DO less   condition.     than 0; DO
                        than 2 mg/L).                  greater than 2
                                                       mg/L).
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Material handling                                     Some require
 safety                                                significant
                       Non-hazardous;  Environmentally health and
                       Minor dust      friendly        safety
                       consideration.  materials.      precautions
                                                       during
                                                       installation.
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                                                      Active towards a
                                                       wide range of
                                                       COIs, including
                       Active towards a wide range of  chlorinated and
                         COIs, including ethenes and   non-chlorinated
                          ethanes.  Can reduce and     compounds;
Treatable Constituents   immobilize / adsorb certain   Reactivity
 of interest (COI)      metals; Not effective on BTEX  sometimes
                         and other refined petroleum   variable and
                                hydrocarbons.          dependent upon
                                                       activators;
                                                       Active on BTEX
                                                       and related
                                                       COIs.
----------------------------------------------------------------------
                                                      Not applicable
                                                       for PRBs due to
                     Very applicable   Very applicable liquid nature
                        to PRBs for     to PRBs for    of products;
                        plume control-  plume control  Usually too
PRB applicability       an estimated    -an estimated  expensive for
                        lifetime of 3   lifetime of    treatment of
                        to 5 years for  20+ years for  larger plumes
                        EHC.            iron PRBs.     or situations
                                                       where the
                                                       source cannot
                                                       be treated.
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                                                       Some
                                                       technologies
                       Not widely      Iron or iron/   have shown
                        considered       clay can be   success on
NAPL applicability      applicable for   mixed into    NAPL; ISBS
                        NAPL             NAPL zones.   technology
                        situations.                    demonstrated
                                                       for flux
                                                       reduction.
----------------------------------------------------------------------
Non-NAPL source        Potentially applicable to non-NAPL sources, if
 applicability           reagents are appropriately distributed and
                               source is accurately delineated.
----------------------------------------------------------------------
                                       Particularly
                       More cost        effective at
COI concentrations in   efficient at    reducing large Effective at
 groundwater plumes     lower COI       concentrations various COI
                        concentrations. in a short     concentrations.
                                        period of
                                        time.
----------------------------------------------------------------------
                                                      Best suited to
                                                       oxic soils with
                     Applicable to                     low organic
                      soils of high   Application      content due to
Organic content of    or low organic  independent of   increased
 soils                content.        soil organic     reagent loading
                                      content.         requirements
                                                       for soils high
                                                       in organic
                                                       content.
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                       High
                        concentrations                Usually
                        of competing                   difficult to
                        electron       Nitrate will    accurately
                        acceptors such  increase rate  assess Total
                        as oxygen,      of iron        Oxidant Demand
                        sulfate and     passivation.   (TOD); May need
                        nitrate will                   to repeat
                        increase EHC                   applications.
                        loading
Other factors           requirements.
 influencing           -----------------------------------------------
 application rate      Field                          Field
                        performance                    performance
                        highly                         highly
                        dependent upon                 dependent upon
                        effective                      effective
                        construction   Predictable     construction
                        techniques;     performance.   techniques;
                        Field                          Field
                        performance                    performance
                        usually adheres                does not always
                        to engineered                  adhere to
                        variables.                     engineered
                                                       variables.
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