Highlighted Technology: Provect-IR™ Solid, Antimethanogenic ISCR Reagent

Over the past 25 years, many formulations of organic substrates have been added to impacted aquifers with the intent of liberating hydrogen to enhance reductive dechlorination reactions (i.e.,ERD). When combined with zero-valent metals –  such as zero-valent iron (ZVI) – the intent is to induce in situ chemical reduction (ISCR) conditions.  A very common problem, however, is that indigenous methanogens often bloom following the addition of the organic hydrogen donors thereby liberating what can be very large amounts of methane gas (>1,000 ppm in groundwater have been observed).  There are at least three important consequences of this response:

i)      By utilizing hydrogen, the methanogens compete with dechlorinating microbes thus making inefficient use of the remedial amendment;

ii)   Rapid growth of methanogens consumes alkalinity while generating acids thereby having the potential for aquifer acidification (which may liberate heavy metals causing secondary contaminant issues); and

iii)    Elevated methane concentrations can exceed current and pending regulations of < 10 to <28 ppm in groundwater and/or 0.5% v/v methane in soil gas (e.g., 10% of the LEL) and/or indoor air regulations (methane is flammable between 5 and 15% v/v).

In an effort to manage this problem, we developed Provect-IR solid, antimethanogenic ISCR reagent.  As summarized in Table 1, Provect-IR is a genuinely new ISCR reagent that uniquely combines nutrient rich, engineered-release, hydrophilic carbon sources + ZVI + other reagents along with a specially modified red yeast rice extract (RYR) as an inhibitor of enzyme systems that are responsible for the production of methane (US Patent 14268637; PCT/US14/36632).  This improved ISCR Reagent contains natural monacolins (most importantly monacolin K, or Lovastatin) which have the unique ability to block enzyme systems specific to methane production. Sold as Provect-CH4™, the modified RYR extract itself can be used as a stand-alone supplement to other ERD amendments such as molasses, sugars, EVO, et cetera to make them safer and to improve their overall efficacy.

Independent data have shown that when aplied at ca. 40 mg/L the amendment reduced the concentation of methane in biogass by > 95% within 5 days time without changing pH and maintaining reducing conditions < -300 mV.  Performance of the basic technology under field conditions is summarized in the linked Case Study. Continue to Case Study.

 

TABLE 1:  Provect-IR™ Conventional ISCR Reagent
Component / Feature Provect-IR
Multiple Complex, Mixed-Release Organic Hydrogen Donors
YES
Integrated Methanogenic Inhibitor (patents pending)
YES
Chemical Oxygen Scavenger to maintain reduced ZVI during Mixing and Injection
YES
Integrated Vitamins, Micro-Nutrients and Macro-Nutrients selected for Enrichment of Indigenous Anaerobes
YES
Calcium Propionate Primer for Enrichment of Indigenous Anaerobes
YES
Modified formulations for heavy metal immobilization
YES
ZVI Component Average Particle Size (micron)
15
% by weight ZVI
10
Square Feet of ZVI Surface per Pound of Product
2.27
Grams of Organic Hydrogen Donor/ Pound of Product
400
List Price
$2.35/lb**

** Includes methane inhibitor: volume discounts will apply

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