It has long been recognized that excessive production of methane during remedial actions presents significant challenges to our industry. Similar challenges associated within excessive methanogenesis are encountered in landfills, sewer septic systems, and other settings. IET, in our latest scientific developments, further addresses these issues by offering advanced technologies to control methane production thereby offering significant improvements in terms of safety and efficiency.
PRLog – Jan. 22, 2015 – HARRISBURG, Pa. — As an expansion to our intellectual property in which natural statins are utilized to inhibit methane formation, IET has identified additional, supplemental mechanisms for addressing methane in the environmental services industry and related business sectors. Specifically, at sites where elevated methane levels have been identified as problematic, the utilization of selected essential plant oils (e.g., garlic oil, lemon grass oil, cinnamon bark oil, etc.) can be utilized alone or in conjunction with natural statins to actively control methanogens (patents pending – Scalzi et. al, 2014).
Nearly all remedial processes targeting chlorinated solvents rely on evolved hydrogen – generally from fermented sugars, carbohydrates or other organic compounds – to drive the biological processes. The competition for the hydrogen by methanogens results in loss of efficacy and a loss of alkalinity due to the conversion of carbon dioxide to methane. The ability of natural statins to target and block the enzyme systems that are responsible for methane production has been well demonstrated, and we have pioneered their application in the remediation industry. However, where pre-existing methanogenic process predominate the microbial flora a more aggressive methane “kill” is often necessary. Together with the statin technology, this newly defined essential oil mechanism for remedial actions will significantly change the way soil and groundwater remedial programs are implemented. Regardless of the organic hydrogen donor utilized, this technology will improve the efficiency and performance of those donors in situ. In essence, all reductive bioremediation processes will benefit.
The present invention relates to the use of various inhibitors of different enzymes and coenzymes systems that are responsible for the production of methane and therefore compete with halo-respiring bacteria during the anaerobic reductive dechlorination process. The inhibition of methanogenesis will result in lower methane production, which positively affects numerous environmental aspects of major concern, and will also help dehalogenating bacteria to more effectively utilize the environmental conditions that promote reductive dechlorination of chlorinated volatile organic compounds (CVOCs). Additional benefits include:
More Efficient: Significantly lower costs as a result of more efficient amendment utilization via controlled methanogenesis = can use at least 30% less organic amendment
Safer: Fewer health and safety concerns as compared with use of traditional ERD or ISCR reagents; Avoid issues associated with new and emerging methane regulations
Green and Sustainable
Simultaneous Immobilization of Heavy Metals: Will not mobilize or methylate arsenic or other heavy metals yielding secondary plumes (as is common with [emulsified] oils and sources of carbon only). Can be formulated to manage environments that are co-impacted by various inorganic contaminants (e.g., As, [Hg], Ni, Pb, Zn) while simultaneously mineralizing the organic compounds.
Accelerated Site Closure: Provect-IR rapidly removes COI mass via a combination of biogeochemical degradation processes without relying on physical sorption / sequestration as a major “removal” mechanism, a la emulsified oils.
A wide variety of organic substrates will stimulate reductive dechlorination including acetate, propionate, butyrate, benzoate, glucose, lactate and methanol. Inexpensive, complex substrates such as molasses, cheese whey, corn steep liquor, corn oil, hydrogenated cottonseed oil beads, solid food shortening, beef tallow, melted corn oil margarine, coconut oil, soybean oil, and hydrogenated soybean oil have the potential to support complete reductive dechlorination.
Reductive dechlorination only occurs in the absence of oxygen; and, the chlorinated solvent actually substitutes for oxygen in the physiology of the microorganisms carrying out the process. As a result of the use of the chlorinated solvent during this physiological process, it is at least in part dechlorinated. Remedial treatment technologies usually introduce an oxygen scavenger to the subsurface in order to ensure that this process would occur immediately.
Heterotrophic bacteria are often used to consume dissolved oxygen, thereby reducing the redox potential in the ground water. In addition, as the bacteria grow on the organic particles, they ferment carbon and release a variety of volatile fatty acids (e.g., acetic, propionic, butyric), which diffuse from the site of fermentation into the ground water plume and serve as electron donors for other bacteria, including dehalogenators and halorespiring species. An iron source usually provides substantial reactive surface area that stimulates direct chemical dechlorination and an additional drop in the redox potential of the ground water via chemical oxygen scavenging.
Bacteria generally are categorized by: 1) the means by which they derive energy, 2) the type of electron donors they require, or 3) the source of carbon that they require. Typically, bacteria that are involved in the biodegradation of CAHs in the subsurface are chemotrophs (bacteria that derive their energy from chemical redox reactions) and use organic compounds as electron donors and sources of organic carbon (organoheterotrophs). However, bacteria are classified further by the electron acceptor that they use, and therefore the type of zone that will dominate in the subsurface. A bacteria electron acceptor class causing a redox reaction generating relatively more energy, will dominate over a bacteria electron acceptor class causing a redox reaction generating relatively less energy.
Halophiles are salt-loving organisms that inhabit hypersaline environments. They include mainly prokaryotic and eukaryotic microorganisms with the capacity to balance the osmotic pressure of the environment and resist the denaturing effects of salts. Among halophilic microorganisms are a variety of heterotrophic and methanogenic archaea; photosynthetic, lithotrophic, and heterotrophic bacteria; and photosynthetic and heterotrophic eukaryotes.
One the other hand, methanogens, play a vital ecological role in anaerobic environments, since they remove excess hydrogen and fermentation products that have been produced by other forms of anaerobic respiration. Methanogens typically thrive in environments in which all electron acceptors other than CO2 (such as oxygen, nitrate, trivalent iron, and sulfate) have been depleted.
Based on thermodynamic considerations, reductive dechlorination will occur only after both oxygen and nitrate have been depleted from the aquifer since oxygen and nitrate are more energetically favorable electron acceptors than chlorinated solvents. Almost any substrate that can be fermented to hydrogen and acetate can be used to enhance reductive dechlorination since these materials are used by dechlorinating microorganisms. However, hydrogen is also a substrate for methanogenic bacteria that convert it to methane. By utilizing hydrogen, the methanogens compete with dechlorinating microbes.
The method of restricting methane production in methanogenic bacteria, by the use of the enzyme inhibitors, can be very useful during in-situ remediation of chlorinated solvents. This method is expected to positively affect the competition of the methanogen and halo bacteria for the organic hydrogen donors that are injected in the soil and groundwater system during the remediation process.
Michael Scalzi, President IET