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Controlling Methane Production in Groundwater Proximal to Landfill Settings

Controlling Methane Production in Groundwater Proximal to Landfill Settings

 Controlling Methane Production

Controlling Methane Production in Groundwater Proximal to Landfill Settings

Jim Mueller, PhD (Provectus Enviromental Products, Inc – Freeport IL), and

Ramon Rivera (Diamond Systems, LLC –Titusville, FL)

Introduction

Over the past 25 years, various remedial amendments have been used to treat groundwater impacted by chlorinated solvents and other VOC, pesticides, and heavy metals that have, presumably, emanated from landfill sources. A very common problem, however, is that indigenous methanogens often bloom following the addition of the organic hydrogen donors thereby liberating large amounts of methane gas. This is because methanogens are the most ubiquitous indigenous microbes in anoxic aquifer settings. This problem can be greatly exacerbated by methane also being produced proximal to the landfill areas.

What is the Problem with Methane?

There are recognized benefits to methanogens and of limited methanogenesis. For example, methanogens play important roles in synergistic microbial ecology, and they support natural degradation of landfill contents and managed gas production. However, extended production of methane can result in elevated groundwater concentrations (as high as >100 ppm have been reported) which can lead to accumulation in soil gas subsequently impacting indoor air. While this is perhaps more relevant in urban settings where methane can accumulate in basements, under slabs/foundations and/or migrate along utility corridors, excessive methane production has also been observed in more rural settings and other open spaces. Accordingly, 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 (methane is flammable between 5% and 15% v/v). Many remedial practitioners proactively design contingencies for implementation in the event that methane exceeds a threshold level ranging from 1 to 10 ppm groundwater. These contingencies often entail expensive and extensive systems for treating methane in soil gas/vapor captured via SVE systems. Moreover, from a sustainability perspective, it can be argued that controlling methane production has a positive impact on greenhouse gases. The comparative impact of CH4 on climate change is about 20x greater than that of CO2 when averaged over a 100-year period (US EPA, 2014).

Technical Solution

Portable Methane Gas Detector Provect-CH4â„¢ is a genuinely new, antimethanogenic reagent that contains natural statin compounds with the unique ability to block protein and enzyme systems specific to methanogens thereby controlling their growth and proliferation (Woese and Fox, 1977). The technology has been widely used in the cattle industry for many years to manage rumen microbiology (Henderson et al, 2010)), but is being newly applied to the environmental industry as a remedial supplement, a landfill gas management tool, et cetera. The methane inhibitor itself can be used as a stand-alone supplement, or it can be added to myriad amendments used during remedial actions to make them safer and to greatly improve their overall efficacy in a predictable manner (US Patent Office Scalzi et al, 2013, 2014).

Proof of Concept

There are at least two scenarios where methane inhibitors can be used: i) “preemptively”, or in a proactive effort to prevent excesses methane production, or ii) “curatively”, in an attempt to ameliorate a situation where excessive methanogenesis has been established. Laboratory work documented that the methane inhibitors (40 ppm) yielded rapid (within 2 to 3 days) and significant (>90%) reduction of methane production by an active, adapted culture of Archaea in a closed bioreactor system (Figure 1). Laboratory work using simulated aquifer microcosms (soil and groundwater) inoculated with an active culture of methanogens also demonstrated rapid (within 1 to 3 days) and significant (>90%) reduction of methane in the presence of ca. 100 ppm inhibitor (data not shown).

Figure 1. Changes in Methane Concentrations over Time.

Graph_Mueller-Rivera

Field application of the methane inhibitors at a former dry cleaning site in Georgia showed that the presence of ca. 75 ppm methane inhibitor used to supplement a conventional amendment reduced dissolved methane in groundwater by >65% (from ca. 12 ppm to 4 ppm) and reduced methane in well head space gas >97% (from 35% vol to <1 % vol) after 6 weeks of application.

Conclusions:

Provect-CH4methane control technology may be an effective part of an overall landfill management practice. When used to help manage or ameliorate impacted groundwater it can facilitate the rapid and completer destruction of targeted contaminants in a safer, more efficacious manner. More information can be found at: www.DiamondSci.com

LITERATURE CITED:

Henderson, G., G.E. Naylor, S.C. Leahy and P.H. Janssen. 2010. Presence of novel, potentially homoacetogenic bacteria in the rumen as determined by the analysis of formyltetrahydrofolate synthetase sequences from ruminants. Appl. Environ. Microbiol. 76:2058-2066. Scalzi, M. and A. Karachalios. 2013 and 2014. Inhibition of Methane Production during Anaerobic Reductive Dechlorination. US PTO 13/ 785,840 and CIP 14/268,637. US EPA. 2014. http://epa.gov/climatechange/ghgemissions/gases/ch4.html Woese, C.R. and G.E. Fox. 1977. Phylogenetic Structure of the Prokaryotic Domain: the Primary Kingdoms. Proceedings of the National Academy of Sciences of the United States of America 74 (11): 5088–5090.
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