Antimethanogenic Reagents (AMR) to Control Excessive Methanogenesis During Remedial Actions

Background/Objectives: At many groundwater remediation sites, excessive production of methane has been observed following the addition of conventional organic hydrogen donors such as (emulsified) oils/lecithin, sugars and conventional ISCR reagents. This is because methanogens are commonly the most ubiquitous indigenous microbes in anoxic aquifer settings. And given that methanogens replicate in 1 to 2 hours (whereas Dehalococcoides spp. for example double in 24 to 48 hours), they often bloom and dominate following the addition of organic hydrogen donors, thereby liberating large amounts of methane gas. There are multiple potential consequences of this response: i) decreased efficiency/performance, ii) increased costs, iii) reduced safety, and iv) lack of regulatory compliance. Hence, evaluating the need to actively control excessive methanogenesis during remedial actions is now commonplace among seasoned professionals as the positive effects on remedial performance, safety, regulatory compliance and sustainability become well understood.

Approach/Activities: Antimethanogenic reagents (AMRs) have been developed to specifically and proactively control Archaea growth during ERD and ISCR remedial actions. In various trials, the AMRs were effective at rapidly reducing ORP, stimulating reductive dechlorination reactions, maintaining pH, and reducing methane production as compared to their controls. The AMRs have been integrated into various remedial amendments (e.g., liquid ERD, solid ISCR, EZVI materials, sediment capping materials) and are currently the subject of independent laboratory and field studies evaluating performance, efficacy, longevity and impacts on environmental microbiology. Information on the reagents modes of action, dosing / application requirements, and lessons learned during their field implementation will be presented along with results of field performance monitoring and application costs.