The term Enhanced Reductive Dechlorination (ERD) is a remediation approach being applied to groundwater at chlorinated volatile organic compound (cVOCs) impacted sites. These sites are commonly former dry cleaner or manufacturing operations which operated from the late 1960's to early 2000's utilizing perchloroethylene (PCE), or perc, or trichloroethylene (TCE), a degreaser product.
ERD is typically the application of a biodegradable organic carbon source for the anaerobic degradation of cVOCs. The organic carbon source is applied using a direct push drilling unit and pressure injected into the saturated subsurface (e.g., groundwater table). The organic carbon source is a viscous material which is mixed with water (i.e., emulsified) using tanks and pumps and injected into the subsurface using a pressure pump connected to the drill unit tooling. A measured volume of the organic carbon mixture is forced into the subsurface and distributed over the targeted vertical injection interval (zone of groundwater treatment). Using typically a grid of injection points, the targeted horizontal extent of cVOC impacted groundwater receives treatment.
The injected organic source slowly releases electron donors (organic acids) into the groundwater which through microbial biodegradation produces hydrogen and through further biodegradation results in reductive dechlorination. The process utilizes two types of bacteria, lactic acid fermenting bacteria and dechlorinating bacteria. The injection process commonly includes the supplemental injection of dechlorinating bacteria (Dehalococcoides, [DHC]) to optimize the ERD process. The lactic acid degrading bacteria are common in the environment. The biological process reduces the source product cVOC (PCE or TCE) into degradation daughter products (e.g., dichloroethene [DCE] , cis-1,2-DCE, vinyl chloride) and ultimately at complete degradation to ethene. Commercially available organic source products can continue to release electron donors for two to four years following a single treatment.
The successful application of ERD to a site does require the delineation of cVOCs in the groundwater plume, and the assessment of groundwater chemistry and water quality. The groundwater chemistry should include: dissolved gases (methane, ethane, ethane, carbon dioxide), terminal electron receptors (Iron, manganese, sulfate, nitrate, total organic carbon), BOD, COD, alkalinity, and DHC population analysis. Water quality includes the field measured parameters of: dissolved oxygen, ORP, and pH.
KERAMIDA has completed multiple ERD injection projects and has several cVOC impacted sites undergoing active ERD groundwater remediation. We have obtained regulatory closure or achieved closure levels at multiple sites using ERD remediation. KERAMIDA provides turn-key services for cVOC impacted sites from investigation and delineation, remediation design and implementation, monitoring, and ultimately regulatory closure by our staff of expert professionals and in-house injection and drilling resources.