Innovative applications of subgrade biogeochemical reactors: Three case studies

Abstract

Subgrade biogeochemical reactors (SBGRs) are an in situ remediation technology shown to be effective in treating contaminant source areas and groundwater hot spots, while being sustainable and economical. This technology has been applied for over a decade to treat chlorinated volatile organic compound source areas where groundwater is shallow (e.g., less than approximately 30 feet below ground surface [ft bgs]). However, this article provides three case studies describing innovative SBGR configurations recently developed and tested that are outside of this norm, which enable use of this technology under more challenging site conditions or for treatment of alternative contaminant classes. The first SBGR case study addresses a site with groundwater deeper than 30 ft bgs and limited space for construction, where an SBGR column configuration reduced the maximum trichloroethene (TCE) groundwater concentration from 9,900 micrograms per liter ( g/L) to <1 g/L (nondetect) within approximately 15 months. The second SBGR is a recirculating trench configuration that is supporting remediation of a 5.7-acre TCE plume, which has significant surface footprint constraints due to the presence of endangered species habitat. The third SBGR was constructed with a new amendment mixture and reduced groundwater contaminant concentrations in a petroleum hydrocarbon source area by over 97% within approximately 1 year. Additionally, a summary is provided for new SBGR configurations that are planned for treatment of additional classes of contaminants (e.g., hexavalent chromium, 1,4-dioxane, dissolved explosives constituents, etc.). A discussion is also provided describing research being conducted to further understand and optimize treatment mechanisms within SBGRs, including a recently developed sampling approach called the aquifer matrix probe. K E Y W O R D Schlorinated solvents, groundwater treatment, in situ remediation, subgrade biogeochmical reactors wileyonlinelibrary.com/journal/rem

Ten years later: The progress and future of integrating sustainable principles, practices, and metrics into remediation projects

“…Natural treatment systems, such as constructed wetlands (Kassenga, Pardue, Blair, & Ferraro, ) phytoremediation (Legault et al, ), and in situ bioreactors (Gamlin, Cox, & Castor, ) using locally available materials, and the progress in understanding microbiology hold great promise for contaminated site remediation. Natural treatment systems leverage the power of nature and decrease emphasis on intensive engineered elements.…”