Combining Advanced In-Situ Remedial Technologies to Mitigate Free Phase Hydrocarbons Trapped Below Structure
Eric Raes (E&LP, Clinton, NJ), Kerry Sublette, Ph.D. (Bio-Enhance, High Bridge, NJ), Duane Guilfoil, Derek Pizarro (AST Environmental, Midway, KY), George Ivey (Ivey International, Surrey, British Columbia, Canada)”
Background/Objectives: Free phase petroleum hydrocarbons are extremely difficult to mitigate especially when released immediately adjacent to structures because the product migrates and accumulates as sorbed, globule, and free phases throughout the more permeable fill material surrounding the structure and utility conduits. A treatment train of three proven technologies was employed to remediate the readily available free phase product and promote subsequent biodegradation: (1) surfactants to enhance hydrocarbon desorption and dissolution allowing for push-pull mass recovery, (2) sorption of residual contaminants to a microbial-inoculated activated carbon-based amendment for stabilization and enhanced biodegradation, and (3) sustained bio-augmentation via in situ bio-reactors to expedite the enhanced bio-degradation component of the remedial strategy.
Approach/Activities: Prior to this three-pronged treatment approach, a fifteen-point remediation well network had been installed as part of the previous remediation plan that was suspended due to the presence of free phase product. Subsequently, a series of enhanced fluid recovery events over a two-year period. When these events failed to eliminate the free phase product at the site, the treatment train approach was implemented as the revised remedial strategy. In order to remove the free phase petroleum and significantly reduce contaminant mass to be treated by the subsequent remediation technologies, a series of push pull surfactant injections and extractions were implemented in the spring of 2020. More specifically, approximately 265 gallons of 2% or 4% Ivey-sol®/water mixture were injected and subsequently vacuum extracted after 48 hours of aquifer contact. Once the available free product was removed, 3,300-lbs of BOS 200® and 2,000-lbs of gypsum were injected into the subsurface between the existing remediation wells. BOS 200® is a Trap & Treat® in situ remediation technology containing carbon-based media and a non-indigenous, proprietary bio-inoculum. Following BOS 200® injection, Bio-Enhance In-Situ Bio-Reactors (ISBRs) were installed in three (3) of the remediation wells. Through the extensive well network, the shifts in chemical, geo-chemical, and microbial populations were quantified throughout the remedial phases.
Results/Lessons Learned: The Ivey-sol® surfactant flush events achieved the remedial objective to remove the readily available free product and facilitate the enhanced bio-degradation elements of the remedial strategy. The concentrations and migration of the petroleum degrading bacteria following the BOS 200® injection were quantified over a one-year period. These shifts in the petroleum degrading microbial community were compared to the abundance and migration of the indigenous microbial community based on the presence of three ISBRs on the north side of the treatment cell. The synergetic efficiency of these combined remedial technologies will be presented.