Low-Impact Pilot Study Leads to Expanded Treatability Evaluation Confirming Biostimulation Safe, Sustainable and Cost-Effective cVOC Remediation Strategy

Site, inactive manufacturing facility in Belmont County Ohio. Chlorinated Volatile Organic Compound (cVOC) contaminants documented in groundwater, saturated, non-saturated soils and fractured bedrock. Existing pump-and-treat (PT) system utilizes 3 extraction wells for hydraulic containment; operating since mid-2000’s, one (EW-3) realizing minimal recovery. Geology consists of fill/alluvial soils overlying sandstone/shale bedrock; ‘Water table aquifer’ hydraulically connected unconsolidated alluvial sediments atop fractured sandstone bedrock; vertical component downward near source, upwards downgradient at discharge to abutting creek. Contaminant-of-Concern (COC) Trichloroethylene (TCE) in fractured bedrock above State of Ohio-EPA standards. Daughter cVOCs Dichloroethylene (DCE), Vinyl Chloride (VC) present. Baseline total [cVOCtotal] >50,000 µg/L to >1,000,000 µg/L; Parent:Parent Daughter (P:PD) molar ratios 78%-97%.
On-site pilot evaluation performed March 2013-May 2014; followed by expanded treatability evaluation September 2015, to identify sustainable alternative to current remediation strategy/costs. Additive evaluated ERDenhanced™; patented biostimulant proven to enhance native dehalorespiring bacteria, establish sustainable reducing conditions, while facilitating complete biotransformation. Groundwater monitoring data collected March 2013 – October 2016. Pilot used additive filled Passive-Release-Sock (PRS) deployment units to amend ≈3ft area-of-influence (AOI) around monitoring wells’ open bedrock interval. Three wells amended, 4th non-amended used as Control. PRSs replaced at 8-10 week intervals (5-8 replacements, location dependent) with no amendment deployed post September 2014. Groundwater monitored/sampled concurrent with PRS replacement; monitored monthly thereafter, analytical data collected quarterly through October 2016.
At completion of 14-month PRS evaluation >95% reductions in [cVOCtotal] and P:PD ratios realized at each amended location. No additive enhanced changes at Control. During pilot key biomarkers increased at amended locations, no change at Control. Geochemical metrics provide secondary evidence supportive of additive enhanced reductive dechlorination. Each amended location at T=17 months realized >98% reductions.
PRS evaluation prompted expanded 2014 treatability evaluation; amending 35ft x 35ft treatment zone, with assumed 10ft vertical component. Treatability evaluation performed downgradient from PRS amended areas. Dissolve phase and residual source mass cVOCs present. Extraction well EW-3, downgradient from TZ, shut-down and monitored during evaluation. ERDenhanced™ slurry (1,089 lbs/1,000 gal water) passively deployed in each of two injection wells (IW-1A & MW-40A). Geochemistry monitored monthly over 14 month period from both injection wells, extraction well EW-3, and six groundwater monitoring wells. Analytical testing performed quarterly through October 2016.
T=14months post deployment, [cVOCtotal] remained asymptotic at upgradient location MW-39A with unchanged [TOC/Cl-]/ORP values. Lateral well MW-27A recorded >99.9%↓ decrease [TCE], 79.3%↓ decrease [cVOCtotal]. Monitoring location MW-41A, downgradient ≈35ft and between injection locations, recorded ≈74.0%↓ reduction [TCE]. Downgradient ≈50-60ft, MW-42A, MW-43A and MW-44A recorded >99.9%↓, 97.8%↓, and >99.9%↓ reductions [TCE] with 82.2%↓, 92.1%↓ and 90.8%↓ reductions [cVOCtotal], respectively. [Ethene] recorded at all locations except MW-39A.
Treatability evaluation demonstrated pilot results transferable to full-scale application and ERDenhanced™ a safe, sustainable and cost-effective remediation strategy for dissolve phase/residual mass cVOCs: positively affecting treatment zone geochemistry, realizing reduced ORP values; Fe/Mn/Sulphate utilization; and, generally >90% reductions in P:PD molar ratios.

Primary Author/Conference Presenter:
Kent Armstrong
TerraStryke Products LLC
Andover, New Hampshire

Barbara L. Forslund, Project Manager, Advanced Geoservices, Inc., Westchester, PA