Optimizing Post Remediation Groundwater Performance with Enhanced Microbiological Analyses

Results of geophysics and pneumatic injection pilot tests during 2003 – 2007 yielded significant positive results for injection delivery design and contaminant mass treatment, resulting in permanent shut-down of an existing groundwater Pump & Treat system.

Accessible source areas were subsequently removed (2011) by soil excavation and treated with the placement of Emulsified Vegetable Oil EVO and zero-valent iron ZVI to accelerate treatment of impacted groundwater in overburden and weathered fractured bedrock. Post pilot test and post remediation groundwater monitoring has included analyses of CVOCs, organic fatty acids, dissolved gases and QuantArray® -Chlor to quantify key microorganisms (e.g., Dehalococcoides, Dehalobacter, etc.) and functional genes (e.g., vinyl chloride reductase, methane monooxygenase, etc.) to assess potential for reductive dechlorination and aerobic cometabolism of CVOCs.

In 2022, the first commercial application of MetaArray™ was performed at the site. MetaArray™ utilizes statistical analysis, such as principal component analysis and multivariate analysis to provide evidence that reductive dechlorination is active or even that it is slowing. This creates actionable data allowing users to save money by making important site management decisions earlier.

The results of the MetaArray™ analysis’ support vector machine (SVM) identified groundwater monitoring wells with a 80% confidence that were characterized as either Limited for Reductive Decholorination or had a High Reductive Reduction Dechlorination potential. The results of MetaArray™ will be used to further optimize the site’s post remediation monitoring program for monitored natural attenuation.

1. Optimizing Post Remediation Groundwater Performance with
Enhanced Microbiological Analysis

Authors: Joshua Orris, Antea Group USA and Jack Sheldon, Antea Group USA

Session: G2
Group: #1

INTRODUCTION APPROACH
RESULTS AND
CONCLUSIONS
Case Study:
Former specialty chemical manufacturing facility located New Jersey was actively undergoing investigations and remediation
since the late 1990’s.
• Chlorinated volatile organic compounds (CVOCs); 1,1,1–
trichloroethane (TCA), trichloroethylene (TCE) and their respective
degradation products were identified as primary Chemicals of
Concern (COCs)
• An Interim Remedial Measure (IRM), groundwater recovery and
treatment system was operational from 2001 to 2006 designed for
hydraulic control
• A unique strain of dehalococcoides were identified during bench
scale testing that were naturally degrading CVOCs at a low pH
range of 5.8-6.0
• Significant concentrations of both Biotic and Abiotic degradation
products had been detected in groundwater samples
• August 2002, a microbiological bench scale study was completed to
evaluate the potential for anaerobic biodegradation, specifically
reductive dechlorination to occur

August 2002 Bench Scale Results
• Confirmed anaerobic conditions along with elevated Chloride concentrations were detected at select monitoring wells
suggesting prior CVOC reduction had occurred
• Low concentrations of chloroethane and a lack of preferable organic acids indicated that the microbial degradation of TCA
was limited by a lack of nutrients
• Abiotic breakdown product pathways of TCA to Vinyl Chloride were detected
• Hypothesis: if sufficient nutrients were provided it was likely that the abiotic degradation of TCA would decrease and the
anaerobic biodegradation of TCA would increase
• Elevated concentrations of 1,1-DCE, the abiotic breakdown product, were detected; but with lower concentrations of Vinyl
Chloride, which is the biotic byproduct of 1,1-DCE. This conditions suggested that the microbial degradation system was
nutrient limited
HRSC—MiHPT
Enhanced Pilot Tests & Full Scale Design:
• Borehole geophysics completed in bedrock open borehole injection wells and existing
groundwater monitoring well network
• Leveraged data visualization with development of a 3D-Conceptual Site Model (3DCSM)
• Co-Injection application of Emulsified Vegetable Oil (EVO) and zero-valent iron (ZVI) delivery for
enhanced dechlorination biodegradation
• Enhanced targeted injection well design for pneumatic fracturing and injection that yielded
increased Radius of Influence for contaminant treatment
• Successful pilot testing resulted in a broader pneumatic injection full scale application of EVO/
ZVI
• Due to the efficiently targeted injection design, the groundwater Pump and Treatment system
was permanently shut-down and decommissioned resulting in a cost savings of $180,000 per
year
• Accessible source areas were removed during facility renovations and expansions in 2007 and a supplemental source area that was
delineated with High Resolution Site Characterization (HRSC), MiHPT was removed and treated with EVO/ZVI prior to backfilling to
accelerate treatment of contaminated groundwater present within the perched and intermediate upper bedrock
• Excavated contaminated materials were treated onsite with a patented process called Mobile Steam Distillationby EVO Corporation





3D-Conceptual Site Model
Excavation of Source Material
Pneumatic Injection Manifold Mobile Steam Distillationtreatment
Post Remediation Monitoring:
• Optimized Monitoring Well Network
• Sampling & Analysis Plan included: CVOCs, organic fatty acids,
dissolved gases and QuantArray® - Chlor by Microbial Insights to
quantify key microorganisms (e.g. Dehalococcoides, Dehalobacter)
and functional genes (e.g. vinyl chloride reductase, methane
monooxygenase etc..) to assess potential for reductive
dechlorination and aerobic co-metabolism of CVOCs
QuantArray®- Chlor
Microbial Population Summary
Enhanced Post Remediation Monitoring:
• The site’s remedial strategy remains aligned with Monitored Natural Attenuation in association with dechlorination
• In 2022, the FIRST commercial application of MetaArrayby Microbial Insights was performed at the site
• MetaArrayutilizes statistical analysis, such as principal component analysis and multivariate analysis to provide evidence that
reductive dechlorination is active or even that is slowing

• The results of MetaArray analysis identified groundwater
monitoring wells with a 80% confidence that were characterized as
either Limited for Reductive Dechlorination or had a High Reductive
Dechlorination potential
• The results of MetaArraywill be used to further optimize the site’s
post remediation monitoring program for natural attenuation




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