Evaluating the Necessity of Bioaugmentation in Conjunction with an Electron Donor Injection at a Large Chlorinated Solvent Plume in the Midwest David Jeffers (
[email protected]) and Jeff Roberts (Roberts Environmental Services LLC, Goshen, IN); Doug Davis (Regenesis, San Clemente, CA)
PILOT STUDY
The objective of this presentation is to share the results of a bioaugmentation pilot study completed in conjunction with an in situ injection of an electron donor substrate at a commercial manufacturing facility in northern Indiana. The results of the pilot study may be useful for guiding stakeholder decisions as to whether or not bioaugmentation should be implemented at similar project sites where an enhanced reductive dechlorination (ERD) approach is being considered.
The remedy selected for pilot testing in the offsite, downgradient section of the plume was ERD through the in situ injection of an engineered electron donor--3-D Microemulsion®--manufactured and distributed by Regenesis. As part of the pilot test for this remedy, testing the efficacy of bioaugmentation, in addition to electron donor treatment, was also completed. The bioaugmentation substrate used for the test, also available through Regenesis, was Bio-Dechlor INOCULUM® Plus (BDI Plus or BDI), a consortium of chlorinated solvent degrading bacteria including Dehalococcoides sp. (DHC).
As follows, we present a brief summary of investigative and remedial activities completed to date, describe how the pilot study was conducted, summarize the results of the pilot study and discuss the implications of these results.
A field scale pilot study was initiated within 3 treatment cells in October 2011. Two of the pilot test cells, centered around test wells MW-24i and MW-26i, were used to test efficacy of an electron donor injection with and without bioaugmentation culture. At MW-24i, the bioaugmentation culture was added. No bioaugmentation culture was added to MW-26i. A 3rd pilot test cell, centered at MW-18i was located within the commingled plume area which contained chlorinated VOCs and approximately 1 to 2 mg/L residual petroleum hydrocarbons in the C6 to C10 carbon range. This cell was evaluated following injection of electron donor only.
An air sparging/soil vapor extraction (AS/SVE) system was installed to remediate heavily impacted soil and groundwater in the source area. The AS/SVE system operation occurred from May 2009 to July 2011 in the eastern area of the onsite plume and from May 2011 to present in the western area of the onsite plume. A field-scale pilot study consisting of the in situ injection of an electron donor and bioaugmentation substrate was initiated in the offsite, downgradient portion of the plume in October 2011. Based on the results of the pilot study, full scale injection of the electron donor in a large section of the offsite, downgradient section of the plume occurred in April/June 2012. Treatment extended from onsite to a roadway approximately 800 ft downgradient of the facility. The combined remedial methods employed have resulted in a significantly diminished chlorinated solvent plume both witihin the treatment area and downgradient. Source area reductions from the AS/SVE system are currently approaching 90% and, based on the success of the electron donor in situ treatment described herein, expansion of the offsite plume treatment is in the planning stages to ultimately move the project toward final closure.
RobertsEnvironmental_1.indd 1
Pilot Test Performance Monitoring
++ Chlorinated Solvents - PCE, TCE, cis-DCE, VC
RESULTS Microbial Results Comparison DHC populations were roughly similar at MW-24i (bioaugmented) and at MW-26i (no bioaugmentation) at the 3-month (Dec 2011) post application monitoring event. DHC populations were modestly more robust at MW-24i thereafter. including Dehalococcoides sp. (DHC).
++ Microbial Analyses - Dehalococcoides (DHC) and functional genes tceA, bvcA, VCR
In contrast to DHC, functional gene population growth was markedly more robust in the bioaugmented test cell (MW-24i) compared to the non-bioaugmented test cell (MW-26i).
++ Dissolved Gases – CO2, ethene, ethane, methane
Chlorinated VOC Degradation Results Comparison Over a 12-month period, the rate of chlorinated VOC degradation, measured in PCE mass equivalents, was approximately 3 times faster in the bioaugmented test cell (MW-24i) than in the non-bioaugmented cell (MW-26i).
1,000,000 1,000,000 100,000 100,000 10,000 1,000,000 10,000 1,000 100,000 1,000 100 10,000 100 10 1,000 101 100 1010 10 0
Over the initial 6 month pilot test period, differences in chlorinated VOC degradation rates were more pronounced, with the bioaugmentation test cell (MW-24i) outperforming the mixed PHC/CVOC plume cell by greater than 2x. Over the same time period, PCE mass equivalents increased slightly at the nonbioaugmented test cell (MW-26i).
DISCUSSION – TO BIOAUGMENT OR NOT TO BIOAUGMENT
1,000,000 1,000,000 100,000
100,000 10,000 1,000,000 10,000 1,000 100,000 1,000 100 10,000
As with most decisions in the field of environmental remediation, deciding whether or not to bioaugment is a site-specific determination that is chiefly predicated by the: 1) goals for treatment to be deemed complete; 2) time required to achieve these goals; and, 3) cost to implement. The incremental cost to bioaugment is often in the range of less than $5 to $10 per cubic yard of saturated zone treated, as applied, for shallow (less than 30 ft), unconsolidated aquifers (such as presented here). In scenarios where achieving goals as quickly as practicable is desired, this study indicates that bioaugmentation may be a useful tool to enhance the degradation rates and reach closure objectives more quickly. Pilot tests, in particular, represent one such scenario since a shortened time-frame to make a go/no go full scale implementation decision is often required by project stakeholders. Where the time required to reach the closure objectives is more relaxed, this study suggests degradation rates in non-bioaugmented electron donor applications may eventually reach levels similar to bioaugmented applications. Further testing of this sort at project sites across different hydrogeologic settings and with differing levels/signatures of chlorinated solvent contamination would be useful to create a population of sites where this issue can be further studied.
100 10 1,000 101 100 1010 10 0
1,000,000 1,000,000 100,000 100,000 10,000 1,000,000 10,000 1,000 100,000 1,000 100 10,000 100 10 1,000 101 100 1010 10 0
MW-24i Microbial Results (3DME+BDI) MW-24i Microbial Results (3DME+BDI) MW-24i Microbial Results (3DME+BDI) MW-24i Microbial Results (3DME+BDI) 1,000,000 Microbial MW-24i MW-24i Results Microbial (3DME+BDI) Results (3DME+BDI) 1,000,000
100,000 100,000 1,000,000 10,000 10,000 100,000 1,000 1,000 10,000 100 100 1,000 10 10 100 1 110 0 0 90 01 0 90 0 0 90
DHC DHC tceA DHC tceA bvcA tceA bvcA VCR bvcA VCR
cells/mL cells/mL cells/mL
Both DHC and functional gene populations were similar between the bioaugmented test cell (MW24i) and the commingled plume test cell (MW-18i) beginning at the 3 month event. DHC and VCR populations were elevated at baseline at MW-18i. This is due to the PHCs being utilized as an electron donor for ERD.
++ CEAs - sulfate, nitrate, dissolved iron and manganese
cells/mL cells/mL cells/mL
Investigation work completed in 2008 confirmed chlorinated solvents (i.e., PCE and daughter products trichloroethene (TCE), cis-dichloroethene (DCE) and vinyl chloride (VC) had migrated through Source of Spill - Former UST System the sandy aquifer beneath the facility and extended 3,000 Commercial Manufacturing Facility in Northern Indiana - Looking North at Facility Exterior feet downgradient. Petroleum hydrocarbons (PHC) from the mineral spirits had migrated a few hundred feet downgradient of the source area. Vinyl chloride concentrations in the mixed plume were in the parts per million range due to microbial utilization of the PHC as a growth substrate.
Pilot Test Injection Point Configuration
cells/mL cells/mL cells/mL
A release occurred from an underground storage tank (UST) system at the southern end of the facility in the mid 1980s. The spilled products consisted of virgin tetrachloroethene (PCE) and “high-test” mineral spirits (mineral spirits with added ethylbenzene and xylenes).
cells/mL cells/mL cells/mL
PROJECT SUMMARY
Pilot Test Specifications for Each Treatment Cell Primary Contaminants - Chlorinated VOCs (PCE, TCE, cis-DCE, VC) ++ Soil Type - Sand (predominant) ++ Surface Area - 1,500 square feet ++ Treatment Thickness - 18-24 feet below ground surface ++ Treatment Volume - 330 cubic yards ++ Injection Points - 9 each for 3-D Microemulsion and BDI Plus (sequentially applied) ++ 3-D Microemulsion Applied - 1,920 gallons (4% active ingredient) ++ BDI Plus Applied - 18 Liters of culture containing >1010 cells (gene copies) per liter mixed with a nominal volume 200 gallons of de-oxygenated water
140 0 0140 140 0
181 90 181 90 181 90
219 140 219 140 219 140
273 181 273 181 273 181
317 219 317 219 317 219
273 273 273
VCR 317 317 317
10000 10000 DHC DHC tceA DHC tceA bvcA tceA bvcA VCR bvcA VCR VCR
MW-26i Microbial Results (3DME Only) MW-26i Microbial Results (3DME Only) MW-26i Microbial Results (3DME Only) MW-26i Microbial Results (3DME Only) 1,000,000 Microbial MW-26i MW-26i Results Microbial (3DME Results Only)(3DME Only) 1,000,000
100,000 1,000,000 100,000 10,000 100,000 10,000 1,000 10,000 1,000 100 1,000 100 10 100 10 1 110 0 0 90 01 0 90 0
140 0 140 0
181 90 181 90
219 140 219 140
273 181 273 181
317 219 317 219
0
140 0
181 90
219 140
273 181
317 219
DHC DHC tceA DHC tceA bvcA tceA bvcA VCR bvcA VCR
cells/mL cells/mL cells/mL
Vinyl Chloride Plume Isocontour Maps – July 2008 vs. March 2013
90
VCR 273 317 273 317 273 317
100,000 1,000,000 100,000 10,000 100,000 10,000 1,000 10,000 1,000 100 1,000 100 10 100 10 1 110 0 0 90 01 0 90 0 0 90
DHC DHC tceA DHC tceA bvcA tceA bvcA VCR bvcA VCR 140 0 140 0
181 90 181 90
219 140 219 140
273 181 273 181
317 219 317 219
140 0
181 90
219 140
273 181
317 219
VCR 273 317 273 317 273 317
10000 1000 1000 1000 100 100 100
10000 10000 DHC DHC tceA DHC tceA bvcA tceA bvcA VCR bvcA VCR VCR
MW-18i (mixed plume) Microbial Results (3DME MW-18i (mixed plume) Microbial Results (3DME MW-18i (mixed plume) Microbial Results (3DME MW-18i (mixed Microbial Results (3DME Only)plume) Only) MW-18i (mixed MW-18i plume) (mixed Microbial plume) Results Microbial (3DME Results (3DME Only) Only) 1,000,000 Only) Only) 1,000,000 cells/mL cells/mL cells/mL
OBJECTIVE
Advanced Technologies for Contaminated Site Remediation
DHC DHC tceA DHC tceA bvcA tceA bvcA VCR bvcA VCR VCR
10000 1000 1000 1000 100 100 100
10000 10000 10000 1000 1000 1000 100 100 100
MW-24i PCE Equivalents MW-24i PCE Equivalents Equivalents MW-24i PCE Equivalents MW-24i PCE MW-24i PCE 10000 MW-24i PCE MW-24i Equivalents PCE Equivalents 10000 Equivalents MW-24i PCE 10000
1000 1000 1000 100 0 90 100 140 181 219 0 90 days 0 90 140 181 219 0 90 100 days days 90 0 90 140 days 1810 219 days days
273 140 273 140
317 181 317 181
MW-24i PCE MW-24i PCE Equivalents (ug/L) Equivalents Equivalents MW-24i PCE MW-24i PCE (ug/L) (ug/L) (ug/L) Equivalents Equivalents -0.435x y = 6910e -0.435x (ug/L) (ug/L) y = 6910e y = 6910e -0.435x y = 6910e -0.435x y = 6910e -0.435x y = 6910e -0.435x
371 219 273 317 371 371 273 317 371 219 140 317 181 371 219 273 317 371 273
MW-26i PCE Equivalents MW-26i PCE Equivalents MW-26i PCE Equivalents MW-26i PCE Equivalents 10000 MW-26i PCE MW-26i PCE MW-26i Equivalents PCE Equivalents 10000
MW-26i PCE Equivalents MW-26i PCE MW-26i PCE Equivalents (ug/L) Equivalents Equivalents MW-26i PCE MW-26i PCE (ug/L) (ug/L) (ug/L) Equivalents Equivalents y = (ug/L) 1963.9e -0.138x (ug/L)-0.138x y = 1963.9e y = 1963.9e -0.138x y = 1963.9e -0.138x
10000 1000 1000 1000 100 0 90 100 140 181 0 days 0 90 100 140 181 0 days days 0 90 140 days 1810 days days
y = 1963.9e -0.138x 219 90 219 90 219 90
273 140 273 140 273 140
317 181 317 181 317 181
y = 1963.9e -0.138x
371 219 273 317 371 371 273 317 371 219 371 219 273 317 371
MW-18i PCE Equivalents MW-18i PCE Equivalents MW-18i PCE Equivalents MW-18i PCE Equivalents 10000 MW-18i PCE MW-18i Equivalents PCE Equivalents 10000 10000 1000 1000 1000 100 0 90 100 140 181 219 0 90 days 0 90 140 181 219 0 90 100 days days 0 90 140 days 1810 219 90 days days
MW-18i PCE MW-18i PCE Equivalents MW-18i PCE (µg/L)MW-18i PCE Equivalents (µg/L) Equivalents (µg/L) Equivalents (µg/L) MW-18i PCE MW-18i PCE (µg/L) Equivalents (µg/L y Equivalents = 6245.7e -0.454x y = 6245.7e -0.454x -0.454x y = 6245.7e y = 6245.7e -0.454x
y = 6245.7e -0.454x
273 317 371 140 181 219 273 317 371 273 181 317 219 371 273 317 371 140 273 140 317 181 371 219 273 317 371
y = 6245.7e -0.454x
6/5/2013 5:42:12 PM