Technology:
Bioaugmentation
A field demonstration was conducted at the MAG-1 Area in Fort Dix, New Jersey, using Shaw Environmental, Inc.'s (Shaw) dechlorinating consortium (SDC-9), a Dehalococcoides (DHC)-containing culture, to bioaugment a chlorinated ethene groundwater plume. Details about the demonstration are provided below:
- The field demonstration involved the construction and operation of four groundwater recirculation loops to test various amendment and inoculum dosages, as follows:
- Loop 1: Lactate, buffer, nutrients, and 100 liters (L) of SDC-9
- Loop 2: Lactate, buffer, nutrients, and 10 L of SDC-9
- Loop 3: Lactate, buffer, nutrients, and 1 L of SDC-9
Loop 4: Lactate, buffer, and nutrients only (control loop).
- The lactate, buffer (sodium bicarbonate or sodium carbonate), and nutrients (diammonium phosphate and yeast extract) were injected into each of the four injection wells in equal amounts.
- Each recirculation loop consisted of an injection and extraction well pair with intermediate monitoring wells. Each recirculation loop was separated by approximately 25 feet (ft) from other test areas and was installed parallel to groundwater flow. The distance between the injection well and extraction well in each loop was approximately 30 ft.
- To minimize injection pressure at the injection wells during the start-up period, groundwater extraction rates at each extraction well were reduced incrementally from 0.5 gallons per minute (gpm) to 0.3 gpm.
- Two performance monitoring wells were installed approximately 10 and 20 ft from the injection well, respectively, along each of the injection/extraction well transects. To monitor lateral distribution of amendments and possible cross flow between loops, three additional monitoring wells were installed along a side-gradient of Loop 1.
- The groundwater recirculation and amendment delivery systems operated for nine and a half months. The initial period consisted of continuous operation for 39 days from January 24 through March 3, 2008. Between March 3, 2008, and November 5, 2008, the systems were operated in an "active-passive" mode. In active mode, groundwater recirculation and amendment addition into the aquifer were continuously performed. During passive mode, the systems did not operate, and the injected amendments were allowed to move naturally with the groundwater.
- All four injection wells were redeveloped twice, once in December 2007 during the start-up phase, and again in June 2008 during the system operation phase.
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Cleanup Authority:
Department of Defense (DoD)
Contacts:
Principal Investigator
Robert Steffan
Shaw Environmental, Inc.
17 Princess Road
Lawrenceville, NJ 08648
Phone: 609-895-5350
Email: rob.steffan@shawgrp.com
Project Geologist
David Lippincott
Shaw Environmental, Inc.
17 Princess Road
Lawrenceville, NJ 08648
Phone: 609-895-5350
Email: david.lippincott@shawgrp.com
Project Engineer
Charles Schaefer
Shaw Environmental, Inc.
17 Princess Road
Lawrenceville, NJ 08648
Phone: 609-895-5372
Email: charles.schaefer@shawgrp.com
Contracting Officer's Representative
Naval Facilities Engineering Command Engineering Service Center (NAVFAC ESC) Restoration Development Branch
ESC 411 1100 23rd Avenue Port Hueneme, CA 93043
Phone: 805-982-1155
Email: nancy.ruiz@navy.mil
Environmental Restoration Program Manager
Andrea Leeson
ESTCP Office
901 North Stuart Street, Suite 303
Arlington, VA 22203
Phone: 703-696-2118
Email: andrea.leeson@osd.mil |
Contaminants:
Trichloroethene (TCE), cis-dichloroethene (cDCE) |
Waste Source:
Chlorinated volatile organic compound (CVOC)-contaminated aquifer |
Type/Quantity of Media Treated:
Groundwater. Approximately 900 cubic yards of contaminated aquifer were treated. |
Purpose/Significance of Application:
The key objectives of the demonstration were (1) to determine the amount of culture required for effective bioremediation of the CVOCs, (2) to determine if inoculum dose affects remedial time, (3) to evaluate the effect of site characteristics on technology effectiveness, and (4) to determine whether addition of buffers can maintain the subsurface pH at a level needed for bioremediation. |
Regulatory Requirements/Cleanup Goals:
The primary performance criteria for the demonstration included: - Achieve a greater than 90 percent reduction of TCE and cDCE
- Achieve complete dechlorination of TCE and cDCE to ethene in the three recirculation test loops
- Demonstrate slow or incomplete dechlorination of TCE and cDCE in the control loop
- Achieve a SDC-9 concentration greater than 107 cells/L at downgradient monitoring wells
- Achieve volatile fatty acid concentrations greater then 5 mg/L at downgradient monitoring wells
- Increase and maintain groundwater pH levels between 5.5 and 8.0 standard units
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Results:
Sampling results from the demonstration indicated the following: - Results for Loops 1 and 2 showed similar rates of dechlorination. TCE concentrations declined significantly during the demonstration, ranging from 90 to 100% reductions.
- Concentrations of cis-1,2-dichloroethene (cDCE) in test loops declined between 73 and 99% and continued to decrease at the end of the demonstration, while cDCE concentrations in the control loop increased during the demonstration.
- Transient increases (followed by decreases) in vinyl chloride (VC) were observed in five of the six test loop performance wells, with VC in two of the wells below detection at the end of the demonstration. VC was not observed in the control loop monitoring wells.
- Final DHC concentrations in the three test loops ranged from 1.8 x 107 to 2.0 x 109 cells/L.
- Groundwater sampling results indicated that aqueous SDC-9 concentration increases were orders of magnitude higher in the test loops, compared to the control loop.
- Ethene data collected clearly indicated that complete TCE degradation was occurring within loops 1, 2, and 3 and not within the control loop (loop 4).
- Volatile fatty acid (VFA) data collected during the demonstration indicated that lactate injection and groundwater recirculation rates used during the demonstration were effective in distributing the electron donor in all four recirculation loops.
- Increasing and maintaining pH levels within the recirculation loops was challenging. Typically, pH increased from below 5.0 to between 6.0 and 7.1 standard units, except at injection wells where pH levels were higher due to sodium carbonate injection. However, the pH levels sometimes dropped below 5.5 in some of the monitoring wells during periods of the demonstration.
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Cost Factors:
The total cost of the bioaugmentation demonstration at Fort Dix, from July 2006 (site selection) until July 2009 (preparation of the final report and cost and performance report), was $786,700. This corresponded to a unit cost of approximately $875 per cubic yard of the treated contaminated aquifer. Costs included the following: - Capital costs (system design and installation) — $385,400 (or 49% of the demonstration costs).
- O&M and reporting costs (groundwater monitoring, system operation and maintenance, amendments and SDC-9 culture, reporting costs) — $242,400 (or 31% of the demonstrations cost).
- Other demonstration-specific costs (preparation of various research reports, site selection, laboratory and tracer testing, additional demonstration reporting and in-progress review meeting requirements) — $158,900 (or 20% of the demonstration cost).
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Description:
Fort Dix is located in Burlington and Ocean counties, approximately 25 miles southeast of Trenton, New Jersey. The site chosen for the field demonstration, MAG-1 area, is located in the northern part of Fort Dix and has been shown to have the highest CVOC concentrations. Some other characteristics of this area that made it useful for this demonstration include: (1) TCE concentrations >250 micrograms per liter (µg/L) without VC or ethene; (2) a shallow sand or silty sand aquifer; and (3) an area large enough to accommodate four recirculation loops.
In the 14-month field demonstration, bioaugmentation using Shaw's SDC-9 DHC-containing culture was used to treat the CVOC-contaminated plume. The field demonstration involved the construction and operation of four groundwater recirculation loops — three test loops inoculated with a different amounts of Shaw's SDC-9 dechlorinating culture and one control loop which received only electron donor, buffer, and nutrients. Installation of the field demonstration wells and equipment occurred between June and September 2007. Field testing began in November 2007 and lasted for approximately 14 months. Testing was performed in three operational phases, including system testing; system start-up and tracer testing; and bioaugmentation, system operation, and performance monitoring. A total of 12 performance monitoring groundwater sampling events were conducted in the demonstration area between January 30, 2008, and January 5, 2009, to monitor treatment performance. Project results demonstrated that the CVOC-contaminated aquifer was effectively remediated using active groundwater recirculation, bioaugmentation with Shaw's SDC-9, and pH adjustment. All performance criteria established for this demonstration were met. |
