ADVENTUS GROUP

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In-Situ Soil Bioremediation of Petroleum Hydrocarbons

Using Aerobic DARAMEND - A Case Study from Taiwan

Soil Bioremediation Theory

Soil impacted with petroleum hydrocarbons (TPH) along with polynuclear aromatic hydrocarbons (PAHs) and pentachlorophenol (PCP) were treated at an inactive manufacturing site in Taiwan using DARAMEND soil treatment technology from ADVENTUS. DARAMEND promotes aerobic biodegradation of these compounds by providing timed-release nutrients such as nitrogen, organic carbon, phosphorus etc. as well as creating the right conditions of pH, alkalinity etc. to enhance the microbial activity of indigenous microorganisms. Oxygen for aerobic biodegradation is provided by tilling the soils periodically and moisture is provided by simple irrigation system. The benefit of in-situ bioremediation at this site allowed the treatment to occur on site avoiding the need for the often expensive off-site treatment and disposal option.

Bioremediation Operation:

There are several critical factors for effective bioremediation of hydrocarbon contaminated soil, including soil moisture content (a function of the water holding capacity (WHC)), pH, aeration of the soil via tilling, and the application rate of DARAMEND based on the concentration of contaminants. These variables must be controlled at optimum levels to realize the highest effectiveness of treatment. At the beginning of this study, baseline soil analysis was conducted to determine the concentrations of target compounds. The soil was also analyzed for pH and WHC. DARAMEND was applied at an application rate of 1% to soil mass (approximately 52 kg of DARAMEND to 5,200 kg of soil to be treated). Immediately after adding the DARAMEND, soil samples were collected and analyzed for pH, soil moisture content and WHC for both the control soil pile and the soil pile amended with DARAMEND (See Table 1). The soil pH was in the neutral range and ideal for promoting bioremediation.

Both, the control and the treatment soil piles were aerated twice a week using a tiller and irrigated to maintain moisture. Soil samples were analyzed weekly for operational monitoring (pH and moisture). The target moisture content was set at 70% of the WHC. The initial WHC of treatment soil pile was at 44.2%.

Results and Conclusion

Analytical results indicate that there was a 68% reduction in TPH-D during the first three weeks after DRAMEND was applied. No significant reductions were observed over the next four weeks suggesting that another dose of DARAMEND was required. However, soil samples collected on Dec 8, 2009 showed a sudden drop in TPH-G (almost 50% from that observed after the first three weeks). This could be due to the fact that between week 4 and week 8, the high molecular weight and long-chain TPH were being broken down to lighter intermediates but there was no net reduction in TPH. After week 9, the lighter intermediates started to mineralize. It appears that additional DARAMEND will be required to increase the removal efficiency. The final results of soil analysis of this study were successful in achieving the regulated soil TPH limits of 646 mg/kg

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ISGS Pilot Study Report

Field Performance Assessment

Cabot Carbon/Koppers Superfund Site in Gainesville, Florida

EXECUTIVE SUMMARY:

In situ geochemical stabilization (ISGS) entails the use of a modified solution of sodium permanganate (NaMnO₄) designed for in situ management of non-aqueous phase liquids (NAPL). When added to an impacted aquifer, the technology is designed to rapidly react with organic (and certain inorganic) constituents of interest (COI) present as soil residuals (e.g., NAPL or ganglia).  Various reactions associated with ISGS processes serve to rapidly reduce aquifer permeability and stabilize the NAPL residuals thereby leading to enhanced passive remediation or accelerated remediation by natural attenuation. 

Using subsurface soils from the Cabot Carbon / Koppers wood-treating site in Gainesville, Florida (Site), bench-scale engineering optimization tests previously demonstrated that such stabilization of creosote/penta NAPL residuals at the Site was technically feasible, and that this combination of reagents could potentially yield effective long-term NAPL stabilization and flux reduction of all monitored COI (Adventus Americas, Inc., 2004). Field testing of the ISGS approach was subsequently undertaken in January 2008 to yield site-specific field data necessary to validate full-scale technology efficacy. Implementation of the ISBS field test was completed in the surficial aquifer at the former North Lagoon Area of the Site during the period January 22-26, 2008 (Adventus Americas, Inc. - March 31, 2008).  Post-treatment soil cores were collected approximately 60 days after the Remox EC reagents were injected (Appendix E).

This report describes the initial performance monitoring activities conducted for pilot-scale field validation of the ISBS technology.  Specifically, the report summarizes field observations, analytical results for soil cores and "crust" analyses on soil cores collected approximately 60 days after treatment.  In addition, it presents the data associated with the Variance requirements associated with the use of the material.

As described herein, multiple units of measure were used to define the effectiveness of the ISGS technology, and to assess the long-term permanence of the stabilization process.  After only 60 days post-treatment, the ISBS technology was shown to provide safe, rapid, effective and predicted long-term treatment as follows:

Field NAPL Measurement: There was no measurable free-phase NAPL in any of the monitoring wells.

Reduced Soil COI Concentrations. Using data from all samples, the concentrations of total soil polycyclic aromatic hydrocarbons (PAHs) were reduced by an average of 11% (for the DIP area) to 98% (for the TIP area). Considering data from the best paired cores (as described below), a 50% reduction of total PAHs in soil was observed, with the average soil PAH concentration being reduced from of 7,250 mg/kg soil to 3,600 mg/kg soil.

Reduced COI Concentrations in Soil Leachate: Using data from all leachate samples, the average concentrations of COIs in the soil leachates post ISGS treatment were reduced by 71% (for the DIP area) to 98% (for the TIP area).  Using data from the best paired cores, the amount of site-specific COIs present in soil leachate was reduced by 95%, with an average total of 11,700 mg/L total PAHs present in the leachates prior to Remox EC treatment and an average of 560 mg/L of total PAHs being present in the leachates from the soil cores collected 60 days after treatment.

Rapid, Uniform and Environmentally Stable Encrustation of NAPL residuals:  Using optical microscopy, electron probe microscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM), independent expert studies by Dr. Tom Al (University of New Brunswick; UNB) showed that the ISBS precipitates formed coatings around aquifer grains and NAPL droplets.  The coatings were composed of crystalline aluminum silicate hydroxides that were not representative of conventional manganese oxyhydroxides that would typically form with the use of standard permanganate.  Unlike the manganese oxyhydroxide coatings, the ISGS coatings are not expected to be affected by changes in the redox potential of the aquifer and are therefore considered to be stable and persistent with time.

Reduced Permeability: Adventus' lab tests showed a qualitative decrease in "leachability" post-ISGS treatment.  Independent studies by UNB indicated that 27 to 81% of the pre-injection pore space was filled in lightly coated to heavily coated areas, respectively. It was noted that field aquifer permeability reductions were likely even greater than 81%. This is consistent with the bench-scale column testing work conducted previously, which showed >90% reduction in permeability / transmissivity within 8 days of ISGS treatment.

Minor Exceedance of Variance Secondary Analytes: There was an apparent increase in Aluminum (Al) in some wells, but there was no clear pattern identified with the distribution. There was a slight increase in pH noted in two wells (HG-10D and UHG-HG-16S), both of which have had a history of containing small amounts of basic NAPL.

No Significant Exceedance of Variance Primary Analytes: Groundwater monitoring showed that the ISGS treatment did not induce any significant exceedance of primary analytes, and there were no impacts observed at either the newly installed zone of discharge monitoring well (ZOD-1) nor in any of the other six Variance monitoring wells. In particular, no Chromium (Cr) exceedance was noted at any well location. There was a minor exceedance in Arsenic (As) noted in one well (supplemental Variance monitoring well UHG-HG-16S) that is located far down gradient of the treated area. 

Beazer East, Inc.

Prepared by:

Adventus Americas Inc.

Freeport, IL

8153/235-3503

In cooperation with:

GeoTrans, Inc.

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OVERVIEW

A chlorinated solvent plume (PCE) was migrating onto a commercial site in Toronto area and a lending institution required mitigating measures implemented. An in-situ approach was required due to the proximity of the property boundary, on-site building and depth to water table (~5 m). The dissolved concentrations of the compounds of concern were:

The dissolved concentrations of the compounds of concern were:

• PCE (maximum concentration of 450 μg/L)
• TCE (maximum concentration of 47 μg/L)
• cis 1,2- DCE (maximum concentration of 50 μg/L)
• Vinyl chloride (maximum concentration of 12 μg/L)

SCOPE OF WORK

Acquired all relevant permits to complete the remediation program.

Designed and optimized an in situ program to maximize treatment efficiencies.

Implemented a program that minimized impact to the Site given the presence of buildings and property boundary.

THE VERTEX APPROACH

Reductive dechlorination.

Reactive Zone including:

• Permanent Injection Wells
• Temporary Injection Points

Eight permeable reactive zones.

Injection/placement of reactive compounds:

• >225 kg of EHC®
• >80 kg of EHC®-A

OUTCOME

Successful installation of a reactive zone.

Reductive dechlorination conditions created:

• Redox reductions of up to -175mV
• PCE decreased from 450 g/Lt o 60 g/L
• No vinyl chloride generation