Progress 02/01/09 to 01/31/14
Outputs
Target Audience: The target audience includes research scientists, teachers, environmental professionals and communities in need of remediation services. These services include techniques and products that treat contaminated soil and water. Efforts include acts that delivered science-based knowledge through publications and field-scale demonstrations. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided? The following graduate students have been trained under this project: Manmeet Waria (MS, Dec. 2007). Field-scale remediation of pesticide-contaminated soil by a combined chemical-biological approach. Chanat Chokejaroenrat (MS, Aug. 2008). Laboratory and pilot-scale investigations of RDX treatment by permanganate. Jeff Albano (MS, Jan. 2009). In situ chemical oxidation of RDX-contaminated groundwater with permanganate at the Nebraska Ordnance Plant. Mark Christenson (MS, Aug. 2011). Using slow-release permanganate to remove TCE from a low permeable aquifer at a former landfill. Ann Kambhu (MS, Dec. 2011). Developing slow-release persulfate candles to treat BTEX-contaminated groundwater. Chanat Chokejaroenrat (Ph.D., Dec. 2012). Improving the sweeping efficiency of permanganate into low permeable zones to treat pure-phase and dissolved-phase TCE. Chainarong Sakulthaew (Ph.D., May. 2013). Removing PAHs from urban runoff water by combining ozonation, adsorption, and biodegradation How have the results been disseminated to communities of interest? Multiple publications were published from this project. Moreover, direct assistance was given to communities impacted by contaminated groundwater by performing field-scale demonstrations of remedial treatments. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Considerable progress was achieved in the laboratory over the timeframe of this project. These included: (i) identifying the mechanisms by which permanganate degrades RDX; (ii) development of persulfate-iron candles for treating BTEX compounds and (iii) improving the sweeping efficiency of permanganate into low permeable zones. In addition, two field-scale treatments of contaminated groundwater were also performed under this project. These included an in situ chemical oxidation (ISCO) treatment of a RDX plume at the Nebraska Ordnance plant (Mead, NE) and the development of slow-release permanganate candles for treating TCE-contaminated groundwater at an abandoned landfill.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Chokejaroenrat, C., Kananizadeh, N., Sakulthaew, C., Comfort,S., and Li,Y., (2013). Improving the sweeping efficiency of permanganate into low permeable zones to treat TCE: Experimental results and model development. Environ. Sci. Technol. 47:13031-13038
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
Chokejaroenrat, C., Sakulthaew,C., Comfort,S., and Dvorak, B. (2014). Improving the treatment of non-aqueous phase TCE in low permeability zones with permanganate. J. Hazard. Materials. 268:177-184.
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
Sakulthaew, C., Comfort, S., Chokejaroenrat, C., Harris, C., and Li, X. (2014). A combined chemical and biological approach to transforming and mineralizing PAHs in runoff water. Chemosphere, 117:1-9
- Type:
Journal Articles
Status:
Published
Year Published:
2014
Citation:
Huang, Y.H., Zhang, T.C., Shea, P.J., Comfort, S.D. (2014). Competitive reduction of nitrate, nitrite, and Nitrobenzene in Fe0-water systems. J. Environ. Eng. 140(8), 04014029
- Type:
Book Chapters
Status:
Published
Year Published:
2014
Citation:
Szecsody, J.E., Comfort, S., Fredrickson, H.L., Riley, R.E., Crocker, F., Shea, P., McKinley, J.P., Gamerdinger, A.P., Boparai, H.K., Girvin, D.C., Moser, J.V., Thompson, K., Resch, T., DeVary, B.J., Durkin, L., Breshears, A.T. (2014). In Situ Degradation and Remediation of Energetics TNT, RDX, HMX, and CL-20 and a Byproduct NDMA in the Sub-Surface Environment. In Shree Nath Singh (ed) Biological Remediation of Explosive Residues. pp. 313-369. Springer International Publishing, Switzerland.
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Progress 10/01/12 to 09/30/13
Outputs
Target Audience: The population of Nebraska, national and international environmental scientist Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?
Nothing Reported
How have the results been disseminated to communities of interest? Public meetings with city officials and environmental scientists from Nebraska's Department of Environmental Quality What do you plan to do during the next reporting period to accomplish the goals? Initial more field trials to demonstrate the remedial technologies developed
Impacts
What was accomplished under these goals?
Permanganate candles developed were shown to be effective in reducing the concentration TCE at an abandoned landfill and for treating PAHs in runoff water. Persulfate-zerovalent iron candles were effective in treating BTEX compounds.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2012
Citation:
Christenson, M.D., A. Kambhu, and S.D. Comfort. 2012. Using slow-release permanganate candles to remove TCE from a low permeable aquifer at a former landfill. Chemosphere 89:680-687.
- Type:
Journal Articles
Status:
Published
Year Published:
2012
Citation:
Halihan, T., J. Albano, S.D. Comfort, and V.A. Zlotnik. 2012. Electrical resistivity imaging of a permanganate injection during in situ treatment of RDX-contaminated groundwater. Ground Water Monitoring & Remediation 32:43-52.
- Type:
Journal Articles
Status:
Published
Year Published:
2012
Citation:
Kambhu, A., S. Comfort, C. Chokejaroenrat, and C. Chainarong. 2012. Developing slow-release persulfate candles to treat BTEX contaminated water. Chemosphere 89:656-664.
- Type:
Journal Articles
Status:
Published
Year Published:
2012
Citation:
Rauscher, Lindy, Chainarong Sakulthaew, and Steve Comfort. 2012. Using slow-release permanganate candles to remediate PAH-contaminated water. J. Hazard. Materials 241-242:441-449.
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Progress 10/01/11 to 09/30/12
Outputs
OUTPUTS: Water quality is one of the biggest issues related to public health in the United States. Two of the biggest threats to groundwater quality in the U.S. are contamination from either chlorinated solvents or petroleum. One technology that is relatively mature is the injection of liquid oxidants into contaminated aquifers or in situ chemical oxidation (ISCO). Two roadblocks to successfully implementing ISCO treatments are when contaminants are located in low permeable layers and these finer textured zones do not readily accept liquid injections or when the aquifer is porous enough for liquid injections,but the cohesive properties of the chemical oxidant results in density-driven flow,thereby causing the oxidant to sink and not treat the desired target zone. To address both problems, we developed slow release oxidant-paraffin candles, that when inserted into low permeable zones, slowly dissolve and intercept the contaminant. To prevent the oxidant from migrating downward from the candles, pneumatic circulators were developed that aerate or release bubbles at the base of the candle and prevent the oxidant from sinking while greatly facilitating its horizontal distribution. This research has been shared with the research community and industry and is now being used to treat contaminated aquifers. PARTICIPANTS: Graduate students: Mark Christenson, Ann Kambhu, Chanat Chokejaroenrat, and Chainarong Sakulthaew. TARGET AUDIENCES: Research community and environmental scientists and engineers working for private and government agencies whose focus is to remediate contaminated groundwater. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The main outcomes from this research has been the development of slow-release chemical oxidant "candles" for treating contaminants in low permeable zones. Two types of candles were developed: permanganate-paraffin candles for treating chlorinated solvents and persulfate-iron candles for treating petroleum contaminants.
Publications
- Kambhu, A.,Comfort S., Chokejaroenrat C., Chainarong, C. 2012. Developing slow-release persulfate candles to treat BTEX contaminated water. Chemosphere 89:656-664.
- Christenson, M.D., Kambhu, A., and Comfort, S.D. 2012. Using slow-release permanganate candles to remove TCE from a low permeable aquifer at a former landfill. Chemosphere 89:680-687
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Progress 10/01/10 to 09/30/11
Outputs
OUTPUTS: In situ chemical oxidation (ISCO) is the accepted practice of injecting liquid oxidants into an aquifer for remediating contaminated groundwater. Two roadblocks to successfully implementing ISCO treatments are: (i) When contaminants of interest are located in low permeable layers and these finer textured zones do not readily accept liquid injections or (ii) When the aquifer is porous enough for liquid injections, but the cohesive properties of the chemical oxidant results in density-driven flow, thereby causing the oxidant to sink and not treat the desired target zone. To address both problems, we recently developed and manufactured slow-release chemical oxidant-paraffin candles for treating contaminants in low permeable zones. Two types of candles were developed: permanganate-paraffin candles for treating chlorinated solvents and persulfate-iron (activator) candles for treating petroleum contaminants. To prevent the oxidant from migrating downward from the candles, recent laboratory results have shown that aerators (i.e., bubbles) placed at the base of a candle prevent the oxidant from sinking while greatly facilitating its horizontal distribution. Scale-up of this idea is currently being tested in the form of field-scale aerators that have been placed at the bottom of slow-release candles in designated wells. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Slow-release chemical oxidants are a relatively new technology proposed for sub-surface remediation but examples of field-scale applications are limited. Part of the impediment to using slow-release oxidants by practitioners was the lack of a marketable product and commercial source. Specifically, practitioners were unsure on how to make use of the various formulations of slow-release oxidants reported in research publications. The permanganate candles developed and field-tested by the University of Nebraska represents the first field trial of this technology. Advantages to formulating slow-release oxidants as candles are that it negates the need for specialized equipment (mixing trailer, pumps, hoses, etc), curtails health and safety issues associated with handling liquid oxidants, and greatly simplifies the application process. Candles can either be placed in designated wells or dropped down rods with direct push equipment. One of the largest manufacturers of permanganate recently adopted this approach and is now manufacturing permanganate candles that are very similar to those developed by UNL.
Publications
- Chokejaroenrat, C., Comfort,S.D., Harris,C., Snow, D., Cassada, D., Sakulthaew, C., and Satapanajaru, T. (2011). Transformation of Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) by Permanganate. Environ. Sci. Technol., 45:3643-3649
- Halihan, T., Albano, J., Comfort, S.D., and Zlotnik, V.A., (2011). Electrical Resistivity Imaging of a Permanganate Injection During In Situ Treatment of RDX-Contaminated Groundwater. Ground Water Monitoring & Remediation. doi: 10.1111/j.1745-6592.2011.01361.x
- Kalderis, D, Juhasz, A., Boopathy, R., and Comfort, S.D., (2011). Soil contaminated by explosives - environmental fate and evaluation of state of the art remediation processes (IUPAC Technical Report). Pure and Applied Chemistry. 83:1407-1484.
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Progress 10/01/09 to 09/30/10
Outputs
OUTPUTS: A field-scale demonstration of in situ chemical oxidation using slow-release permanganate candles was initiated during the summer of 2010. To our knowledge, this trial is the first field-scale testing of a permanganate-paraffin matrix. The candles were placed into TCE-contaminated groundwater by installing some designated wells and by inserting them directly into the formation by direct push technology. PARTICIPANTS: The Nebraska Department of Environmental Quality Mark Christianson and Ann Kambhu (graduate students) TARGET AUDIENCES: The city of Cozad, NE and other small communities with closed landfills. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Initial results indicate that the permanganate candles are reducing TCE concentrations and its degradation product. There permanganate candles are particularly well suited for low permeable aquifers where injection of liquid permanganate would be difficult.
Publications
- Albano, J., Comfort, S.D., Zlotnik, V., Halihan,T., Burbach, M., Chokejaroenrat, C., Onanong, S., Clayton. W. (2010). In Situ Chemical Oxidation of RDX-Contaminated Ground Water with Permanganate at the Nebraska Ordnance Plant. Ground Water Monitoring & Remediation 30:96-106.
- Hardiljeet K. B., Comfort, S.D., Satapanajaru, T., Szecsody, J.E., Grossl, P.R., and Shea, P.J. (2010). Abiotic transformation of high explosives by freshly precipitated iron minerals in aqueous FeII solutions. Chemosphere, 79:865-872.
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Progress 10/01/08 to 09/30/09
Outputs
OUTPUTS: NEBRASKA ORDNANCE PLANT. Ground water beneath the former Nebraska Ordnance Plant (NOP) is contaminated with the explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). The current pump and treat facility is preventing offsite migration but does not offer a short term solution. Our objective was to demonstrate that permanganate can effectively degrade RDX in situ. This was accomplished by performing treatability experiments, ground water characterization and a pilot-scale in situ chemical oxidation (ISCO) demonstration. Treatability experiments confirmed that permanganate could mineralize RDX in the presence of NOP aquifer solids. The pilot-scale ISCO was performed by using an extraction-injection well configuration to create a curtain of permanganate between two injection wells. RDX destruction was then quantified as the RDX-permanganate plume migrated down gradient through the monitoring well field. Electrical Resistivity Imaging (ERI) was used to identify the location of the permanganate after injection. COZAD LANDFILL. Electrical Resistivity was used to survey contaminated plume beneath abandoned landfill in Cozad, NE. ERI images were used to guide direct-push groundwater sampling. Characterizing extent of contaminated plume will be used in future design of remedial treatments. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
NEBRASKA ORDNANCE PLANT. Results showed that RDX concentrations temporally decreased in wells closest to the injection wells by 70 to 80%. Observed degradation rates (0.12 d-1 and 0.087 d-1) were lower than those observed under laboratory batch conditions at 11.5 degrees C (0.20 d-1) and resulted from lower than projected permanganate concentrations. Differencing between ERI images taken pre and post injection allowed us to successfully determine the initial size and distribution of the injected permanganate plume. ERI also quantitatively mapped the hydraulic conductivity distribution across the test plot. Although ISCO reduced RDX concentrations by 70 to 80%, ground water samples from twelve down gradient wells and eight direct push profiles did not provide enough data to construct the distribution and flow of the injected permanganate. ERI however, showed that the permanganate injection flowed against the regional ground water gradient and migrated below the monitoring well screens. ERI results combined with spatial determinations of permanganate concentrations entering the monitoring wells helped explain why permanganate was not observed in all down gradient wells and RDX concentrations did not decline below the EPA health advisory level (2 micrograms/L).
Publications
- Waria, M., Comfort, S.D., Onanong, S., Satapanajaru, T., Boparai, H. Harris, C., Snow, D. and Cassada, D.A. (2009). Field-scale cleanup of atrazine and cyanazine contaminated soil with a combined chemical-biological approach. J. Environ. Qual.38: 1803-1811.
- Satapanajaru, T., Onanong, S., Comfort, S.D., Snow, D.D., Cassada, D.A., and Harris, C. (2009). Remediating dinoseb-contaminated soil with zerovalent iron. J. Hazardous Materials 168:930-937.
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Progress 10/01/07 to 09/30/08
Outputs
OUTPUTS: A field demonstration of treating pesticide-contaminated soil was performed in 9/2008 in Maywood, NE using zerovalent iron and ferrous sulfate as chemical amendments. This field-scale demonstration cleaned up 279 cubic yards of contaminated soil. PARTICIPANTS: Graduate students and postdoctoral associates (Chanat Chokejaroenrat, Manmeet Waria, Jeff Albano, Hardiljeet Boparai). TARGET AUDIENCES: Soil remediation projects were targeted toward agricultural cooperatives that sell and distribute pesticides and fertilizers. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
We demonstrated that accelerated destruction of soil and water contaminants can occur through chemical (abiotic) oxidation, reduction or biological treatments of contaminated water and soil. We also identified intermediates and terminal degradates produced from these treatments and proposed chemical degradation mechanisms.
Publications
- Boparai, H.K., P.J. Shea, S.D. Comfort, and T.A. Machacek. 2008. Sequencing zerovalent iron treatment with carbon amendments to remediate agrichemical-contaminated soil. Water, Air and Soil Pollution.193:189-196.
- Boparai, H.K., S.D. Comfort, P.J. Shea, and J.E. Szecsody. 2008. Remediating explosive-contaminated groundwater by in situ redox manipulation (ISRM) of aquifer sediments. Chemosphere 71:933-941
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Progress 10/01/06 to 09/30/07
Outputs
A former agrichemical dealership in western Nebraska was suspected of having contaminated soil from multiple work-related spills. Dealership property was grid sampled and found to contain high concentrations of atrazine (>300 mg kg-1) and cyanazine (>500 mg kg-1). Our objective was to remediate the contaminated site by a combined chemical-biological approach. This was accomplished by creating contour maps of the on-site contamination, removing the top 60-cm of contaminated soil, placing it windrows, and mixing with a mechanical high-speed mixer. Homogenized soil was then used in laboratory investigations to determine optimum treatments for pesticide destruction using a chemical, biological and combined approach.
Impacts
Solutions experiments verified that the chemical treatment of zerovalent iron (Fe0) plus ferrous sulfate (FeSO4) removed >90% of both pesticides within 14 d. LC/MS analysis of Fe0-treated atrazine identified several degradation products commonly associated with biodegradation (i.e., deethlyatrazine (DEA), deisopropylatrazine (DIA), hydroxyatrazine (HA), atraton and ammelines). Biological treatment evaluated emulsified soybean oil (EOS) as a carbon source to stimulate biodegradation in static soil microcosms. Pesticide concentrations in the C-amended soils decreased by 74 to 78% within 21 d. Combining emulsified soybean oil with the chemical amendments resulted in higher destruction efficiencies (80-85%) and reduced the percentage of FeSO4 needed. This chemical-biological treatment (2.5% Fe0 + 1% FeSO4 + EOS) was then applied with water (0.30 kg water kg-1 soil) by a high speed mixer to the contaminated soil (~360 yd3) at the field site. Windrows were tightly covered
with clear plastic to increase soil temperature and maintain soil water content. Temporal sampling (0-342 d) showed atrazine and cyanazine destruction decreased by 79 to 91%. These results provide evidence that both chemical and biological approaches can be used for on-site, field-scale treatment of pesticide-contaminated soil.
Publications
- Onanong, S. S.D. Comfort, P.D. Burrow, and P.J. Shea. 2007. Using gas phase molecular descriptors to predict dechlorination rates of chloroalkanes by zerovalent iron. Environ. Sci. Technol.41:1200-1205.
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Progress 10/01/05 to 09/30/06
Outputs
Research in 2005/2006 has focused on remediating two distinct sources of contamination: (i)pesticide-contaminated soil at an abandoned Nebraska agrichemical facility and (ii)RDX-contaminated groundwater at the Nebraska Ordnance Plant. In the pesticide study, we delineated the extent of soil contamination at the site by grid sampling and then evaluated a variety of abiotic treatments in the laboratory. In September, 2006 we treated approximately 360 cubic yards of contaminated soil in the field with zerovalent iron, ferrous sulfate and emulsified soybean oil. Results thus far indicate that pesticide concentrations in the treated soil have decreased between 70 and 80%. In the groundwater study, we plan to demonstrate an in situ chemical oxidation treatment of RDX in groundwater using permanganate. To accomplish this, we have characterized the hydraulic conductivity of the test site and performed numerous laboratory experiments with permanganate in preparation for the
field trial.
Impacts
A pesticide-contaminated site in Nebraska has been remediated. By next summer (2007)we will have the data needed to evaluate the efficacy of using permanganate to remediate RDX-contaminated groundwater.
Publications
- Onanong, S., P.D. Burrow, S.D. Comfort, and P.J. Shea. 2006.Electron capture detector response and dissociative electron attachment cross sections in chloroalkanes and chloroalkenes. J. Phys. Chem. A 110:4363-4368.
- Adam, M.A., S.D. Comfort, D.D. Snow, D. Cassada, M.C. Morley, and W. Clayton. 2006. Evaluating ozone as a remedial treatment for removing RDX from unsaturated soils. Journal of Environmental Engineering.132:1580-1588.
- Boparai, H.K., P.J. Shea, S.D. Comfort, and D.D. Snow. 2006. Dechlorinating chloroacetanilide herbicides by dithionite-treated aquifer sediment and surface soil. Environ. Sci. Technol. 40:3043-3049.
- Park, J., S.D. Comfort, P.J. Shea, and J.S. Kim. 2005. Increasing Fe0-mediated HMX destruction in highly contaminated soil with didecyldimethylammonium bromide surfactant. Environ. Sci. Technol. 39:9683-9688.
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Progress 10/01/04 to 09/30/05
Outputs
Years of wastewater discharge at the Department of Energys Pantex Plant have contaminated the vadose zone and underlying perched aquifer with RDX. Because the vadose zone is acting as a continual source of groundwater contamination, removing RDX from the unsaturated zone is paramount to prevent further contamination. We determined the efficacy of ozone to degrade and mineralize RDX. Solution experiments showed that ozone (27 mg/L; 150 mL/min) was effective in mineralizing 80% of the RDX (30 mg RDX/L) provided that some Pantex soil was present to buffer the solution pH. Soil columns treated with ozone produced 50% RDX mineralization within 1 d and >80% within 7 d. Experiments designed to evaluate aerobic biodegradation following partial ozonation of a RDX solution showed that ozone-generated RDX products were much more biodegradable than untreated controls in aerobic microcosms (35% vs. <0.3% cumulative mineralization). These results support the use of ozone as a
remedial treatment for the contaminated vadose zone at the Pantex facility
Impacts
Initial solution trials showed that 27 mg O3/L (4.1 mg/min) was effective in mineralizing RDX (80%) provided that some Pantex soil was present to buffer the solution. Based on solution pH experiments, the pH of the Pantex soil is conducive to RDX destruction during ozonation. Unsaturated soil columns treated with ozone revealed that 50% RDX mineralization was achieved within 1 d and >80% within 7 d. Soil water content (initially 11-28%, w/w) had little effect on cumulative mineralization. Biodegradation of ozone-generated RDX products were much more rapid and complete than untreated RDX in aerobic microcosms. Moreover, the products of RDX ozonation appeared to stimulate biodegradation of native RDX in the soil. These results support the use of ozone as a remedial treatment for the contaminated vadose zone at the Department of Energys Pantex site.
Publications
- Comfort, S.D. 2005. Remediating RDX and HMX Contaminated Soil and Water. In M. Fingerman and R. Nagabhushanam (eds) Bioremediation of Aquatic and Terrestrial EcoSystems. Science Publishers, Inc. Enfield, NH. p. 263-310
- Adam, M.L., Comfort,S.D., Zhang,T.C., and Morley, M.C. 2005. Evaluating Biodegradation as a Primary and Secondary Treatment for Removing RDX (Hexahydro-1,3,5-trinitro-1,3,5-triazine) from a Perched Aquifer. Bioremediation Journal 9:9-19.
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Progress 10/01/03 to 09/30/04
Outputs
Extensive soil sampling at the U.S. Department of Energy Pantex Plant has revealed that the vadose zone beneath Solid Waste Management Unit 122b is highly contaminated and acting as a continual source of ground water pollution. The depth and extent of contamination combined with the formidable logistics of removing source soils make ex-situ treatments impractical and in-situ treatment technologies the most desirable. Ozonation is an in-situ chemical oxidation (ISCO) treatment has been used to remediate unsaturated soils contaminated with compounds resistant to soil vapor extraction. Our objective was to determine the efficacy of ozone to degrade and mineralize RDX in solution batch experiments and unsaturated soil columns. 14C-RDX was used to spike RDX solutions and soil columns packed with Pantex vadose soil; ozone was then bubbled through the solutions or passed through the 20-cm soil columns (5.08 cm id) with the final gas stream flowing through two carbon dioxide
traps (0.5 M sodium hydroxide) to quantify cumulative mineralization. Aqueous-solution trials showed that 2% (w/w) ozone was effective in mineralizing 80% of the RDX in solution (25 mg RDX/L) provided a small mass of Pantex soil was present in the solution matrix (1 g Pantex soil/100 mL). Samples from ozonated solutions were analyzed for RDX degradates by LC/MS. Preliminary results show the possibility of several ring fragments. Soil-column experiments using sieved (2-mm) Pantex soil and 2% ozone revealed that 50% RDX mineralization was achieved within 1 d and >80% within 7 d. A series of columns experiments indicated that initial soil water content (11-28%, w/w) had little effect on cumulative mineralization. Assuming mineralization may be incomplete under field conditions, we evaluated aerobic biodegradation as a secondary treatment following partial ozonation of a RDX solution. Results showed that ozonated RDX solutions were much more biodegradable than untreated controls in
aerobic microcosms (25% vs. <2% cumulative mineralization). Moreover, microcosms treated with ozonated-RDX solutions showed a decrease in native (unlabeled) RDX concentration, while the control did not, providing some evidence that the degradates produced during ozonation may stimulate aerobic RDX biodegradation. These results support the use of ozone as a remedial treatment for the contaminated vadose zone at the Pantex site.
Impacts
This research demonstrated that ozone was highly effective in mineralizing RDX in soils under unsaturated conditions. Moreover, when mineralization is incomplete, the products produced from ozone treatment appear to be more biodegradable than the parent RDX. These results indicate ozonation should be considered as a potential candidate for in situ chemical oxidation of contaminated source soils containing munitions residues.
Publications
- Shea, P.J., T.A. Machacek, and S.D. Comfort. 2004. Accelerated remediation of pesticide-contaminated soil with zerovalent iron. Environmental Pollution. 132:183-188.
- Park, J., S.D. Comfort, P.J. Shea, and T.A. Machacek. 2004. Remediating munitions-contaminated soil with zerovalent iron and cationic surfactants. J. Environ. Qual. 33:1305-1313.
- Gibb, C., T. Satapanajaru, S.D. Comfort and P.J. Shea. 2004. Remediating dicamba-contaminated water with zerovalent iron. Chemosphere. 54:841-848.
- Satapanajaru, T., P.J. Shea, S.D. Comfort, and Y. Roh. 2003. Green rust and iron oxide formation influences metolachlor dechlorination during zerovalent iron treatment. Environ. Sci. Technol. 37:5219-5227
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Progress 10/01/02 to 09/30/03
Outputs
Pesticide spills and inadvertent discharges result in normally beneficial chemicals becoming point-sources of ground and surface water contamination. We determined the effectiveness of zerovalent iron (Fe0) to dechlorinate metolachlor in the presence of aluminum and iron salts. By treating aqueous solutions of metolachlor with Fe0, we found destruction kinetics were greatly enhanced when Al, Fe(II) or Fe(III) salts were added during corrosion of iron. Salt composition was important, with the following order of destruction kinetics observed: Al2(SO4)3>AlCl3>Fe2(SO4)3>FeCl3. A common observation from these experiments was the visible formation of green rusts, mixed Fe(II)/Fe(III) hydroxides with interlayer anions that impart a greenish-blue color. Central to the underlying mechanism responsible for enhanced metolachlor loss may be the role these salts play in facilitating Fe(II) release. By tracking Al and Fe(II) in a Fe0 + Al2(SO4)3 treatment of metolachlor, we
observed that Al was readily sorbed by the corroding iron with a corresponding release of Fe(II). The source and commercial manufacturing process used to create the Fe0 also had profound effects on destruction rates. Metolachlor destruction rates with salt-amended Fe0 were greater with annealed iron (indirectly heated under reducing atmosphere) than unannealed iron. Moreover, the optimum pH for dechlorinating metolachlor differed between iron sources (pH 3 for unannealed, pH 5 for annealed). These results indicate that zerovalent iron treatment of metolachlor-contaminated soils may be enhanced by augmenting the Fe0-H2O-soil system with iron or Al salts and creating pH and redox conditions that favor green rust formation.
Impacts
This research demonstrated that dechlorination of metolachlor (and other pesticides) is enhanced by zerovalent iron when redox and pH conditions result in the formation of iron oxides that have a high density of reactive surface sites and sufficient Fe(II) is available. The formation of green rust is a good indicator of these conditions and should facilitate the use of zerovalent for remediating pesticide-contaminated soils.
Publications
- Comfort, S.D., P.J. Shea, T.A. Machacek, and T. Satapanajaru. 2003. Pilot-scale treatment of RDX-contaminated soil with zerovalent iron. J. Environ. Qual.,32:1717-1725.
- Satapanajaru, T., S.D. Comfort, and P.J. Shea. 2003. Enhancing metolachlor destruction rates with aluminum and iron salts during zerovalent iron treatment. J. Environ. Qual.32: 1726-1734.
- Huang, Y.H., T.C. Zhang, P.J. Shea, and S.D. Comfort. 2003. Effects of oxide coating and selected cations on nitrate reduction by iron metal. J. Environ. Qual. 32: 1306-1315.
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Progress 10/01/01 to 09/30/02
Outputs
Electron transfer from zerovalent iron (Fe0) to targeted contaminants is affected by the initial Fe0 composition, characteristics of the surface iron oxides formed during corrosion, and surrounding electrolytes. Past research has shown that metolachlor destruction by Fe0 can be significantly enhanced when either iron or Al salts are present in the aqueous matrix. To investigate this catalytic effect, we characterized changes in Fe0 composition during the treatment of metolachlor. Raman microscopic analysis and X-ray diffraction indicated that the iron source was initially coated with a thin layer of magnetite (Fe3O4), maghemite (Fe2O3), and wusite (FeO). Temporal mineralogical analysis indicated akaganeite, goethite, magnetite, and lepidocrocite formed in the Fe0-metolachlor suspension when Al2(SO4)3 or FeSO4 were present. Green rust II (Fe6(OH)12SO4) was also transiently identified in Fe0 treatments containing FeSO4. Although conditions favoring green rust formation
in a Fe0-batch system increased metolachlor dechlorination, we determined that green rust itself can only marginally contribute to transforming metolachlor. This was confirmed in three separate experiments designed to isolate the role of green rust. By creating green rust in the presence of metolachlor and then changing Eh/pH conditions to favor either lepidocrocite or magnetite, we observed metolachlor adsorption but no dechlorination. In contrast, metolachlor dechlorination was observed in a batch system containing magnetite or goethite and FeSO4 at pH 8. These results indicate that creating conditions favoring green rust facilitate Fe0-mediated dechlorination of metolachlor by providing an available source of Fe(II) and generating iron oxide surfaces that can coordinate Fe(II).
Impacts
Results from this research indicate that zerovalent iron augmented with aluminum and iron salts can significantly increase pesticide destruction rates. Much of this catalytic effect appears to a function of the oxide mineralogy formed on the zerovalent iron and the ability of these oxides to coordinate Fe(II), which can then serve as an additional reductant. This research provides approaches for manipulating iron oxide formation on zerovalent iron and improving remediation efficiencies.
Publications
- Gaber, H.M., S.D. Comfort, P.J. Shea, and T.A. Machacek. 2002. Metolachlor dechlorination by zerovalent iron during unsaturated transport. J. Environ. Qual.31:962-969
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Progress 10/01/00 to 09/30/01
Outputs
Previous work from this project has demonstrated that zerovalent iron can be used to remediate pesticide-contaminated soil. Last year's efforts investigated the mechanisms surface oxides play in mitigating the dechlorination of metolachlor. Once zerovalent iron is added to an aqueous solution, corrosion begins and the only exposure of bare iron to the contaminants will occur when the iron grain is scratched through agitation. Most of the iron surfaces will be covered with an oxide film that is complex and changing with time. Batch experiments were conducted to characterize the oxides forming on the zerovalent iron and their influence on metolachlor destruction. By adding FeSO4 or Al2(SO4)3 to zerovalent iron, we observed metolachlor destruction rates were significantly increased. Corresponding XRD and SEM measurements confirmed that the addition of aluminum or ferrous salts can promote the formation of green rusts followed by magnetite and/or goethite. These oxides
enhance metolachlor dechlorination by either promoting electron transfer from the iron core or facilitating reactive Fe(II) species on the surface oxides.
Impacts
Results from this research indicate that zerovalent iron augmented with aluminum sulfate or ferrous sulfate can significantly increase metolachlor destruction kinetics. The reason for this enhanced destruction is related to the nature of the oxides formed on the zerovalent. By understanding how to manipulate surface oxide formation, more efficient treatments involving zerovalent iron can be achieved.
Publications
- Satapanajaru, T., Comfort, S.D., Shea, P.J., Machacek, T.A., and Roh, Y. 2001. Iron-mediated destruction of metolachlor: roles of surface oxides. Abstr. Am. Soc. Agron.
- Comfort, S.D., Shea, P.J., Machacek, T.A., Gaber, H., and Oh, B.-T. 2001. Field-scale remediation of a metolachlor spill site using zerovalent iron. J. Environ. Qual. 30:1636-1643.
- Park, J., Shea, P.J., Comfort, S.D., and Machacek, T.A. 2001. Remediating munitions-contaminated soil with zerovalent iron and surfactants. Abstr. Am. Soc. Agron.
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Progress 10/01/99 to 09/30/00
Outputs
Pesticide spills are common occurrences at agricultural cooperatives and farmsteads. When inadvertent spills occur, normally beneficial chemicals become point-sources of ground and surface water contamination. We recently completed a field trial where approximately 765 m3 of soil from a metolachlor spill site was treated with zerovalent iron (Fe0). Preliminary laboratory experiments were conducted to determine optimum treatments for use in the field. Laboratory results confirmed Fe0 transformed metolachlor in aqueous solution and static soil microcosms and that this process could be accelerated by adding aluminum sulfate (Al2(SO4)3) or acetic acid (CH3COOH). The field project was initiated by moving the stockpiled, contaminated soil into windrows using common earthmoving equipment. The soil was then mixed with water (0.35-0.40 kg H2O/kg) and various combinations of 5% Fe0 (w/w), 2% Al2(SO4)3 (w/w), and 0.5% acetic acid (v/w). Windrows were covered with clear plastic
and incubated without additional mixing for 90 d. Approximately every 14 d, the plastic sheeting was removed for soil sampling and the surface of the windrows re-wetted. Results indicated metolachlor concentrations were significantly reduced and varied among treatments. The addition of Fe0 alone decreased metolachlor concentration from 1789 to 504 mg/kg within 90 d whereas adding Fe0 with Al2(SO4)3 and CH3COOH dropped the concentration from 1402 to 13 mg/kg. These results provide evidence that zerovalent iron can be used for on-site, field-scale treatment of pesticide-contaminated soil.
Impacts
Results from this project demonstrate that zerovalent iron augmented with aluminum sulfate can be successfully used to remediate pesticide-contaminated soils. Although land spreading is currently the most economical treatment available, this option would not be available for soils contaminated with banned pesticides. Therefore, when land spreading is not an option, results from this research support the use of zerovalent iron as an alternative treatment.
Publications
- Oh, B.-T., Shea, P.J., Drijber, R.A., Sarath, G. and Comfort, S.D. 1999. Variables affecting microbial-mediated TNT transformation and detoxification. Abstr. Soc. Environ. Toxicol. Chem. 20:272.
- Oh, B.-T., Sarath, G., Shea, P.J., Drijber, R.A. and Comfort, S.D. 2000. Rapid spectrophotometric determination of 2,4,6-trinitrotoluene in a Pseudomonas enzyme assay. J. Microbiol. Methods. 42:149-158.
- Satapanajaru, T., Gibb., C., Shea, P.J., Comfort, S.D. and Machacek, T.A. 2000. Aluminum and ferrous sulfate catalyzed destruction of metolachlor by zerovalent iron. Abstr. Am. Soc. Agron. 92:411.
- Shea, P.J. and Comfort, S.D. 2000. Remediating munitions and pesticide-contaminated soils: Application of zerovalent iron. Abstr. DOE EPSCoR Workshop, Aug 16-17, Berkeley, CA. p 46.
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Progress 10/01/98 to 09/30/99
Outputs
Problem: A half-acre bentonite clay-lined lagoon was constructed in 1979 at a farm cooperative in southwestern Nebraska. The original purpose of the lagoon was to receive and contain potentially contaminated storm water runoff and "other" excess wastewater. In 1995, an accidental release of metolachlor from a storage tank resulted in 755 gallons of unrecovered product, some of which ran into the sump that drains into the lagoon. The spill resulted in approximately 1000 cubic yards of contaminated soil that was excavated from the lagoon and held for remedial treatment. The targeted contaminant is metolachlor, which was present at initial concentrations >1800 mg/kg, but soil analysis revealed additional pesticides were also present, such as atrazine (600 mg/kg), alachlor (400 mg/kg), pendimethalin (50 mg/kg) and chlorpyrifos (30 mg/kg). Given the combined toxicity of these pesticides, it was unlikely that natural attenuation would proceed rapidly enough to significantly
reduce the soil contamination and the stockpiled soil represented a sustained point source for groundwater contamination. Research: In the summer of 1999, we initiated a field-scale demonstration project in which the contaminated soil was placed in windrows and amended with various treatments involving zerovalent iron. Following treatment, the extractable metolachlor concentrations rapidly decreased with destruction rates between 72 and 99% within 90 d. Although the metolachlor concentrations were reduced, the potential for leaching still existed, especially if the treated soil was placed back into the runoff pit. To counteract this possible problem, we proposed placing a protective permeable iron barrier in the bottom of the excavated pit before returning the treated soil. Transport experiments, using 20-cm soil columns with 14C-labeled metolachlor, were initiated to determine if permeable iron barriers could be effective in reducing metolachlor leaching under unsaturated flow.
Results indicated near complete destruction of metolachlor with the dechlorinated metolachlor product observed as the primary degradate.
Impacts
The field demonstration project provide clear proof that treatments using zerovalent iron can be used at the field scale to remediate pesticide-contaminated soil. Results from the transport experiments provide proof-of-concept that permeable zerovalent iron barriers can be effective in dechlorinating metolachlor under unsaturated flow.
Publications
- Singh, J, S.D. Comfort, and P.J. Shea. 1999. Optimizing Eh/pH for iron-mediated remediation of RDX-contaminated water and soil. Environ. Sci. Technol. 33:1488-1494.
- Bier, E.L., J. Singh, Z. Li, S.D. Comfort and P.J. Shea. 1999. Remediating hexahydro-1,3,5-trinitro-1,3,5-triazine-contaminated water and soil by Fenton oxidation. Environ. Toxicol. Chem. 18:1078-1084.
- Kreslavski, V.D., G.K. Vasilyeva, S.D. Comfort, R.A. Drijber, and P.J. Shea. 1999. Accelerated transformation and binding of 2,4,6-trinitrotoluene in rhizosphere soil. Bioremediation.3:59-67.
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