Stimulation of Anaerobic BTEX Bioremediation Using Epsom Salt (Magnesium Sulfate)
Richard A. Royer, General Electric Global Research Center, K1 3D61 1 Research Circle, Niskayuna, NY 12309, Tel: 518-387-4635, Fax: 518-387-6972, Email: royer@research.ge.com
Angela S. Fisher, General Electric Global Research Center, K1 3D59 1 Research Circle, Niskayuna, NY 12309,Tel: 518-387-7392, Fax: 518- 387-6972, Email: fishera@research.ge.com
Rachel L. Farnum, General Electric Global Research Center, K1 3D49 1 Research Circle, Niskayuna, NY 12309, Tel: 518-387-5951, Fax: 518-387-6972, Email: farnum@research.ge.com
Angelo A. Bracco, General Electric Global Research Center, K1 3D56A 1 Research Circle, Niskayuna, NY 12309, Tel: 518-387-6647, Fax: 518-387-6972, Email: braccoa@research.ge.com
Damian D. Foti, General Electric Energy, 1 River Road, Schenectady, NY, 12345, Tel: 518-385-3716, Fax: 518-385-4074, Email: damian.foti@ge.com
Paul B. Hatzinger, Shaw Environmental, Inc., 17 Princess Road, Lawrenceville, NJ 08648, Tel: 609-895-5356, Fax: 609-895-1858, Email: Paul.Hatzinger@shawgrp.com
Charles E. Schaefer, Shaw Environmental, Inc., 17 Princess Road, Lawrenceville, NJ 08648, Tel: 609-895-5372, Fax: 609-895-1858, Email: Charles.Schaefer@shawgrp.com
Stewart H. Abrams, Langan Engineering & Environmental Services Inc., River Drive Center 1, Elmwood Park, NJ 07470, Tel: 201-398-4543, Fax: 201-398-4743, Email: sabrams@Langan.com

Enhanced anaerobic bioremediation of benzene, toluene, ethylbenzene, and xylenes (BTEX) was evaluated in aquifer microcosm and column studies.  Anaerobic remediation is preferable to aerobic treatment when natural site conditions are anoxic, due to the potential precipitation of large quantities of iron oxides and iron-related biofouling upon oxygen addition.  Initial microcosm experiments conducted with site materials revealed that BTEX degradation was most favorable under aerobic, denitrifying, and sulfate-reducing conditions.  Subsequently, a column study was performed under sulfate-reducing conditions to quantify the rates and extents of BTEX biodegradation under continuous-flow conditions.  Three columns were tested over 3 months of active treatment: a control column receiving only groundwater at a “low” flow rate, a treatment column receiving 400 mg/L magnesium sulfate at a similar “low” flow rate, and a treatment column receiving groundwater and magnesium sulfate (400 mg/L) at a “high” flow rate (4.6x the flow and 7.9x the BTEX loading relative to the “low” flow treatment column).   The influent site groundwater had average contaminant concentrations in mg/L as follows: benzene = 0.09, toluene = 9.6, ethylbenzene = 1.9, m,p-xylenes = 7.8, and o-xylene = 2.0.  BTEX, iron, and sulfate concentrations as well as COD and TOC were monitored over time.  All columns exhibited a decrease in contaminant concentrations from influent to effluent, with the most significant decrease being observed in the “low“ flow treatment column.  Estimated maximum rates of loss for the key contaminants were 50, 1.9, 42, and 6.4 mg/l/d for toluene, ethylbenzene, m,p-xylenes and o-xylenes.  Low benzene concentrations did not allow for degradation rate estimation.  Effluent toluene and xylene concentrations were below detection (maximum of 350 ug/L) by the end of the study in the sulfate-amended columns.  The results of the study were used as a component of a design model employed for development of a full-scale bioremediation system design.

Temporal Fluctuations in Soil Water Potential Alter Soil Biochemistry: Relationship to Taggant-based Sensor Performance
C.M. Reynolds, USA Engineering Research & Development Center, Cold Regions Research and Engineering Laboratory, 72 Lyme Road, Hanover, NH, USA 03755 Tel: 603-646-4394, Fax:  603-646-4785, Email: charles.m.reynold@us.army.mil
K.L. Foley, USA Engineering Research & Development Center, Cold Regions Research and Engineering Laboratory, 72 Lyme Road, Hanover, NH 03755, Tel: 603-646-4563, Fax: 603-646-4785, Email: karen.l.foley@usace.army.mil
D.B. Ringelberg, USA Engineering Research & Development Center, Cold Regions Research and Engineering Laboratory, 72 Lyme Road, Hanover, NH 03755, Tel:  603-646-4394, Fax:  603-646-4785, Email: david.b.ringelberg@usace.army.mil
J.E. Anderson, USA Engineering Research & Development Center, Topographic Engineering Center, 7701 Telegraph Road, Alexandria, VA 22315, Tel: 703-428-6698, Fax: 703-428-8176, Email:  john.anderson@usace.army.mil
J.D. Nelson, USA Engineering Research & Development Center, Topographic Engineering Center, 7701 Telegraph Road, Alexandria, VA 22315, Tel: 703-428-3636, Fax: 703-428-8176, Email: jean.d.nelson@usace.army.mil

Direct chemical sensing using taggants that alter the signature of a target molecule in soil can be achieved but uncertainty in results limits their utility.  We hypothesized that much of the variation is a function of fluctuations in soil conditions, such as soil water potential, which can have direct and indirect effects on soil parameters, such as pH.  In this study we varied soil water potential and measured soil solution pH and microbial community changes to better understand direct and indirect effects of water potential dynamics.  Soil water pH was measured over three consecutive moisture cycles.  During each cycle, soil water potential decreased from -33 kPa to below -200 kPa in 8 h.  Using a fluorescent pH sensitive dye, SNARF-5F carboxylic acid, we found that decreasing pH was positively correlated with decreasing soil water potential.  Using lipid biomarker analyses we also observed that the decrease in soil water potential was associated with changes in in-situ microbiota.  The decrease in soil solution pH was correlated with increased relative percentages of cyclopropane fatty acids and a decrease in branched saturated fatty acids.  The results identified associated biochemical responses to temporal fluctuations in soil water potential, but we do not yet fully understand cause and effect.  Because pH can also affect both the formation and response of uranyl fluoride, these results begin to provide the information needed to accurately predict performance of sensors based on direct chemical taggants in dynamic surface soil conditions.

Bioremediation of Organochlorine Pesticides in Soil via In-situ Chemical Reduction
Ravikumar Srirangam, Adventus Americas, Inc., 1435 Morris Avenue, 2nd Flr., Union, NJ 07083, Tel: 908-688-8543, Fax: 908-688-8563, Email: Ravi.Srirangam@AdventusGroup.com
Fayaz Lakhwala, Adventus Americas, Inc., 1435 Morris Avenue, 2nd Flr., Union, NJ 07083, Tel: 908-688-8543, Fax: 908-688-8563, Email: Fayaz.Lakhwala@AdventusGroup.com
David Hill, The Adventus Group, 1345 Fewster Drive, Mississauga, ON L4W 2A5 Canada, Tel: 905-273-5374 x233, Fax: 905-273-4367, Email: david.hill@adventusgroup.com

As cities and communities grow, the need to remediate and use brownfields and greenfields increases. Former agricultural land can often be impacted with chlorinated pesticides, or more specifically, organochlorine pesticides. These include compounds such as DDT (Dichlorodiphenyltrichloroethane), DDE, DDD, Dieldrin, Toxaphene, and many others. Although use of most of these compounds has been discontinued in most countries, they persist in the environment due to their relatively low volatility and high resistance to biodegradation.

A case study will be presented on a former agricultural area that is being converted to residential use. The traditional approach for remediation of this type of soil contamination has been excavation and off-site disposal at a landfill. At this site, however, the decision was made to treat the soil on-site using a bioremediation process known as in-situ chemical reduction (ISCR). 

The process used to treat the OCPs to residential-use criteria was one in which the soil’s oxidation reduction potential (ORP) is cycled between anaerobic and aerobic conditions. The anaerobic phase is initiated through the addition of rapidly degradable solid organic carbon to stimulate the growth of indigenous microorganisms. Simultaneous with the carbon addition, zero-valent iron (ZVI) is also added for chemical reduction of chlorinated compounds. This combination results in the depletion of electron acceptors until ORP values of typically less than -400 mV are reached. Once the amendments are tilled into the soil, water is added to begin the fermentation process and restrict the ability of atmospheric oxygen to enter the soil. Once the anaerobic phase of the treatment is complete, the soil is aerated by tilling to initiate the aerobic phase of treatment.

At the given site, attainment of the treatment goals was achieved for half the site using one treatment cycle, and for the other half using a second treatment cycle.

1,4-Dioxane Cometabolic Biodegradation Treatability Results at an NPL Site With a Wide Range of Contaminants
Frank T. Barranco, Jr., Ph.D., EA Engineering, Science, and Technology, 15 Loveton Circle, Sparks, MD 21152
Robert C. Borden, Ph.D. P.E., North Carolina State University, 208 Man Hall, Stinson St., Raleigh, N.C.  27695
Scott R. Miller, P.E., Clean Sites Environmental Services Inc., 46161 West Lake Drive, Suite 230B, Potomac Falls, VA   20165

1,4-Dioxane, a cyclic ether that represents an emerging contaminant, is a highly soluble contaminant that is very mobile in groundwater and resistant to biodegradation under ambient conditions in well-oxygenated aquifers as well as anaerobic settings.  There is, however, some laboratory evidence suggesting that 1,4-dioxane will cometabolize in the presence of tetrahydrofuran, amended propane, and/or a variety of branched alkanes under well oxygenated conditions.  The challenge of 1,4-dioxane biodegradation is being addressed at a National Priority List cleanup to mitigate a wide range of groundwater contaminants including petroleum aromatics, chloroaromatics, ketones, and chlorinated aliphatics.  In addition, 1,4-dioxane was identified in groundwater, presumably resulting from the presence of 1,1,1-TCA from which it commonly originates as a solvent stabilizer.  Lab treatability studies were performed to assess the potential for cometabolic biodegradation of 1,4-dioxane when oxygen was added to stimulate aerobic biodegradation of other co-substrates present as contaminants in soil and groundwater.  Batch microcosms were constructed in the laboratory using contaminated soil (with indigenous microorganisms) and spiked groundwater.  The lab microcosms were incubated at ambient groundwater temperature under aerobic conditions to induce cometabolic conditions for 1,4-dioxane biodegradation.  There was clear evidence of aerobic respiration of all compounds expected to undergo direct biological oxidation (ketones, aromatic hydrocarbons, and chlorobenzenes).  In many cases, these contaminants were reduced below analytical detection limits within 2 months.  Under this same short-term timeframe, there was no evidence of cometabolic biodegradation of 1,4-dioxane; a testament to the recalcitrance of this compound considering the wide range of co-substrates present as contaminants in site media as well as the optimal conditions provided for the laboratory microcosms.  In light of the microcosm findings, observed groundwater trends were evaluated with analytical modeling to identify if the recalcitrant behavior of 1,4-Dioxane from the microcosm study was evident with collected Site data.

Membrane-Delivered Ethene to Stimulate Microbial Degradation of DCE
Student Presenter
Nash A. Saleh, Edwards Air Force Base, 5 East Popson Avenue, Edwards, California, CA 93524, USA, Tel: 661-277-1434, Fax: 661-277-6145
Aditi Bandyopadhyay, Avanti Kavathekar, Kumal Patel, and Lee Clapp, Texas A&M University – Kingsville, 700 University Blvd., Kingsville, TX, 78363, USA, Tel: 361-593-4007, Fax: 361-593-2069

A significant obstacle to the application of microbial reductive dechlorination of PCE and TCE at many sites is the undesirable accumulation of cis-1,2-dichloroethene (cis-DCE) and vinyl chloride (VC). Although microbial dechlorination of PCE and TCE generally occurs readily under anaerobic conditions, cis-DCE and VC may be best degraded under aerobic conditions. In this study, experiments were performed to evaluate the feasibility of using ethene to stimulate cometabolic and/or auxiliary aerobic degradation of cis-DCE present in groundwater at Edwards Air Force Base (EAFB).  Initial efforts to stimulate significant growth of indigenous ethenotrophs in batch microcosms and continuous-flow columns containing EAFB aquifer sediments by supplying ethene and air were unsuccessful (gas-permeable hollow-fiber membranes were used to supply ethene and air to the sediment columns). Subsequently, both an enriched mixed ethenotrophic culture and a pure culture of Nocardioides strain JS614 were obtained and grown in mineral salts media. Both cultures rapidly degraded cis-DCE via cometabolism, with transformation yields comparable to the highest values reported for methanotrophs. These cultures were then used to bioaugment the batch microcosm bottles and continuous-flow columns containing EAFB aquifer sediments. Both the sediment microcosms and the sediment columns were supplied with approximately 6% ethene in air, nitrate and phosphate, and had pH maintained at between 7.0 and 8.5. However, active cis-DCE degrading ethenotrophs failed to grow in either the batch microcosms or the continuous-flow columns. Since unfavorable pH and insufficient ethene, oxygen, nitrogen, or phosphorus were ruled out, it was not clear why the bioaugmented ethenotrophs failed to grow in the EAFB aquifer sediments. Possible explanations included the lack of essential micronutrients or presence of inhibitory substances within the EAFB sediments.

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