Use of Degradable Non-oxidizing Biocides and Biodispersants for Maintenance of Capacity in Nutrient Injection Wells 
Brad Horn, Redux Technology, Newfane, VT

Mechanisms and Kinetics of Extracellular Electron Shuttle Mediated Cyclic Nitramine (RDX and HMX) Biodegradation            
Man Jae Kwon, University of Illinois - Urbana Champaign, Urbana, IL

Influence of Carbon Source on Microbial Community in Passive ARD Treatment System                    
Jana Schmidtova, University of British Columbia, Vancouver, BC

Replacement of a Groundwater Extraction System with Bioremediation to Treat Trichloroethylene in Fractured Bedrock
Douglas G. Larson, Geosyntec Consultants, Inc., Acton, MA

Transport of Lactate and in-situ Bioremediation of Tetrachloroethylene (PCE) under Direct Current  
David B. Gent, US Army Engineer Research and Development Center, Vicksburg, MS

Using Field Pilot-Testing Results to Design a Full-Scale Enhanced Bioremediation Approach to Remediate DNAPL TCE

Lucas A. Hellerich, PhD, PE, Metcalf & Eddy /AECOM, 860 North Main Street Extension, Wallingford, CT 06492, Tel: 203-741-2821, Fax: 203-269-8788, Email: lucas.hellerich@m-e.aecom.com
Paul Dombrowski, Metcalf & Eddy / AECOM, 701 Edgewater, Wakefield , MA 01880 , Tel: 781-224-6585, Fax: 781-224-6542, Email: paulm.dombrowski@m-e.aecom.com
John L. Albrecht, LEP, Metcalf & Eddy / AECOM, 860 North Main Street Extension, Wallingford, CT 06492, Tel: 203-741-2826, Fax: 203-269-8788, Email: john.albrecht@m-e.aecom.com
Dave Hart, Noranda Metals Industries, Inc., P.O. Box 70 , New Madrid , MO   63869 , Tel: 573-643-6763,  Fax: 573-643-6715, Email: DHart@xstrata.ca 

Several field pilot studies of enhanced bioremediation (reductive dechlorination) of trichloroethene (TCE) were conducted at a site located in western Connecticut .  The concentration of TCE in the groundwater plume varied spatially, but was up to 768 mg/L (~ 70% solubility of TCE), indicating the presence of dense-non-aqueous-phase-liquid.  At the source area and within the groundwater plume, emulsified soybean oil, amended with a bromide tracer, was injected into the subsurface, providing a slow-release source of carbon and reducing power for the naturally-occurring microbial populations.  Reducing conditions, characterized by negative oxidation-reduction potential and decreased dissolved oxygen levels, were achieved within several weeks of the injection events.  The distribution of the carbon substrate was evaluated using total organic carbon (TOC) and bromide concentrations.  After operating the pilot tests for several months, bioaugmentation of dehalococcoides spp. bacteria was performed at each of the test locations. Chlorinated ethenes, TOC, geochemical parameters, and microbial populations were monitored to determine the effectiveness of the treatment. 

The results of the pilot tests were utilized to design a full-scale enhanced bioremediation approach for the chlorinated solvent groundwater plume.  A reaction and transport groundwater model was developed for the site and used in the design of the bioremediation approach.  Biodegradation reaction rates were estimated and incorporated into the modeling.  Injection radii of influence, and carbon substrate composition, quantities, and loading rates were determined.  In addition, required biodegradation geochemistry, and carbon delivery locations, rates, and methods were incorporated into the design.  The design also included a plan to monitor the performance of the enhanced bioremediation approach.   

Use of Degradable Non-oxidizing Biocides and Biodispersants for Maintenance of Capacity in Nutrient Injection Wells

Brad Horn, PE, Redux Technology, P.O. Box 331, Newfane, VT 05345, Tel: 802-365-7200, Fax:  802-365-4652, Email: bhorn@reduxtech.com
Gary Richards, Redux Technology, 1317 Pennsridge Court, Downingtown, PA 19335, Tel:  610-716-2561, Fax:  610-873-3967, Email:  grichards@reduxtech.com

Fouling of water supply wells is a common problem, dating from the time humans started using groundwater resources for water supply.  In the groundwater remediation field, fouling of recovery and treatment systems has been a similarly common operating problem.  Thus it is not surprising, with the increased use of in-situ remedial methods, that fouling of in-situ treatment units is becoming a major design concern.  In-situ treatment units include recovery wells, injection wells, recirculating wells, flow-through treatment cells, and in some cases, geologic formations themselves.  The very effectiveness of these units depends greatly upon retention of permeability or hydraulic capacity.  Capacity can be dramatically reduced due to fouling by naturally occurring inorganic precipitates or by microbial deposits. 

One of the least surprising instances of fouling of an in-situ treatment unit involves various bioenhancement techniques, where nutrients are injected with the intention of enhancing certain types of bioactivity and subsequent biodegradation of contamination.  The data presented in this paper are derived from experience at remedial sites where bioenhancement activities have been self-defeating by causing a loss of permeability in injection wells, surrounding geological formations, or down-gradient recovery or recirculation wells.  In these cases, non-oxidizing biocides, bio-dispersants, saponification agents or other additives have been applied to retain permeability in the hydraulic “bottlenecks” of these systems, such as injection wells and surrounding formations.  Data collected from such applications shows that proper characterization of fouling mechanisms and subsequent application of well-designed deposit control programs can eliminate operational problems associated with fouling arising from bioenhancement.

This paper introduces the key concepts in deposit control practices as they apply to fouling of in-situ treatment units.  It provides an overview of the various agents and techniques used in such deposit control programs.  Regulatory and design issues are discussed, and subsequently illustrated by a series of brief case studies.

Mechanisms and Kinetics of Extracellular Electron Shuttle Mediated Cyclic Nitramine (RDX and HMX) Biodegradation

Student Presenter

Man Jae Kwon, University of Illinois - Urbana Champaign, Dept of Civil and Environmental Engineering, NCEL 205 N. Mathews, Urbana, IL, 61801, Tel: 217-333-6851, Fax: 217-333-6967, Email: mankwon@uiuc.edu
Kevin T. Finneran, PhD, University of Illinois - Urbana Champaign, Dept of Civil and Environmental Engineering, NCEL 205 N. Mathews, Urbana, IL, 61801, Tel: 217-333-1514, Fax: 217-333-6967, Email: finneran@uiuc.edu

Microbial enrichments were generated using RDX-contaminated aquifer material that was incubated under a variety of extracellular electron shuttle (EES)-amended conditions. Electron donors tested included H2, benzoate, formate, lactate, or acetate; electron acceptors included poorly crystalline Fe(III) oxide, AQDS, or RDX. Enriched cultures were sequentially transferred (10%) into new media containing the same electron donors and acceptors.

AQDS and Fe(III) reducing enrichments were developed with H2 or acetate as the sole electron donors. Although the enrichments have not reduced RDX directly, it is known that reduced EES and Fe(II) can reduce RDX by abiotic mechanisms. Lactate and RDX (15mM) were used to develop specific RDX-reducing enrichments and these microorganisms reduced RDX below the detection limit within 7 days suggesting enriched microorganisms can utilize RDX directly as the sole electron acceptor. Microorganisms grown in a medium containing lactate and RDX also grew with lactate and with quinone-based military smoke dye as the sole electron acceptor. Additional experiments with the resting cell suspensions of G. metallireducens indicated that RDX reduction rate was 8 times faster with military smoke dye (12 mM), suggesting that military smoke dye could be another optimal source of EES and applicable to RDX remediation in military areas.  In addition, RDX ring cleavage was fastest and most complete in the presence of EES; approximately 70% of the available RDX carbon was recovered as formaldehyde (a labile compound) when EES were present versus 12% when the cultures received only an electron donor.

These results indicate that indigenous microorganisms in sediments can utilize EES to stimulate RDX biodegradation. EES-mediated RDX biodegradation is an effective remediation option in various environmental settings. Future study will identify the dominant microorganisms associated with EES-mediated RDX biotransformation by DNA quantification using real-time PCR and total microbial community analysis using amplified rDNA restriction analysis (ARDRA).

Influence of Carbon Source on Microbial Community in Passive ARD Treatment System

Student Presenter

Jana Schmidtova, Chemical and Biological Engineering, University of British Columbia, 2360 East Mall, Vancouver, BC, V6T 1Z3 Canada, Tel: 604-827-5760, Fax: 604-822-6003
Susan A. Baldwin, Chemical and Biological Engineering, University of British Columbia, 2360 East Mall, Vancouver, BC, V6T 1Z3 Canada, Tel: 604-822-1973, Fax: 604-822-6003

Passive anaerobic remediation using bacterial sulfate reduction is a low-cost, effective, and long-term treatment option for acid rock drainage. This approach was used by Nature Works Remediation Corporation to build a six-stage treatment wetland system for removal of arsenic, cadmium and zinc from a waste pile leachate stream near Trail, British Columbia. The leachate flows through two anaerobic bioreactors filled with pulp mill biosolids as organic material and then through three cattails plant cells and a wetland pond. Over the five years of operation, the arsenic removal efficiency remained above 96.6%. However, it is not known how much carbon is left available for the microbial growth in the system, thus the long-term successful treatment cannot be predicted.

In this study, five different carbon sources: pulp mill biosolids, vegetable compost, silage, molasses, and composted cattails were compared in situ to determine the influence of organic material on the sulfate reducing bacteria  (SRB) community and on the long-term treatment efficiency. Subsamples of the materials were removed from the system after 3 and 5 months to evaluate the carbon degradation kinetics. Rapid and reliable molecular techniques, such as quantitative polymerase chain reaction (q-PCR) was developed to specifically target and quantify SRB groups present.

The results of this study will bring new information on the relationship between carbon degradation and the microbial community for different commonly used carbon materials. This will potentially aid in design and choice of the most suitable material for new passive treatment systems, as well as estimate the time scale of efficient treatment for existing systems.

Replacement of a Groundwater Extraction System with Bioremediation to Treat Trichloroethylene in Fractured Bedrock

Carl R. Elder, Geosyntec Consultants, Inc., 289 Great Road, Suite 105, Acton, MA  01720, Tel: 978-263-9588, Fax: 978-263-9594, Email:  celder@geosyntec.com
Douglas G. Larson, Geosyntec Consultants, Inc., 289 Great Road, Suite 105, Acton, MA  01720, Tel: 978-263-9588, Fax: 978-263-9594, Email:  dlarson@geosyntec.com
John E. Vidumsky, DuPont Corporate Remediation Group, Barley Mill Plaza 19 – 2164, 4417 Lancaster Pike, Wilmington, DE  19805, Tel: 302-892-1378, Fax: 302-892-7621, Email:  John.E.Vidumsky@usa.dupont.com

Bioremediation was used to replace a 15-year old groundwater extraction and treatment system that had been installed to address trichloroethylene (TCE) and its daughter products at an active chemical manufacturing facility in Tennessee. Most of the TCE mass in the source area was detected in fractured limestone bedrock at depths of approximately 9 to 12 meters below ground surface. The groundwater extraction and treatment system had reached a point of diminishing returns, yielding less than 0.5 kg of TCE per year of operation even though average TCE concentrations in source area wells remained on the order of 5,000 ug/L. Bioremediation was implemented by adding emulsified soybean oil at a concentration of approximately 1% by volume into five source area wells. After achieving anaerobic and reducing conditions in the amended wells, 5 liters of a microbial culture (KB-1™) containing dehalococcoides bacteria was added to each well. Within six months after addition of the microbial culture, total chlorinated volatile organic compound (CVOC) concentrations decreased by approximately 85%. The estimated dissolved mass of TCE destroyed by bioremediation in the source area was approximately 6.7 kg; the total TCE mass destroyed is likely much greater due to biodegradation of CVOCs sorbed or trapped in the rock matrix. The cost of the bioremediation remedy was roughly equivalent to the cost of 18 months of operation of the groundwater extraction and treatment system. Based on the data obtained from bioremediation in the source area, a line of downgradient biobarrier wells was installed in December 2006 to mitigate offsite migration of the residual CVOC plume.

Transport of Lactate and in-situ Bioremediation of Tetrachloroethylene (PCE) under Direct Current

Xingzhi Wu, Department of Civil and Environmental Engineering, 400 Snell Engineering Center, Northeastern University, 360 Huntington Avenue, Boston, MA 02115, Tel: 617-373-3994, Email:  wuxingzhifu@yahoo.com
David B. Gent, Environmental Laboratory, US Army Engineer Research and Development Center, 3909 Halls Ferry Road, Vicksburg, MS 39180, Tel: 1-601-634-4822, Fax: 1-601-634-3518, Email: David.B.Gent@erdc.usace.amry.mil
Akram Alshawabkeh, Associate Professor, Department of Civil and Environmental Engineering, 400 Snell Engineering Center, Northeastern University, 360 Huntington Avenue, Boston, MA 02115, Tel: 617-373-3994, Fax: 617-373-4419, Email:  aalsha@neu.edu
Jeffrey L. Davis, Environmental Laboratory, US Army Engineer Research and Development Center, 3909 Halls Ferry Road, Vicksburg, MS 39180, Tel: 601-634-4822, Fax: 601-634-3518, Email: Jeffery.L.Davis@erdc.usace.amry.mil

Bioremediation of tetrachloroethylene (PCE) by reductive dechlorination has been successful when the microorganisms are supplied an additional electron donor such as lactate. However in heterogeneous PCE contaminated aquifers, uniform delivery and mixing of electron donor amendment have met limited success because the electron donors cannot be delivered into the low permeable zones.  Electrochemical amendment injection provides an alternative to hydraulic methods by delivering the electron donor to microorganisms in the low permeable zones where hydraulic delivery fails.  Lactate injection experiments were conducted in clay (kh = 2x10^-7 cm s^-1) and heterogeneous soil under 1.2 A m^-2 and 5.3 A m^-2 current densities.  Additional experiments mixed Dehalococcoides dechlorinator KB-1™ culture ( SiREM , Ontario , Canada ) with PCE (20 mg L^-1 in the pore water) in a clay-water slurry and consolidated the slurry in a nitrogen filled anaerobic chamber.  Electroosmotic and ion migration transport rates averaged 2.16 cm² V^-1day^-1 and 3.4 cm day^-1, respectively. Pore water lactate concentrations reached as high as 800 mg L^-1.  The ion migration rate was more than 191 times faster than transport under a hydraulic gradient.  No biological fouling was observed under the experiments using electrochemical injection.  The PCE and the KB-1™ culture mixed (no electricity) with the clay resulted in partial dechlorination of PCE halting at cis-DCE presumably because of absence of an electron donor.  The duplicate PCE and KB-1™ culture experiments with lactate injection by electrochemical means completely degraded PCE to ethene within 4 months across the 40 cm long silty clay medium.  PCE was transformed to DCE following a zero order rate of 0.0063 to 0.027 mmol L^-1∙day^-1 and the transformation of DCE to ethane followed a first order specific remediation rate of 0.0577 to 0.254 day^-1.  The soil pH remained between 7 and 7.5 throughout the experiment.

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