Treatability Study of Enhanced Anaerobic Bioremediation in a Low-pH Aquifer
Ge Chen, CDM, Edison, NJ
Kent S. Sorenson, CDM, Denver, CO
Chorfan Tsang, CDM, New York, NY 

Ferric Iron Amendment Increases Carbon Oxidation and Phosphorus Removal in On-Site Wastewater (Septic Systems) 
Hossain M Azam, University of Illinois at Urbana Chamapign, Urbana, IL
Kevin T Finneran, University of Illinois at Urbana Chamapign, Urbana, IL

Bioremediation at Low PCE Levels in an Aerobic Sand Aquifer
Shamim Wright, AECOM Environment, Westford, MA             
Daniel Groher, AECOM Environment, Westford, MA
Art Taddeo, AECOM Environment, Westford, MA
Lelia McAdams, AECOM Environment, Cincinnati, OH 

Adjusting Aquifer pH to Improve the Performance of Halorespiring Bacteria
Robert Borden, North Carolina State University, Raleigh, NC
Mark Kluger, Dajak, LLC, Wilmington, DE      

Perchlorate Reduction Using Fine Media Fluidized Bed Bioreactor with Oxidation-Reduction Potential-based Feed Control
Mamie Nozawa-Inoue, Environmental Resolutions, Inc., Lake Forest, CA
Dallas E. Weaver, Scientific Hatcheries, Huntington Beach, CA
Joseph E. O’Connell, Environmental Resolutions, Inc., Lake Forest, CA  

Perchlorate Bioremediation Using Novel Sulfur Oxidizing Bacteria: Pilot-Scale Bioreactor Studies at the Massachusetts Military Reservation
Sarina J. Ergas, University of Massachusetts, Amherst, MA
Amber Boles, University of Massachusetts, Amherst, MA
Klaus Nüsslein, University of Massachusetts, Amherst, MA
Paul S. Nixon, Army Environmental Command Impact Area Groundwater Study Program, Camp Edwards, MA
Robert McKeever, University of Massachusetts, Amherst, MA
Teresa Conneely, University of Massachusetts, Amherst, MA.

Treatability Study of Enhanced Anaerobic Bioremediation in a Low-pH Aquifer

Ge Chen, P.E. CDM, Raritan Plaza I, Raritan Center, Edison, NJ, 08818, USA, Tel: 732-225-7000, Fax: 732-225-7851, Email: cheng@cdm.com
Kent S. Sorenson, Ph.D., P.E.,  CDM, 555 17^th Street, Suite 1100, Denver, CO 80202, USA. Tel: 303-383-2300, Fax: 303-308-3003, Email: sorensonks@cdm.com
Chorfan Tsang, P.E., CDM, 125 Maiden Lane, 5^th Floor, New York, NY 10038, USA. Tel: 212-785-9123, Fax: 212-785-6114, Email: tsangc@cdm.com

Implementing cost-effective and low maintenance groundwater treatment technologies for large chlorinated solvent plumes at depth remains a significant challenge. Enhanced anaerobic bioremediation (EAB) using bio-barrier technology with slow-release amendments is a promising innovative technology for remediating such a contaminant plume. This presentation discusses the challenges encountered during an EAB treatability study (TS) in a low-pH aquifer, the mitigation measures, and the results 

The TS was conducted in a sandy aquifer in southern New Jersey. The contaminant plume is located between 65 and 95 feet below ground surface, with the maximum tetrachloroethene (PCE) concentration at 250 µg/L. To evaluate the effectiveness of EAB, emulsified vegetable oil was selected as the electron donor and injected into four injection wells to form a bio-barrier. The progress of EAB was monitored in the injection well and monitoring wells located downgradient of the injection wells. Two challenges were encountered: 1) a native bacterial strain, Dehalococcoides spp. (DHC), responsible for complete dechlorination of PCE and TCE, was not present; 2) the ambient groundwater pH ranges from 4.5 to 6, lower than the optimal pH necessary for complete reductive dechlorination. To facilitate and expedite the EAB process, sodium bicarbonate was used to correct the low-pH groundwater conditions and bioaugmentation was conducted.  

Two years after the injection of emulsified vegetable oil, groundwater results demonstrate that:  1) strong reducing conditions were created and dechlorination of PCE and TCE occurred in the test area, although reductive dechlorination stalled at dichloroethene (DCE); 2) pH adjustment with bicarbonate appeared to be effective and alkalinity increased on its own due to biological activities; and 3) even with improved pH, the growth of DHC is minimal.

Ferric Iron Amendment Increases Carbon Oxidation and Phosphorus Removal in On-Site Wastewater (Septic Systems)

Student Presenter

Hossain M Azam, University of Illinois at Urbana Chamapign, 4162 NCEL, 205 North Mathews Ave, Urbana, IL 61801-2352, USA, Tel: 1-919-271-5347, Email: hossain.azam@gmail.com
Kevin T Finneran, University of Illinois at Urbana Chamapign,  3221 NCEL, 205 North Mathews Ave, Urbana, IL 61801-2352, USA, Tel: 1-217-244-7956, Fax: 1-217-333-6967, Email: finneran@illinois.edu

Onsite wastewater treatment systems (OWSs), mostly anaerobic septic tanks, serve approximately 25% of the U.S. population. Though septic systems are well equipped to deal with labile organic carbon BOD and nitrogenous waste, the systems only remove a fraction of the total carbon and allow trace nutrients, primarily phosphorus, to escape.  The objectives of the present study were to characterize the influence of microbial Fe (III) reduction on carbon oxidation from septic wastewater together with removal of phosphate from the system, as the mineral vivianite. Fe(III) amendment to septic systems essentially opened an “untapped” metabolic niche that allowed greater carbon oxidation in a shorter time frame.  Additionally, biological Fe(III) reduction generated the insoluble mineral vivianite Fe₃(PO₄)₂-(H₂O)₈, which removed phosphorus from the effluent. Native septic material was incubated with ¹⁴C-labeled substrates (acetate, glucose, lactate, propionate, butyrate, starch) with different Fe(III) forms  (Fe(III)-citrate, Ferrihydrite, Lepidocrocite, Fe(III)-NTA, Fe(III)-EDTA and Fe(III)-Pyrophosphate) relative to un-amended  material. Fe(III) amendment increased mineralization to ¹⁴CO₂ by an average of 20-25% for all carbon substrates, relative to unamended septic material.  ¹⁴C acetate and glucose were mineralized 40% and 60% to CO₂ compared to 20 and 25%, respectively, in the unamended system. Average rates of mineralization for ¹⁴C acetate and glucose were 4.13% and 3.85% CO₂/hr compare to 1.05% and 0.85% CO₂/hr in the unamended system. Mineralization of carbon compounds to CH₄ was not present in any experimental system. Phosphorus was removed concurrently with Fe (III) reduction, and TEM-EDX characterization is being used to quantify the extent of vivianite formation by different Fe(III) forms.  Subsequent modeling and experiemnt on vivianite formation at different pH, Fe (III) and PO₄ concentration are being used to characterize the conditions for optimum vivianite formation. Moreover, experiments on total and soluble COD removal as well as total gas production from septic wastewater are being used to observe, further, the effects of Fe (III) amendment to the septic system.

Bioremediation at Low PCE Levels in an Aerobic Sand Aquifer

Shamim Wright, AECOM Environment, 2 Technology Park Drive, Westford, Massachusetts, 01886,Tel: 978-589-3000, Email: shamim.wright@aecom.com
Daniel Groher, AECOM Environment, 2 Technology Park Drive, Westford, Massachusetts, 01886,Tel: 978-589-3000, Email: daniel.groher@aecom.com
Art Taddeo, AECOM Environment, 2 Technology Park Drive, Westford, Massachusetts, 01886,Tel: 978-589-3000, Email: arthur.taddeo@.aecom.com
Lelia McAdams, AECOM Environment, 135 Merchant Street, Suite 160, Cincinnati, Ohio, 45246, 513-772-7800, Email: lelia.mcadams@aecom.com

The majority of Enhanced Reductive Dechlorination projects have been performed at sites with chlorinated VOCs where evidence of natural attenuation is occurring, or at least where dissolved organic carbon is present, dissolved oxygen levels are low, and CVOC levels are moderate.  This case study presents results of a project in which the subsurface conditions were sub-optimal. 

The contaminants were PCE with minor amounts of TCE.  The highest concentration of PCE measured at the site within the last 4 years was 190 ug/L, with most areas below 100 ug/L.  The aquifer is comprised of fine to medium dune sand with a groundwater velocity of 1 – 2 feet per day.  Dissolved oxygen concentrations are generally greater than 5 mg/L.  The aquifer has very low natural concentrations of organic carbon, electron acceptors, and mineral nutrients.  The objective of the pilot study was to determine the feasibility of developing anaerobic conditions using a long-lasting electron donor (emulsified vegetable oil) and then bioaugmenting with Dehalococcoides (DHC).

Bench testing indicated that native organisms could utilize electron donors and reduce nitrate, but did not reduce sulfate in site groundwater.  Field monitoring after injection of EOS™ vegetable oil confirmed this.  Reducing conditions in the aquifer required months to develop.   Microbiological tests showed that the sand lacked bacteria necessary to ferment the oil and support PCE degradation.  Suitable anaerobic conditions required supplementing the native bacteria with anaerobes and nutrients before inoculation with DHC, as well as nutrients.  Over time, PCE was degraded to DCE and VC, which then attenuated to below cleanup standards. 

The performance of bioaugmentation and natural attenuation in this highly aerobic, low-PCE environment will be discussed. The results from over a year of testing indicated that reducing conditions can be created to support bioaugmentation.  Scale-up of pilot results to implement a full-scale biobarrier at the down-gradient site property boundary and performance of the full-scale system will also be presented. 

Adjusting Aquifer pH to Improve the Performance of Halorespiring Bacteria

Robert Borden, Ph.D., P.E., North Carolina State University, 1101 Nowell Road, Raleigh, NC 27607, Tel: 919-515-1625, Email: rcborden@solutions-ies.com
Mark Kluger, Dajak, LLC, 7 Red Oak Road, Wilmington, DE  19806, Tel: 302-655-6651, Email: mkluger@dajak.com 

Enhanced reductive dechlorination is an effective approach for bioremediation of chlorinated solvents and other groundwater contaminants. However, many dechlorinators are pH sensitive and dechlorination rates can decline significantly below a pH of 6. Furthermore, the reductive dechlorination process can reduce the pH in poorly buffered aquifers where a neutral pH is required for biodegradation to proceed. A neutral pH can be maintained using aqueous buffers, commonly sodium bicarbonate or calcium carbonate. However, this procedure is maintenance intensive. Also, sodium bicarbonate can significantly increase the salt concentration of the aquifer.

An alternative and more effective approach is to simultaneously inject a combined soybean oil-solid pH buffer emulsion. As the oil-buffer emulsion migrates through the aquifer, chlorinated solvents will partition into the oil. Within a short period of time, the oil-buffer droplets attach to the aquifer solids, providing an ideal environment for reductive dechlorination, since the oil droplet contains electron donor (oil), electron acceptor (chlorinated solvent) and a pH buffer to maintain a neutral pH. The presentation will provide information and strategies on anaerobic biodegradation and pH, aquifer pH adjustment and case studies.

Perchlorate Reduction Using Fine Media Fluidized Bed Bioreactor with Oxidation-Reduction Potential-based Feed Control

Mamie Nozawa-Inoue, Ph.D. Environmental Resolutions, Inc. 25371 Commercentre Dr., Suite 250, Lake Forest, CA 92630, USA, Tel: 949-273-6307, Fax: 949-457-8956, Email: minoue@eri-us.com
Dallas E. Weaver, Ph.D., P.E., Scientific Hatcheries, 8152 Evelyn Cr., Huntington Beach, CA 92646, USA, Tel: 714-960-4171, Email: deweaver@mac.com
Joseph E. O’Connell, Sc.D., P.E., Environmental Resolutions, Inc. 25371 Commercentre Dr., Suite 250, Lake Forest, CA 92630, USA, Tel: 949-457-8953, Fax: 949-457-8956, Email: joconnell@eri-us.com

Certain bacteria, prevalent in the environment, use perchlorate as an electron acceptor and reduce it to chloride under anaerobic conditions. To develop an ex-situ treatment system for perchlorate-contaminated groundwater, we performed a large bench-scale test using a fine media fluidized bed reactor (FMFBR; 0.5-ft diameter, 8-ft high) inoculated with a perchlorate-reducing culture. Artificial perchlorate-contaminated water was introduced into a recirculating stream in the anaerobic FMFBR at an upward velocity of 16 cm/min. Acetate (acetic acid) was fed as an electron donor. The objective of this study was to establish a minimal acetate feed ratio for sufficient perchlorate reduction by monitoring oxidation-reduction potential (ORP) and, consequently, prevent ORP from falling to a range of sulfate reduction and limit the biomass growth from excess acetate.

The FMFBR was able to degrade 3000 - 5000 μg/l perchlorate to less than 4 μg/l in a single pass (16 min empty bed contact time) without excessive hydrogen sulfide production, when effluent ORP (vs. Ag/AgCl) was -290 - -410 mV. Accurate feed control is essential since an imbalance in acetate feed ratio results in unreacted perchlorate or sulfide production. A base feed pump was used to provide 60 - 80 % of the acetate required and an ORP controller was used to trim and balance the feed rate using a second pump. The second feed pump was activated when effluent ORP rose to or above -315 mV and deactivated when it fell to or below -320 mV. Some oscillation of effluent ORP was observed, but perchlorate was not detected in the effluent when the oscillation was kept relatively small. Average acetate feed ratio was approximately 1.1-times stoichiometry. For more stable perchlorate degradation, we will examine an earlier ORP detection in the bioreactor column and a more flexible control method of acetate feed rate.

Perchlorate Bioremediation Using Novel Sulfur Oxidizing Bacteria: Pilot-Scale Bioreactor Studies at the Massachusetts Military Reservation

Student Presenter

Sarina J. Ergas, Dept. Civil & Environmental Engineering, University of Massachusetts, 18 Marston Hall, Amherst MA 01003, Tel: 413-545-3424, Fax: 413-545-2202, Email: ergas@ecs.umass.edu.
Amber Boles, Dept. Civil & Environmental Engineering, University of Massachusetts, 18 Marston Hall, Amherst MA 01003, Tel: 413-545-3424, Fax: 413-545-2202, Email: boles@ecs.umass.edu.
Klaus Nüsslein, Dept. Microbiology, University of Massachusetts, Morrill IV North, Amherst MA 01003, Tel: 413-545-1356, Fax: 413-545-1578, Email: nusslein@microbio.umass.edu.
Paul S. Nixon, P.E., Army Environmental Command Impact Area Groundwater Study Program, Camp Edwards, MA 02542, Tel: 508-968-5620, Email: paul.nixon@us.army.mil.
Robert McKeever, Dept. Civil & Environmental Engineering, University of Massachusetts, 18 Marston Hall, Amherst MA 01003, Tel: 413-545-3424, Fax: 413-545-2202, Email: rmckeeve@student.umass.edu.
Teresa Conneely, Dept. Microbiology, University of Massachusetts, Morrill IV North, Amherst MA 01003, Tel: 413-545-1356, Fax: 413-545-1578, Email: tconneel@bio.umass.edu.

Perchlorate (ClO₄^-) has been used as a solid rocket fuel and in flares, fireworks, fertilizers, some military munitions and other items and has been detected in ground and surface water in more than 38 states.  This paper reports on a microbial consortium capable of coupling elemental sulfur (S⁰) oxidation with ClO₄^- reduction.  Advantages of using S⁰ as an electron donor for biological ClO₄^- reduction include: (1) ClO₄^- is reduced to harmless products (Cl^- and O₂), (2) S⁰ is an inexpensive by-product of petroleum refining, (3) the slow growing autotrophic bacteria produce little excess sludge and (4) S⁰ can be used in simple packed bed bio-reactors (PBRs).  In prior studies, bench-scale S⁰-oxidizing PBRs operated at an eight hour residence time reduced ClO₄^- from 100 to less than 4 ppb.  In this study, we investigate a pilot-scale (~200 L) PBR, packed with a mixture of S0 particles and crushed oyster shells and seeded with a laboratory grown consortium of S⁰-oxidizing ClO₄^- reducing bacteria.  Microscopic and molecular analyses of the microbial consortium indicates that it is dominated by rod morphology and composed of Beta- and Gamma-Proteobacteria, as previously seen with other S⁰-oxidizing ClO₄- reducing cultures.  The pilot-PBR is treating groundwater from a plume on the Massachusetts Military Reservation on Cape Cod.  The plume is currently being contained using a nearby extraction well, and treated using ion exchange (IX) resin and granular activated carbon (GAC).  Groundwater for the pilot-PBR is extracted from a monitoring well with a ClO₄^- concentration of more than 100 ppb.  Current research is focused on investigating the effect of ClO₄^- mass loading rate and backwashing on PBR process performance.  The results of the pilot-PBR study will be compared to the performance of the full scale IX-GAC treatment system.  The fate of the co-contaminant, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), will also be discussed.

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