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Waste Science Inc. Hot Spots - Bioremediation |
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A storm water drainage ditch drains a large warehouse facility known as the Naval Support Activity (NSA) in Mechanicsburg, Pennsylvania. The ditch contains sediments contaminated from base activities. These Contaminants of Concern (COCs) include: polychlorinated biphenyl (PCB) Aroclor 1260, polycyclic aromatic hydrocarbons (PAH), arsenic, and other metals. The ditch has been extensively investigated and partially remediated, including excavation of sediment from the most contaminated, upstream 2,200 feet (ft), known as Segment 1. However, portions of Segment 1 and downstream areas still contain COC concentrations significantly above cleanup goals. Bioremediation is being considered as the final remedy since it can be applied in-situ with minimal disturbance to the vegetation and ecosystem (important since most risk is from exposure of ecological receptors to COC), and is very cost-effective compared with alternatives involving soil excavation. To address whether or not bioremediation could be effective against the particular COC in the ditch, the project team developed a pilot test employing a unique consortium approach. In March, 2004, the team of Waste Science Inc. (WSI) and Lambda Bioremediation Systems, Inc. (Lambda) out of Columbus, OH, were subcontracted to Weiss Associates (out of Emeryville, CA) to perform this work. Weiss won a contract with EA Engineering and the Navy to perform a large-scale biotreatability demonstration on a 1220-foot long portion of a drainage ditch's Segment 1. The objectives of the project were to demonstrate that the technology will work on the contaminants at the site under actual field conditions and to address the issues that would arise from a large-scale application of the technology. 
Site 9 Looking Upstream Toward Section 1 Culvert Portions of Segment 1 were excavated and replaced with riprap in an effort to remove the contamination and stabilize the banks. The banks above the riprap, which did not undergo excavation, contain the highest concentrations of COCs. Bioremediation offers an elegant solution as to how the contamination on steeply sloping banks and in the channel could be addressed without removing vegetation or performing costly and ineffective excavation.
The main COCs and their concentrations are:
As described in another article found on this website (Bioremediation - Taking the Microbes' Perspective), Lambda's unique process is custom designed for the contaminant mixtures and concentrations found at the site. The process uses indigenous site microbes - bacteria, fungus, algae, and protozoa - that have already started adapting to the contamination and fortifies them to do a better job by hybridizing them with type cultures and through natural selection (without genetic engineering). COC concentrations that would normally be toxic to the microbes are slowly introduced to "acclimated bugs" in Lambda's laboratory. This process took approximately six weeks. Designing the right mix of microbes to make up the consortium is as much art as science. Research was performed to identify the microorganisms needed to destroy or transform the contamination, generate needed enzymes, and adjust the pH and oxygen levels in the treated area to optimize conditions for their survival. In a complex interaction, over 500 individual microbes worked both aerobically and anaerobically over time, painstakingly degrading the contamination and all daughter and by-products, step-by-step. Balance within the ecosystem is critical. As an example, the degradation of Aroclor 1260 (a heavy PCB) was one of the most challenging aspects of the project. Their destruction required 35 steps and 51 microbes to transform Aroclor 1260 into carbon dioxide and water, essentially by stripping off chlorines and breaking apart the biphenyls. Each contaminant received the same careful process design. Then all processes are assembled into the consortium and fine-tuned so they will work in concert, rather than at cross-purposes, within the contaminated site environment. Because each site is unique, a custom-designed formulation is required to optimize the effectiveness of the treatment under site conditions. This requires extensive research and literature review for information on the biochemistry and interrelationships of the COC. Baseline Site characterization revealed that the low (acidic) pH and lack of nutrients in the shallow Site soil would impede the cleanup by depriving the microbes of required nutrients and exposing them to below-optimal pH. This meant that the project team had to supplement the site soil to raise the pH to within acceptable ranges (7 to 8.5) and to add nutrients using a generic soil enhancer, termed BioBooster©, and a specifically designed compost. BioBooster© conditions a nutrient-depleted soil by adding those elements that are essential for bioremediation success. The compost was used to raise the pH and supply added nutrients-SO4, NO3, NH4, PO4, K-and trace elements that were negligible or missing from the Site soil. These components are essential for reductive dechlorination and the reduction of most of the metals on the Site. The reductive dechlorination and anaerobic bioremediation was encouraged by the consortium design to decrease or detoxify the pesticides and metals first, then start breaking down the PCB. When crucial nutrients are present in the soil, microbes can achieve a reducing environment. By making these adjustments, the inoculum was given the best chance of achieving success within a reasonable timeframe. 
Inoculating Test Site Lambda assembled 50-pound BioCarb© bags to act as small microbe incubators and placed them in the channel under the water line when water is actively flowing in the ditch. (These BioCarb© bags are composed of granular, activated carbon soaked in the inoculum and will withstand the rigors of flowing water without being dislodged.) Smaller, 30-pound bags were places just above the riprap. Inoculum was injected along the banks and sprayed onto the surface soils, pressure-injected into the shallow channel sediments, and deposited under the water in BioCarb© bags. 
Applying Compost to Raise Nutriet Levels A total of 3,200 gallons of inoculum was grown. The feed protocol was based on site chemistry and data on the COC. The pH was balanced to produce and environment that was friendlier to facultative anaerobes, methanogenic bacteria, fungi, algae, and protozoa, a complex balance to achieve. Based on microbe density and viability, supplemented with 20 years of professional judgment, the consortium was deemed ready to be delivered to the site four weeks after it was placed in the growth tank. Sediment samples were collected five and 15 weeks after inoculation. Additional samples will continue to be collected for a period of two years. Analysis of the trends exhibited pre- and post-treatment in soil samples collected from the 1,200-ft long study area of this pilot project indicate that bioremediation is a suitable and effective treatment technology for the mixture of Site contaminants. Despite only having 15 weeks from inoculation for the initial assessment period, statistically significant declining trends in two COC were evident and downward trends were shown in all classes of COCs. While the evaluation period is too short to make a definitive statement about the long-term efficacy of this bioremediation treatment, the short-term trends that are exhibited demonstrate success in treating pesticides and vanadium, and encouraging trends may be present for PCB Aroclor 1260 and the other COCs and analysis over the next two years is planned to document bioremediation progress toward the clean-up goals. WSI would be happy to discuss the details with interested companies or clients. Please contact either WSI or Lambda at the links below for more information. Email Lambda Metropolitan Washington, DC 1411 Fallswood Drive Rockville, MD 20854 phone 301-340-3301 fax 800-869-1763  Previous Page   Next Page
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PCB Aroclor 1260 up to 140 mg/kg