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Waste Science Inc. Hot Spots - Bioremediation |
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The Mahoning River flows through eastern Ohio and across the boarder into western Pennsylvania, passing through Trumbull County, Ohio and near Youngstown, 45 minutes west of Pittsburgh, PA. As with most waterways in this part of the country, the Mahoning played a key role in the development and success of Rust Belt industries. After receiving industrial discharges for years, the river and bank sediments have become contaminated. The enforcement of environmental regulations on discharges to surface water has stopped most of the major discharges and provided the river a chance to begin recovery. As a result, older contaminated bank sediments are buried under cleaner deposits. A series of low dams on the river has allowed contaminated river sediments to accumulate and concentrate in the channel upstream of these dams. The river looks unaffected. Its banks are thickly vegetated and the undisturbed water appears relatively clear. However, use a stick to unsettle the mud along the bank, and black, oily sediments will be stirred up and an oil sheen will appear on the water. The Ohio Environmental Protection Agency (OEPA) has issued a health advisory for 31 miles of the Ohio portion of the river, from Leavittsburg to the Ohio border with Pennsylvania. A cocktail of contaminants is present, including polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), heavy metals, and total petroleum hydrocarbons (TPHs). 
Mahoning River, Leavittsburg, OH Eastgate Regional Council of Governments (Eastgate), a regional planning council, in conjunction with the US Army Corps of Engineers - Pittsburgh District (USACE), are performing a feasibility study to identify and evaluate remedial alternatives for the cleanup of both the river and contaminated bank sediments. To date, private funds have been used to dredge a one-mile stretch of the river in the study area, with mixed results. A major criterion of the stakeholders and regulators is for the scenic nature of the river to be preserved. They fear that invasive and disruptive remedies, such as dredging or containment, might destroy the much-needed recreational and commercial development potential of the river. In other words, they are looking for remedies that would not put at risk the beauty of the river during or after cleanup.
Bioremediation appears to be a potential remedy with many desirable benefits:
In March, 2003, Waste Science Inc. (WSI) and our subcontactor Lambda Bioremediation Systems, Inc. (Lambda) out of Columbus, OH, won a nationally-competed contract with Eastgate and the USACE to perform a small-scale biotreatability demonstration on a Test Site selected by the Corps. The objectives of the project were to: 1) demonstrate that the technology will work on the contaminants at the site under actual field conditions, 2) provide a basis for cost comparison with more traditional remedies, and 3) address the issues that would arise from a large-scale application of the technology. 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 (without genetic engineering). COC concentrations that would normally be toxic to the microbes are slowly introduced to "acclimated bugs" in Lambda's laboratory. Designing the right mix of microbes that 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 corsortium and fine-tuned so they will work in concert, rather than at cross-purposes, within the contaminated site environment. 
Acclimation Process in Lambda's Lab The designated Test Site was a 50-x-50-foot plot on the western bank of the Mahoning River, just upstream of the Liberty Street dam in Girard, OH. The boundaries extended approximately 18 feet into the water. Not only was this an area where contaminated sediments had accumulated behind the dam in the river channel and where COCs were buried as deep as six feet below clean soils in the bank areas, but the concentrations of those contaminants were found to be among the highest in the entire 31-mile study area. TPH was as high as 20,000 mg/kg; PCBs were as high as 3443 ug/kg; selenium, zinc, arsenic, and iron was found in leachable form in the hundreds to tens of thousands of ug/L; and 16 PAHs were at total concentrations as high as 108 mg/kg. 
Test Site Looking Downstream Toward Liberty Street Dam Sediment samples in the Model Reach (uncontaminated upstream area of the river) and Test Site were collected at the beginning of the study to establish a baseline. Cleanup targets were designated as those concentrations found in the Model Reach. Samples of sediments from the Model Reach, a Recovering Area (of moderate contamination), and the Test Site were taken to Lambda's laboratory to be evaluated for indigenous microbial communities, and microbe viability, density, and variability. These sediment samples also were used to acclimate the consortium. Four hundred gallons of inoculum, consisting of acclimated microbes, vitamins, enzymes, nutrient broth, and a variety of other ingredients, was grown to inoculate the site. Lambda assembled BioCarb© bags to act as small microbe incubators to be placed in the river under the water line. (These BioCarb bags are composed of granular, activated carbon soaked in the inoculum and will withstand the rigors of flowing water without being dislodged.) The site was inoculated on September 3, 2003. Inoculum was injected along the banks in pre-drilled holes, sprayed onto the surface soils, pressure-injected into the shallow river sediments, and deposited under the water in BioCarb bags. 
Wand Used to Inoculate Below the Surface on the Banks of the Test Site Sediment samples were collected six weeks and five months after inoculation at the Test Site. Based on these results, it was shown that bank sediments exhibited reductions in all types of COCs, while the sediments in the river remained fairly unresponsive to treatment. Total PAHs were reduced 35.9% in the river sediments, and from 21.5% to 92.6% on the banks. Total pesticides were reduced 43.2% to 98.0% in the bank sediments, but were not reduced in the river sediments. Total petroleum hydrocarbons were not reduced in the river sediments, but were reduced up to 93.7% in the bank sediments. Aroclor 1260 was shown to be transforming into lighter aroclors in the bank sediments, while arsenic was reduced 15%, chromium 96%, and manganese 40%. It was concluded that the technology showed promise as a remedy for treating the contamination on shore, but was less effective in near-shore river sediments, while minimizing potential damage that could result from the use of a more invasive remedy. Although the study has been concluded, treatment is passively continuing and it anticipated that further reductions would be exhibited should additional samples be collected. Costs for treating the bank sediments in a large scale-up for the entire 31 miles of contaminated river were estimated and the considerations for regional-scale application were outlined. The client was pleased with the results and thought bioremediation was an potentially attractive remedy for the contamination along the river banks. It was thought that either another application method was needed to increase the effectiveness in the river, or that bioremediation of the bank sediments would have to be coupled with another, more aggressive technology, such as dredging, in the river. The timeframe for completion of the feasibility study and selection of a final remedy is around 2006. WSI would be happy to discuss the details or cost estimates 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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it is non-invasive