United States Department of Transportation
i
Bench-Scale Electrochemical Treatment of Co-Contaminated Clayey Soil
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2021-06-01
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[PDF-5.98 MB]
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Edition:Task 3 report 2/1/18–6/30/21
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Abstract:Industrial soil contamination is frequently unearthed by transportation agencies during construction within the right-of-way. As a result, transportation agencies may experience construction delays. Soils co-contaminated with high-molecular-weight polycyclic aromatic hydrocarbons (HMW-PAHs) and metals are commonly encountered in Illinois and exhibit recalcitrance towards conventional treatment technologies. This issue is exacerbated in the fine-grained soils common to Illinois, where low-permeability and immense sorption capacity increase treatment complexity, cost, and duration. Contaminated sites are spatially and temporally restrictive and require rapid in situ treatments, whereas conventional soil remediation requires 1 to 3 years on average. Consequently, transportation agencies typically pursue excavation and off-site disposal for expediency. However, this solution is expensive, so a comparatively expeditious and affordable treatment alternative is needed to combat the increasing cost of hazardous waste disposal. The objective of this work was to develop an accelerated in situ treatment approach adaptable for use at any construction site to cost-effectively remove HMW-PAHs and metals from clayey soil. It was hypothesized that an in situ electrochemical treatment which augments electrokinetics with H2O2 could remediate both HMW-PAHs and metals in less than a month. Bench-scale reactors resemblant of field-scale in situ electrokinetic systems were designed and fabricated to assess the electrochemical treatment of clayey soils contaminated with HMW-PAHs and metals. Pyrene, chromium, and manganese were used as model contaminants, spiked into kaolinite as a model clay. Electrokinetics were imposed by a low-intensity electrical field distributed by graphite rods. Electrolytic H2O2 systems were leveraged to distribute electrical current and facilitate contaminant removal. Average contaminant removals of 100%, 42.3%, and 4.5% were achieved for pyrene, manganese, and chromium, respectively. Successful development of this bench-scale treatment approach will serve to guide transportation agencies in field-scale implementation. The results from this work signify that electrochemical systems that leverage eco-friendly oxidant addition can replace excavation and disposal as a means of addressing clayey soils co-contaminated with HMW-PAHs and metals.
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