Electrochemical remediation of co-contaminated clayey soil

Austin James Pelletier

doi:10.7273/000003994

Industrial soil contamination is frequently unearthed by transportation agencies during right-of-way (ROW) construction, threatening both public health and the environment. As a result, transportation agencies may experience regulatory violations, fines, and 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 ROW sites are spatially and temporally restrictive and require rapid in-situ treatments, whereas conventional soil remediation requires 1-3 years on average. Consequently, transportation agencies typically pursue excavation and off-site disposal to prevent construction delays. However, this solution is expensive, so a comparatively expeditious and affordable treatment alternative is needed to combat the ever-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 ROW 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 remediation of clayey soils contaminated with HMW-PAHs and metals. Pyrene, chromium, and manganese were used as model ROW 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. Future work will evaluate the treatment of an Illinois field soil co-contaminated with arsenic, benzo(a)pyrene and manganese. 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 which leverage eco-friendly oxidant addition can replace excavation and disposal as a means of addressing clayey soils co-contaminated with HMW-PAHs and metals.

Electrochemical remediation of co-contaminated clayey soil

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