Theme: 08. Metals

Topic Area: 8c. Precipitation and Stabilization of Metals

Formatted Title:

Transformation of Mercury-Contaminated Soil and Building Materials to Non-Hazardous Using MercLok™

Background/Objectives:

An industrial site in the United States was redeveloped for residential housing. The site was contaminated with mercury and PCBs due to manufacturing processes. Visible elemental mercury was found in drains, pipes, beneath floors, and in the soil around and under some of the factory buildings. The remedial plan called for digging up the contamination and sending it for land disposal or to a retort facility. Generally, materials with visible mercury went to a retort facility which recovered the elemental mercury, and highly contaminated materials without visible mercury went to be processed and landfilled in Canada. The retort facility was not permitted to handle PCBs, which was problematic for materials having both visible mercury and PCBs.

Approach/Activities:

For product development research Albemarle collaborated with an environmental consulting company to run bench-scale treatability studies on soil and cinders from this site using a novel mercury amendment capable of immobilizing organic, inorganic, and elemental mercury. The cinders are a material that was placed in the floors for vibration damping.

Near the end of the site’s remedial action, some cinders were segregated due to high mercury concentration, visible mercury, and high PCBs. This material could not be land disposed because of the visible mercury and could not be retorted due to the high PCBs content. Albemarle provided the amendment to the responsible party for treatment of these cinders with the goal of eliminating visible mercury and immobilizing the mercury to a concentration below the hazardous limit of 0.2 mg/l. As a result of the treatment, the cinders were reclassified from a hazardous waste to a high mercury, non-hazardous waste which allowed for economically attractive land disposal options.

Results/Lessons Learned:

This presentation will include a technical review of the results of the bench-scale treatability studies and the results of the field treatment.

In bench studies of media from the site, MercLok was able to reduce leachable mercury from the soil and cinders by over 98% and below the TCLP hazardous limit of 0.2 mg/l. Soil was further evaluated using the EPA 1314 method, which is an up-flow percolation column method. Method 1314 results showed that mercury mass release from the MercLok treated soil was reduced by more than 90% compared to untreated soil and eluate concentrations were below the MCL of 2 ug/L.

The TCLP results from the field treated cinder samples showed mercury leachability was reduced to as low as 0.004 mg/l, which was a reduction of 99.98% and is far below the TCLP limit of 0.2 mg/l. Measurable PCBs using test Method 8082A was also reduced from more than 3 mg/kg to the detection limit of 0.023 mg/kg.

Due to the timing of MercLok commercialization, the product was not available when most of the contaminated material was removed and sent for disposal. However, the bench study results suggest that the amendment product could have stabilized the mercury in the soil which would have resulted in lower disposal costs.

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Kim Pingree