Sep 03, 2020

Clean Up Act

Remediation contractors turn to sulfur-impregnated clay for mercury remediation

mercury remidiation
Groundwater extracted from site dewatering activities was first pumped through filtration vessels filled with 16,000 pounds of Organoclay MRM before being pumped through another set of vessels containing granular activated carbon.

As the health and safety risks associated with mercury contamination became known, governments made efforts to protect humans and the environment from mercury emissions.

For instance, the U.S. passed several mercury-related regulations, including The Clean Air Act (1990) and Mercury-Containing and Rechargeable Battery Management Act (1996). Globally, 140 nations agreed in 2013 to the Minamata Convention on Mercury.

It is against this backdrop that New Jersey instituted its own mercury-related regulations and task forces, which govern the legal exchange of real estate. When a party is looking to sell property, it triggers an analysis to determine mercury levels, as well as levels of other toxic elements and chemicals. When certain thresholds are recorded, the seller must remediate the contamination before concluding the property transfer.

organoclay

This dynamic has played out countless times over the past few years, with the majority of contaminated sites facing two potential remediation options: incineration, which requires removing the contaminated water and soil to an off site facility and incinerating it; or carbon filtration, where large masses of carbon are deployed to neutralize the contamination. While both are effective means at remediation mercury contamination, CETCO sought another way to improve efficiency and eliminate the need for removal.

Mercury Remediation

CETCO tapped into its research and development team to find a way to utilize sodium bentonite as a means for remediation. Through that process, Organoclay mercury removal media (MRM) was born. This solution is a sulfur-impregnated organophilic clay that adsorbs non-aqueous phase liquids (NAPL) and dissolved low-solubility organics. It also sequesters mercury and arsenic. 

It deploys quickly and easily while efficiently adsorbing a variety of elemental and methylmercury species. In fact, the material absorbs up to 50% of its own weight in contaminants. It can be used for groundwater pump and treat filtration applications, as a permeable reactive barrier media, or as a stabilization additive to Portland cement.

The media sequesters mercury in the presence of dissolved organic compounds without blinding or fouling. It effectively treats four forms of mercury: methyl-mercury, HgO, Hg+1 and Hg+2. Additionally, it adsorbs long-chain organics, including polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAH) and dioxins. 

organoclay
This graph demonstrates how Organoclay MRM performs against a commercial media in terms of effectiveness and capacity when filtering Hg (II) at a concentration of 10 parts per million.

Meanwhile, Back in New Jersey

In 2012, a large excavation site in East Rutherford, New Jersey, was discovered to contain high levels of mercury along with arsenic and other organics. Its site owner, a multinational chemical company, tasked a remediation contractor with building and operating a groundwater treatment system.

The contractor decided to deploy Organoclay MRM within the treatment system, which consisted of two processes: 

  1. Groundwater was extracted from the site and pumped through filtration vessels, which contained 16,000 pounds of the media. 
  2. The effluent from these vessels was pumped through a set of similarly sized vessels that contained granular activated carbon. The final effluent had to meet the New Jersey Department of Environmental Protection discharge parameters for all the contaminants of concern. 

A primary focus for this project was the varied chemical composition of the waste stream, which contained both organics and metals. Traditional sorptive media tend to exhibit interference effects in these mixed waste streams, leading to organic contaminants that prevent the efficient uptake of metals. However, during the treatment process, the media selected adsorbed both classes of contaminants. 

After a second round of treatment with Organoclay MRM, the site had reduced its level of mercury to acceptable state levels, allowing for the completion of the property transfer.

bentonite

 

Final Tally

The remediation process was effective and efficient. It took two months for the initial groundwater treatment, and after Hurricane Sandy hit, another four months of treatment was needed to complete the process. The removal media allowed for all work to be accomplished on site, resulting in a more practical and cost-effective mercury remediation strategy. 

About the author

Michael T. Kozak, J.D. is the vice president, Building Materials & Environmental Products for Minerals Technologies Inc.  Kozak can be reached at [email protected]

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