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Klean Earth Environmental Company (KEECO) has developed a high-performance, lowcost technology for the prevention, treatment and remediation of metals contamination. Silica Micro Encapsulation (SME) does precisely what its name implies – it encapsulates metals in an impervious silica matrix (essentially locking them up in very small grains of sand) which prevents the metals from migrating, becoming bioavailable, and causing adverse impacts on human health or the environment.

SME usually achieves control of contaminants in a single step, without the need for pretreatment with chemicals or post-treatment flocculation or filtration. Its physical/chemical components include an initial exothermic reaction and pH adjustment followed by metal hydroxyl formation and an electrokinetic reaction that initiates the process of silica encapsulation. Over time, the silica matrix strengthens and thickens, further isolating the contaminants from the environment.

SME is a very robust technology which has been demonstrated to work effectively on heavy metals (such as chromium, copper and zinc), metalloids (such as arsenic), and radionuclides (such as uranium). It can be applied to wastewaters, sediments, sludges, soils, mine tailings, and other complex media. In addition to the control of metals, SME chemicals have been shown to reduce dissolved solids (such as sulfates) and to break down hydrocarbons (such as gasoline and fuel oil) and other organic chemicals through a high-energy oxidation process.

SME has been or can be applied to the following situations:

Neutralization of mine drainage and mine process water

Treatment of industrial wastewater

Treatment of radioactive wastes

Treatment of stormwater

Treatment of landfill leachate

Polishing of water supplies

Resource recovery from metals-rich waters

On-site remediation of contaminated soil and groundwater

Stabilization of sediments and industrial and municipal sludges

The majority of KEECO's applications have been in treating acid mine drainage; experience in applying SME to industrial wastewaters is limited but offers tremendous potential as a better, faster, and cheaper means of treatment. Industrial applications have primarily consisted of the treatment of metal finishing wastes, radioactive sumpwaters, metal contaminated sediments, and stormwater runoff.

Within industry, precipitants such as lime, sodium hydroxide, and alum, are commonly used in the treatment of heavy metals. However, these typical precipitants carry serious environmental drawbacks and high life-cycle costs. The SME technology has been proven to have all the positive characteristics of conventional metal precipitation but none of the drawbacks. SME typically provides effective treatment in a single step, requires lower capital expenditures, generates smaller volumes of higher-density sludge, consistently passes leach tests, and reduces or eliminates long-term liabilities associated with potential metal remobilization and hazardous waste landfilling. Stabilization of soils, sediments, and sludges is commonly performed with agents such as lime, fly ash, and kiln dust. Resolubilization of heavy metals in stabilized waste is common, thereby increasing long-term liabilities. SME treatment offers a permanent solution to the stabilization of metal contaminated solid wastes.

Document Type: Research Article

DOI: http://dx.doi.org/10.2175/193864700785155948

Publication date: January 1, 2000

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  • Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed.

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