Superfund Innovative Technology Evaluation (SITE)
Note: EPA no longer updates this information, but it may be useful as a reference or resource.
This Applications Analysis Report evaluates the solidification/stabilization treatment process of Silicate Technology Corporation (STC) for the on-site treatment of hazardous waste. The STC immobilization technology utilizes a proprietary product (FMS Silicate) to chemically stabilize and microencapsulate both organic and inorganic wastes, and to physically solidify contaminated soils.
The STC treatment technology demonstration was conducted under EPA's Superfund Innovative Technology Evaluation (SITE) Program in November, 1990, at the Selma Pressure Treating (SPT) wood preserving site in Selma, California. The SPT site was contaminated with both organics, predominantly pentachlorophenol (PCP), and inorganics, mainly arsenic, chromium, and copper. Extensive sampling and analyses were performed on the waste both before and after treatment to compare physical, chemical, and leaching characteristics of raw and treated wastes. STC's contaminated soil treatment process was evaluated based on contaminant mobility, measured by numerous leaching tests; structural integrity of the solidified material, measured by physical and engineering tests and morphological examinations; and economic analysis, using cost information supplied by STC and supplemented by information generated during the demonstration. This report summarizes the results of the SITE demonstration, the vendor's design and test data, and other laboratory and field applications of the technology. It discusses the advantages, disadvantages, and limitations, as well as estimated costs of the technology.
Conclusions resulting from this SITE demonstration evaluation are that (1) the STC process chemically stabilized contaminated soils containing both inorganic and semivolatile organic contaminants; (2) PCP concentrations were reduced by 91 to 97 percent as determined by total waste analysis (SW-846, Method 8270); (3) arsenic and copper were immobilized based on various leach-test criteria; (4) chromium concentrations were very low prior to and after treatment, but showed a slight to moderate increase in leachability after treatment; (5) PCP concentrations remained above California state regulatory threshold levels after treatment, and metal contamination in the treated waste did not consistently meet California state regulatory thresholds; (6) the short-term physical stability of the treated waste was good, with unconfined compressive strengths well above landfill solidification recommendations; (7) due to the addition of reagents, treatment resulted in a volume increase of 59 to 75 percent (68 percent average) and a slight bulk density increase; (8) six-month monitoring showed increased concentrations of the contaminants released from the treated waste; (9) eighteen-month monitoring showed improved percent reductions for arsenic and PCP relative to the 6-month cured sample test results; chromium and copper showed slight to moderate increases in leachate concentrations over time; and unconfined compressive strengths increased an average of 71 percent relative to the 28-day values; (10) the reagent cost to treat a cubic yard of contaminated waste using STC's technology is estimated to range from $80 to $153 depending on the initial organic content of the waste; and (11) treatment processing costs are expected to range from $40 to $175 per cubic yard when used to treat 15,000 cubic yards of waste similar to that found at the STC demonstration site.