TCLP result

To test the effectiveness of the CHEMFIX process as a treatment option, the solidified samples were subjected to the TCLP test and a comparison made with the TCLP results on a raw sample. This test was designed to determine the mobility of contaminants present in liquid, solid and multiphasic wastes. If the TCLP extract from a representative sample contained any of the listed contaminants above the regulatory levels it would be considered a hazardous waste and should adhere to the strict disposal requirements. )... 

TCLP RESULTS OF CHEMFIX PRODUCTS FOR SUPERFUND SOILS... 

Five-gallon size waste forms were fabricated. Typical waste loading was 35-40 wt%. A small amount of potassium sulfide was added to the Ceramicrete binder mixture for stabilization of Hg, and dense and hard ceramic waste forms were produced. Just before solidification, TCLP results were obtained on small aliquots of the mixing slurry that was separated and allowed to set. Mercury levels in the leachate were found to be 0.05 /rg/1, well below the LfTS limit of 0.025 mg/1. The entire waste was treated, removed from the inventory, and sent to the Radioactive Waste Management Complex at the Idaho National Engineering and Environmental Laboratory for disposal. 

Wagh et al. [45] demonstrated stabilization of Cr, along with Cd, Pb, and Hg from contaminated soil and wastewater in the Ceramicrete waste form. Table 16.8 shows the contaminant levels in the waste and the wastewater, and the corresponding TCLP result for the stabilized waste. The wastewater in the Ceramicrete slurry was equal in amount to the stoichiometric water needed for the stabihzation process. Including this wastewater, the total waste loading was 77 wt%. The waste forms had open porosity of 2.7 vol% and a density of 2.17 g/cm. Compression strength was 34 MPa (4910 psi). 

In another similar case, Wagh et al. [59] simulated Pu-contaminated ash from Rocky Hats (one of the DOE sites) by incorporating various hazardous contaminants, including Cr as Cr203, and stabilizing them in the CBPC matrix at a loading of 54 wt%. The TCLP results of their study are presented in Table 16.9. 

As mentioned before, subsequent phosphate treatment does not affect the stable sulfide, and TCLP results show excellent stabihzation of Cr in any oxidation state. Alternatively, a small amount of reductant in the waste will convert chromate into lower oxidation states. Such methods, however, are not preferred, because the reductant may also affect the solubility of other hazardous compounds. The exception is technetium-containing radioactive waste, in which chromate is also a contaminant. As we shall see in Chapter 17, a reductant is essential for stabihzation of technetium, and that will also help in stabilization of chromium. 

Contaminant Concentrations in Simulated Supemate Waste from Hanford Tank, their Waste Forms, and the TCLP Results. 

As may be seen from Table 17.8, Cs was added either as CsNOs or CsCl in the first three waste streams, whereas the form of Cs was not known in the last case, but certainly it was soluble because it was detected in wastewater. The TCLP results indicate that Cs, although added as nitrate or some other soluble form, is well immobilized. The LI is not as high as 18 that was reported by Bamba et al. [27] for a glass waste form, but it is certainly higher than the minimum of 6 expected from cement waste forms [28]. 

As in all the waste forms discussed above, the TCLP results showed excellent retention of the hazardous contaminants in the matrix (Cd, Cr, Ag, Pb, and Zn) for both waste forms. The leaching levels for these contaminants were either below the detection limit or well below the UTS limits. While conducting this test for the sludge waste form, the investigators also tested leaching of Na, which is a bulk component, and Cs and Re, which are used as surrogates of radioactive Cs and Tc. 

A further objective was to determine the need for stabilization of residual dunnage solids based on toxicity characteristic leachate procedure (TCLP) results. Except for the DPE-solids, stabilization would not be necessary for the GPCR solid wastes. Stabilization of DPE-derived solids was necessary because in some tests the cadminm and lead criteria were not met by the dunnage treatment. 

Toxicity. Toxicity is estabhshed through the Toxicity Characteristic Leaching Procedure (TCLP), which measures the tendency of certain toxic materials to be leached (extracted) from the waste material under circumstances assumed to reproduce conditions of a landfill. The TCLP list includes a relatively small number of industrially important toxic chemicals and is based on the concentration above which a waste is considered hazardous. Failure to pass the TCLP results in classification of a material as a toxic waste. 

Another level of regulatory significance is the toxic characteristic leach procedure (TCLP) limit of a characteristic waste. A material which is a waste because of the TCLP is ha2ardous if a Hquor resulting from an 18-h leach in an acetic acid buffer exceeds 5 ppm (mg/L) lead in the leach Hquor. 

A sohd waste is considered hazardous if it is either a Hsted waste or a characteristic waste. Listed wastes include a Hst of specific processes that generate a waste and a Hst of discarded commercial chemical products. There are four hazardous waste characteristics ignitabiHty, corrosivity, reactivity, and toxicity. The last refers to the leachabiHty of a waste and the resultant toxicity in the groundwater using the analytical method referred to as toxicity characteristic leaching procedure (TCLP). A Hst of substances included under TCLP is shown in Table 1. 

During bench-scale studies on ACT using sediments from the New Bedford Harbor Superfund Site, the Toxicity Characteristic Leaching Procedure (TCLP) concentrations of many contaminants increased or remained unchanged following treatment. Based on these results, researchers stated that solidification/stabilization methods such as ACT were not appropriate for the treatment of polychlorinated biphenyls (PCBs) or semivolatile organic compounds (SVOCs) at the site. The study also indicated that the compressive strength of ACT [45 to 80 pounds per square inch (psi)] was relatively low compared to other solidification/stabilization materials that were tested. 

A concern raised during full scale operations of the CHEMFIX process was the possibility of contaminant leaching from freshly treated, moist material. During normal processing procedures, treated material would be transferred directly onto the solidification cell. It would be this material that exhibited the potential for contaminant leaching in those 48 hours it took to physically solidify. To determine when the metals were actually bound in the product matrix, a TCLP analysis was done on a series of treated samples over a period of curing times. The results are illustrated in Table 4. 

The Clean Air Act of 1990 has made trace metal content in fuels and wastes the final ash-related compositional characteristic of significance. Considerable attention is paid (ca 1993) to emissions of such metals as arsenic, cadmium, chromium, lead, mercury, silver, and zinc. The concentration of these metals in both grate ash and flyash is of significance as a result of federal and state requirements of particular importance is the mobility of metals. This mobility, and the consequent toxicity of the ash product, is determined by the Toxic Characteristic Leaching Procedure (tclp) test. Tables 8—10 present trace metal contents for wood wastes and agricultural wastes, municipal waste, and refuse-derived fuel, respectively. In Table 8, the specific concentration of various components in the RDF governs the expected average concentration of trace metals. 

The samples were stored for 3 weeks for curing. Each sample was then crushed and was subjected to the TCLP test. The TCLP test results on both the waste stream and the treated CBPC waste form are given in Table 16.6. The results on the untreated waste streams show that the leaching levels far exceed the regulatory limits. The results for the waste forms, on the other hand, are an order of magnitude below the EPA limit. These results indicate superior stabilization of Hg in the phosphate ceramic waste forms coupled with sulfide immobilization. 

Table 1. Result of TCLP extraction test of fully saturated sorbent...

In assessing how well the TCLP compared with the wastes examined in tlie lysimeter model, the distributions of the actual and absolute percent differences were examined. Results of these analyse for the acetate buffer extractions indicate that 75% of the target compound concentrations in the TCLP duplicate field lysimetei target concentrations within one standard deviation. This is particularly significant since the laboratory test duration is lb hours, whereas the field lysnncter experiments were run for about i months. 

In the control plot (TO) where no P amendment was applied, TCLP-extractable Pb concentrations at the surface soil (0 to 10 cm) far exceeded 5 mg L (Melamed et al., 2003). Similar to the distribution of total Pb, the highest concentration of TCLP-extractable Pb was observed at 10 to 20 cm. Even at a depth of 20 to 30 cm, TCLP-Pb still exceeded the critical level. The results showed that P amendments were effective in reducing the TCLP-Pb to below the critical level in the surface soil. These results are of great significance with respect to disposal of the soil, because they show that P amendments can amend the soil to a material that would be considered nonhazardous. Although P treatments did reduce TCLP-Pb in the subsurface soils (10 to 20 cm), TCLP-extractable Pb concentrations in Tl and T3 treatments were still higher than the critical level, except in the T2 treatment. Table 15.2 summarizes all the data for a contaminated site at Jacksonville, Florida. 

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