Leachate long-term production

Physical and chemical tests of the final product may need to address two concerns (1) whether the solidified waste exhibits any RCRA defined toxicity characteristics or could be delisted and (2) the potential long term fate of treated materials in the disposal environment. Three tests are available which address the first concern. These are the Extraction Procedure (EP Tox) (40 CFR 261, Appendix II, 1980) and the Toxicity Characteristic Leaching Procedure (TCLP) (40 CFR 261, Appendix II, 1986), and the Multiple Extraction Procedure Test (40 CFR 261, Appendix II, January 1989). It is important to note that these tests are not indicators of expected leachate quality but of potentials. A solidified product which cannot pass the appropriate test (EP Tox or TCLP) would be subject to classification as a hazardous waste. 

The results showed that there was no increase in leachate metals concentration after ten extractions. Most of the metal concentrations remained the same or decreased during the total MEP run. This proves the long term stability of the CHEMFIX product since the MEP was designed to simulate conditions of 1000 years of acid rain exposure. In addition, throughout the entire MEP analysis the leachable metals concentrations were all below the regulatory limits. Thus once the soil is treated by the CHEMFIX process it remains non-hazardous for extended periods of time. 

Loehr, R.C. and Haikoia, B.M. 2003. Long-term landfill primary and secondary leachate production. Proceedings American Society Civii Engineers, Journal Geotechnical and Geoenvironmental... 

Studies of Baccini and colleagues have shown, that under long-term considerations even products like incineration bottom ash slag are not really inert. After the release of chloride and sulphate, two phases can be distinguished (Fig. 10.7) part of the calcium content, which was formerly present as hydroxide, is now carbona-tized. Iron and aluminium are transformed to oxides. On the long run, the carbonate buffer in the slag will be emptied. This will be correlated by relative low pH-values. Compared to the former conditions, elevated trace metals concentrations in the leachate can be expected. 

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