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SOLID WASTE LEACHING CHEMISTRY AND TESTING: A COMPREHENSIVE APPROACH TO ASSESS FUNDAMENTAL PARAMETERS
Citation:
AL-ABED, S. R. AND G. JEGADEESAN. SOLID WASTE LEACHING CHEMISTRY AND TESTING: A COMPREHENSIVE APPROACH TO ASSESS FUNDAMENTAL PARAMETERS. In Proceedings, International Conference on Energy, Environment and Disasters (INCEED 2005), Charlotte, NC, July 24 - 30, 2005. International Society for Environmental Geotechnology - ISEG, Charlotte, NC, ,, (2005).
Impact/Purpose:
To discuss the effect of the aforementioned factors on metal leaching as a comparison with the regulated testing protocols such as TCLP.
Description:
Worldwide, various anthropogenic activities generate hazardous solid wastes that are abundant in heavy metals, which can cause significant damage to the environment and human health. One of the major problems with solid wastes is the generation of large quantities of heavily contaminated leachate, causing extensive pollution of ground and surface aquatic bodies. The toxicity and the bioavailability of the contaminants present in leachates depend on their reactivity and solubility, which in turn are determined by their speciation. Most heavy metals such as Cr, Ni, Fe and Cu and can exist in multiple oxidation states and undergo redox transformations when they interact in different environments. Classification of the waste based on toxicity, prior to disposal, is done by the United States Environmental Protection Agency (US EPA) regulated Toxicity Characteristic Leaching Procedure (TCLP) test. However this single extraction test is not applicable to the real waste systems due to practical limitations. Most solid wastes are solidified/stabilized heterogeneous mixtures and have large acid neutralizing capacity, thus rendering true assessment of leaching potential impractical. As a regulatory screening test, TCLP is not designed to account for several important internal factors such as pH, redox potential (Eh) and re-precipitation reactions, severely limiting its applicability. This paper discusses the effect of the aforementioned factors on metal leaching as a comparison with the regulated TCLP test. Specific cases on the effect of pH, Eh and duration of contact on leaching were studied on a certain mineral processing waste. Differences in metal leaching estimation between TCLP and bench scale batch studies indicated the need for development of variety of contaminant release tests and test conditions for solid waste assessment.
