Evaluation of a modified TCLP methodology for RCRA toxicity characterization of computer CPUs

A leaching method similar to the toxicity characteristic leaching procedure (TCLP) was designed and evaluated for testing of bulky wastes, such as discarded electronic devices. The objective was to meet the intent of the TCLP (same leaching solution, liquid-to-solid ratio and same leaching time) but to allow more representative and rapid testing. The procedure was evaluated by examining lead leaching from computer CPUs as a test case; disassembled CPUs were leached in their entirety (or close to entirety) in a large vessel using a drum rotator. The difference in rotation speed between the large-scale test and the TCLP was found to have no statistical impact on lead leaching. The lack of size reduction resulted in less reducing conditions than the standard TCLP (because of increased iron and zinc leaching), and this resulted in greater lead leaching. For electronic wastes with large amounts of steel, the large-scale procedure provides a more conservative estimate of TCLP lead leaching. The large-scale procedure greatly reduces sample processing effort but does increase the cost of analysis. Evaluation of this approach by the regulatory community is important as the CPUs tested here tended to leach lead at greater than the toxicity characteristic (TC) limit (5 mg/L) using the large-scale test, but less than the TC limit using the standard TCLP.