Leaching of lead from computer printed wire boards and cathode ray tubes by municipal solid waste landfill leachates

The proper management of discarded electronic devices (E-waste) is an important issue for solid waste professionals because of the magnitude of the waste stream and because these devices often contain a variety of toxic metals (e.g., lead). While recycling of E-waste is developing, much of this waste stream is disposed in landfills. Leaching tests are frequently used to characterize the potential of a solid waste to leach when disposed in a landfill. In the United States, the Toxicity Characteristic Leaching Procedure (TCLP) is used to determine whether a solid waste is a hazardous waste by the toxicity characteristic. The TCLP is designed to simulate worse-case leaching in a landfill environment where the waste is co-disposed with municipal solid waste (MSW). While the TCLP is a required analysis from a regulatory perspective, the leachate concentrations measured may not accurately reflect the concentrations observed under typical landfill conditions. Another method that can be performed to assess the degree a pollutant might leach from a waste in a landfill is to use actual,landfill leachate as the leaching solution. In this study, two lead-containing components found in electronic devices (printed wire boards from computers and cathode ray tubes from computers and televisions) were leached using the TCLP and leachates from 11 Florida landfills. California's Waste Extraction Test (WET) and the Synthetic Precipitation Leaching Procedure were also performed. The results indicated that the extractions using MSW landfill leachates resulted in lower lead concentrations than those by the TCLP. The pH of the leaching solution and the ability of the organic acids in the TCLP and WET to complex with the lead are factors that regulate the amount of lead leached.