Statistical comparison of leachate from hazardous, codisposal, and municipal solid waste landfills

There has been considerable debate regarding the chemical characterization of landfill leachate in general and the comparison of various types of landfill leachate (e.g., hazardous, codisposal, and municipal) in particular. For example, the preamble to the U.S. EPA Subtitle D regulation (40 CFR Parts 257 and 258) suggests that there are no significant differences between the number and concentration of toxic constituents in hazardous versus municipal solid waste landfill leachate. The purpose of this paper is to statistically test this hypothesis in a large leachate database comprising 1490 leachate samples from 283 sample points (i.e., monitoring location such as a leachate sump) in 93 landfill waste cells (i.e., a section of a facility that took a specific waste stream or collection of similar waste streams) from 48 sites with municipal, codisposal. or hazardous waste site histories. Results of the analysis reveal clear differention between landfill leachate types, both in terms of constituents detected and their concentrations. The result of the analysis is a classification function that can estimate the probability that new leachate or ground water sample was produced by the disposal of municipal, codisposal, or hazardous waste. This type of computation is illustrated, and applications of the model to Superfund cost-allocation problems are discussed.