Development and application of techniques for predicting leachate quality in confined disposal facilities : background and theory
Hill, Donald O.; Myers, Tommy E.; Brannon, James M.
A theoretical framework for predicting leachate quality in confined disposal facilities was developed using mass transport theory. The physical-chemical processes governing leaching were identified and described mathematically. Various approaches to describing contaminant transfer from the dredged material solids to the aqueous phase were considered, including equilibrium concepts, dissolution kinetics, intraparticle diffusion, and film effects. The approach recommended for application to dredged material uses an operationally defined distribution (partitioning) coefficient to relate aqueous phase concentration to solid phase concentration. This approach assumes equilibrium within the dredged material between solid and aqueous phases. The equilibrium approach assumes that interphase transfer kinetics are fast compared to the percolation rate of water through dredged material. The theoretical analysis was used to design laboratory tests for determining the leaching characteristics of dredged material. A sequential batch leach test is recommended for obtaining distribution coefficients, and a pressurized column test using divided-flow (double-ring) permeameters is recommended as a physical model of reduced scale for verifying the distribution coefficients obtained in batch tests. The design concepts for the laboratory tests are preliminary, and additional evaluation on the basis of actual test results will be needed before the procedures recommended can be adopted.
Environmental Laboratory (U.S.)U.S. Army Engineer Waterways Experiment Station.
Leachate; Spoil banks--Leaching; Dredging spoil--Environmental aspects