Simulation of the redox buffer depletion rate in landfills of combustion residue waste materials

Simulations have been made of the redox buffer depletion rate in landfills of combustion residue wastes. The model is based upon a one-dimensional mas s balance where oxygen transport results from a combination of advective an d diffusive processes. A simple, generalised representation of redox buffer ing properties is used where dissolved oxygen reacts in accordance with a f irst order rate law. Using certain simplifying assumptions, it is possible to obtain an analytical solution for the time required for complete depleti on of the redox buffering capacity of landfilled solid wastes. The results indicate the overwhelming importance that the effective diffusivity of oxyg en in the landfill has upon the rate of redox buffer depletion. The results also show under which conditions transport effects may be expected to domi nate the leaching processes and determine an upper limit for the depletion rate.