Bioremediation of contaminated soil beds and groundwater - A simulation study

Pollution has reached levels which demand immediate attention and scientific and technological solutions are required on; an urgent basis. We are concerned in this paper with bioremediation of soil and groundwater, i.e. the use of indigenous micro-organisms to clean up soil beds and groundwater contaminated with organic pollutants. To achieve managed in situ bioremediation in practice, treated water is recycled with added nutrients into the ground so that oxygen and nitrogen are carried with the water to the subsurface regions. Sorption, convective-dispersive flow and chemical:and biological transformations are the chief processes involved that have to be modelled. Here we discuss a simulation model developed to aid in designing an:efficient system that maximizes the rate of biodegradation. Simulation models are a must in this case since laboratory experiments take time periods of the Order of months. An unusual feature of this simulation model is that it is governed by coupled partial and ordinary differential equations. Partial differential equations (PDEs) model the diffusion and biodegradation processes occurring in the micropores of soil aggregates while ordinary differential equations (ODEs) describe the bioremediation in the interstitial spaces between soil aggregates, both partial and ordinary differential equations being nonlinear. The model is applied to the case of high initial contaminant concentrations.