A Cellular Automata Model of Soil Bioremediation
S. Di Gregorio
Università della Calabria,
Dipartimento di Matematica,
Cosenza
R. Serra
M. Villani
Centro Ricerche Ambientali Montecatini,
via C. Menotti 48,
I-48023 Marina di Ravenna
Abstract
The remediation of contaminated soils is one of the major environmental problems in industrial countries today. Among the different techniques that can be applied, in situ bioremediation, which relies upon the use of indigeneous microorganisms to degrade the contaminant, is one of the most attractive, both from an environmental and an economic viewpoint. A full-scale bioremediation process requires a number of laboratory and pilot-scale tests, in order to assess the feasibility of the remediation, to define potential health threats, and to find optimal operating conditions. Scaling up from the laboratory to the field can greatly benefit from the development of reliable mathematical models, which need to deal with several interacting physical, chemical, and biological phenomena.
A macroscopic cellular automata (CA) model is presented here, which describes the major phenomena that take place in bioremediation. The reasons for using macroscopic CA are discussed. The model is composed of the following three layers, each layer depending on the others.
- A fluid dynamical layer, which describes multiphase flow through the soil.
- A solute description layer, which deals with solute transport, adsorption/desorption, and chemical reactions.
- A biological layer, which describes biomass growth and its interaction with the different chemicals.
The model has been tested in a pilot plant in the case of contamination by phenol. The values of the phenomenological parameters have been determined by the use of genetic algorithms (GAs). The model has proven capable of carefully describing experimental results for a wide range of experimental conditions. It is therefore an application of CA models to a real-world problem of high social and economic relevance.
