Modelisation of a Iotic ecosystem polluted by a pigstywaste: dynamic of dissolved carbon and benthic microorganism
Several studies have been performed since 1982 on a small organically polluted stream. Their results have been used to conceive a mathematical model with the purpose of simulating the self-purification mechanisms. The physical part of this model includes a hydrodynamic component derived from Saint-Venant's equations which is coupled with a transport model based on the classical convection-dispersion equation. The model is applied to unidirectional, non-uniform, unsteady flow conditions. As the main detritic processes which occur in small streams take place in the sediment, the model has been applied, first, to simulate the dynamics of both dissolved organic matter and benthic microorganisms. The simulation of the biodegradation mechanisms is based, in this work, on the analogy between the detritic processes in streams and the activity of the microbial biomass in wastewater treatment plants. From the structure of the biofilm model proposed, it was assessed that nearly all mechanisms involved in the removal and degradation of dissolved organic matter may be considered. In these studies, the model is used as a cognitive tool intended to increase the understanding of self-purification mechanisms applied to dissolved organic matter is small streams.