A MATHEMATICAL-MODEL FOR WASTE-WATER STABILIZATION PONDS WITH MACROPHYTES AND MICROPHYTES

This paper presents a model for natural systems used in urban waste wa ter treatment. The model includes thermal and biochemical submodels, d erived from the physical and biochemical phenomena involved in the tre atment process. The thermal submodel is based on a heat balance for th e system and the numerical solution of the resulting differential equa tion. The biochemical submodel is based on the mass balances for the d ifferent variables, considering a one-dimensional flow within the pond s, which give rise to a system of linear equations subsequently solved by numerical methods. The model has been calibrated using experimenta l data from existing waste water treatment systems using both microphy tes and macrophytes. The model may be applied to the design of new fac ilities and to improve operating conditions of existing facilities.