A mathematical model for waste water stabilization ponds with macrophytes and microphytes

This paper presents a model for natural systems used in urban waste water treatment. The model includes thermal and biochemical submodels, derived from the physical and biochemical phenomena involved in the treatment process. The thermal submodel is based on a heat balance for the system and the numerical solution of the resulting differential equation. The biochemical submodel is based on the mass balances for the different variables, considering a one-dimensional flow within the ponds, which give rise to a system of linear equations subsequently solved by numerical methods. The model has been calibrated using experimental data from existing waste water treatment systems using both microphytes and macrophytes. The model may be applied to the design of new facilities and to improve operating conditions of existing facilities.