Knowledge-based model and simulations to support decision making in wastewater treatment processes

In this paper, mass and momentum balances are used to model and simulate the most significant phenomena occurring in a continuous urban sludge clarifier. This model is designed to be the core of a digital twin in the future. This has two consequences: the choice of a one-dimensional model only and a numerical scheme for simulation that allows a reasonable runtime. We propose a different way of writing of the dynamic model of the clarifier. Instead of using volume fractions and velocity of solid particles as state variables, we use volume fractions and flux of solid particles. This approach, which is used for conservation law systems, gives more stable simulation results for hyperbolic systems. This paper focuses on comparative discussions of these two different versions of the model. The numerical simulation scheme is presented. In addition, the simulation is compared with experimental data obtained in a full-scale wastewater treatment plant.