Four-substrate design model for single sludge predenitrification system

In this paper a new mathematical steady-state model specifically aimed at the design of biological phases in single sludge predenitrification systems is proposed. The model is based on the mass balance equations of four substrates (dissolved and suspended biodegradable organic matter, ammonia nitrogen, and nitrate nitrogen) and two biomasses (heterotrophic and autotrophic microorganisms). For each specific design problem, if both the influent flow composition and the kinetic parameter values are known and the effluent nitrogen compound concentrations are fixed, the model makes possible an a priori assessment of system applicability and gives the explicit expressions of the biological phase volumes. A sensitivity analysis is also presented in order to evaluate the effect of variations in the influent and effluent characteristics on the biological phase volumes.