Steady-State Design Model for Activated Sludge Pre-Denitrification Systems

A mathematical steady-state model able to evaluate the biological single sludge reactor volumes of the pre-denitrification system is proposed. The model is based on mass balance equations, considering the degradation of four substrates (soluble and particulate biodegradable organic matter, ammonia and nitrate nitrogen), and the growth and decay of two microorganism species (heterotrophic and autotrophic). Once assigned the influent flow composition, the kinetic parameters and the effluent nitrogen compounds concentration, the model makes it possible to define the applicability of the system and gives explicit expression of the biological reactor volumes. It has been used to evaluate the reactor volume trends corresponding to variation of influent organic load, effluent ammonia nitrogen concentration and fundamental kinetic parameter values.