In this paper optimization of nitrogen removal in sewage treatment is accomplished by using the mixed logical dynamic method(MLD).By simplifying activated sludge process No.1 model (ASM1)

nitrogen removal dynamic models in continuously mixed

continuously fed activated sludge process (ASP) are established by expert experience about activated sludge process. Then predictive control approach is applied to optimal control of this process. The simulation results show that it can cover the relative expert experiences more widely by applying MLD to modeling and control of activated sludge process. Such expert experience combined with continuous variable model makes the model more precise and achieves better optimization and control. This study provides a new approach to the research of sewage treatment.