Dynamic Modelling and Analysis of CSTR Activated Sludge Reactor Yang Kai Zhuang Zhonghui Prof.,School of Civil Engineering,Wuhan University,Wuhan 430072,China.This paper models and analyses the dynamics of activated sludge wastewater treatment reactors in different mixing patterns. It is demonstrated that the performance of PFR (plug flow reactor)is superior to the performance of CSTR (continuous stirred tank reactor),but the difference between them will decrease with HRT (hydraulic retention time) extended and the 4 tages CSTR in series is similar to PFR in performance. It is also demonstrated that MCRT (mean cell retention time) and substrate concentration of effluent can't be set at the same time for designing of activated sludge reactor, and also that the attempt is unsuitable to design PFR by inducing MCRT directly.The full paper is divided to two sections, the dynamic performance of CSTR and multi stage CSTR are discussed in this one mainly.active sludge; biological reactor; dynamic modelling; mixing pattern