Aiming at nonlinear

instability and uncertainty of sewage treatment process

nonlinear math model of activated sludge sewage processing system is transformed into a variable parameter canonical equation of state

controllability and stability is analyzed and propose a kind of fuzzy adaptive PID controller based on chaos genetic algorithm（CGA）.Simulation test result shows that CGA improves diversity of individual species

effectively avoid’premature’and local optimal phenomenon

and optimized controller performance is obviously improved in amount of overshoot

rise speed and stability of time.