Operating Optimization Numerical Simulation Research For A CASS Process Wastewater Treatment Plant

Cyclic activated sludge system (CASS) was used widely in domestic and industrial sewage treatment nowadays because of economical use of land and facilitating expansion. Wastewater treatment plant (WWTP) had usually high energy consumption with unreasonable design process parameters and also different sewage characteristic composition parameters in different country, even different zones in the same country. Optimal running strategy of WWTP can be deduced from numerical simulation, and then qualified effluent water was obtained.Taking Chengdu hi-tech industrial development western zone WWTP as an object of study, computer model was built and simulated by BioWin3.0. Trough initial simulating influent data in some day, results showed simulated effluent water corresponding to practical effluent water of CASS except total phosphorus (TP). By sensitivity analysis for model parameters, 12 model parameters had an effect on effluent water. By modifying model kinetic parameters as following: u_maxPAO=1,u_maxP-limited=0.5,K_s,PAO=0.2,K_s,p-limited=0.25 and stoichiometry parameter Y_P/PHA,seq=0.95, the simulation results predicted that it can properly simulate the actual operation of WWTP and qualified effluent water with low energy consumption.It was inevitable to choose proper process running parameters on the premise of eligible effluent water so that lower energy consumption. Study attained factors which affected effluent water of CASS bioreactor and proposed measures for optimal running. Numerical simulation with different temperature,reflux ratio,decant level and cycle time found effluent water had highest quality and lowest energy consumption when cycle time 4h(water inlet,aeration 1.5h,settle 1.5h,idle 1h),SRT 14d,mixed liquid reflux ratio 20%,minimum decant level 65%. The operating condition could reduce difficulty level of follow-up treating and dosages for chemical agent. Meanwhile,study reports proposed operating strategy with meeting the standard of effluent water under low temperature...