Simulation Of Oxygen Transfer Process And Energy Consumption In Aerobic Biological Reactor

Aerobic technology is the main water treatment technology that removes most of the pollutants,but there are problems of aeration control and unbalanc.ed dissolved oxygen utilization.Excessive aeration will disturb the separation of mud water that affect the effluent water quality,and the energy consumption will also increase;A little amount of aeration leads to the reduction of pollutant removal rate.Therefore,The research on oxygen mass transfer and its influencing factors can provide reference for aeration control of wastewater treatment plants,so as to reduce energy consumption.This article includes two aspects,one is the oxygen mass transfer process and energy consumption study of aerobic bio-reactor.Based on the ASM2D model,the wastewater treatment plant is set up,and the aeration control simulation and advanced experimental analysis are used to determine the way to aeration control and optimum operating parameters,Meanwhile,the energy consumption,oxygen mass transfer coefficient and dissolved oxygen concentration under various working conditions are analyzed.The other is the numerical simulation about hydraulic characteristics of aerobic bio-reactor that affect oxygen mass transfer.Based on computational fluid dynamics,the aerobic bio-reactor is simulated by Euler-Euler and standard k-? model.The mixing degree and efficiency of oxygen mass transfer are analyzed by velocity between gas and water,gas volume fraction,and turbulent kinetic energy.The specific conclusions are as follows:(1)The oxygen mass transfer process and energy consumption simulation of aerobic bio-reactor show that:1)Compared with KLa control,the aeration energy consumption of cascade control is lower;2)Global sensitivity analysis:the sensitivities of f_S_A,f_S_F,f_X_S,r_P,v0 to effluent COD are significant;3)Parameter estimation:simulated effluent COD is 20.49?35.97mg/L,f_S_A=0.4905,f_S_F=0.4879;f_X_H=0.0107,f_X_S=0.8670,r_P=0.00157m3/g,v0=468.92m/d;4)Final value optimization:compared with the ground state simulation,the effluent TP is 0.32mg/L,the aeration energy consumption is reduced by 50.36%,and the total energy consumption is reduced by 41.6%.KLa in aerobic tank is 100.56?227.14d-1,DO is 1mg/L or 2mg/L;5)Uncertainty analysis:when S_A is 0.14?0.2mg/L,effluent COD is between 18?26mg/L,and probability distribution is 50%?95%,so the effluent of model is relatively stable.(2)The numerical simulation about hydraulic characteristics of aerobic bio-reactor that affect oxygen mass transfer show that:AAO reactor can be simulated well by Euler model and the standard k-? model,which can truly reflect the hydraulic characteristics of gas-water in the AAO reactor.As for the simulation results of AAO reactor,DO=2mg/L and the oxygen supply is 6m3/h,the velocity of gas-water and turbulent kinetic energy are maximum at z=1.5m,which indicates that the effect of oxygen mass transfer is best.