Research On Simulation And Optimization Of Step-feed A/O Process

As a new method, step-feed A/O process can treat the wastewater without innerrecycle, and thus the energy consumption is reduced. Because of the high cost ofexperiment, the control of the sludge resident time and concentration distributionalways depends on experience, lacking of reasonable optimization method. Based onComputational Fluid Dynamics (CFD), multi-phase model and Discrete Phase Model(DPM) were adopted to simulate the process with Fluent software. Then theoptimization scheme were proposed, computed and evaluated. The main contents andconclusions involved in this research were:(1) Rigid-lid assumption was put forward to avoid the complex simulation ofgas-flow interface, and it was proved to be feasible according to the simulation result.(2) Mixture model was adopted to simulate the flow of wastewater-sludgetwo-phase. According to the flow and sludge concentration distribution in the tank,the relationship between the flow and sludge concentration was studied. The DiscretePhase Model was adopted to simulate the bubble of aerators, and the influence ofaeration was analyzed.(3) The flow condition and sludge concentration distribution of anaerobic, anoxic,and oxic tank were analyzed respectively and compared to each other. The key pointof optimization was anaerobic and anoxic tank.(4) The optimization scheme was proposed by adjusting the position of thebaffles, with the anaerobic tank as a representative. The index of sludge resident timeand concentration distribution were put forward to quantify the value of scheme.12schemes were simulated and evaluated with the index, and the best scheme wasdetermined. The conclusion of anaerobic tank was expended to anoxic tank, and thusthe final scheme was determined, which was, all the baffles in anaerobic tank andanoxic tanks should move back from the inlet by0.5m.