Numerical Simulation Of Gas-liquid Two Phase Flow Of BAF And Denitrification Experimental Study

Biological aeration filter (BAF), as a very kind of sewage treatment process,has good efficiency of decarburization and denitrification. Due to improve theoperation efficiency, domestic and foreign scholars have done a lot ofexperimental, simulate and engineering research. But the experiment and theoryanalysis of the flow field in BAF is less. The numerical simulation of macro flowfield can not explain the oxygen mass transfer well, in addition, the research ofrelationship between sludge morphology and denitrification efficiency is absent.Therefore, the simulation of the small scale particle field had been studied toexplain the mechanism of oxygen mass transfer. Setting up the experimentalresearch of simultaneous nitrification and denitrification, to analyze the removalefficiency under different operating conditions. It was Observed the sludgemorphology in different dissolved oxygen environment, and analyzed organiccontent in sludge after drying and firing.Using Fluent software and selecting Eulerian model as good as k turbulent model to simulate the gas-liquid two phase flow pattern in the smallscale particle field of BAF by analyzing the path lines, velocity vector, stressdistribution and turbulence intensity of different conditions of particle size andparticle space. Through analyzing the results of numerical simulation indicatedthe flow pattern of computational region is best for gas-liquid mixing and oxygenmass transfer process when setting the particle size of3mm and the particlespace of0.5mm.To verify the correctness of the simulation results about particle sizes,comparing the biofilm growth speeds of different particle size under the sameoperating conditions. Through analyzing the changes of removal rate in Start-upof the bio-trickling filter during25days, discovers when the particle size is3mm,the system operation is the most stable and efficient, which is consistent withthe simulation results. in Start-up of the biotrickling experiment, the changedremoval efficiency of COD and NH4+-N have consistend trend, which is rising at the first, and then changes to be stabilize.The efficiency of decarburization and denitrification in BAF are connectedwith operation paramers. As the extension of hydraulic retention time (HRT), theconcentrations of COD, NH4+-N, TN at the export are gradually lowering..Gaswater ratio (GWR) affect system operation efficiency through changing dissolvedoxygen (DO) concentration, the value of GWR is too small or too large can notachieve the best removal efficiency. Through comparing the sludge morphologyand organic content at the bottom and middle, discovery that the sludgemorphology and organic content have something to do with dissolved oxygenconcentration and reaction process.