| A granular sludge SBR of pilot scale was adopted to treat domestic sewage. Granular sludge was directly cultivated through activated sludge acted as seed sludge and domestic sewage acted as nutrients. The characteristics and stabilization of granular sludge were investigated. The operation parameters were optimized. The mathematics modle was set up to simulate oxygen diffusion and be verified by test. The production, distribution and biodegradation of EPS were researched.Two kinds of methods were adopted to cultivate granular sludge. The method of suddenly lowering settling time was failed, because the amount of washout was greater than the amount of growth. However, granular sludge was successfully cultivated by the method of gradually lowering settling time, which made settling time lower to 8~10 minutes by two rapidly settling stage and one gradually settling stage. The granular sludge distributed widely, with an average diameter of 245.4μm,MLSS of 4320.5mg/L and SVI of 46.4 mL/g.Based on adjustment of aeration rate, substrate supplement time and hydraulic retention time of small experiment,the optimal gas-water ratio was 3.0 and the removal efficiency of NH3-N and TN may get better by three methods, which included intermittent aeration instead of continuous aeration, substrate supplementing when COD was reduced to 100 mg/L and extension of operation cycle with restricted aeration. Through adjusting above parameters of pilot scale SBR, the reactor has better pollutants removal efficiency. COD, BOD, NH3-N, TN and TP of effluent could reach First class A standard of "pollutant discharge standard of urban sewage treatment plant" (GB18918-2002).Oxygen diffusion coefficient of granular sludge was 0.3889×10-9m2/s. Oxygen consumption rate was 0.10gO2/gMLSS·h ( 2.64gO2/gMLSS·d ) . Oxygen half-saturation constant was 0.65mg/L. MLSS was 2000mg/L. Oxygen as only limiting substrate,the model could be used to analysis the change of oxygen in granular sludge. The more suface oxygen, the more oxygen gradient and intraparticle diffusion efficiency factor were, the stronger radial transfer ability was, the further oxygen transfer distance was. However, when the diameter of granular sludge was relatively larger (such as 1.5mm), oxygen could not penetrate the whole granule, even if surface oxygen was 4.0 mg/L. when r/R was 0.49~0.65, oxygen gradient was reduced to zero.EPS produced by aerobic granules was composed of 40% biodegradable and 60% nonbiodegradable EPS. Among these, only biodegradable EPS could be utilized by their producers, while nonbiodegradable EPS contributed to maintain the spatial structures of aerobic granules. EPS extracted from fresh aerobic granules was fed as the sole carbon source to their own Producers and activated sludge and was utilized by them. The average biodegradation rate of activated sludge in terms of EPS was 1.5 times faster than that of aerobic granules. When EPS extracted from straved aerobic granules was fed as the sole carbon source to their own producers and activated sludge, it could not be utilized and could not be energy source.
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