Research On Simultaneous Nitrification And Denitrification Of Aerobic Granular Sludge In SBR Process

Accumulation of ammonia in water environment has induced serious deterioration to the quality of water environment. It is a problem that should be solved by using proper measure to prevent the deterioration without delay. The wastewater treatment technology with immobilized microorganism is a new technique developed within these years, which can not only be used to dispose the wastewater with heavy metal, poisonous organic wastewater as well as the wastewater with phosphorus, but also be applied to remove ammonia. Cultivating aerobic granular sludge to realize simultaneous nitrification and denitrification by using self-immobilized microorganism technology is of special advantage and comprehensive benefit, which has become the highlight in the biological de-nitrogen study.Based on the latest research findings on biological nitrogen removal in both domestic and abroad, aerobic granular sludge has been cultivated with the method of decreasing sludge sedimentation time gradually to produce selective pressure by using normal activated sludge as inoculating sludge. After successfully cultivating aerobic granular sludge, we studied the running modes, COD/NH4 - N ratio, DO condition and discussed their effect on nitrogen removal efficiency, then the characteristic of nitrogen removal of aerobic granular sludge is greatly studied.The experiment results show that the floc of activated sludge can flocculate together and form aerobic granular sludge with good settling performance by reducing the sludge sedimentation time and elevating the critical sedimentation velocity of sludge gradually. The aerobic granular sludge appears orange-like granule with the average diameter ranging from 0.5mm to 0.8mm, the Sludge Volumetric Index (SVI) and the Mixed Liquid Suspended Solid (MLSS) are as high as 11.7ml/g and 9.4g/L, respectively. Compared with normal activated sludge, this aerobic granular sludge is of higher hydraulic intensity, volumetric charge and better sedimentation ability, and it can remove nitrogen and COD in domestic wastewater with high efficiency.Compared with different running modes (with and without anaerobic phase) it is found that the ammonia removal rate of phase mode without anaerobic phase is much higher than that of the mode with anaerobic phase. The total inorganic nitrogen (TIN) removal efficiency has also been studied under different COD/NH4-N ratios. The results show that the higher the COD/NH4-N ratio, the greater the TIN removal efficiency. While the COD/NH4 -N ratio increases from 6 to 14, the TIN removalefficiency rises from 40.3% to 74.5%. The profiles of ammonium removal in different ratios of COD/NH4-N (6,10,14) is proved to fit quite well with the linear regression equations that simulate the process by dividing the whole aeration period into two phases: the feast and the famine phase. The slopes of the lines correspond to the ammonia removal rate in these two phases. Reducing DO and replacing the continuous aeration with periodic aeration can benifit TIN removal efficiency and the energy source saving during the aeration period.