Optimal Control Of Simultaneous Nitrification And Nenitrification Of Aerobic Granular Sludge Based On The Change Of Dissolved Oxygen Concentration Monitoring Curve

Due to its own structure,aerobic granular sludge is easy to form aerobic areas on the surface,which is suitable for the survival of nitrifying bacteria and ammoniating bacteria,and gradually forms anoxic and anaerobic areas inward,which is suitable for the growth and reproduction of denitrifying bacteria.This microorganism distribution status Conducive to the realization of simultaneous nitrification and denitrification.At present,many researchers have studied the reaction mechanism and macro-influencing factors of simultaneous nitrification and denitrification of aerobic granular sludge,but there is a lack of real-time monitoring and optimal control of simultaneous nitrification and denitrification.The key to the simultaneous nitrification and denitrification of aerobic granular sludge is to accurately control the dissolved oxygen during the aerobic aeration process,and to understand the change law of dissolved oxygen and the changes of NH4+,NO3-,and NO2-during this process.Based on the changes of the DO concentration monitoring curve in real time and the treatment effect in the aeration process,this paper studies the granulation process and simultaneous nitrification and denitrification process of aerobic granular sludge.This project uses SBR reactors to cultivate granular sludge.Simultaneous nitrification and denitrification of aerobic granular sludge is carried out through experimental methods such as artificially simulated domestic sewage,scanning electron microscope(SEM),and DO monitoring program independently developed by the laboratory.An in-depth understanding of the mechanism of simultaneous nitrification and denitrification of granular sludge will help optimize the control of the simultaneous nitrification and denitrification reaction of aerobic granular sludge and maintain a long-term stable high effluent TN removal rate.Through the experiments,the following conclusions were reached:(1)The average removal rate of COD is closely related to the sludge granulation process,indicating that microbial aggregates with better biological activity and mass transfer have a significant effect on the removal of COD;and the sludge granulation process has the effect of removing NH4+The effect is small,but the initial formation of aerobic granular sludge can stabilize the removal of NH4+,so that the removal rate does not fluctuate greatly;The sludge grows from small particles to large particles,which can provide a good micro-environment for the removal of phosphorus and improve the TP removal rate.However,when aerobic sludge particles are basically formed,the reactor's TP removal effect will gradually decrease and tend to stabilize.(2)The treatment effect of TN on the SBR reactor showed an overall upward trend with the sludge granulation process.The increase in the number of particles can form a wide range of dissolved oxygen gradients,which are aerobic nitrifying bacteria on the surface and internal anaerobic denitrifying bacteria.Provide a good growth environment,compared with ordinary floc sludge,simultaneous nitrification and denitrification ability is stronger.(3)When the NH4+ concentration in the aerobic section of the SBR reactor is high,the initial DO concentration is maintained at a low level;as NH4+ is continuously consumed until the end,the DO concentration will gradually rise from a lower level to a higher concentration level;As NO2-in the reactor is continuously converted by NOB to NO3-,the demand for DO gradually decreases,and the DO curve reaches the highest level.(4)Significantly reducing the amount of aeration has an impact on the initial DO concentration of most NH4+ degradation.The initial DO decreases with higher aeration and the aerobic reaction process slows down the removal of NH4+,which requires prolonged aeration.(5)Through the DO concentration monitoring curve,you can directly see whether the aeration amount is sufficient in the aerobic phase and the respective strengths of the nitrification and denitrification reactions.Combined analysis of DO concentration monitoring curve and NH4+,NO3-,NO2-concentration changes in the aeration section under the conditions of this test device.It was concluded that with the aeration valve rotor flowmeter of 0.3 L/min,the aerobic granular sludge simultaneous nitrification and denitrification achieved the best treatment effect,and the highest removal rate of TN could reach 90.31%.