Research On Fast Realization Methods Of Deep Nitrogen Removal And Nitrogen Conversion Pathways From Domestic Sewage

With the rapid development of biological denitrification technology in sewage treatment,the SBR wastewater treatment process has been widely used,but at the same time,the SBR nitrification system of domestic sewage is also a more complex microbial system,in which the microbial competition among the denitrifying bacteria groups influences and decides the type,rate and product of nitrification.Therefore,the rational operation mode is used to adjust and optimize the process.The effect of chemical treatment is very important.In the aerobic phase of the nitrification system,the removal of inorganic nitrogen is usually accompanied by the removal of the inorganic nitrogen.The higher nitrogen removal rate means that the cost of adding medicament can be saved in the actual operation.The ways of nitrogen removal are usually not unique,but there are no detailed reports on the specific ways of nitrogen removal in the short range nitrification/nitrification system,and few intensification of nitrogen removal in the whole process nitrification process.In this project,the actual domestic sewage was used to inoculate short range nitrification sludge with 22 L SBR reactor.The low dissolved oxygen conditions of0.5 mg/L were strictly controlled during the reaction process.The factors,ways and specific strengthening strategies of nitrogen removal in nitrification system were studied.Low dissolved oxygen condition is more conducive to increase nitrogen removal rate in nitrification system.At the same time,compared with the complete nitrification system,the accumulation of NO₂^--N in short cut nitrification system can also help to increase nitrogen removal rate.But this does not mean that the short range nitration system can directly reach the satisfactory nitrogen loss effect under the condition of low oxygen operation.At the beginning of the experiment,the effect of dissolved oxygen concentration on the sedimentation performance and nitrification performance of the short range nitrification system is studied.It is found that the nitrification rate is greatly reduced,the affinity of AOB to DO decreases and the growth rate of NOB is far greater than that of A under the low oxygen aeration condition of 0.5 mg/L.The number of Nitrobacter and Nitrospira in the system increased significantly,and expressed activity,resulting in the occurrence of shortcut nitrification.At the same time,the change of the concentration of pollutants in a single nitrification cycle was studied.It was found that the single cycle reaction could be divided into 3 stages according to the change of nitrogen removal rate.The main ways of nitrogen removal in each stage were found to be different.By design experiments,nitrogen removal approaches include heterotrophic denitrification,anaerobic ammonia oxidation and N₂O emissions.The relationship between microbial competition among functional bacteria groups in the nitrification system determines the type of nitrification,the removal rate of total inorganic nitrogen and the way,while the concentration of substrate determines the relationship of competition among microorganisms.When COD and ammonia are degraded at the same time,the main way of nitrogen removal is heterotrophic denitrification,but when there is not enough carbon source in the system,the heterotrophic denitrification reaction is inhibited,mainly by the anaerobic ammonia oxidation reaction,which causes nitrogen removal.In the process of decreasing the period of NAR in the nitrification system,the nitrogen removal rate and way of each cycle are studied.It is found that when the NAR is lower than a threshold?34.94%?,there is no sufficient NO₂^--N in the system to make the anaerobic ammonia oxidation proceed smoothly.In other words,because of the stronger competitiveness of NOB to NO₂^--N,the anaerobic ammonia oxidizing bacteria are directly affected.Inhibition,the contribution to total nitrogen loss is greatly reduced.After NO₂^--N accumulation is no longer in the nitrification system,in order to restore and enhance the activity of AOB and NOB,the influent load of COD and ammonia nitrogen is reduced,and the system basically does not have the total nitrogen removal.After running for 16 cycles,the activity of AOB and NOB gradually recovered.Subsequently,the influent load increased and the nitrogen removal rate increased and stabilized at 27±5%.At the same time,autotrophic nitrogen removal occurred during the complete nitrification process.After studying the influence factors and ways of nitrogen removal in the system,the nitrogen removal was strengthened by adding high ammonia nitrogen anaerobic ammonia oxidizing granular sludge into the whole process nitrification system,and the proportion of the anaerobic ammonia oxidizing granular sludge?dry sludge weigher?was the 1:2 of the whole process nitrifying floc activated sludge.After 3cycles of operation,the TIN_ra of the system is stable in 46.16%⁵4.94%.The nitrogen removal ratio caused by ANAMMOX in the whole denitrification system is greatly increased,accounting for 72%.In the nitrification system,after adding the strengthening strategy and reaching the stable operation,the nitrogen removal of the system was further strengthened by the intermittent aeration operation mode of 30min:15 min in the anoxic time.After 5 cycles,the TIN_ra reached 81.23%,and the system reached the level of deep denitrification.