| Aerobic granular sludge process(AGS)is considered to be one of the most promising wastewater treatment technologies due to its advantages such as good sedimentation,strong processing capacity,simultaneous nitrification and denitrification,and land saving.At present,there are few studies on the use of AGS to treat lowconcentration urban sewage in cultivating AGS,mainly because low-load operation will cause difficulties in cultivation and long-term operation will be unstable.According to the AGS nucleus hypothesis theory,the loading body can accelerate the formation of aerobic particles and improve the sludge sedimentation performance.In this study,for the low-concentration sewage,the cultivation of aerobic granular sludge with crystal nuclei was proposed.The strengthening effect of crystal nuclei on the recovery of aerobic granular sludge after instability was investigated,and the aerobic granular sludge enhanced by magnetic particles Changes in the structure of the microbial flora during the operation of the system.First,the start-up,decontamination efficiency and sludge performance of the AGS system with magnetic powder,silt and unloaded body were compared.The results show that magnetic particles can enhance the decontamination performance and stability of AGS.After stabilization,the sludge concentration in the reactor is about 1800 mg/L,the SV is about 10%,and the SS concentration in the effluent is about 15 mg/L.,Indicating that AGS with lower sludge concentration still has better sedimentation performance;the magnetic powder,silt,and blank reactor COD of the reactor have reached the level A standard;the magnetic powder group AGS can remove ammonia nitrogen after 9 days of operation Up to 5 mg/L,and the silt and blank groups need 15 d to achieve the same effect;the magnetic powder group AGS can run stably for more than 60 d,while the other two groups can only run stably for about 30 d,so the magnetic powder was finally selected as the AGS crystal Follow-up studies are conducted.Study the pollutant removal effect and sludge sedimentation performance of AGS treated with magnetic powder as the nucleus of urban domestic sewage,and compare the decontamination effect of the system with different magnetic powder proportions(3 g/L,5 g/L,7 g/L)to determine the most effective Best magnetic powder dosage.Compared with the magnetic powder enhanced AGS system and the traditional AGS system,the two groups of reactors can remove COD below the level A standard,the COD removal effect of the magnetic powder group is relatively more stable;and the removal of ammonia nitrogen by the magnetic powder group can be stable for more than 60 days,After stabilization,the SS concentration in the nucleus-added group was about 20 mg/L,while the blank group was about 40 mg/L;and the SVI value in the nucleus group was higher;and 5 g/L was optimized to determine the optimal magnetic particle dosage.Aiming at the problem of poor stability of AGS under long-term operation,a longterm operation study of AGS system with magnetic particles as the crystal core was carried out.In the long-term operation research of the AGS system with magnetic powder as the crystal nucleus,it was found that the magnetic powder-enhanced AGS system can run stably for up to 65 days,while the blank group maintained stable operation for only 30 days.The disintegration of granular sludge occurred in both systems,and the decontamination effect became worse.However,the AGS system strengthened by magnetic powder finally recovered the decontamination effect and could continue to run stably for more than 50 days.The blank group did not recover after instability.Decontamination effect to stable operation period.Comparing and analyzing the results of light microscope and scanning electron microscope,it can be seen that the granular sludge is not completely disintegrated,and the sludge is still a dense microbial group,but the particle size becomes smaller and the apparent morphology changes.Sequencing analysis was used to analyze the microbial community structure of aerobic granular sludge system with magnetic particles as crystal nuclei.The results show that with the operation of the system,the abundance of microbial species under the elimination mechanism gradually decreases and stabilizes.The instability period has a higher species similarity to the inoculated sludge period and the stable operation period,which may be the reason why the sludge morphology changed after the instability period,but the AGS system still has strong decontamination ability. |
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