| Summary: | 碩士 === 國立中興大學 === 環境工程學系所 === 104 === Membrane Bioreactor, MBR, is one of the emerging biological treatment processes in recent years. It has advantages of lower operating costs such as space-saving (The secondary sedimentation tank), high sludge concentration, and low sludge production. MBR has excellent removal efficiency for the biodegradable carbon and nitrogen in the wastewater system.
This study discussed the removal efficiency of total nitrogen. The treatment is coupled with the circular flat ultrafiltration membrane. MBR was employed to investigate the removal efficiencies of total nitrogen. In this study, the influent is about 200 L/day resulting in the hydraulic retention time of 24 hours, with various different C/N ratios to evaluate the C/N ratio on the impact of total nitrogen removal.
In this study, theoretical total nitrogen concentrations were controlled at about 100 mg/L. Sugar and milk powder were used as carbon sources, and aeration was carried out in a manner of aeration period for 12 hours, cease in aeration for 8 hours, and then re-aeration for 4 hours. The first operation module was under the conditions of C/N initial ratio of 10, and influent COD concentration was 1000 mg/L. The optimum removal efficiency of total nitrogen and the average total nitrogen removal efficiency were 88% and 83%, respectively. And the measured lowest of three modules in NO3--N concentration was 0.35 mg/L. The second operation module was under the conditions of C/N initial ratio of 6.5 and COD concentration of 500 mg/L. The optimum removal efficiency of total nitrogen and the average total nitrogen removal efficiency was 88% and 83%, respectively. A similar result as that in the first operation module occurred in operating time of 16 hr. It is estimated that the total nitrogen removal reached its maximum removal efficiency about 88%. The third operation module was under the conditions of C/N initial ratio of 5 and COD concentration of 500 mg/L. The optimum removal efficiency of total nitrogen and the average total nitrogen removal efficiency was 83% and 78%, respectively. And these results were achieved in operating time of 20 hr, which is 4 hours later than the previous two modules did. The result indicated that these three operation modules resulted in an acceptable N removal with the MBR system. The ammonia nitrogen removal efficiencies are all greater than 90%. However, the experiment results demonstrated that. The higher C/N rations resulted in a better total nitrogen removal, due to the presence of abundant organic carbon to supply the c-source for cell growth. Denitrification occurs when the C/N ratio is high. It indicates mainly more abundant organic carbon is in favor of heterotrophic bacteria to take the place of denitrification.
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