| 摘要: | 本研究以薄膜生物程序（Membrane Bioreactor，MBR）為主探討其對COD、氮、磷之處理效能。MBR程序乃是結合傳統之活性污泥法與薄膜處理程序而形成，首先在傳統活性污泥處理法之好氧槽中，置入薄膜裝置，控制污泥停留時間（SRT）為10天、pH值在6.8?7.1、DO>5mg/L下，探討水力停留時間（HRT）分別為5、10、15、20小時下，對於COD、氮及磷之處理效果。由實驗結果發現，COD之去除率在94%以上，氨氮的去除率更高達100%，而磷的去除並沒有明顯的效果，而以HRT為15小時時，氮的去除效果最佳。 另於好氧槽前增置一個缺氧槽，控制HRT為15小時，其餘操作條件均相同下，探討不同的硝化液迴流比分別為0.5、1.5及2.5下，對於COD、氮及磷之處理效果，並探討其在不同迴流比下，其脫硝及硝化之情形。由實驗結果可知，在不同的硝化液迴流比下，MBR系統對於COD之去除率在95%以上，氨氮的去除效率高達99%以上，而對於磷的去除只有達25%，並無明顯的效果，出流水中的SS均介於2-5mg/l之間，可看出水質分離固體物之效率相當好。而於好氧槽前加入一缺氧槽後，對於硝酸鹽的去除率可看出有略微增加，其中以硝化液迴流比為1.5時除氮效果最好。 利用前面實驗所得之結果，將兩段式MBR程序控制於HRT=15小時、硝化液迴流比為1.5，而其餘控制條件均相同之情形下，探討不同之SRT分別為10天、20天及30天下，對於COD、氮、磷之處理效果，並進一步對各SRT進行活性污泥之菌相分析。結果發現兩段式MBR程序在不同SRT下，其對於COD、氮及磷之處理效果能相當良好且穩定，其中以SRT=30天時去除總氮效果最好，可高達81％。而在菌相分布上，在不同SRT下皆有Proteobacteria及Planctomycetales兩種菌群出現，且均發現好氧脫硝菌之存在。 The Membrane bioreactor (MBR) is the combination of the activated sludge process and the membrane technique process. With the effective filtrating function of the membrane unit, the suspended solid (SS) in the effluent of an MBR can be reduced to a very low concentration, hence eliminating the requirement of a secondary clarifier. This combination could further simplify the complicated operation requirements of the traditional wastewater secondary treatment facilities and is beneficial to the economic aspects of a treatment process for its less land demand. In this study, we first surveyed the impact of different hydraulic retention time (HRT) on an MBR. With a fixed sludge retention time (SRT=10 days), pH value (6.8~7.1), dissolved oxygen concentration (DO=5mg/L) and varied HRT (5, 10, 15, 20 hours), the MBR removed influent ammonia-nitrogen (NH4+-N) and chemical oxygen demand (COD) with high efficiency (100% and 94% respectively), and the best treatment efficiency was obtained with an HRT equaled to15 hours. However, the MBR didn’t display a function of phosphorus removal. To further increase the nitrogen removing efficiency of the MBR system, an anoxic tank was added in the upper stream of the aerobic MBR, which formed a two-stage MBR. With varied reflux ratio of the aerobic tank effluent to the influent (0.5, 1.5 and 2.0 respectively), the two-stage MBR removed COD and NH4+-N significantly, but the removal of phosphorus was not largely increased (efficiency =25%). The best COD and NH4+-N removing efficiency was obtained with the reflux ratio of 1.5. Utilizing the optimized HRT and reflux ratio, we further tested the two-stage MBR system with different sludge retention time (SRT=10, 20 and 30 days). Results showed that the two-stage MBR performed stably and the total nitrogen removal efficiency could reach 81% with a SRT of 30 days. Moreover, 16S rDNA analysis of the system showed that bacteria belonged to Proteobacteria and Planctomycetale groups existed in the microbial community of the two-stage MBR reactor. We also found aerobic denitrifier at varied SRT. |
