| 摘要: | 根據聯合國研究指出若無立即提出水資源解決方案，到2025年時，全球每3人即有2人會感覺到缺水的壓力。因此，開拓多元水資源成為一無可避免之解決方向，其中水資源回收則成為拓展水資源主要管道之一，然而全球氣候變遷與極端氣候對此提示其處理程序之低碳意涵，故而人工濕地因其綠色永續特性廣受注重，惟其低溶氧水環境與質傳障礙造就其低汙染降解效能而抑制其應用發展，前者雖可以曝氣方式解決，然所衍生之高溶氧及低有機碳卻抑制脫氮作用，衍生硝酸鹽氮累積，而無法整體提升總氮之去除。此外，人工濕地對含磷汙染物之去除效能亦相對不彰。本專題原申請應用內外複式循環、零價鐵、在槽曝氣等創新策略提升水平潛流式人工溼地之汙染物降解效能，其中曝氣裝置將置於槽體前端，於中段設內迴流循環抽水設施將水送回曝氣區以提升前段有機碳與氮之去除，此內迴流會於後半段衍生反向環流以確保其厭氣環境，此區將置入零價鐵柱牆以其厭氣氧化反應提升自營性脫氮菌活性，提升硝酸鹽氮之去除，而外部迴流則將含鐵離子之排放水回流至曝氣區，藉磷酸鐵沉澱反應提升其去除效能。由於原申請3年計畫僅獲核准1年，本次計畫執行以探討複式循環對水平潛流式人工濕地汙染處理效能之影響。研究中主為藉由不同曝氣迴流操作模式探討其提升水平潛流式人工溼地之對各類水質參數去除效能之影響，其參數包括；生化需氧量(Biochemical oxygen demand，BOD)、總凱式氮(Total Kjeldahl nitrogen，TKN)、氨氮(Ammonia-nitrogen，NH3-N)、亞硝鹽氮、硝酸鹽氮(Nitrate-nitrogen，NO3–-N)、總氮(Total nitrogen，TN)、總磷(Total phosphorous，TP)等，由相關實驗結果發現曝氣迴流系統對BOD之平均去除率可由對照組之53.8-76.0%提升至82.0-91.7%，此結果屬於顯著提升(p<0.05)，而迴流比(內迴流流量：進流量)>3即能顯著提升BOD去除效能。至於對NH3-N、TKN與TN 的去除而言，迴流比>3即對其去除效能之提升即無顯著影響，而曝氣迴流系統對NH3-N、TKN與TN之去除率分別由對照組之15.1-78.1%、18.2-77.2%、19.4-74.5%顯著提升98.3-98.6%、93.4-94.0%、71.6-81.0%，惟對NO3–-N之抑制仍有其侷限性，當入流濃度超過限度時，系統中仍會發生顯著之累積現象，其平均濃度為4.7 mg/L，即便如此，TN之去除仍有顯著提升現象。而根據實驗結果顯示曝氣迴流系統對於TP則未有顯著之正面提升影響，由前述結果可知曝氣迴流系統可明顯提升有機與含氮汙染物，而內迴流比>3時，其提升效能即無顯著差異。
Two out of three individuals worldwide may be living in a water-stressed condition by 2025, if global water consumption patterns continue without an immediate solution. Based on a strategy of creating more water resources, water recovery is a viable means of offering more qualified water for specific usages. However, low carbon emission during water recovery become a necessary consideration when facing the challenge resulted from the global climate changes and extreme weather. Since regarded as a green technology and sustainability, constructed wetlands (CWs) receive massive attentions. Their application and development are depressed because of low level of dissolved oxygen (DO) and mass transportation barrier. Although DO can be leveled up by artificial aeration, it depresses denitrification which is also restrained by the low carbon source. Consequently, nitrate-nitrogen accumulates in the effluent and decreases total nitrogen removal. In addition, low removal of phosphorous is always found in CWs. In the earlier proposal submitted to MOST, innovative strategies; complex recirculation, zero valent iron (ZVI), and an in-tank intermittent aeration will be used to improve pollution removal efficiencies of horizontal subsurface flow (HSSF) constructed wetlands. Internal recirculation installed in the mid part of HSSF CW increases removal efficiencies of organic and nitrogen contained pollution by pumping water back to aeration area located in the entrance. A counter-direction circulation flow induced be internal recirculation will maintain the anaerobic environment in latter CW. When installing ZVI wall, their oxidation improves the activities of denitrifying microbial which enhances removal efficiencies of nitrate-nitrogen and total nitrogen. Ferrous ion in the effluent recirculates into the aeration area and promotes phosphorous removal by sedimentation with phosphate. This report focuses on the effects of the internal recirculation on the pollutants removal efficiencies of HSSF CW due the financial support limitation of MOST. The water quality parameters; biochemical oxygen demand (BOD), total Kjeldahl nitrogen (TKN), ammonia-nitrogen (NH3-N)、nitrite-nitrogen, nitrate-nitrogen (NO3–-N), total nitrogen (TN), and total phosphorous(TP), were used to evaluate the variation characteristics of pollution removal in HSSF CWs with or without the modifications of artificial aeration and internal recirculation. According to the experimental results, it showed that the average BOD removal ratios could be significantly improved from 53.8-76.0 % in the control system to 82.0-97.1 % in the experimental system (p<0.05). A significant improvement occurred when recirculation ratio (recirculation flow rate : influent flow rate) >3. The removal ratios of NH3-N, TKN, and TN were also significantly improved from 15.1-78.1%, 18.2-77.2%, 19.4-74.5% to 98.3-98.6%, 93.4-94.0%, 71.6-81.0%, respectively. However, an accumulation of NO3–-N would take place when the influent concentration of TKN was large than the denitrification capacity of HSSF CW. A significant improvement was still observed in the removal of TN. As for the removal of TP, no significant improvement was supported by the experimental results. Based on the above discussion, it concluded that the modification of artificial aeration and internal recirculation on HSSF CW could significantly improve the removal efficiencies of organic and nitrogen contained pollutants. |
