|摘要: ||本研究為強化表面流動式(Free water surface；FWS)人工濕地(constructed wetland；CW)在較高負荷條件下的污染去除效率，實驗設置三套表面流動式人工濕地模組系統；其一是採用連續式曝氣模式搭配較短生物礫石牆(FWS-A)，第二套則是使用間歇式曝氣搭配較長生物礫石牆(FWS-B)並與對照組(FWS-C)相比較，以模擬探討不同生物礫石牆厚度及曝氣模式對相關CW系統的污染物去除效能之影響。整體實驗期間分為5個試程，透過水力停留時間(Hydraulic retention time；HRT)與不同曝氣模式的改變來探究其最佳操作條件。其評估依據則是依據相關水質參數之去除效能，其水質參數包括；生化需氧量(Biochemical oxygen demand；BOD)、總氨氮(Total ammonia-nitrogen；TAN)、亞硝酸鹽氮(Nitrite-nitrogen；NO2─-N)、硝酸鹽氮(nitrate-nitrogen；NO3─-N)、總凱氏氮(Total kjeldahl nitrogen；TKN)、總氮(Total nitrogen；TN)和總磷(Total phosphorous；TP)等，藉以結果分析系統間處理效能上的差異。
實驗期間，在Stage-III時，FWS-A採用連續曝氣並不控制溶氧(Dissolved oxygen；DO)，FWS-B採曝氣8小時，停止曝氣16小時之間歇曝氣，FWS-A、FWS-B、FWS-C三者的HRT分別為3.24 d、3.27 d及2.28 d，其BOD去除率分別為70.3 %、64.2 %與9.2 %，TAN去除率分別為99.6 %、95.9 %及81.5 %，TKN去除率為97.9 %、97 %與 77.7 %，TN去除率為81.5 %、89.8 %及 76.4 %。而透過優化曝氣模式後的Stage-IV，FWS-A採連續式曝氣但控制其溶氧濃度，而FWS-B採間歇式曝氣6小時，停止曝氣6小時，FWS-A、FWS-B、FWS-C三系統HRT分別為1.52 d、1.54 d、1.48 d，其BOD去除率分別為76.9%、67.2 %與37.6 %，TAN去除率分別為93.7 %、95.0 %及73.1 %，TKN去除率為79.5 %、84 %與61.4 %，TN去除率為：76.3 %、83.9 %及 61.5 %，結果顯示，在CW操作中，HRT越長對於去除效率越好，但實驗組在較細膩的操作策略下亦能於縮短一半的HRT中創造相當良好的去除效能。
In order to enhance the removal efficiency of constructed wetland (CW) under high load conditions, this study set up three sets of small modular systems for surface flow constructed wetlands which includes FWS-A operated in a continuous aeration mode with a shorter bio-gravel wall, FWS-B operated in an intermittent aeration with a longer bio-gravel wall, and a control one (FWS-C). By these FWS CWs, this study investigated the effects of the bio-gravel wall length and aeration mode on the of pollutants removal efficiency. During the experimental period, it included 5 stages with different hydraulic retention times (HRT) and aeration modes.The performance of FWS CWs was evaluated by the water quality parameters which included biochemical oxygen demand (BOD), total ammonia-nitrogen (TAN), nitrite-nitrogen (NO2－-N), nitrate-nitrogen (NO3－-N), total Kjeldahl nitrogen (TKN), total nitrogen (TN), and total phosphorous (TP)..
During the experimental period at Stage-III, FWS-A operated under a continuous aeration without control dissolved oxygen (DO). FWS-B aerated on an aeration ratio (AR=8 : 16； 8 hours aeration ： 16 hours non-aeration). The HRT of FWS-A, FWS-B, and FWS-C were 3.24. d, 3.27 d, and 2.28 d, respectively. From the experimental results, the removal rates of BOD were 70.3 %, 64.2 %, and 9.2 %, respectively. The TAN removal rates were: 99.6 %, 95.9%, and 81.5 %, respectively. The TKN removal rates were 97.9 %, 97 %, and 77.7 % and TN removal rates were 81.5 %, 89.8 %, and 76.4 %, respectively. By an optimizing process of Stage-IV, FWS-A operated under a continuous aeration but controlled the DO, while FWS-B intermittently aerated for AR=6 : 6. The HRT of FWS-A, FWS-B, and FWS-C system were: 1.52 d, 1.54 d, and 1.48 d, respectively and the responding removal ratios of BOD were 76.9%, 67.2%, and 37.6%, respectively. The TAN removal rates were 93.7%, 95.0%, and 73.1%, respectively. The TKN removal rates were 79.5 %. 84%, and 61.4% and TN removal rates were 76.3 %, 83.9%, and 61.5%, respectively. These results showed that the longer the HRT in CW operation was, the better the removal efficiency would be, but the experimental group can also be used under the finer operation strategy. A half-time reduction in HRT created a quite good removal performance.
According to the results of the experiments in Stage-I~V, the artificial aeration was quite helpful for the removal of nitrogenous pollutants and organic pollutants by CW and the bio-gravel wall in this research system could also improve the artificial aeration of FWS CW. The bio-gravel wall also improved the accumulation of NO3－-N caused by the continuous aeration in FWS CW. For the removal of TP, the removal rate was not affected by the aeration mode and bio-gravel wall.