| 摘要: | 本研究主要探討以分離式間歇曝氣整流生物礫石牆來提升表面流動式(Free water surface , FWS)人工溼地(constructed wetland；CW)的汙染處理效能之影響，實驗廢水來源是以校園廢水並經明溝混合鄰近工業區部分排水之廢水作為進流水，實驗設置二尺寸完全相同之實驗組(FWS-A)及對照組(FWS-B)之FWS CW系統，實驗組在前端放置蜂巢式整流曝氣系統，並在後端放置生物礫石牆，其於空間則種植水生植物(香蒲；Typha orientalis Presl.)，對照組則無放置任何輔助設備，僅種植香蒲作為系統之水生植物。為探討不同操作條件對系統汙染處理功能之影響，相關實驗分成四階段進行。FWS CW系統的功能則藉由生化需氧量(Biochemical oxygen demand；BOD)、總氨氮 (Total ammonium-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)等水質參數來評估間歇曝氣整流對FWS CW污染處理效能的影響。
由本研究依照不同操作條件RUN-I~RUN-IV的實驗結果發現由於BOD的平均進流濃度僅介於6.81 mg/L與18.6 mg/L之間，在水力停留時間(Hydraulic detention time；HRT)由1.3 d到2.2 d的範圍內，對照組FWS-B的平均去除率僅有6.65 %到8.71 %，傳統FWS CW的效能不甚理想，而FWS-A在間歇曝氣狀態下則可以增加到28.2-39.9%。
而由TAN與TKN的實驗結果來看，前者在連續去除率曝氣為92.1%，間歇曝氣模式(曝氣8hrs；停止曝氣8hrs)的去除率為90.3%，兩者皆比間歇曝氣模式(曝氣8hrs；停止曝氣16hrs)的去除率為22.6%要好，當然也比對照組要好，而凱式氮也有類似現象。此外，在連續曝氣試程中曾發現NO3─-N有累積現象，其平均濃度高達8.05mg/L，推測應是高溶氧對脫硝作用產生抑制現象所致，但在間歇曝氣試程中則沒有發現累積現象，這個結果說明間歇曝氣可以避免產生NO3─-N累積問題。藉此，在第四試程中發現TN的去除率可以提升為83.1 %，而對照組僅有60.3 %，由此可知，間歇曝氣模式(曝氣8hrs；停止曝氣8hrs)可以藉由降低對脫硝作用的抑制而成功提升TN的去除率。
至於TP部分，則可以發現對照組於連續曝氣試程的去除率僅14.8 %，而FWS-A CW也僅16.6 %，間歇曝氣(曝氣8hrs；停止曝氣8hrs)時，FWS-A與FWS-B二者的平均TP去除率分別為30.9 %與35.5 %，由此可知，間歇曝氣對TP去除並沒有明顯的影響。綜合所述可以間歇曝氣模式以曝氣8hrs；停止曝氣8hrs對TAN、NO3─-N、TKN、TN等含氮汙染物可以產生最佳去除效能，BOD去除效能也可明顯提升，至於總磷則沒有明顯影響。
The study focused on the promotion of pollution degradation of free water surface flow (FWS) constructed wetland (CW) by installing a system in FWS CW, which contained intermittently artificial aeration, flow rectification, and bio-gravel wall (AABGW), respectively. The campus wastewater mixed with treated industrial wastewater from an industrial area nearby used as the influent of this system. Two FWS CWs with the same dimension, FWS-A (experimental system) and FWS-B (control system), were employed in this study. In the formal, an artificial aeration with flow rectification system was installed in the influent area while there equipped a bio-gravel wall in the effluent area. The rest part planted aquatic plants (cattail; Typha orientalis Presl.). The experiment included 4 runs which could be used to assess the effects of operation factors on the removal efficiency of FWS CWs with or without AABGW. The parameters of water quality, biochemical oxygen demand (BOD), total ammonium-nitrogen (TAN), nitrite-nitrogen (NO2─-N), nitrate-nitrogen (NO3─-N), total kjeldahl nitrogen (TKN), total nitrogen (TN), and total phosphorous (TP) were used to evaluate the removal performance of FWS CW.
According the obtained results, the average BOD concentration of the influent ranged from 6.81 mg/L to 18.6mg/L and the removal ratios of FWS-B was only 6.65-871 % at hydraulic retention time (HRT) of 1.3-2.2 d. With AABGW, FWS-A increased the removal ratios to 82-39.9 %.
For the removal of TAN and TKN, the removal ratio of the formal was 92.1 % in the continuous aeration mode (CA) and it turned to be 90.3 % in the intermitted aeration (IA-I; 8 hrs. aeration: 8 hrs. no aeration). It implied that the intermitted aeration (IA-I) did not significantly affect the removal ration of TAN. However, in intermitted aeration (IA-II; 8 hrs. aeration: 16 hrs. no aeration), a rather poor removal ratio of 22.6% was found. A similar feature was also found in the results of TKN. An accumulation of NO3─-N formed in the continuous aeration mode and vanished in the intermitted aeration mode. Based on the findings, the removal ratio of TN in IA-I became a high removal ratio of 83.1 % while it was only 60. % in FWS-B. It implied that, for the operation of IA-I, it could decrease the suppression of denitrification and increase the removal of TN.
The removal ratios of TP of FWS-A and FWS-B in CA were 14.8 % and 16.6 %, respectively. For IA-I, they became 30.9% and 35.5%, respectively, and no significant difference induced by aeration mode was found. It implies that there was no impact of intermitted aeration on the removal of TP. According to the above results, aeration mode of IA-I played a significantly positive role in improving the removal of TAN, NO3─-N, TKN, and TN, respectively. It also improve the removal of BOD while no impact on the removal of TP was observed in this study. |
