- 學位論文
無氣泡氧氣溶解裝置應用於河川水質改善之效能評估
Evaluating The Effectiveness of The Foam-free Oxygen Dissolution Apparatus Applied to River Restoration
摘要
台灣地狹人稠，中下游河川因工業廢水、家庭污水及畜牧廢水等的不當排放，而受到不同程度的污染。政府機關在改善水質的時候，礙於土地徵收不易及處理經費過高而無法妥善執行，發展土地使用面積較少、容易操作的無腹地工法為當前課題。本研究以現地試驗、實驗室水槽模組、系統動力學模式測試無氣泡氧氣溶解裝置在河川污染整治的應用，其以在槽處理方式來改善水質，本裝置特點為佔地面積小、安靜、操作維護簡易、不影響河道洩洪功能、改善河川底泥功能等，對土地昂貴、人口密集的河川下游，具有高效益低成本的潛力。 為測試無氣泡氧氣溶解裝置的實際水環境改善效能及應用，本研究與該裝置台灣代理商以產學合作方式，以河川現地操作、實驗室水槽測試、水質系統動力模式來實證。河川現地操作選定台南運河民生截流站河段做為現地試驗區域，該河段除零星生活污水外，大部分市鎮廢污水已截流到安平污水處理廠，水流緩滯及底泥有機物沉積為主要的水質污染因素。本研究於2006年5月至2007年1月，以無氣泡氧氣溶解裝置及微生物添加進行河川水質改善。由入、出水口經常性水質監測結果顯示，裝置出水口DO明顯高於入水口。操作8個月，出水口水中BOD及COD分別降低91％及76％；水中ORP由-200mV增高至-125mV；底泥硫化物降低70％。12月3日於民生截流站上、下游各約500m河段進行運河斷面及入、出水口16點採樣調查，結果顯示出水口DO為3.7mg/L，明顯高於其他各採樣點；底泥耗氧率出水口比入水口低0.5 g/m2/day。河川生態方面，在操作8個月後出現豆仔魚、烏魚、吳郭魚、大眼海鰱等。 實驗室水槽以二仁溪河水及底泥作測試，在完全混合、無流動、半控制條件下，收集氧氣超飽和狀況下水質及底泥的變化。原水體溶氧為5.8mg/L；BOD為8.6 mg/L；底泥SOD為4.68mg/m2/day。使用無氣泡氧氣溶解裝置交換後，在幾小時內溶氧即提高至40mg/L，經過28天處理BOD降至0.8mg/L， SOD降至4.24g/m2/day。 以水槽試驗收集的水質及底泥化學參數建構動力模式，所率定之BOD一階降解速率常數Kd為1.6hr-1時與BOD預測值與實測值有最好的相關性(r2=0.986)。模擬無氣泡氧氣溶解裝置(40mg/L)及一般曝氣(8mg/L)，在相同BOD負荷下，無氣泡氧氣溶解裝置所需耗費氧氣量及處理時間皆低於一般曝氣，而由溢散至大氣中的氧氣發現，BOD負荷越高所提供的氧氣量越少，溢散至大氣的比例也越少，說明此裝置在BOD負荷越高的情形下可以更有效利用。由研究結果實證，無氣泡氧氣溶解裝置對於水質改善有一定的成效，為迅速而有效的改善工法。
並列摘要
Due to the improper drainages of wastewaters from factories, households and livestock husbandries, the mid- and downstream river segments in Taiwan have suffered various degrees of water pollution. Considering the high expenses for land requisition, construction and maintenance for river cleanup facilities, it becomes an urge to develop a low land-demanding, easy-operating treatment technology. The present study tested the effectiveness of the foam-free oxygen dissolution apparatus (®Green Harmony T.H.A. system, Daiei Inc., Japan), an on-channel treatment technology, to river restoration. The apparatus was designed to achieve low land demanding, low noise, easy operation, no hindering problem for flood control, improvement of sediment quality, and potentially, cost-effectiveness. In order to test its effectiveness and application, the foam-free oxygen dissolution apparatus was tested on site, in the laboratory-scale tanks, and simulated with a water quality dynamic model by this study. For the on site testing, the apparatus was installed in the Ming-Sheng interception station of the Tainan Canal, where most of the discharged municipal wastewaters were intercepted and treated by the An-Ping Wastewater Treatment Plant. Water stagnation, caused by the bi-direction tidal motion, and accumulation of sedimentary organics are the main reasons resulting in the deteriorating water quality of this river reach. The 8-month trial was from May, 2006 to January, 2007. The routine water quality monitoring indicated that the dissolved oxygen in water was raised at the outlet of the apparatus. After 8 months of operation, water BOD and COD were dropped 91% and 76%, respectively. Sedimentary sulfur was dropped 70%. Sedimentary ORP was increased from -200mV to -125mV. A cross-sectional, detail investigation was conducted to examine the water quality, sediment quality, and community structures of benthos and fishes on the 25-meter radius of the treatment area. The results showed that the sampling spot most close to the outlet of the treatment apparatus had the highest DO than other ones. Sediment oxygen consumption rate was 0.5g/m2/day lower in the outlet of apparatus, comparing with the inlet. Large-scale mullet, Mugil cephalus, grey mullet fishes that had never present in this river reach were appeared after 8 months of treatment. For the laboratory-scale study, water and sediment from Erhjen River were filled in three replicated tanks and treated by the foam-free oxygen dissolution apparatus for 28 days. The tanks were operated at completely mixed, no-flow, and semi-environmental control conditions. After 28 days of treatment, DO was increased from 5.8 to 40mg/L; BOD was dropped from 8.6 to 0.8mg/L; SOD was dropped from 4.68 to 4.24 g/m2/day. Water quality dynamic model, based on the chemical parameters collected in the laboratory-scale study, was established. The model with the first order BOD degradation rate of 1.6hr-1 offered the best correlation (r2 =0.986) between simulation and real BOD values. The model further simulated and compared the effectiveness of the foam-free oxygen dissolution apparatus (DO = 40mg/L) and of traditional aeration device (DO = 8mg/L). At the same BOD loading, the foam-free oxygen dissolution apparatus is more effective in terms of the amount of O2 demand and of the time requirement to achieve a BOD level of the non-polluted criteria. The comparison of different BOD loadings from 10 to 200 mg/L suggested the foam-free oxygen dissolution apparatus performs better at higher loadings for its relative less oxygen waste to the atmosphere. The study has concluded that the foam-free oxygen dissolution apparatus is an effective technology to improve water quality on channel and its effectiveness is more eminent upon applying to mitigate heavily polluted conditions.