感潮河川的溶氧分層特徵與增氧設備效率研究 -以淡水河中游大稻埕與愛河中游水區為例-

Abstract

由於淡水河中游底水層呈低溶氧狀態，本研究嘗試使用低耗能間歇式湧升裝置促進上下水層交換以間接增氧，達到改善底水層溶氧特徵。 調查中游大稻埕水域的水理水質特徵，作為設計湧升柱的參考。夏、冬兩季現地量測大稻埕水域的底泥耗氧速率。設計增加湧升柱內的空氣室體積（Ⅲ型），分別於大稻埕水域現場與露天止水式湖泊進行增氧效率、交換上下水體能力、擴散能力等測試。且在實驗室以止水式水體進行湧升柱的標準試驗，比較湧升柱Ⅲ型與文獻Ⅰ型的效率差異。另外，也實地測試連續增氧式曝氣船在高雄愛河中游的增氧效率與擴散能力，協助建立整治河川水質的工程資料。 研究得知，大稻埕水域在漲退潮期間，溶氧無明顯分層，但溶氧偏低，在漲潮時全水層的溶氧低於3ppm，退潮時甚至降至1ppm以下。夏、冬兩季底泥表面的耗氧速率分別為9±6mg/m2/min (水溫26℃)、5±5 mg/m2/min (水溫19℃)。湧升柱Ⅲ型的標準曝氣效率為1.50 kgO2/kw/hr，揚升水量約621~629ml。Ⅲ型應用於緩流水域，攪水能力範圍可達3公尺，出水口處的增氧能力約0.86mg/l，耗電成本為0.38元/mgO2/l/hr。高雄愛河曝氣船，出水口處的增氧能力約1.8mg/l，耗電成本為6.99元/mgO2/l/hr。 比較本研究間接增氧式湧升柱與連續增氧式曝氣船工法，對河川水質改善增氧及擴散能力的成效可知，在節能與效率、經濟等方面，間接增氧方式應優於連續增氧方式。因此，湧升柱應可作為河川增氧物理工法的方法之一。

The dissolved oxygen（DO）is nearly none at the bottom of water at the midstream of Tanshui river. Therefore, this study is applying an air-lift column to deal with low DO condition of water and investigating hydraulic characteristic of Dadaocheng Basin as air-lift column design reference resources. In this study, the air-lift column is a low energy costing and intermittently operating device which can mix different water layers. Field experiments in summer and winter are operated to measure the oxygen consumption rate of the sediment. And the air-lift column efficiency of the increased oxygen rate、the water mixing ability and the oxygen spread of ability are fast. Standard experiment of air-lift column is carried out in static state water. And compare the efficiency of the two types of column design. In addition, this study measures the increased oxygen efficiency and diffusive ability of the aeration boat to build up the database for river renovation. Results show DO below 3ppm and without-delaminating during the period of flood tide and only about 1ppm in the ebb tide in the Dadaocheng watershed. The oxygen consumption rate of the sediment are 9±6 mg/m2/min in summer (water temp. 26℃) and 5±5 mg/m2/min in winter (water temp. 19℃). The standard aeration efficiency (SAE) of air-lift column is 1.50 kgO2/kw/hr, up-welled water volume is 621~629 ml. when it is applied to the low speed flow watershed, the agitated range is about 3 m、the increased oxygen rate at the outlet is 0.86mg/l and the electric cost is 0.38 NT dollar/mgO2/l/hour. The increased oxygen rate of the aeration boat in Kaohsiung is 1.8mg/l and electric cost is 6.99 NT dollar/mgO2/lhour. Comparing water quality improvement ability and the oxygen spread of ability between indirect oxygen increasing air-lift column and continuous aeration boat, indirect oxygen increasing method has better performance than continuous oxygen increasing method. To sum up, the air-lift column can be one of the physics methods to effect oxygen increasing.