| 摘要: | 台灣地區大部份的淨水場都將快濾池反沖洗水回流至上游單元，容易造成原蟲生物累積和加藥劑量控制問題，尤其在颱風及暴雨期間，回流處理衝擊影響淨水程序更大。本研究將以截流式(Dead-end)微過濾薄膜去除快濾池反沖洗水中之懸浮物質及微生物等污染物質，以利過濾水經消毒後可直接作為公共給水；同時薄膜微過濾將配合不同前處理方法，期望能增加薄膜之產水率。本研究主要採集潭頂淨水場、坪頂淨水場及彰化第三淨水場之反沖洗水，首先分析各個淨水場之反沖洗水的水質項目，接著以不同處理方式進行實驗，分別為反沖洗水直接微過濾，或者是經沉澱處理、混凝/膠凝前處理後，再分別進行過濾並分析各反沖洗水處理後的水質，所採用的薄膜孔徑為0.5m及2.0 m之微過濾薄膜，以固定壓力0.65 kg/m2抽真空方式進行過濾。在未使用薄膜微過濾的研究方面，則是採用多元氯化鋁搭配幾丁聚醣之混凝與沈降實驗。
結果顯示，以地表水（潭頂、坪頂淨水場）而言，不同的前處理方式搭配微過濾薄膜處理，發現直接過濾及沉澱前處理搭配薄膜微過濾將會產生嚴重阻塞，然而採用混凝/膠凝前處理搭配薄膜孔徑0.5m或2.0m可以增加產水率，但考量於薄膜過濾水須符合飲用水水質標準之因素，由實驗結果得知反沖洗水經混凝/膠凝前處理搭配薄膜孔徑0.5m之過濾水，在濁度、大腸桿菌及總菌落數方面皆符合飲用水水質標準，綜合上述可知，若採用混凝/膠凝前處理後搭配孔徑0.5m之MF薄膜過濾，對薄膜之產水率及過濾水之品質皆是最好的選擇。以地下水（彰化第三淨水場）而言，反沖洗水微過濾，是採用薄膜孔徑0.5m及2.0m之微過濾薄膜，結果顯示，通過薄膜孔徑0.5m之過濾水優於通過薄膜孔徑2.0m之過濾水，且不論是採用直接過濾薄膜孔徑0.5m或混凝/膠凝前處理搭配薄膜孔徑0.5m，在濁度、色度、大腸桿菌及總菌落數皆符合飲用水水質標準，因此可以建議彰化第三淨水場採用直接過濾MF0.5m即可。至於未使用薄膜微過濾的研究方面，多元氯化鋁搭配幾丁聚醣之混凝實驗雖然加藥量較少，但濁度的去除效果優於多元氯化鋁或幾丁聚醣的單獨使用，亦可減少混凝劑藥量。
In Taiwan, the filter backwash water needs to be recycled back to rapid-mixing tank in most of water treatment plants. However, this process caused several critical problems, including unstable chemicals control and accumulation of microorganism, which seriously affect the treated water quality. In this research, the supernatant of the waste backwash water treated by Dead-end type microfiltration (MF) process combined with coagulation and sedimentation was evaluated. The raw backwash water samples in this research were collected from Tanding Water Treatment Plant, Pingding Water Treatment Plant and Chang-Hwa Third Water Treatment Plant. First of all, water qualities for each treatment plants. First, the raw water qualities were analyzed. And then, several treatment processes were considered and executed, such as coagulation/sedimentation combined with MF Process and direct MF Process. PACl, alum and Chitosan were used as coagulation agents in the coagulation/sedimentation process. In the membrane process, there were two different MF membranes used in this research, including 0.5 µm and 2.0 µm pore sizes, which were filtered by vacuum pump at fixing pressure (0.65 kg/m2).
The results indicated that the backwash wastewater from surface water source treated directly by sedimentation only combined with MF process was confirmed to demonstrate the serious scaling problems. However, the water treated by coagulation/sedimentation combined with MF Process (0.5 µm and 2.0 µm pore sizes) reached high efficiency of clean water. Coagulation/sedimentation combined with MF Process specifically for (0.5 µm pore size) executed the optimal result that reached the standards of turbidity, coliforms and total bacterial counts. As the result, this process was considered to be the best one for backwash water reclamation using MF process.
This research also executed that the backwash wastewater from groundwater source treated by MF process (0.5 µm and 2.0 µm pore sizes). The result indicated that the 0.5 µm pore size exhibited higher treatment efficiency than 2.0 µm pore size. Moreover, the water quality treated by 0.5 µm pore size reached drinking water standards in turbidity, coliforms and total bacterial counts, no mater combined with filtration only or with coagulation /sedimentation. Therefore, direct filtration combined with MF process (0.5 µm pore size) was consider to be the optimal backwash water reclamation for Chang-Hwa Third Water Treatment Plant. |
