- 學位論文
薄膜蒸餾產製再生水之實驗探討
Experimental study on producing reclaimed water by membrane distillation
摘要
台灣水源的供給以地面水及地下水為主，而因氣候變遷及工業用水需求上升等，常導致缺水危機，因此期望以再生水解決缺水問題，再生水是指生活汙水及事業廢水經處理產生可再利用之水。 本研究利用薄膜蒸餾針對鳳山、福田、內湖及迪化汙水廠等之放流水產製再生水進行實驗探討，實驗分為直接接觸式薄膜蒸餾(DCMD)及氣隔式薄膜蒸餾(AGMD)試驗，藉由改變進料溫度及流量，進行通量及膜面結垢的探討。量測滲透液離子濃度及化學需氧量進行水質分析。 DCMD試驗結果顯示，當進料溫度50℃，Re=6550，鳳山水樣其通量接近一般RO逆滲透產水速率30 kg/m2hr，福田、內湖及迪化水樣在相同操作條件下其通量接近鳳山水樣。藉由量測進料端及滲透端電導度以推算離子阻擋率部分，鳳山及福田水樣阻擋率較高，分別約95%及85%，而內湖及迪化則較低，僅約50-60%，後兩者為都市汙水，進料中揮發性有機物質通過薄膜而滲透液pH值改變，影響電導度量測。SEM-EDX分析結果顯示，膜面僅些微結垢物附著，而結垢物主要元素為碳、氧。 AGMD的試驗結果顯示，當進料溫度60℃，Re=3611，迪化水樣其通量為13.33 kg/m2hr，離子阻擋率可達90%。本研究最後則藉由Memstill®概念，將熱能回收，進行平板式AGMD能源預估，薄膜有效面積為1×1 m2，進料及冷水入口溫度分別為80及30℃，流速0.01 m/s的設定下，其每立方公尺所需耗能146 MJ/m3。
並列摘要
Recently, Taiwan frequently faces an acute problem of water scarcity due to climate change and the increasing demand of water for industry. Because the sewage treatment plants have large and stable discharge of water, reclamation of water from the effluent of sewage treatment plants is expected to solve this problem. In this study, experiments on producing reclaimed water by direct contact membrane distillation (DCMD) and air gap membrane distillation (AGMD) were carried out to investigate the effects of feed rate and feed temperature on the flux, ion rejection and produced water quality. Four water sources from Fongshan, Futien, Neihu and Dihua treatment plant effluents were employed as the feed for DCMD experiments, while AGMD experiment was only with Dihua treatment plant effluent. DCMD experimental results showed that, under the same operating conditions, no significant difference in flux for feed streams from the four different sewage treatment plants. When feed temperature was at 50℃ and Re=6550 for feed flow through the module channel, the flux obtained was about 30 LMH which is very close to that reported by RO treatment. Based on the measurement of conductivity in feed and permeate, respectively, to determine the ion rejection, results showed that feeds from Fongshan and Futien plant have the ion rejection reaching 95 and 85%, respectively. However, the ion rejection for Neihu and Dihua effluent samples were only 50-60%. SEM-EDS analysis for membranes after 12 operations with Dihua plant effluent showed that only a slight fouling was observed, which is mainly from organic matter. AGMD experimental results showed that, when feed temperature is 60℃, Reynolds number of feed channel is 3611, air gap= 0.711 m, and cooling water= 30oC , the flux was 13 LMH and ion rejection was about 90%. Based on Memstill® concept for heat recovery, the thermal energy consumption of AGMD was also estimated. Under the given conditions of flat plate module 1x1 m2 ,feed and cooling inlet temperature were 80 and 30℃, respectively, and flow velocity was 0.01 m/s, the thermal energy consumption estimated was 146 MJ/m3.