薄膜外加電場處理程序：水中天然有機物及黏土礦物之影響研究

Effects of Treating Natural Organic Matter and Clay Mineral by Electrically Enhanced Membrane Filtration

鄧淞駿(Sung-Chun Teng)

指導教授 ： 李公哲

國立臺灣大學/工學院/環境工程學研究所/碩士(2007年)

https://doi.org/10.6342/NTU.2007.01234

摘要

本研究以濃度為5mg/L的腐植酸(HA)及40mg/L的黏土礦物，包括高嶺土(K)及蒙脫土(B)，配製成五種配比水樣(HA、K、B、HA+K、HA+B)，探討薄膜外加電場過濾程序在不同壓差及不同電場強度下，對於模擬水樣去除效率的影響，並就各項積垢阻力加以分析。
在無施加電場下，水中同時存在腐植酸與黏土礦物時，滲出液通量會大幅度衰減，阻力分析結果顯示HA+K與HA+B於49kPa或98kPa的操作壓力下，積垢阻力(Rf)約為HA的3倍左右；DOC去除率方面，在98kPa的操作壓力下，HA+K(49.88%)>HA(26.08%)>HA+B
(8.03%)，結果顯示水中濁度主要來源為蒙脫土時，不但使通量嚴重衰減，且對DOC的去除率也遠低於濁度主要來源為高嶺土之原水。
施加電場後，各水樣因電泳與電滲透作用，通量皆有明顯提高的現象，結果顯示在低壓力(49kPa)操作下，施加有效電場強度維持在臨界電場強度附近即可有最佳效果，高壓力(98kPa)下若施加有效電場強度過高，反而對滲出液通量無益，於HA+K溶液中施加77.21V/cm(高於臨界電場)的通量反而比施加59.9V/cm(低於臨界電場)的通量為低。
外加電場對於HA、HA+K、HA+B三種配比水樣的DOC與UV254去除率皆能有效提升，UV254的去除率甚至高達90%左右；在低壓力(49kPa)操作下，施加24.13 V/cm的電場後，DOC去除率分別上升至74.37%、72.59%、74.7%，而施加有效電場強度高於臨界電場強度時，DOC的去除率已無顯著提升。再者，施加電場後的SUVA值也下降50%以上，可見外加電場確實能有效降低消毒副產物的前驅質。至於積垢阻力方面，薄膜總積垢阻力(Rt) 於施加電場後也有明顯降低的情形，除電泳作用減少積垢外，電滲透作用亦會增加通量，降低薄膜於過濾時的本質阻力(Rm)。
腐植酸與黏土礦物同時存在天然原水中是不可避免的，外加電場在不同配比的水樣中，不論是對於DOC的去除率、減緩通量的衰減，增加淨總出水量、減少消毒副產物前驅質，皆有實質的助益，足見外加電場程序確實有廣泛的適用性與顯著的效益；再加上應用臨界電場理論配合HA+K及HA+B之高電泳動能特性，可以較低臨界電場強度，達成減緩積垢、增加腐植酸去除率、減緩通量衰減及適應多種類濁度黏土礦物等特性，使薄膜外加電場過濾程序於實務操作方面更具有工程及經濟可行性。

關鍵字

腐植酸 ； 黏土礦物 ； 高嶺土 ； 蒙脫土 ； 薄膜外加電場過濾程序 ； SUVA

並列摘要

5mg/L humic acid(HA) and 40mg/L clay mineral, including Kaolin (K) and Bentonite (B), were used to produce five experimental solutions (HA、K、B、HA+K、HA+B) in this study. Both the fouling resistances and the effects of electrically enhanced membrane process on various synthetic solutions under different pressures and electric field strength were investigated.
Under no electric field, the flux declined obviously when humic acid and clay minerals co-existed in water. The result of resistance analysis showed that the fouling resistances (Rf) of HA+K and HA+B solutions was three times of HA under 49kPa or 98kPa. The DOC rejection showed that HA+K(49.88%)>HA(26.08%)>HA+B(8.03%) under 98kPa pressure condition. Comparing to the Kaolin solution, the flux of the Bentonite solution declined obviously. The results also showed that the DOC rejection of Bentonite solution was much lower than that of Kaolin solution.
When electric field was applied, the flux of five blended solutions increased obviously. Under the low pressure(49kPa), the best performance could be resulted when applied electric field strength near critical electric field(Ec). Under high pressure(98kPa), further improvement could not be obtained if the applied electric field strength were overdone. The flux of HA+K solution applied with 77.21V/cm (above critical electric field strength) was lower than that applied with 59.9V/cm (below critical electric field strength).
When applied electric field strength, DOC and UV254 rejection of HA、HA+K、HA+B solutions increased a lot. The rejection of UV254 almost reached 90%. When applied with 24.13 V/cm electric field strength under 49kPa, the DOC rejection increased to 74.37%、72.59%、74.7%, respectively. The DOC rejection had no obvious increase when applied electric field strength exceeded critical electric field strength. Moreover, the SUVA value declined more than 50% under the electric field application. It showed that the electric field application could effectively decrease the DBP precursors. The total fouling resistances (Rt) declined dramatically under the electric field application. Both the effect of electrophoresis and electro-osmosis decreased the membrane intrinsic resistances(Rm) in electric enhanced membrane process.
It is unavoidable that humic acid and clay minerals coexist in raw water. The application of electric field did enhance the DOC rejection, ease the decline of flux, enhance the net water production, and decrease the DBP precursors of the various blended solutions. It showed that electric enhanced membrane process did have the extensive applicability and obvious benefit. With the use of combination of critical electric field strength theory and the characteristics of high electrophoretic mobility of HA+K and HA+B which caused lower Ec to reduce the fouling, enhance the HA rejection, ease the declination of the flux and be adapted to various clay minerals. Thus, electric enhanced membrane process could be practically operated and have a higher engineering and economical practicability.

並列關鍵字

humic acid ； clay mineral ； Kaolin ； Bentonite ； Electric enhanced membrane process ； SUVA

參考文獻

翁堉翔（2005），以外加電場薄膜程序處理水中腐植質，國立台灣大學環境工程研究所碩士論文。

許家銘（2001），以電場掃流超過濾分離蛋白質混合液，私立中原大學化學工程

蔡宇庭(2006)，水中天然有機物與濁度物質對外加電場薄膜處理程序之影響研究，國立台灣大學環境工程研究所碩士論文。

蘇佳琪（2001），氧化鋁及氧化鐵插層蒙特石吸附水中天然有機物之研究。國立成功大學環境工程研究所碩士論文。

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