Effects of Treating Natural Organic Matter and Clay Mineral by Electrically Enhanced Membrane Filtration
Date Issued
2007
Date
2007
Author(s)
Teng, Sung-Chun
DOI
zh-TW
Abstract
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.
Subjects
腐植酸
黏土礦物
蒙脫土
薄膜外加電場過濾程序
SUVA
humic acid
clay mineral
Kaolin
Bentonite
Electric enhanced membrane process
Type
thesis
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