結合凝聚程序與活性碳動態膜於掃流微過濾以應用於海水淡化前處理

Using of cross-flow microfiltration combined with coagulation process and PAC dynamic membrane filtration for pretreatment of seawater desalination

鄭喬維(Chiao-Wei Cheng)

指導教授 ： 黃國楨

淡江大學/工學院/化學工程與材料工程學系碩士班/碩士(2015年)

https://doi.org/10.6846/TKU.2015.00132

摘要

本研究以複合式的掃流過濾系統進行海水淡化前處理。比較不同程序對於濾速與出水品質的提升。本研究使用0.1μm親水性MCE膜與活性碳動態膜對模擬海水進行過濾，並探討加入凝聚程序對於整個;系統的過濾性質與水質影響。其中活性碳動態膜的生成，為預過濾多孔性粉末狀活性碳(PAC)，使其於0.45μm之PVDF膜面上形成一固定高度之濾餅層，此層濾餅層就稱之為動態膜。希望利用複合式的系統，將海水中之有機物質及無機微粒去除，以減少逆滲透程序中薄膜結垢的發生。
結果顯示，使用0.1μm MCE膜過濾模擬海水，當透膜壓差增加至180kPa，相較於100kPa，於過濾初期可使濾速增加70%，但於高壓操作下濾速衰退的情形也會增加。比較活性碳動態膜與0.1μm MCE膜之膜阻力可發現，使用活性碳動態膜即使於高壓操作下仍比0.1 μm MCE膜還低21%，因活性碳動態膜由較大之粒子排列構成，因此結構較為鬆散，易使濾液通過。使用活性碳動態膜過濾海水，過濾初期濾速隨透膜壓差增加而上升，但隨時間增加，透膜壓差越大則濾速下降越快，其阻力主要來源為活性碳吸附攔截所新形成之濾餅所造成。而比較加入凝聚程序，本實驗先以硫酸鋁、氯化鐵、幾丁聚醣三種凝聚劑進行杯瓶試驗以找到最佳劑量，由結果顯示使用幾丁聚醣為凝聚劑於劑量5mg/L下可獲得最大之膠羽且其上清液濁度為最低。若使用凝聚程序之系統可使海水中之物質形成較大之粒子，因此於過濾時粒子排列較為鬆散，因此無論使用0.1μmMCE膜或活性碳動態膜皆可使濾速提升。綜合比較出水品質(DOC、COD、濁度、腐植酸濃度)與濾速之提升可知結合使用凝聚程序結合活性碳動態膜之複合系統可使上述移除率達最大，且有效使濾速提升。

關鍵字

掃流微過濾 ； 海水淡化前處理 ； 活性碳 ； 吸附

並列摘要

Hybrid cross-flow microfiltration systems for pretreatment of seawater desalination were studied. The permeate flux and quality among different operations, such as hydrophilic membranes with different pore size, dynamic membrane formed by powder activated carbon (PAC), dynamic membrane coupled with coagulation operation, were measured and compared. The PAC dynamic membranes, constructed by pre-coating PAC on the primary membrane, was used for removing organic material and inorganic fine particles in seawater to prevent the membrane fouling in following Reverse Osmosis (RO) units.
Artificial seawater was filtered using 0.1 μm MCE membrane, the filtration flux increased 70% as the transmembrane pressure increased from 100 to 180 kPa. However, the flux decayed more quickly under higher pressures. The membrane resistance of the PAC dynamic membrane was 21% lower than that of 0.1 μm MCE membrane even under high transmembrane pressures. It was attributed to the large PAC particle size and loose packing structure of dynamic membrane. When PAC dynamic membrane was used for filtering artificial seawater, the flux increased with increasing transmembrane pressure. However, the flux declined dramatically at the beginning of filtration, the major resistance sources were those organic materials adsorbed and captured in PAC dynamic membranes. Three kinds of coagulants, ferric chloride, aluminum sulfate and chitosan, were used to enlarge floc sizes, . The results of jar tester indicated that the use of chitosan with a dose of 5 mg/L was optimal. To combine coagulation operations with cross-flow filtration processes, either the use of 0.1 μm MCE membrane or PAC dynamic membrane, the flux was improved. Comparing the performances of different operations, the hybrid system coupled with coagulation and PAC dynamic membrane behaved the highest efficiency of pollutant removal and highest permeate flux. The quality of permeate water, DOC, COD, turbidity and concentration of humic acid, for each operation was measured. The permeate quality met the requirement of RO feed.,

並列關鍵字

desalination pretreatment ； coagulation ； dynamic microfiltration ； cross-flow microfiltration

參考文獻

Choi, Y.H., Kweon, J.H., Kim, D.I., and Lee, S. “Evaluation of various pretreatment for particle and inorganic fouling control on performance of SWRO”, Desalination, 247 (1-3), 137-147(2009).

Chu, H., Zhang, Y., Dong, B., Zhou, X., Cao, D., Qiang, Z., Yu, Z., and Wang, H. “Pretreatment of micro-polluted surface water with a biologically enhanced PAC-diatomite dynamic membrane reactor to produce drinking water”, Desalin. Water Treat., 40 (1-6), 84-91(2012).

Gregor, J.E., Nokes, C.J., and Fenton, E. “Optimising natural organic matter removal from low turbidity waters by controlled pH adjustment of aluminium coagulation”, Water Research, 31 (12), 2949-2958(1997).

Hu, C.-Y., Lo, S.-L., Chang, C.-L., Chen, F.-L., Wu, Y.-D., and Ma, J.-L. “Treatment of highly turbid water using chitosan and aluminum salts”, Sep. Purif. Technol., 104, 322-326(2013).

Hwang, K. J., Y. L. Hsu and K. L. Tung, “Effect of particle size on the performance of cross-flow microfiltration”, Adv. Powder Technol., 17, 189-206 (2006).