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    題名: 非熱電漿技術液相殺菌之研究;Inactiviation of Aquatic Microorganisms by Nonthermal Plasma Technology
    作者: 陳志維;Chih-wei Chen
    貢獻者: 環境工程研究所
    關鍵詞: 超音波;廢水處理;非熱電漿;消毒;環境適應力;Nonthermal plasma (NTP);Disinfection;Wastewater treatment;Environmental adaptation ability;Mutation;Ultrasound
    日期: 2009-06-13
    上傳時間: 2009-09-21 12:16:28 (UTC+8)
    出版者: 國立中央大學圖書館
    摘要: 為了避免飲用水受微生物污染,原水在飲用之前應當經過消毒及過濾除臭的程序,但是目前並沒有一套統一最有效的淨水處理法廣為世界各國所採納。 近年來廢水的高級氧化技術(AOTs)越來越受到重視且蓬勃發展,特別是針對殺菌及生物難分解污染物的去除方面。高級氧化程序種類很多,其中,非熱電漿技術在廢水處理的應用已被廣泛的應用於食品或液體的殺菌、大氣的殺菌及去除有害化學物質。本研究將以非熱電漿技術進行液體的殺菌研究,並分別以兩種電源供應器(A C及脈衝式電源供應器),利用氣-液混合式反應器對大腸桿菌及酵母菌進行實驗。 AC液相電漿實驗結果,發現刷對面的實驗結果比針對面的實驗具有較佳的殺菌效果,可能是刷狀電極在放電的過程中,產生較多的震波及自由基生成而使其殺菌效果較佳。AC (13 kV, 60 Hz)及脈衝式液相電漿技術(10 kV, 30 Hz)對於革蘭氏陰性菌(大腸桿菌)的殺菌效果較真菌(酵母菌)佳。AC及脈衝式液相電漿的放電過程,pH值均會下降 (放電15分鐘,pH由6.9降至4),但是其在電漿系統中的殺菌效能不大。AC及脈衝式液相電漿實驗發現放電前後大腸桿菌似乎有突變的情形發生,而且都造成環境適應力的上升。 超音波輔助電漿的加成效應只發生在無曝氣的純液相系統,曝氣時則不會發生。加成效應並不會發生於氣-液混合式的反應器,無論有無曝氣都不會發生。微生物的物種也不會影響加成效應的發生與否。造成加成效應的可能機制,為超音波處理時會造成空穴現象,此現象會生成小氣泡,而在超音波輔助電漿中,放電比較容易發生在氣泡中,因為氣泡中的電場強度是液體中的數百倍,也因此造成了加成效應,進而提升了殺菌效率。 超音波輔助電漿將可能是未來殺菌的新技術,相信此技術將可為廢污水及食物的殺菌效能帶來更大的提升。 Disinfection techniques have been utilized to killing microorganisms in water treatments to prevent diseases. Recently, AOTs technologies have been developed for killing microbes. Nonthermal plasma is one of AOTs technologies and it can be applied for sterilization and degrading chemical. Hybrid gas-liquid electrical discharge has been investigated in recent years as an innovative technology for contaminated water treatment. A high-voltage pulsed power supply is commonly needed for generation of electrical discharges. One of this study aims, in lieu of cost effectiveness, to evaluate the degradation efficiency of electrical discharges with alternating current (AC) power since it is generally cheaper than a pulsed one. An AC power supply with a fixed voltage of 13 kV and a fixed frequency of 60 Hz is therefore adopted in this study for inactivation of aquatic microorganism. Pulsed electrical discharge (10 kV, 30 Hz) was also produced to kill E. coli and Yeast in water. The time courses of pH, conductivity and inactivation efficiency were determined in a hybrid gas-liquid reactor. The obtained results showed that the pH decreased from 6.9 to 4 within 15 min of (AC or pulsed) electrical discharges. By compared with a set of comparative experiment, the inactivation of E. coli is mainly contributed by electrical discharges but not by the low pH solution. On the other hand, buffer solutions (carbonate and phosphate) could reduce the inactivation efficiency due to consumption of chemically active species formed in electrical discharges. This study also found that the plasma-treated water has the residual inactivation ability to kill E. coli, and E. coli might own the environmental adaptation ability to electrical discharges. Either ultrasound (US) or plasma discharge is capable of inactivation of microorganisms in liquid phase. A novel method by combining these two techniques or calls ultrasound-assisted plasma (USaP) is proposed. Extensive experimental tests were carried out with two kinds of electrode layout (submerged and hybrid reactors), aeration or not, and two microorganisms E. coli and yeast. For a submerged reactor without aeration, the inactivation efficiency achieved with USaP (?USaP) is not only greater than ?US or ?plasma, but also greater than the summation of ?US and ?plasma. In other words, a synergistic effect was observed. It is also noted that synergistic effect was neither observed in hybrid reactor nor in aeration cases. Synergism mechanism is speculatively in virtue of the bubbles generated by ultrasound which lead plasma discharges easily induced in water.
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