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| Water disinfection of E. coli by pulsed low electric fields |
| KOU Yan-qin1, ZHENG Chao1,2, XU Yu-zhen1, HUANG Yi-fan1, LIU Zhen1, YAN Ke-ping1 |
| 1. Key Laboratory of Biomass Chemical Engineering of Ministry of Education, Zhejiang University, Hangzhou 310027, China; 2. Zhejiang Institute of Medical Device, Hangzhou 310009, China |
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Abstract Water disinfection of E. coli by high frequency pulsed low electric fields was investigated. The effects of constructional, electrical and aqueous parameters on disinfection efficiency and energy efficiency were evaluated. Experiments were performed with a 500 mL cylindrical reactor. Average electric intensity of 3-12 kV/cm was applied and pulsed frequency was up to 20 000 Hz. Optimized structure of high voltage electrode were six equally distributed mesh electrodes with diameter of 40 mm. Both the disinfection efficiency and energy efficiency were enhanced by increasing the electric strength and pulse duration. Water conductivity could influence the pulsed waveforms and single pulse energy, which changed the disinfection results. Reducing the initial bacterial density made the process more effective and easily realized sterilization. Pulsed frequency did not show any effect on disinfection, but high frequency could greatly reduce treatment time. When pulsed voltage, pulsed width, water conductivity and initial bacteria density were 6 kV, 30 μs, 2.5 μS/cm and 103-106 cfu/mL, respectively, 1-2 logarithmic reduction were obtained with energy consumption less than 200 J/mL and water temperature lower than 40 ℃. If initial bacterial density was less than 1 250 cfu/mL, all the cells could be sterilized, which was a non-thermal processing.
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Published: 01 April 2015
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低场强脉冲电场杀灭水中大肠杆菌的实验研究
采用高频低场强脉冲电场系统对水中的大肠杆菌进行灭菌研究,探索反应器结构、电气参数及水质参数等对脉冲电场灭菌效率和能量效率的影响.圆筒式反应器体积为500 mL,平均脉冲场强为3～12 kV/cm,脉冲频率可以高达20 kHz.最佳高压电极结构为6层均匀分布的直径为40 mm的网电极.脉冲电场的杀菌效率和能量效率随着脉宽和场强的增大而提高,水的电导率影响波形和单脉冲能量的变化,从而影响杀菌效果,当初始细菌密度降低时有利于彻底杀光.脉冲频率对杀菌无明显影响,但高频率能够大幅缩短处理时间.当脉冲电压为6 kV,脉宽为30 μs,水的电导率为2.5 μS/cm,细胞初始密度为103～106 cfu/mL时,在消耗能量<200 J/mL,水温<40 ℃的前提下,脉冲电场处理后细菌密度下降了1、2个对数.当细菌初始密度低于1 250 cfu/mL时,细菌被全部杀光,实现了非热低温灭菌.
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