二氧化氯后接游离氯顺序消毒对大肠杆菌的灭活研究

Sequential inactivation of Escherichia coli with low concentration of chlorine dioxide followed by free chlorine

摘要：目的探究低浓度二氧化氯预处理对游离氯灭活大肠杆菌的协同机制，为改进现有消毒工艺，提高消毒效果提供理论依据。方法以大肠杆菌为指示生物，磷酸盐缓冲液为介质，二氧化氯及游离氯为消毒剂，分别研究单一消毒剂消毒（0．005—0．05mg／L二氧化氯作用30min或0．05mg／L游离氯作用120min）、顺序消毒（0．02mg／L二氧化氯作用5min，0．5mg／L游离氯作用120min）、传统顺序消毒（0．02mg／L二氧化氯作用5min后，离心重悬，0．5mg／L游离氯作用120min）以及混合消毒方式（同时加入0．02mg／L二氧化氯和0．5mg／L游离氯作用120min）对大肠杆菌的杀灭效果。结果大肠杆菌的细胞壁通透性在0．02mg／L二氧化氯作用后增加，但其可培养性未见改变。在pH7．1、20℃条件下，CT值小于0．46mg／L·min时，灭活大肠杆菌的效果依次为：顺序消毒〉传统顺序消毒〉混合消毒〉单一消毒；而当CT值大于0．46mg／L·min时，消毒效果依次为顺序消毒〉混合消毒〉传统顺序消毒〉单一消毒。当CT值大于1．4mg／L·min时，顺序消毒、传统顺序消毒以及混合消毒方式的消毒效果无明显改变。顺序消毒灭活大肠杆菌效果随温度升高而升高；在酸性及中性条件下对大肠杆菌的灭活效果差别不明显，但都强于碱性条件下的消毒效果。结论低浓度二氧化氯的作用增加了大肠杆菌细胞壁通透性，从而加快了后续游离氯进入细胞内的速率，提高了对大肠杆菌的灭活效果。

Objective To explore the synergistic effects of low concentrations of chlorine dioxide on the inactivation of E. coli by chlorine,and to provide a theoretical supports for the improvement of the existing disinfection process and the disinfection effect. Methods E.coli was selected as a model microbial,phosphate buffer as the media,chlorine and chlorine dioxide as disinfectants and four disinfection procedures,such as sequential disinfection （SD, 5 min for 0.02 mg/L chlorine dioxide following by 120 rain for 0.5 mg/L free ehlorine）,traditional sequential disinfection （TSD, centrifugation and resuspendation for E.coli after 5 mix for 0.02 mg/L chlorine dioxide and following treated by 0.5 mg/L free chlorine for 120 min）,mixed disinfectants disinfection （MDD, 120 mix for 0.5 mg/L free chlorine and 0.02 mg/L free chlorine dioxide） and single step disinfection （SSD, 30 mix for 0.005-0.05 mg/L chlorine dioxide or 120 mix for 0.02 mg/L chlorine dioxide） were investigated for the disinfection effects. Results The disinfection ability was SD〉TSD〉MDD〉SSD in the first 0.46 mg/L.min at pH 7.1,20 ℃ and SD〉MDD〉TSD〉SSD after 0.46 mg/L-min,no difference of disinfection efficiency was found among MDD,TSD and SD procedures after 1.4 mg/L.min,it is also observed ONPG hydrolysis rate increased to （148.0-＋8.9） nmol/（min-mg cell dry weight） from （52.7±6.5） nmol/（min.mg cell dry weight） within 5 rain, but no viability changes under 0.02 mg/L ClO2 treatment. The SD inactivation efficiency increased with increasing temperature,but the effect of pH on E.coli inactivation was inconclusive ,a neglectable difference was observed between neutral and acid conditions, the effects at which were better than that at alkaline condition. Conclusion The E.coli cell wall permeability increases under the treatment by low concentration of chlorine dioxide,which enhance the transfer rate of chlorine into E.coli cell, and so results in a higher E.coli inactivation effect.