Water Research ( IF 11.4 ) Pub Date : 2023-08-26 , DOI: 10.1016/j.watres.2023.120531
Yu-Qing Xu 1 , Yin-Hu Wu 1 , Li-Wei Luo 1 , Bang-Hao Huang 1 , Zhuo Chen 1 , Hao-Bin Wang 1 , Han Liu 1 , Nozomu Ikuno 2 , Nakata Koji 2 , Hong-Ying Hu 3
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With the widespread use of chlorine disinfection, chlorine-resistant bacteria (CRB) in water treatment systems have gained public attention. Bacterial chlorine resistance has been found positively correlated with extracellular polymeric substance (EPS) secretion. In this study, we selected the most suitable CRB controlling method against eight bacterial strains with different chlorine resistance among chloramine, ozone, and ultraviolet (UV) disinfection, analyzed the resistance mechanisms, clarified the contribution of EPS to disinfection resistance, and explored the role of carbon source metabolism capacity. Among all the disinfectants, UV disinfection showed the highest disinfection capacity by achieving the highest average and median log inactivation rates for the tested strains. For Bacillus cereus CR19, the strain with the highest chlorine resistance, 40 mJ/cm2 UV showed a 1.90 log inactivation, which was much higher than that of 2 mg-Cl2/L chlorine (0.67 log), 2 mg-Cl2/L chloramine (1.68 log), and 2 mg/L ozone (0.19 log). Meanwhile, the UV resistance of the bacteria did not correlate with EPS secretion. These characteristics render UV irradiation the best CRB controlling disinfection method. Chloramine was found to have a generally high inactivation efficiency for bacteria with high chlorine-resistance, but a low inactivation efficiency for low chlorine-resistant ones. Although EPS consumed up to 56.7% of chloramine which an intact bacterial cell consumed, EPS secretion could not explain chloramine resistance. Thus, chloramine is an acceptable CRB control method. Similar to chlorine, ozone generally selected high EPS-secreting bacteria, with EPS consuming up to 100% ozone. Therefore, ozone is not an appropriate method for controlling CRB with high EPS secretion. EPS played an important role in all types of disinfection resistance, and can be considered the main mechanism for bacterial chlorine and ozone disinfection resistance. However, as EPS was not the main resistance mechanism in UV and chloramine disinfection, CRB with high EPS secretion were inactivated more effectively. Furthermore, carbon source metabolism was found related to the multiple resistance of bacteria. Those with low carbon source metabolism capacity tended to have higher multiple resistance, especially to chlorine, ozone, and UV light. Distinctively, among the tested gram-negative bacteria, in contrast to other disinfectants, chloramine resistance was negatively correlated with EPS secretion and positively correlated with carbon source metabolism capacity, suggesting a special disinfection mechanism.
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多种消毒方法灭活耐氯菌(CRB):耐药机制及其与碳源代谢的关系
随着氯消毒的广泛使用,水处理系统中的抗氯细菌(CRB)引起了公众的关注。已发现细菌耐氯性与细胞外聚合物 (EPS) 分泌呈正相关。在本研究中,我们针对氯胺、臭氧和紫外线(UV)消毒中8种不同耐氯性的细菌菌株选择了最合适的CRB控制方法,分析了耐药机制,阐明了EPS对消毒耐药性的贡献,并探讨了其作用碳源代谢能力。在所有消毒剂中,紫外线消毒显示出最高的消毒能力,对测试菌株实现了最高的平均和中值对数灭活率。对于蜡样芽孢杆菌CR19,耐氯性最高的菌株,40 mJ/cm 2 UV表现出1.90 log灭活,远高于2 mg-Cl 2 /L氯(0.67 log)、2 mg-Cl 2 /L 氯胺(1.68 log)和 2 mg/L 臭氧(0.19 log)。同时,细菌的抗紫外线能力与EPS分泌无关。这些特性使得紫外线照射成为最好的 CRB 控制消毒方法。发现氯胺对耐氯性高的细菌总体灭活效率较高,但对耐氯性低的细菌灭活效率较低。尽管 EPS 消耗了完整细菌细胞消耗的氯胺的 56.7%,但 EPS 的分泌并不能解释氯胺抗性。因此,氯胺是一种可接受的 CRB 控制方法。与氯类似,臭氧通常选择高EPS分泌细菌,EPS消耗高达100%的臭氧。因此,臭氧不是控制高EPS分泌的CRB的合适方法。EPS在各类消毒耐药中发挥着重要作用,可以认为是细菌对氯和臭氧消毒耐药的主要机制。然而,由于EPS并不是紫外线和氯胺消毒的主要耐药机制,因此EPS分泌量高的CRB被更有效地灭活。此外,碳源代谢被发现与细菌的多重耐药性有关。碳源代谢能力低的人往往具有较高的多重抵抗力,尤其是对氯、臭氧和紫外线的抵抗力。值得注意的是,在测试的革兰氏阴性菌中,与其他消毒剂相比,氯胺耐受性与EPS分泌呈负相关,与碳源代谢能力呈正相关,表明其具有特殊的消毒机制。