Department of Biological and Agricultural Engineering, Texas A&M University, 375 Olsen Blvd, College Station, TX, 77843, USA.
Environ Sci Pollut Res Int. 2019 Apr;26(11):10790-10799. doi: 10.1007/s11356-019-04501-x. Epub 2019 Feb 18.
Novel and efficient animal wastewater treatment technologies of bacteria reduction are needed for preventing disease outbreak in animal herds and safeguarding environmental health. Zero-valent iron (ZVI) has been used to treat bacteria contaminated water for the past decades, but its passivation issue has been a major challenge. In this study, batch tests were performed to evaluate the effect of a hybrid zero-valent iron (h-ZVI) or a mixed ZVI/FeO media system on reduction of Escherichia coli (E. coli) levels. The h-ZVI media was created through a wet chemical process that uses nitrate to oxidize ZVI in the presence of externally added Fe (aq.). Transforming ZVI into a h-ZVI system could overcome the passivation of ZVI and increase the reactivity of the media. The results demonstrated that E. coli cells in the bulk phase were removed rapidly by h-ZVI media. Majority of E. coli was attached (or adsorbed) to the surface of h-ZVI media within a few minutes, which suggested that adsorption was the dominant mechanism for bacterial removal in the initial phase. This adsorption was confirmed by fluorescence microscopy with CTC-DAPI double staining and transmission electron microscopy (TEM). Increasing contact time steadily inactivated E. coli; all cells were inactivated after 120 min of contact. The TEM results indicated that h-ZVI inactivated E. coli by causing direct damage on bacterial cell membrane. The results of this study strongly suggest that h-ZVI treatment can be used in water treatment industry where bacterial contamination is concerned.
为了预防动物群中的疾病爆发和保护环境卫生，需要新型且高效的细菌减少型动物废水处理技术。数十年来，零价铁（ZVI）已被用于处理受细菌污染的水，但钝化问题一直是一个主要挑战。在这项研究中，进行了批量测试，以评估混合零价铁（h-ZVI）或混合 ZVI/FeO 介质系统对减少大肠杆菌（E. coli）水平的效果。h-ZVI 介质是通过湿法化学工艺创建的，该工艺使用硝酸盐在外部添加的 Fe(aq.)存在下氧化 ZVI。将 ZVI 转化为 h-ZVI 系统可以克服 ZVI 的钝化并提高介质的反应性。结果表明，h-ZVI 介质可迅速去除体相中的大肠杆菌细胞。大多数大肠杆菌在几分钟内被吸附到 h-ZVI 介质的表面上，这表明在初始阶段吸附是去除细菌的主要机制。这一吸附通过 CTC-DAPI 双重染色和透射电子显微镜（TEM）的荧光显微镜得到证实。接触时间的增加可稳定地使大肠杆菌失活；接触 120 分钟后，所有细胞均失活。TEM 结果表明，h-ZVI 通过直接破坏细菌细胞膜使大肠杆菌失活。这项研究的结果强烈表明，h-ZVI 处理可用于涉及细菌污染的水处理行业。
