Inactivation effect and mechanisms of combined ultraviolet and metal-doped nano-TiO 2 on treating Escherichia coli and E
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RESEARCH ARTICLE
Inactivation effect and mechanisms of combined ultraviolet and metal-doped nano-TiO2 on treating Escherichia coli and Enterococci in ballast water Xixi Wang 1 & Yanli Huang 1 & Kun Zhang 1 & Yue Shi 1 & Zheng Lu 1 & Yinhao Wang 1 Received: 8 December 2019 / Accepted: 6 July 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The discharge of ship ballast water (containing large amounts of alien organisms) has caused severe ecological hazards to marine environments. In this study, three metal elements (Ag, Fe, and Gd) were doped to nano-TiO2 material respectively (content: 0.4%, 0.7%, and 1.0%) to improve inactivation effect of Escherichia coli and Enterococci in ballast water. Experimental results indicate that compared with the sole ultraviolet (UV) and the UV and original nano-TiO2, the UV and metal-doped nano-TiO2 increased the bacterial inactivation rate to different extents. For each metal element, high external metal content (1.0%) corresponded to high inactivation effort. The doping of Ag resulted in optimal inactivation effort, and the addition of Fe and Gd caused unobvious effort. At the end of the inactivation process (20 s), the UV and 1% Ag-doped nano-TiO2 reached the highest logarithmic sterilization rates (0.915 for Escherichia coli and 0.805 for Enterococcus). The doping of Ag, Fe, and Gd did not change the anatase phase TiO2 crystal form, and 1% Ag-doped nano-TiO2 had the smallest particle diameter and the evenest distribution of nanoparticles. Compared with the sole UV, the UV and Ag-doped nano-TiO2 treatment resulted in higher malondialdehyde contents (0.0646 μmol/L for Escherichia coli and 0.0529 μmol/L for Enterococci) and lower superoxide dismutase activities (0.672 U/mL for Escherichia coli and 0.792 U/mL for Enterococci), which were in accordance with high inactivation rates in these cases. Keywords Ship ballast water . Metal-doped nano-TiO2 . Inactivation . Material characteristics . Malondialdehyde (MDA) . Superoxide dismutase (SOD)
Introduction With the prosperity of shipping industry, the discharge of ship ballast water has become a serious threat to marine ecological environment. It is estimated that about 10 billion tons of ballast water are transferred worldwide each year, resulting in unexpected introduction of non-indigenous organisms to their new habitat. Once the alien organisms (such as microalgae and bacteria) adapt to the new environmental conditions, their Responsible Editor: Sami Rtimi * Kun Zhang [email protected] * Yue Shi [email protected] 1
College of Power and Energy Engineering, Harbin Engineering University, Harbin 150001, China
proliferation might lead to severe ecological disaster, such as algal blooms. In addition, many researches indicated that heterotrophic microorganisms (bacteria, viruses, etc.) could be introduced into uncontaminated areas by ship ballast water, posing a potential hazard to human health (Leichsenring and Lawrence 2011; Seiden et al. 2010). The International Maritime Organization (IMO) has set st
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