Abstract
Abstract A lot of human activities have negative impact on water quality and sometimes result in the biological water contamination. Currently used chemical (chlorine, ozone, and etc.) and physical (UV) water disinfection methods have strong environmental disadvantages or suffers from limited efficiency. To overcome these problems, scientists suggest to use photocatalyst activated advanced oxidation processes. One of the most studied photocatalysts which attracts a lot of research interest is titanium dioxide. TiO2 application for the disinfection of water, air or surfaces is increasingly encouraged by researchers. However, to unlock its full potential it is highly desirable to make it suitable for the visible light activation. In the current study the effect of visible light assisted photocatalytic treatment to the outer membrane permeability of Salmonella enterica bacteria and how it changes under different titanium dioxide concentrations was analysed. The results from the treatment of relatively complex Salmonella enterica bacteria organism were compared to the visible light activated TiO2 ability to oxidise considerably simpler objects like methylene blue molecules. The efficiency of TiO2 photocatalytic disinfection process was evaluated using spread plate technique. Membrane permeability of the treated Salmonella enterica bacteria was determined by NPN uptake factor assay. Generation of intracellular reactive oxygen species was evaluated by Dichlorodihydrofluorescein diacetate fluorescence measurements. The key finding of this study was that intense wide spectrum visible light irradiation and TiO2 powder synergistically inactivate S. enterica bacteria and halt its potential to form colonies. High amounts of intracellular reactive oxygen species could be seen as the main suspects for the observed inactivation of S. enterica.
Highlights
The world is changing rapidly due to fast economic growth, industrial development and increasing population
The obtained results indicated that UV light increased the uptake of NPN by more than two times (Fig. 1A), visible light and titanium dioxide just by half of that
It should be noted, that UV light decreased the ability of bacteria to form colonies by approximately 20–30 %, while the NPN uptake to the cells treated by UV light was the highest amongst all tested samples
Summary
The world is changing rapidly due to fast economic growth, industrial development and increasing population. Lakes and rivers are the major sources of drinking water. Many of human activities have negative impacts on these water sources and result in the water contamination. Around the world one out of three people or 2.2 billion people in total lack safe drinking water [1] and one of the main causes is water contamination by pathogenic microorganisms and viruses. Sedimentation, filtration and other water treatment methods are routinely used to remove solid and chemical contaminants. Along with these contaminants some microorganisms are separated. There are some specific methods to remove microorganisms from the water and they are known as disinfection methods
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