Abstract
In the actual water environment, the health risk of waterborne viruses is evaluated to be 101–104 times higher at a similar level of exposure compared with bacteria and has aroused strong concern in many countries in the world. Photocatalytic membrane reactor (PMR), a new process for virus inactivation in water, has gradually become one of the main tools to inactivate pathogenic organisms in water. However, there is relatively little attention to the effect of natural organic matters (NOMs) on the PMR system, which actually exists in the water environment. In this paper, the TiO2-P25, a common type in sales and marketing, was selected as the photocatalyst, and humic acid was regarded as the representative substance of NOMs for investigating thoroughly the influence of humic acid on virus removal by the PMR system. It was found that competitive adsorption between the virus and humic acid occurred, which markedly reduced the amount of virus adsorbed on the surface of the photocatalyst. Moreover, with humic acid, the direct contact behavior between the virus and the photocatalyst was blocked to some extent, and the disinfection of phage f2 by the active free radicals produced by photocatalysis was furthermore badly affected. Meanwhile, the special structure of humic acid, which made humic acid be able to absorb light of 270–500 nm, led to the reduction of photocatalytic efficiency. Further experiments showed that when there was a certain concentration of humic acid in water, intermittent operation mode or higher membrane flux (>40 L/(m2·h)) was selected to partly alleviate the adverse effects of humic acid.
Highlights
Pathogens causing waterborne diseases usually include bacteria, viruses, protozoans, and parasitic worms
The adsorption process is usually related to the photocatalysts and happens firstly after the pollutants entering the Photocatalytic membrane reactor (PMR) system
The adsorption efficiency of TiO2 -P25 on phage f2 decreased in the presence of humic acid, possibly due to the competition of adsorption sites between humic acid and phage f2 in the PMR
Summary
Pathogens causing waterborne diseases usually include bacteria, viruses, protozoans, and parasitic worms. In the actual water environment, there are noxious bacteria and viruses, even though the number of virus or bacteria in drinking water is generally low, they can pose tremendous risks to human health [2,3]. In the developing countries, the supplies of drinking water are extremely scare, resulting in a higher risk of waterborne-disease transmission [4]. The health risk of waterborne viruses, in particular, is evaluated to be 101 –104 times higher at a similar level of exposure compared with bacteria and has aroused strong concern in many countries around the world [5]. The current disinfection processes, such as chlorination, ozone, and ultraviolet disinfection, can be used to remove virus to a certain extent in drinking water, but harmful disinfection by-products of chlorination, including three trihalomethanes, haloacetic acid, bromate, and strong carcinogens
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