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S. Gong et al.
maintaining UV lamps and quartz bushings. Besides, the UV treatment may lose its
edge in sustained disinfection when treating high-level turbidity wastewater (Cecili
and Claudio 2003; Shaban et al. 1997). UV disinfection method adapted to water
treatment was firstly applied in the United States. In 1970, the US Environmental
Protection Agency (EPA) completed a first project of treating sewage by UV irradiation. And then, UV disinfection in sewage treatment has been widely used in the
United States and Canada. Up to now, there are approximately 4000 large-scaled
systems of UV disinfection having been installed in sewage treatment plants in western developed countries, accounting for about 10% of the total number of sewage
treatment plants (Hijnen et al. 2006; Jolis et al. 1999; Liberti et al. 2000).
2.3 Ozone Action
Ozone is an inorganic molecule with the chemical formula O 3 . It is a pale blue gas
with a distinctively pungent smell. Studies have shown that ozone can be applied to
removal of organic contaminants and inactivation of bacteria and virus due to comprehensive effect of physical, chemical, and biological actions. The related mechanisms
can be summarized as follows: (1) Ozone can oxidize and decompose the glucose
oxidase which is necessary for oxidizing glucose in bacteria, and it can directly
interact with bacteria and viruses, destroying cells and ribonucleic acids, decomposing DNA, RNA, protein, and macromolecules such as fats and polysaccharides,
interfering metabolic process, and reproduction of bacteria; (2) ozone can penetrate
the membrane of cells and invade the outer membrane lipoprotein and the internal
lipopolysaccharide, causing aberration and lysis of the cells (Cooper and Burch 1999;
Larson and Marifias 2003; Wen et al. 2018). Ozone is formed from dioxygen by the
action of UV irradiation. The advantage of utilizing UV light to produce ozone is
that the method is not sensitive to humidity or temperature. Besides, the concentration and yield of ozone can be controlled linearly by UV power. However, the
disadvantage is that the amount of ozone is so small, and the current electro-optical
conversion rate of UV irradiation is ≤15% with the 185 nm wavelength producing
the higher level of ozone (Al-Shamma’a et al. 2001).
2.4 Synergistic Combination of UV and Ozone
Ozone can produce ·OH with extremely strong oxidation ability under the irradiation
of UV light emitted by an electrodeless UV device (Fu et al. 2009), then enhancing
sterilization and algae-inactivation.
S. Gong et al.
maintaining UV lamps and quartz bushings. Besides, the UV treatment may lose its
edge in sustained disinfection when treating high-level turbidity wastewater (Cecili
and Claudio 2003; Shaban et al. 1997). UV disinfection method adapted to water
treatment was firstly applied in the United States. In 1970, the US Environmental
Protection Agency (EPA) completed a first project of treating sewage by UV irradiation. And then, UV disinfection in sewage treatment has been widely used in the
United States and Canada. Up to now, there are approximately 4000 large-scaled
systems of UV disinfection having been installed in sewage treatment plants in western developed countries, accounting for about 10% of the total number of sewage
treatment plants (Hijnen et al. 2006; Jolis et al. 1999; Liberti et al. 2000).
2.3 Ozone Action
Ozone is an inorganic molecule with the chemical formula O 3 . It is a pale blue gas
with a distinctively pungent smell. Studies have shown that ozone can be applied to
removal of organic contaminants and inactivation of bacteria and virus due to comprehensive effect of physical, chemical, and biological actions. The related mechanisms
can be summarized as follows: (1) Ozone can oxidize and decompose the glucose
oxidase which is necessary for oxidizing glucose in bacteria, and it can directly
interact with bacteria and viruses, destroying cells and ribonucleic acids, decomposing DNA, RNA, protein, and macromolecules such as fats and polysaccharides,
interfering metabolic process, and reproduction of bacteria; (2) ozone can penetrate
the membrane of cells and invade the outer membrane lipoprotein and the internal
lipopolysaccharide, causing aberration and lysis of the cells (Cooper and Burch 1999;
Larson and Marifias 2003; Wen et al. 2018). Ozone is formed from dioxygen by the
action of UV irradiation. The advantage of utilizing UV light to produce ozone is
that the method is not sensitive to humidity or temperature. Besides, the concentration and yield of ozone can be controlled linearly by UV power. However, the
disadvantage is that the amount of ozone is so small, and the current electro-optical
conversion rate of UV irradiation is ≤15% with the 185 nm wavelength producing
the higher level of ozone (Al-Shamma’a et al. 2001).
2.4 Synergistic Combination of UV and Ozone
Ozone can produce ·OH with extremely strong oxidation ability under the irradiation
of UV light emitted by an electrodeless UV device (Fu et al. 2009), then enhancing
sterilization and algae-inactivation.