Advanced Treatment of Campus Sewage...
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2 Theory Basis of MV/UV/O 3 Disinfection Technology
When adapting MV/UV/O 3 process for disinfection, the microwave is used to excite
the electrodeless UV lamp which was surrounded in the microwave field. The excited
UV light irradiates the air to generate a trace of ozone, and that could be combined
with UV light for disinfection. The disinfection mechanisms of MV/UV/O 3 involved
the bactericidal action of microwave, UV irradiation, and ozonation as well as the
strong oxidation of hydroxyl radical (·OH) produced by UV/O 3 process (Fu et al.
2009; Larson and Marifias 2003). OH is one of the most reactive and nonselective
species and can react at high rates with almost any organic substances (Sun et al.
2018; Zeng et al. 2009).
2.1 Microwave Action
Microwave is a kind of electromagnetic radiation with a wavelength ranging from
1 mm to 1 m and a frequency between 300 MHz and 300 GHz. The sterilization function of microwave is resulted from the thermal effect and nonthermal effect as well
as other factors. Microwaves have shorter wavelengths and higher frequencies, and
when they go through the medium, some polar molecules such as water, protein, and
nucleic acid are about to move with the changes of alternating electric field (AEF),
thereby generating quite an amount of friction heat (Fu et al. 2010a). And as a result,
the temperature of the medium raises which results in structural change and inactivation of protein and nucleic acid molecules. At the same time, the polar molecules in
microbes including protein, nucleic acid, and water will rotate and vibrate at a high
frequency due to the change of microwave polarity in the strong electric field, which
result in the denaturation of protein molecules and killing microorganisms (Mima
et al. 2008).
2.2 UV Light Action
The UV light disinfection is relatively a complicated process. It mainly kills microorganisms (i.e., bacteria, viruses, spores, and other pathogens) by activating radiation
damage to nucleic acids. UV irradiation on nucleic acids can lead to interference with
the biological activity of DNA, when breaking the chemical bonds and crosslinking
between DNA strands. The alteration in the chemical structure of DNA results in
errors during DNA replication, which causes mutation or disinfection to microorganism (Hu et al. 2005; Oguma et al. 2002, 2004). The advantages of UV disinfection
include non-chemicals input, or not increasing the effluent smell, no disinfection
byproducts (DBPs), high efficiency of disinfection and easy operation. However, the
main disadvantages are large consumption of electricity, and high cost of routinely
247
2 Theory Basis of MV/UV/O 3 Disinfection Technology
When adapting MV/UV/O 3 process for disinfection, the microwave is used to excite
the electrodeless UV lamp which was surrounded in the microwave field. The excited
UV light irradiates the air to generate a trace of ozone, and that could be combined
with UV light for disinfection. The disinfection mechanisms of MV/UV/O 3 involved
the bactericidal action of microwave, UV irradiation, and ozonation as well as the
strong oxidation of hydroxyl radical (·OH) produced by UV/O 3 process (Fu et al.
2009; Larson and Marifias 2003). OH is one of the most reactive and nonselective
species and can react at high rates with almost any organic substances (Sun et al.
2018; Zeng et al. 2009).
2.1 Microwave Action
Microwave is a kind of electromagnetic radiation with a wavelength ranging from
1 mm to 1 m and a frequency between 300 MHz and 300 GHz. The sterilization function of microwave is resulted from the thermal effect and nonthermal effect as well
as other factors. Microwaves have shorter wavelengths and higher frequencies, and
when they go through the medium, some polar molecules such as water, protein, and
nucleic acid are about to move with the changes of alternating electric field (AEF),
thereby generating quite an amount of friction heat (Fu et al. 2010a). And as a result,
the temperature of the medium raises which results in structural change and inactivation of protein and nucleic acid molecules. At the same time, the polar molecules in
microbes including protein, nucleic acid, and water will rotate and vibrate at a high
frequency due to the change of microwave polarity in the strong electric field, which
result in the denaturation of protein molecules and killing microorganisms (Mima
et al. 2008).
2.2 UV Light Action
The UV light disinfection is relatively a complicated process. It mainly kills microorganisms (i.e., bacteria, viruses, spores, and other pathogens) by activating radiation
damage to nucleic acids. UV irradiation on nucleic acids can lead to interference with
the biological activity of DNA, when breaking the chemical bonds and crosslinking
between DNA strands. The alteration in the chemical structure of DNA results in
errors during DNA replication, which causes mutation or disinfection to microorganism (Hu et al. 2005; Oguma et al. 2002, 2004). The advantages of UV disinfection
include non-chemicals input, or not increasing the effluent smell, no disinfection
byproducts (DBPs), high efficiency of disinfection and easy operation. However, the
main disadvantages are large consumption of electricity, and high cost of routinely