Disinfection of municipal secondary effluents with microwave-induced electrodeless ultraviolet irradiation for water reuse

Abstract

BACKGROUND: Disinfection is an essential way to ensure the safety of recycled water. Ultraviolet (UV) is an effective and environmentally friendly technique suitable for the disinfection of recycled water. However, UV disinfection also leads to photoreactivation. This work proposes a combined use of UV irradiation and microwave technique to compensate for the limitations of UV disinfection. RESULTS: The process of microwave-induced electrodeless ultraviolet (MW-EUV) irradiation was utilized to disinfect municipal secondary effluents. A homemade columnar electrodeless UV lamp was used as the source of UV irradiation. Good disinfection results under optimal microwave power at 600 W were obtained. There was no photoreactivation after sufficient irradiation. Cell damage to Escherichia coli by MW-EUV irradiation was investigated by measuring the leakage of K + and protein from cells and was observed by atomic force microscopy (AFM).CONCLUSION: The MW-EUV irradiation was demonstrated to be a faster and more effective disinfection method than UV or microwave irradiation alone. The irradiated samples met the hygiene standard for the reuse of urban recycling water (Standard Number GB/T 18920-2002) in China. Disinfection depended mainly on UV irradiation, while microwaves were the main cause of bacterial breakup and deformation. This irreversible damage offsets the biological self-healing phenomenon of UV disinfection.

A Review and Perspective of Environmental Disinfection Technology Based on Microwave Irradiation

“…With the continuous development of microwave disinfection technology, it has been widely used in food, solid, and water bodies, and a small amount of researches on air disinfection. Besides, microwave irradiation, as a physical field, can act synergistically with other disinfection techniques, such as UV irradiation and ozone disinfection [ 13 , 15 ]. The heating rate of sample by microwave is an important factor that may be limiting the application of microwave disinfection technology if the sample has a weak absorbing ability of microwave, such as airborne media.…”

“…For example, in order to compensate the shortcoming of UV disinfection, a combined disinfection with microwave and UV irradiation was proposed to disinfect municipal secondary effluents. The evaluated parameters influencing disinfection included microwave power, irradiation duration, and UV light intensity [ 13 ]. By combining microwave irradiation with the chemical disinfection method to treat siloxane impression material, the highest antimicrobial efficacies were shown without adverse effects on the material itself [ 14 ].…”

A new structure of microwave‐driven UV lamp

“…The disposal of sewage is a worldwide concern, while UV light sterilization has been demonstrated an environmentally friendly sewage treatment method. In 2017, Zhang et al conducted relevant research on ultraviolet sterilization treatment of urban secondary sewage, and the treated water was reused 2 . As a special light source, UV lamps have been widely used in various aspects of human life and industry 3‐6 .…”