Disinfection of wastewater by a complete equipment based on a novel ultraviolet light source of microwave discharge electrodeless lamp: Characteristics of bacteria inactivation, reactivation and full-scale studies

• Published in: The Science of the total environment 2024-03, Vol.917, p.170200-170200, Article 170200
• Main Authors: Wang, Jun-Jie, Zhou, Yun-Yi, Xiang, Jue-Lin, Du, Hai-Sheng, Zhang, Jin, Zheng, Ti-Gang, Liu, Min, Ye, Ming-Qi, Chen, Zhuo, Du, Ye
• Format: Article
• Language: English
• Subjects: Disinfection; Escherichia coli; Full-scale application; Microwave discharge electrodeless lamp; Microwave ultraviolet; Microwaves; Ultraviolet Rays; Wastewater
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2024.170200

Ultraviolet (UV) light is widely used for wastewater disinfection. Traditional electrode-excited UV lamps, such as low-pressure mercy lamps (LPUV), encounter drawbacks like electrode aging and rapid light attenuation. A novel UV source of microwave discharge electrodeless lamp (MDEL) has aroused attention, yet its disinfection performance is unclear and still far from practical application. Here, we successfully developed a complete piece of equipment based on MDELs and achieved the application for disinfection in wastewater treatment plants (WWTPs). The light emitted by an MDEL (MWUV) shared a spectrum similar to that of LPUV, with the main emission wavelength at 254 nm. The inactivation rate of Gram-negative E. coli by MWUV reached 4.5 log at an intensity of 1.6 mW/cm2 and a dose of 20 mJ/cm2. For Gram-positive B. subtilis, an MWUV dose of 50 mJ/cm2 and a light intensity of 1.2 mW/cm2 reached an inactivation rate of 3.4 log. A higher MWUV intensity led to a better disinfection effect and a lower photoreactivation rate of E. coli. When inactivated by MWUV with an intensity of 1.2 mW/cm2 and a dose of 16 mJ/cm2, the maximum photoreactivation rate and reactivation rate constant Kmax of E. coli were 0.63 % and 0.11 % h−1 respectively. Compared with the photoreactivation, the dark repair of E. coli was insignificant. The full-scale application of the MDEL equipment was conducted in two WWTPs (10,000 m3/d and 15,000 m3/d). Generally 2–3 log inactivation rates of fecal coliforms in secondary effluent were achieved within 5–6 s contact time, and the disinfected effluent met the emission standard (1000 CFU/L). This study successfully applied MDEL for disinfection in WWTPs for the first time and demonstrated that MDEL has broad application prospects. [Display omitted] •The developed MDEL module and equipment emitted similar spectra to LPUV.•MDEL can effectively inactivated Gram-negative E. coli and Gram-positive B. subtilis.•A stronger MWUV light intensity led to a lower photoreactivation degree of E. coli.•Fecal coliforms in wastewater disinfected by the MDEL met the emission standards in full-scale studies.