Organic Micropollutant Wastewater Treatment using a DBD Plasma and Flat 222 nm Far UV-C Excilamp

Conventional low-pressure UV (LP-UV) lamps emit light with a wavelength of 254 nm, which is efficient in deactivation of microorganisms but can also be harmful to the skin and eyes upon exposure. In contrast, KrCl* excimer lamps emit ultraviolet (UV) light in the far-UVC range, specifically between 200 and 222 nanometers (nm). These lamps have been demonstrated to successfully eliminate harmful microorganisms without posing a risk of harming human cells. Several studies have been published that provide evidence that far-UVC is a safer option for human exposure and more efficient in terms of disinfection than LP-UV  [1]  [2]. Nevertheless, few studies have examined the utilization of KrCl* excimer lamps for UV/advanced oxidation processes (AOPs)  [3].

In this study, two organic micropollutants have been degraded by means of an environmentally friendly mercury-free far UV-C excimer light source along with an advanced oxidation process (AOP) using H₂O₂. For this purpose, a dielectric barrier discharge (DBD) plasma-based 222 nm wavelength excilamp has been designed and developed. The production of OH radicals in three different Advanced Oxidation Process (AOP) systems—LP-UV/H₂O₂, KrCl*/H₂O₂, and KrCl*/nitrate—was then compared. The results indicate that the UV/nitrate combination exhibited the highest level of steady-state OH concentration, followed by KrCl*/H₂O₂, and then LP-UV/H₂O₂. Additionally, we examined the differences in contaminant degradation for carbamazepine and sulfamethoxazole between KrCl* excimer lamps and low-pressure ultraviolet (LPUV) lamps. The findings show that, in comparison to LP-UV treatment, direct photolysis employing KrCl* excimer lamps significantly improves the degradation rate constants of carbamazepine and sulfamethoxazole. This improvement is likely due to a molar absorption coefficient that is more prominent at 222 nm rather than 254 nm. Compared to KrCl* excimer direct photolysis, KrCl*/AOP demonstrated improved degradation of carbamazepine; however, it did not increase the degradation of sulfamethoxazole. The analysis of this study will be presented.