Microplasma UV lamp as a new source for UV-induced water treatment: Protocols for characterization and kinetic study

The newly emerged microplasma UV radiating technology can be a viable alternative to conventional radiation sources for UV water treatment. The capability of the microplasma UV lamp to monochromatically irradiate various wavelengths with different pulsation frequencies in a flat form opens new pathways for the development of novel UV-based water purifiers. This study is the first to systematically examine the microplasma UV lamp and develop a robust experimental method and apparatus for its operation to study the kinetics of both microbial and chemical pollutant degradation. The microplasma UV lamp was characterized in terms of its radiation profile and the impact of operating parameters on the lamp radiant power output. It was shown to be an instant-on and fast stabilized source. The radiant power output was a linear function of the electrical current and was not influenced by the lamp operating temperature and intermittent on/off cycles. A protocol was developed for obtaining reliable kinetic data for UV-induced elimination of microorganisms and micropollutants. An experimental setup was proposed for the kinetic studies, where the characteristics of the incident irradiance of the lamp, including uniformity, collimation, and divergence, were quantitatively evaluated. In addition, the water factor (WF) for calculating the average fluence rate was redefined for both the transient and steady state conditions. This modification is essential to account for changes in the UV transmittance of the medium, which could be an important factor for kinetic study of chemical contaminants. Two studied cases of microbial direct inactivation and the chemical photo-initiated oxidation process in different setups, based on the developed protocol, confirmed the reproducibility of the fluence-based kinetic data independent of the reactor size. The proposed protocol can be applied to the kinetic study of the elimination of microbial and chemical contaminants using microplasma UV lamps of any size, power, and peak wavelength.