Effect of UV-C LED arrangement on the sterilization of Escherichia coli in planar water disinfection reactors

Abstract

In this study, a planar UV reactor with five distinct UV-C LED arrangements was proposed to treat drinking water. The particle tracing method combined with computational fluid dynamics were used to simulate water velocity field, microbial trajectory and residence time. The ray tracing method was used to determine the irradiance distribution in water. The simulated variables were then integrated to determine the distribution of fluence in water. Both experimental and theoretical results among the five distinct UV light modules used in this study, turn-enhanced emission exhibited the highest efficiency in sterilizing Escherichia coli owning to the synergic effect of hydrodynamics and UV radiation. Turn-enhanced emission combined with turn-induced secondary flow effectively improved the reactor performance. At a flow rate of 300 mL/min, turn-enhanced emission resulted in an inactivation value of 4.56 log, which was approximately 0.90, 0.82, 0.84, and 2.41 log higher than the values obtained with top, staggered, lined, and side emission, respectively. According to the particle count and cumulative count of the fluid particles, turn-enhanced emission effectively enhanced the UV fluence to which microbes in water were subjected. In conclusion, optimal combinations of LED arrangements and channel configurations effectively improve the sterilization efficiency of UV reactors.