Efficiency improvement of a flow-through water disinfection reactor using UV-C light emitting diodes

Abstract

In this study, the effects of irradiance distribution, outer radius (Ro), radiative power, and flow rate were investigated in a flow-through reactor using a 280 nm ultraviolet-C (UV-C) light emitting diodes (LEDs) to improve Escherichia coli (E. coli) inactivation efficiency. The length (L) and inner radius (Ri) of the reactor were 10 cm and 17 mm, respectively. The results demonstrated that the use of 24 LEDs offered the highest inactivation efficiency due to a significant improvement in irradiance uniformity under the same input power. An optimal log inactivation was obtained when Ro = 23 mm for the three UV-C LED arrays. An increase in Ro increases the exposure time but also significantly reduces average irradiance. Furthermore, the log inactivation decreased sharply as the flow rate was increased from 40 to 60 mL/min due to the significant decrement of exposure time. The reactor can achieve 4.0 log at a flow rate of 47 mL/min with an exposure time of 15.6 s at a radiative power of 10 mW. The inactivation rate constant K was obtained at 0.18 cm2/mJ for the two radiative powers in the fluence-response curve. The present results provide key implications for portable application of flow-through UV LED water disinfection reactor.