Efficiency improvement of batch reactors for water sterilization using UV-C LED arrays.

The UV-C light emitting diode (LED) has shown numerous advantages over the traditional UV mercury lamp for water sterilization applications. Multi-chip LED array was used to provide sufficient UV fluence for bacteria inactivation in limited time. According to the point light source characteristic of LEDs, the arrangement of LEDs in the batch reactor is crucial to optimize the inactivation efficiency. In this study, the inactivation of Escherichia coli (E. coli) was investigated using the 280 nm UV-C LED array. Input electrical power, chip interspace (L) and distance (D) between the reactor and water surface were analysed in terms of their effects on the inactivation of the microorganisms. An optimal inactivation efficiency of E. coli was obtained under the condition of L = D=25 mm to reach 4.0 log without using a magnetic stirrer. Additionally, the increasing rate of log inactivation of E. coli decreased with input power due to the significant decrease of wall plug efficiency of the UV-C LEDs.