Investigation of baffle configurations on the water disinfection efficiency using ultraviolet C light-emitting diodes

In this study, the effect of baffle configuration on the water disinfection efficiency of a planar photoreactor equipped with ultraviolet C light-emitting diodes (UV-C LEDs) was investigated. The results indicated that the configuration of the baffles influenced the hydrodynamics inside the flow channel and thus affected the microbial trajectory, and exposure time. Accordingly, a modified serpentine configuration was developed to enhance the UV light exposure of microbes in water and improve the reactor performance for microbial inactivation. According to the simulation results, the quarter-circle baffles used in the modified serpentine configuration increased the microbial path length along the flow channel. However, because the cross-sectional area of the flow channel decreased, this configuration increased the water velocity. A modified serpentine configuration with a baffle radius of 5 mm achieved the longest microbial exposure time and highest inactivation value for Escherichia coli. At a water flow rate of 160 mL/min, this configuration achieved a UV fluence of 15.2 mJ/cm² and an inactivation value of 3.8 log, which were approximately 22% and 0.4 log higher than those obtained with the traditional serpentine configuration, respectively. In addition, the maximum water flow rate at which the UV reactor achieved an inactivation value of 4.0 log was 154 mL/min at a baffle radius of 5 mm. This flow rate was 11.5% higher than that obtained with the traditional serpentine configuration. These close agreements between the experimental and simulation results confirmed the strong capability of the proposed modified serpentine configuration to improve reactor performance.