Influence of aspect ratios on water disinfection efficiency in a serpentine flow channel using ultraviolet C light-emitting diode

The flow channel configuration affects microbial inactivation efficiency in water because it considerably influences hydrodynamics and ultraviolet (UV) light distribution. The ratio of channel length to breadth (α) and the ratio of channel width to depth (β) of a serpentine flow channel on <i>Escherichia coli</i> inactivation efficiency were investigated. Simulations revealed that when α was 1.0, the flow channel had a uniform velocity distribution and performed the longest microbial residence time. Furthermore, biodosimetry tests indicated that when β was 1.0, the reactor resulted in a maximum inactivation efficiency of 3.7 log when the distance between the UV LEDs and the water was 11.5 mm. The optimal aspect ratio β led to the ideal balance between microbial residence time and UV irradiance, resulting in the highest UV fluence (10.6 mJ/cm²) for the bacteria. The inactivation efficiency observed at the aforementioned aspect ratio was approximately 48% higher than that observed at an aspect ratio of 2.56. Additionally, decreasing the distance between the UV LEDs and the water from 11.5 to 3.5 mm enhanced the inactivation efficiency at all aspect ratios because of the considerable increase in UV irradiance in the water.