Field Test of Ultraviolet Light-Emitting Diode (UV-LED) Apparatuses as an Option of Decentralized Water Treatment Technologies

Assuming application in areas with difficulties in installing, maintaining and operating large-scale water supply systems, the effectiveness of decentralized systems was examined by a one-year field test of disinfection apparatuses equipped with ultraviolet light-emitting diodes (UV-LED) at a faucet supplying untreated water from a mountain stream. The untreated water was sporadically positive with Escherichia coli and had a high heterotrophic plate count (HPC) of bacteria exceeding the target value of drinking water, indicating the need of disinfection process for potable use. In UV-LED treated water, both the concentration and the positive ratio of bacteria decreased, and the maximum concentration of positive samples for E. coli, total coliforms, standard plate count and HPC were 0.5, 1.0, 6.0 and 485 CFU mL, respectively. One model of the UV-LED apparatus achieved all-negative detection of E. coli throughout the one-year test period. No apparatus showed any notable trend of performance deterioration for HPC inactivation with operation time, and scale formation was not apparent inside the body of the apparatuses after the test. This study shows the potential of UV-LED apparatuses as an option of decentralized water treatment technologies.