This device utilizes ultraviolet light with a wavelength range of 225-275nm, peaking at 254nm, which has a strong germicidal effect to achieve disinfection. When water flows through the treatment chamber, it is irradiated by UV light, effectively killing bacteria present in the water. A flow transmitter converts the collected flow signal into a standard analog signal, which is then input into the analog input unit of a programmable logic controller (PLC). The PLC compares and calculates the received analog signal to determine the appropriate number of UV lamps to activate based on the flow rate. This product is suitable for small-scale domestic water supply systems using rivers, lakes, ponds, or well water as the source—especially for systems with elevated water tanks or standby reservoirs. It is also applicable for water disinfection in the food, beverage, brewing industries, as well as swimming pools.