Performance evaluation of point-of-use UVC-LED water disinfection photoreactors using CFD and response surface methodology

Chlorination has been the traditional method of water disinfection. With the advent of new technologies and significant issues encountered in chlorination, physical methods gradually prevailed. Ultraviolet (UV) radiation technology is a physical disinfection method that has been improved rapidly in recent years. This technology, mainly based on UV mercury lamps, has excellent potential to inactivate microorganisms in water. However, UV lamps are fragile and may cause the leakage of mercury into the environment. As the extension of visible light emitting diodes (LED) progress in solid-state physics, the nature-friendly technology of UV-LEDs has emerged. This paper analyzes the performance of cylindrical water disinfection UV-LED photoreactors made of UV reflective materials using computational fluid dynamics (CFD). The response surface methodology (RSM) is used for shape optimization of the photoreactors working with one UV-LED at the flow rate of liter per minute (LPM). Typical configurations including the U-, L-, and S-shaped are examined. The analyses provide the optimal radius and length of the photoreactors for different configurations. The performance of photoreactors can be enhanced by more than 1-Log of E. Coli by choosing the appropriate length and radius for each configuration. Also, the choice of configuration and LED location may affect the performance up to 2-Log of E. Coli. Our results show that the U- and S-shaped photoreactors can outperform the L-shaped for photoreactors made of UV reflective materials. The right choice of length, radius, and LED location can lead to 4-Log of E. Coli for a S-shaped photoreactor with a single 25 mW UVC-LED.