Journal of Water and Wastewater; Ab va Fazilab (in persian)

Journal of Water and Wastewater; Ab va Fazilab (in persian)

Experimental and Numerical Investigation of a Novel Ultraviolet Water Disinfection Reactor with External Lamps

Document Type : Research Paper

Authors
Seyed Mahdi Safavi 1
Amirhossein Hassanpour 2
Alireza Jalali 3
1 MSc. Student, School of Mechanical Engineering, University of Tehran, Tehran, Iran
2 PhD. Student, School of Mechanical Engineering, University of Tehran, Tehran, Iran
3 Assoc. Prof., School of Mechanical Engineering, University of Tehran, Tehran, Iran
10.22093/wwj.2026.592599.3567
Abstract
Ultraviolet disinfection serves as a safe physical method that generates no chemical by-products, making it a highly desirable alternative to traditional water treatment processes. However, conventional submerged reactors encounter severe operational challenges such as significant pressure drops along the fluid path. This study presents the first physical fabrication and comprehensive validation of a novel UV photoreactor featuring a fully segregated architecture. In this configuration, a central quartz water channel is accompanied by two mercury radiation sources situated in the surrounding air and outside the fluid domain. A concentric cylindrical reflector encloses this entire assembly. This specific design optimally reflects the omnidirectional radiation emitted by the mercury lamps back into the fluid domain. To develop a deeper understanding of the transport phenomena, computational fluid dynamics simulations were conducted. These simulations simultaneously integrated flow hydrodynamics, the discrete ordinates radiation model, and first-order inactivation kinetics. To validate the developed model, an experimental setup was constructed and subjected to biodosimetry testing utilizing Escherichia coli (strain ATCC 8739). The implementation of a thermal management mechanism based on forced convection stabilized the lamp surface temperature at an optimal 36.3 ºC. This stabilization ensured the consistency of the radiant power output. Microbial evaluations revealed that at the maximum operational flow rate of 27.5 liters per minute, the experimental log reduction value was 3.48. This value demonstrates excellent agreement with the calculated numerical value of 3.29. At lower flow rates of 21.7 and 17.6 LPM, complete pathogen inactivation was achieved, exceeding the laboratory detection limit. The numerical model predicted LRVs of 4.10 and 4.93 for these flow rates, respectively. These findings demonstrate that the synergy between direct and reflected radiation significantly enhances the uniformity of the radiation dose. The successful alignment of experimental and numerical data confirms that this segregated reactor design offers a new paradigm for developing efficient and economical water treatment systems with minimal maintenance requirements.
Keywords
Ultraviolet Water Disinfection
Computational Fluid Dynamics
Decoupled Photoreactor
Biodosimetry
Cylindrical Reflector.
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Journal of Water and Wastewater; Ab va Fazilab (in persian)
Volume 37, Issue 1 - Serial Number 162
March and April 2026
Pages 64-80