Improvement of UV disinfection reactor performance by ring baffles: The matching between the hydrodynamics and UV radiation

Abstract

The performance of a UV disinfection reactor can be improved with an optimized configuration but its correlation with the fundamental reactor features (i.e., the hydrodynamics and UV radiation) remains indistinct. In this study, the impact of hydrodynamics/radiation on UV disinfection reactor performance was investigated in reactors retrofitted with ring baffles, by using computational fluid dynamics (CFD) simulations. The results showed that proper baffle allocations could increase reduction equivalent fluences (REFs, a performance indicator for UV disinfection reactors) of the 1-lamp and 3-lamp reactor by 37–45% and 36–69%, respectively, depending on the influent UV transmittance. The optimal baffle width was 10 mm for the 1-lamp reactor (i.d. 90 mm) and 30 mm for the 3-lamp reactor (i.d. 150 mm) which led to a maximal matching between the velocity and fluence rate distributions inside the reactor chamber. It was manifested that for UV disinfection reactors retrofitted with ring baffles it was the matching between the hydrodynamics and UV radiation rather than the mixing of the flow that determined the reactor performance improvement. A new parameter named as the specific fluence rate (SFR, ratio of fluence rate to velocity) was defined to characterize the matching level between the hydrodynamics and UV radiation, and the REF was found to relate linearly (R2 ≥ 0.972) with the 10th percentile SFR of the reactor. This study revealed the contribution of ring baffles to UV disinfection reactor performance and for the first time, correlated it quantitatively with the hydrodynamics and UV radiation in the reactor.