On-Site Determination and Monitoring of Real-Time Fluence Delivery for an Operating UV Reactor Based on a True Fluence Rate Detector

Abstract

At present, on-site fluence (distribution) determination and monitoring of an operating UV system represent a considerable challenge. The recently developed microfluorescent silica detector (MFSD) is able to measure the approximate true fluence rate (FR) at a fixed position in a UV reactor that can be compared with a FR model directly. Hence it has provided a connection between model calculation and real-time fluence determination. In this study, an on-site determination and monitoring method of fluence delivery for an operating UV reactor was developed. True FR detectors, a UV transmittance (UVT) meter, and a flow rate meter were used for fundamental measurements. The fluence distribution, as well as reduction equivalent fluence (REF), 10th percentile dose in the UV fluence distribution (F), minimum fluence (F), and mean fluence (F) of a test reactor, was calculated in advance by the combined use of computational fluid dynamics and FR field modeling. A field test was carried out on the test reactor for disinfection of a secondary water supply. The estimated real-time REF, F, F, and F decreased 73.6%, 71.4%, 69.6%, and 72.9%, respectively, during a 6-month period, which was attributable to lamp output attenuation and sleeve fouling. The results were analyzed with synchronous data from a previously developed triparameter UV monitoring system and water temperature sensor. This study allowed demonstration of an accurate method for on-site, real-time fluence determination which could be used to enhance the security and public confidence of UV-based water treatment processes.

Ray Tracing for Fluence Rate Simulations in Ultraviolet Photoreactors

“…and its ability to accept incident photons from virtually all angles allows it to accurately measure E o at essentially any location in a UV photoreactor, including near-source regions such as the gap between the lamp and the sleeve. The MFSD has been used successfully to examine in situ, real-time E o distributions in reactors with single or multiple LP lamps in different media and with a wide range of UV transmittance . It has also been used to measure photon fluence rate distributions in photoreactors with polychromatic UV sources (e.g., medium-pressure Hg lamps) …”

“…The MFSD has been used successfully to examine in situ, realtime E o distributions in reactors with single or multiple LP lamps in different media and with a wide range of UV transmittance. 19 It has also been used to measure photon fluence rate distributions in photoreactors with polychromatic UV sources (e.g., medium-pressure Hg lamps). 20 For the work described herein, ray tracing was applied to simulate fluence rate fields for several single-lamp UV photoreactors.…”