The lodide/lodate Actinometer in UV Disinfection: Determination of the Fluence Rate Distribution in UV Reactors

Abstract

Thirty-seven Suprasil quartz spheres, each approximately 1 cm in diameter and containing an iodide-iodate actinometric solution, were attached to a metal rack and inserted into a bench-scale UV reactor filled with water. The spheres were located at various distances and heights around a 12.4 W low-pressure Hg lamp housed inside a 3.2 cm-radius quartz sleeve in the middle of an annular batch reactor. UV light exposure at 254 nm was performed with the percent transmittance of the water present in the reactor at either 73% or 100% defined over a 1 cm path length. The spheres were simultaneously exposed to the UV light for a given period of time, after which the solutions were removed from the spheres and the yield of triiodide determined from the increase in absorbance at 352 nm. The resulting fluence rate at each site was then calculated on basis of the yield of triiodide. These results were compared with the predictions of a mathematical model based on the multiple point source summation approximation, including reflection and refraction at the air-quartz-water interface. Initially, the agreement was not satisfactory, especially in regions at an oblique angle to the lamp. The model was modified from a multiple point source model to a multiple cylindrical segment model by incorporating a cosine factor. The agreement between the new model and the experimental data was excellent and these experiments provide a strong validation of the model, even under conditions in which the fluence rate varied by >1000-fold between extreme sites in the reactor.

Virus removal and inactivation in a hybrid microfiltration–UV process with a photocatalytic membrane

“…Chemical actinometry [29][30][31] was used to measure UV fluence by determining the UV absorbance of a KI/KIO 3 solution. The exposure of the KI/KIO 3 solution to UV light results in the formation of triiodide, the concentration of which can be determined spectrophotometrically at 352 nm (MultiSpec 1501, Shimadzu).…”

Evaluation of reflection and refraction in simulations of ultraviolet disinfection using the discrete ordinates radiation model

“…An equation from Rahn et al (2000) was used to relate measured quantities (e.g., temperature, change of absorption coefficient, volume of actinometer solution, cross-sectional area of the spherical vessels, exposure time), as well as reflection from the quartz vessel, to the incident radiation for each actinometer. Results were reported for a water UV transmittance of 88%.…”

In situ detailed fluence rate distributions in a UV reactor with multiple low-pressure lamps: Comparison of experimental and model results

“…Moreover, experimental measurements also provide an alternative method to pure model prediction for the determination of FR distributions in a UV reactor. Many researchers have attempted such efforts in a single-lamp reactor, such as the use of spherical actinometer [12][13][14], a radiometer-type detector [15,16], and a micro-fluorescent silica detector (MFSD) [17,18].…”