A Potential New Method for Determination of the Fluence (UV Dose) Delivered in UV Reactors Involving the Photodegradation of Free Chlorine

In the operation of UV reactors, an important step is to validate if the UV reactor can deliver the design fluence (UV dose) to achieve the required disinfection credit. Free chlorine is used widely in water and wastewater treatment and often is found in the water passing through a UV reactor. Free chlorine is degraded when passing through a UV reactor. This study investigates the potential application of the photodegradation of free chlorine (PFC) to determine the fluence (UV dose) delivered in UV reactors. Using a bench-scale UV reactor, the PFC was investigated at difference UV doses, which also were measured by a biodosimetry method. The results obtained here show that the PFC method has a high correlation with the delivered UV dose (as estimated from the biodosimetry measurements) and is independent of operating conditions, such as flowrate and UV transmittance. In addition, this study indicates that only chloride and chlorate are generated when free chlorine is photodegraded. Water Environ. Res., 82, 328 (2010).