Estimating the fluence delivery in UV disinfection reactors using a ‘detector-model’ combination method Zhimin Qiang a,⇑ , Mengkai Li a , James R. Bolton b , Jiuhui Qu a , Chen Wang a a State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, 18 Shuang-qing Road, Beijing 100085, China b Department of Civil and Environmental Engineering, University of Alberta, Edmonton, AB T6G 2W2, Canada highlights  A ‘detector-model’ combination method was developed for fluence estimation.  An in situ measurement platform was constructed for the developed method.  The practical fluence was obviously affected by water temperature and UVT.  The developed method and biodosimetry agreed well on fluence determination.  This new method was fast and cost- effective in comparison to biodosimetry. graphical abstract article info Article history: Received 20 March 2013 Received in revised form 6 August 2013 Accepted 9 August 2013 Available online 16 August 2013 Keywords: Fluence Mathematical model Micro-fluorescent silica detector UV reactor Water temperature UV transmittance abstract Current mathematical models for estimating the fluence delivery in an annular ultraviolet (UV) disinfec- tion reactor are not adequate because some critical input parameters (e.g., lamp output, sleeve transmit- tance, and water temperature) concerning various reactor characteristics are difficult to quantify. In this study, a fluence rate (FR) model (UVCalc Ò version 2A), combined with experimental measurements using an FR detector, namely a 360-degree response micro-fluorescent silica detector (MFSD), was used as a new method to determine the practical fluence. The FR values at representative test points were mea- sured by the MFSD in the temperature range of 10–30 °C and water transmittance range of 85–95% (per cm). The radius-weighted average of the measured to model FR ratios at these test points was adopted as a ‘correction factor’ to calibrate the model fluence (i.e., reference fluence) to the practical flu- ence at a certain water temperature and UV transmittance. The fluences estimated by the ‘detector- model’ combination method agreed well with those determined by biodosimetry. This fast and cost- effective method has potential applications for estimation and on-site inspection of the practical fluence in UV facilities. Ó 2013 Elsevier B.V. All rights reserved. 1. Introduction In recent years, ultraviolet (UV) technologies have been used increasingly for disinfection of drinking water and municipal wastewater as well as for photochemical oxidation of various or- ganic pollutants. Operation security and energy conservation are two key factors controlling further application and dissemination of UV technologies [1,2]. Accurate validation of the delivered flu- ence (UV dose) is required by both users and manufacturers of UV facilities. A number of validation protocols have been devel- oped for UV reactors [3–5]. Although some differences are evident among these protocols, all of them call for UV reactors to be vali- dated by biodosimetry. 1385-8947/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.cej.2013.08.024 ⇑ Corresponding author. Tel.: +86 10 62849632; fax: +86 10 62923541. E-mail address: qiangz@rcees.ac.cn (Z. Qiang). Chemical Engineering Journal 233 (2013) 39–46 Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej