UV/chlorine control of drinking water taste and odour at pilot and full-scale Ding Wang a,⇑ , James R. Bolton b , Susan A. Andrews a , Ron Hofmann a a Department of Civil Engineering, University of Toronto, 35. St. George St., Toronto, Ontario M5S 1A4, Canada b Bolton Photosciences Inc., 628 Cheriton Cres., NW, Edmonton, AB T6R 2M5, Canada highlights  UV/chlorine is more efficient than UV/H 2 O 2 at pH 6.5 for geosmin and MIB removal.  UV/chlorine efficiency is comparable to UV/H 2 O 2 at pH 7.5 and 8.5.  Caffeine is a suitable surrogate for geosmin and MIB. graphical abstract article info Article history: Received 24 March 2015 Received in revised form 13 May 2015 Accepted 18 May 2015 Keywords: UV Chlorine Advanced oxidation Taste and odour Efficiency abstract Advanced oxidation processes (AOPs) can be used to destroy taste and odour-causing compounds in drinking water. This work investigated both pilot- and full-scale performance of the novel ultraviolet (UV)/chlorine AOP for the destruction of geosmin, 2-methylisoborneol (MIB) and caffeine (as a surrogate) in two different surface waters. The efficiency of the UV/chlorine process at pH 7.5 and 8.5 was compa- rable to that of the UV/hydrogen peroxide (UV/H 2 O 2 ) process under parallel conditions, and was superior at pH 6.5. Caffeine was found to be a suitable surrogate for geosmin and MIB, and could be used as a more economical alternative to geosmin or MIB spiking for site-specific full-scale testing. Ó 2015 Elsevier Ltd. All rights reserved. 1. Introduction Geosmin and 2-methylisoborneol (MIB) can be destroyed dur- ing drinking water treatment by advanced oxidation processes (AOPs), which generate hydroxyl radicals (ÅOH) (reaction rate con- stants of 7.8  10 9 and 5.1  10 9 M 1 s 1 , respectively) (Peter and von Gunten, 2007). Ultraviolet light (UV)-based AOPs—usually UV with hydrogen peroxide (H 2 O 2 )—are becoming more popular. The UV/H 2 O 2 process is used at the City of Cornwall Water Purification Plant (Ontario, Canada) for the control of seasonal taste and odour events that occur in late summer. The UV/H 2 O 2 process, while effective, can create operational problems. Most of the applied H 2 O 2 survives UV exposure, and the residual therefore needs to be quenched to avoid a strong chlorine demand during secondary disinfection. At Cornwall, the residual H 2 O 2 is quenched http://dx.doi.org/10.1016/j.chemosphere.2015.05.049 0045-6535/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: dingwork.wang@mail.utoronto.ca (D. Wang). Chemosphere 136 (2015) 239–244 Contents lists available at ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere