The effect of water components on the photocatalytic degradation of organic pollutants was incompletely understood, especially in the case of hydroxyl radical ((OH)-O-center dot) generation and scavenging. Previous studies have used various methods to determine the rate constants for the reactions between (OH)-O-center dot and water components, but the interactions between water components were not taken into concern. In this study, a sequential relative rate technique was used to investigate the effects of water components on the rates of (OH)-O-center dot generation and EE2 degradation in a modified flat plate serpentine reactor, including NO3-, H2PO4-, SO42-, CO32-, Cl-, Na+, Fe3+, dissolved organic matter (DOM) etc. The results reflected that NO3- and DOM accelerated the photodegradation of 17 alpha-ethynylestradiol (EE2) (3.2% and 21.2%, respectively). Cl- and Fe3+ inhibited that process (5.2% and 3.1%, respectively). Finally, a model for the photocatalytic degradation of EE2 was developed for the first time, taking the obtained rate constants, catalyst concentrations, flow velocities and light intensities into concern. A good agreement was observed between the model and experimental profiles. (C) 2013 Elsevier B.V. All rights reserved.