BACKGROUND: Sulfamethazine (SMT) has received little attention in the water treatment literature. Yet, SMT is among the non-biodegradable substances increasingly found in aqueous media and affecting both public health and wastewater treatments. For a long time, advanced oxidation processes (AOPs) were studied via pure empirical modeling, although the surface response models resulting from lumped information (TOC, COD, etc.) present limitations regarding extrapolation and optimization. Conversely, detailed first-principles modeling may not be affordable due to the computational burden and the chemical analysis needs. Thus, a balanced approach may be practical in many cases. RESULTS: Experiments on SMT solutions (500 mL, 50 mg L(-1)) were performed under conditions set by an experimental design. A set of replicated degradation time-profiles (TOC and SMT concentrations) was obtained and a semi-empirical kinetic model was fitted to these data to determine maximum conversion and kinetic rate. CONCLUSIONS: SMT can be completely degraded from water via photo-Fenton treatment. Conditions for this treatment were investigated and its outcomes were systematically characterized by a simple kinetic model and two lumped parameters, conversion and kinetic rate. Both, the model and the corresponding parametrical characterization are introduced as a means to discriminate the most efficient treatment conditions in a practical and efficient way. (C) 2011 Society of Chemical Industry