This paper deals with the cost assessment of different hydrogen peroxide addition strategies with the assistance of dissolved oxygen on-line monitoring as the controlled variable. In this way, manual, automatic and controlled hydrogen peroxide supplies were assayed. Although the application of the photo-Fenton process to remove persistent pollutants in wastewater is accepted, there are few studies linking existing scientific and economic knowledge to evaluate further improvements in the decontamination processes. This economic study relates total costs to water treatment capacity and mineralization for a 100 m(2) CPC plant. Results showed that the amount of H2O2 added and the treatment time are decisive in cost reduction, dissolved oxygen monitoring being a key tool in predicting both variables. Furthermore, for low mineralization values, the addition strategy is not significant in financial terms, obtaining a mean cost of 0.53 (sic)/m(3) for 50-60% mineralization. However, for higher mineralization levels, the cost is quite sensitive to mineralization changes and, so, Proportional and Integral controlled hydrogen peroxide dosing would be a better option. (C) 2012 Elsevier B.V. All rights reserved.