The scope of the present study was to explore the treatment possibilities for the simulated dyehouse wastewater (WW) by the Fenton oxidation ultrasonic (US) or UV-A assisted. Composition of WW included reactive azo dye, C.I. Reactive Violet 2 (RV2), anionic surfactant (LAS) and auxiliary chemicals. An emphasis was put on the influence of the LAS on the treatment efficiency. To explore the pseudo-catalytic effect of LAS and reagent dosages on the extents of decolourization and mineralization, different experimental design techniques were utilized. Box-Behnken design was used as a base for optimization and determination of the influencing factors; numerical (Fe(2+)/(3+), H(2)O(2) and LAS concentration) and categorical factors (iron oxidation state and type of additional energy; US or UV-A). Furthermore, a mixture design methodology was applied. This two-step optimization approach lead to a single optimal point for two advanced oxidation processes studied in comparison. Models describing the dependency of the overall efficiency on influencing factors were obtained. Application of US/Fe(2+)/H(2)O(2) and UV-A/Fe(2+)/H(2)O(2) processes for the treatment of WW was assessed. Only 26% of mineralization was achieved by Fenton process alone applied for the treatment of the dyehouse effluent in 10-fold dilution, while 43% of mineralization was achieved by US or UV-A assisted Fenton after the 60 min. (C) 2011 Elsevier B.V. All rights reserved.