Mineralization of Acid blue 29 (AB 29), an anionic azo dye, was carried out at various pHs using UV254 in the presence of H2O2 (HP) or Na2S2O8 (SPS) as oxidants. The influence of operational variables such as pH and intensity of UV light on mineralization was analyzed and their electrical efficiency were evaluated in terms of electrical energy per order (EE/O). It was observed that although HP and SPS worked as good oxidants at all pHs, mineralization ability of SPS was higher than HP. In fact it was noted in general that at a particular time, the mineralization increased with increase in intensity, e.g. the mineralization by UV/SPS system in 90 min at pH 6.69 (natural pH of AB 29) increased from 37.9% to 95.6% when the intensity was increased from 213 to 1755 mu W cm(-2). The most important finding of the work is that >95% mineralization was achieved at all pHs except at pH 13, where it was 80%. Under the present experimental conditions, SPS showed higher biotoxicity removal efficiency (90.2%) than HP (64.6%) after adjusting the pH of the treated solution to 7. Thus, we have been able to generate eco-friendly effluent, which makes our work suitable for real scale applications. (C) 2013 Elsevier B.V. All rights reserved.