BACKGROUND: The accumulation of bicarbonates during the biological treatment of high organic strength wastewater has a negative impact on the remaining micropollutant removal through chemical oxidation due to its scavenging effect on hydroxyl radicals. In this study, a lab-scale sequencing batch reactor (SBR) was operated at circumneutral pH to avoid inorganic carbon accumulation, followed by Fenton and photo-Fenton processes to treat an agro-food industrial effluent with acetamiprid as a model pollutant at 100 mu g L-1. A cost analysis of the operation strategy was performed. RESULTS: The pH control did not affect SBR efficiency (98% organic carbon biodegradation) but gave rise to different inorganic carbon concentrations in the effluents: 75.32, 10.81 and 5.7 mg L-1 at pH 8.0, 7.0 and 6.5, respectively. Both Fenton and photo-Fenton resulted in complete acetamiprid removal at pH 6.5 and 7.0 with high iron dosage (up to 80 mg L-1) but only photo-Fenton achieved this at acidic pH with 20 mg Fe L-1. CONCLUSION: To remove micropollutant from biotreated wastewater by Fenton processes it is highly recommended to control pH at circumneutral values during the biotreatment. The reactant cost analysis showed a reduction of similar to 80% to remove the micropollutant, even with photo-Fenton being carried out at pH 2.8. (C) 2014 Society of Chemical Industry