Combining photo-Fenton process with aerobic sequencing batch reactor for commercial hetero-bireactive dye removal

A synthetic textile effluent containing an hetero-bireactive dye (Cibacron Red FN-R, 250 mg l−1) was treated by coupling photo-Fenton process with an aerobic sequencing batch reactor (SBR). The study is focused on the selection of suitable mild photo-Fenton conditions (Fe(II)/H2O2 reagents and irradiation time) that performs as a pre-treatment of a secondary biological treatment. Decolourisation (Abs542.5), biodegradability enhancement (determined by BOD5/COD index and respirometric methods) and dye degradation intermediates toxicity (Biotox® technique) were the parameters employed to verify the chemical stage effectiveness. From different assessed photo-Fenton conditions, a Fenton reagent concentration of 20 mg l−1 Fe(II) and 250 mg l−1 H2O2, applied for an irradiation time of 90 min, was found to be an effective process to bio-compatibilize the studied wastewater. The SBR, working under steady conditions in a 24-h-cycle mode, made available an 80% DOC removal in the combined oxidation system.