Reactor performances and fate of aromatic amines through decolorization of Direct Black 38 dye under anaerobic/aerobic sequentials

The removal of aromatic amines was evaluated by decolorization of CI Direct Black 38 (DB 38) dye varying between 100 and 3200 mg l−1 using an anaerobic upflow anaerobic sludge blanket reactor and an aerobic completely stirred tank reactor system. The effect of increasing dye loadings from 6.1 to 213.0 g m−3 h−1 on decolorization and COD removal efficiency was investigated at constant glucose-COD (2000 mg l−1) concentrations in an UASB reactor. For 3200 mg l−1 of DB 38 and 2000 mg l−1 glucose-COD as co-substrate in the feed, 48.4% COD and 80% color removal efficiencies were observed at a maximum COD and dye loading rates of 5.37 kg COD m−3 per day and 213 g dye m−3 h−1, respectively at a hydraulic retention time (HRT) of 15 h in the UASB reactor. Sixty seven percentage remaining COD was removed at an HRT of 2.3 days and a maximum organic loading rate of 0.77 kg COD m−3 per day in the aerobic stage. Eighty four percentage COD, 86% color and 52.2% total aromatic amine (TAA) was removed at an HRT of 2.9 days and at an organic loading rate of 1.17 kg COD m−3 per day and a maximum DB 38 dye loading rate of 46.4 g dye m−3 h−1, respectively in a total system treating 3200 mg l−1 CI Direct Black 38 dye. The TAA produced under anaerobic conditions was ultimately removed in the aerobic stage and aromatic amine recoveries such as 45-50% were obtained in the aerobic reactor. The anaerobic/aerobic sequential process provides simultaneous color, COD and carcinogenic amine removal.