Evaluation of macrocomposite based sequencing batch biofilm reactor (MC-SBBR) for decolorization and biodegradation of azo dye Acid Orange 7

• Decolorization of Acid Orange 7 using MC-SBBR.
• Investigation of biofilm thickness towards Acid Orange 7 decolorization.
• Removal of aromatic amines by sequencing batch biofilm reactor.
• Kinetics of AO7 decolorization followed the first order kinetic model.

The present study deals with the decolorization of azo dye Acid Orange 7 (AO7) using a macrocomposite based sequencing batch biofilm reactor (MC-SBBR). The effect of biofilm thickness towards the decolorization as well as the biodegradation of aromatic amines formed through AO7 treatment process was investigated. The results obtained indicate that the biofilm thickness reached its steady state at development period of 7 days with average biofilm thickness of about 115 μm. Almost complete decolorization of AO7 within 3 h of treatment time and more than 80% of the COD removal were achieved by the applied biofilm system. Decolorization of AO7 in this study nicely followed first order kinetic with a k value of 3.36 h−1. Fourier transform infrared (FTIR) and UV–Vis spectral analysis further confirmed the decolorization of AO7. Monitoring the dye metabolites through HPLC suggested that more than 90% of facultative anaerobically formed aromatic amines i.e. p-benzoquinone and 1,2-naphtolquinone were successfully removed by the MC-SBBR system. Phytotoxicity study also showed that AO7 metabolites produced by MC-SBBR system were less phytotoxic than the parent compound.