Accelerating biodegradation of an azo dye by using its inorganic intermediates

Abstract

AbstractBACKGROUNDThe discharge of textile wastewater can cause various environment problems. How to remove these dyes in effluents effectively remains a major concern in wastewater treatment. In this work, the accelerating biodegradation effect of two inorganic intermediates generated by UV irradiation on a monoazo dye, Acid Orange 7 (AO7), was studied in a biofilm reactor.RESULTSThe biodegradation reaction fitted well with fractional‐order kinetics. The promotion effects of k trend for the two inorganic intermediates were NH4+ addition > SO42− addition (> AO7 biodegradation alone). NH4+ ions increased biochemical oxygen demand (BOD) gradually: compared with 0.5 mg L−1 addition protocol, the BOD of 3 mg L−1 addition protocol was enhanced about five‐fold. SO42− ions showed a positive effect at low concentration and a negative effect at high concentration. In addition, the effect of the two inorganic intermediates on aerobic microbial respiration rate (i.e. SOUR) was similar to BOD. Based on the analysis of high‐throughput sequencing and cluster of orthologous groups, a mechanism of accelerating azo dye biodegradation by using its available intermediates was proposed.CONCLUSIONThis work revealed that the main inorganic intermediates of the azo dye could accelerate its biodegradation rates. In addition, the bioreactor provided an integrated anaerobic/aerobic micro‐environment that was beneficial to promoting this acceleration effect. © 2021 Society of Chemical Industry (SCI).