Rapid formation of aniline-degrading aerobic granular sludge and investigation of its microbial community succession

Aniline is one of common by-products in several industries such as petroleum and chemical and its discharge attracts increasing concern in recent years. Aerobic granular sludge (AGS) technology is regarded as one of the most promising biological processes. However, there are some drawbacks such as long start-up especially when the system is fed with toxic pollutants (e.g., aromatic compounds). In this study, rapid formation of AGS for aniline biodegradation was investigated. The aerobic granules were successfully developed in a sequencing batch airlift reactor (SBAR) fed with aniline-containing wastewater within 15 days. The sludge volume index decreased from 58.47 to 30.31 mL g⁻¹ after AGS was formed. It was also found that extracellular polymeric substances (EPS) especially protein was increased significantly during aerobic granulation. Besides, the average removal efficiencies of aniline and COD from day 3–15 (the period since early observation of pinpoint particles in the mixed liquor) were 99.93% and 90.59%, respectively. NH₄⁺-N was also remarkably reduced in the SBAR. Through pyrosequencing analysis, Proteobacteria was the most abundant phylum during granulation. There were several genera responsible for aniline biodegradation and EPS secretion such as Pseudomonas was found to be predominant in the system. The rapid formation of AGS and high removal efficiency of aniline and COD in the present system might provide an alternative for treating industrial effluents with presence of aniline.