Investigation of rapid granulation in SBRs treating aniline-rich wastewater with different aniline loading rates

Abstract

In this work, aerobic granules were cultivated in two reactors which were denoted as RL and RH under 0.6 and 1.8 kg m−3 d−1 of aniline loading rates, respectively. The aerobic granular sludge (AGS) in the two sequential batch reactors for treating aniline-rich wastewater was compared. The results showed that the AGS could be rapidly formed with sludge volume index below 30 mL g−1. The AGS in RL had more filamentous bacteria than that in RH by microstructural observations while the secretion of protein in extracellular polymeric substances was improved in RH and in turn increased relative hydrophobicity of AGS. Within 4-h cycle, the excellent removal of aniline and chemical oxygen demand (COD) were achieved in the two reactors. The removal efficiencies of aniline and COD were consistently over 99.7%, 89.6%, respectively in RL and 98.6%, 86.6%, respectively in RH. As for nitrogen removal, NH4+-N released from aniline biodegradation could also be reduced efficiently via nitrification and no nitrite accumulation occurred in both the reactors. Total nitrogen removal performance in RH was better, due to a more compact structure of AGS. The investigation of microbial community succession by pyrosequencing showed that the diversity of microorganisms decreased when AGS was developed. Proteobacteria especially Gammaproteobacteria significantly increased during aerobic granulation in both reactors. It was also found that the relative abundance of Actinobacteria was higher in RH than that in RL. Furthermore, the strains responsible for aniline biodegradation, nitrification, denitrification, and phosphorous accumulation were detected in the systems.