Formation of anaerobic granules and microbial community structure analysis in anaerobic hydrolysis denitrification reactor

Abstract

An anaerobic hydrolysis denitrification (AnHD) process was developed to pretreat municipal wastewater for integrating partial nitration/anammox process. The results indicated that the carbon to nitrogen (C/N) ratio of municipal wastewater changed from 4.4 ± 0.3 to 2.2 ± 0.2 after pretreatment by AnHD process, which was favorable to the partial nitration/anammox process. The influent C/N ratio had influence on the formation of anaerobic granules. Two intrinsic factors, cyclic diguanylic acid (c-di-GMP) concentration and core bacterial community, were mainly responsible for the anaerobic granular formation. The higher c-di-GMP content increased the extracellular polymeric substances and decreased the motility of the bacteria, which was beneficial for the formation of anaerobic granules. The microbial community analysis showed that the lactic acid bacteria (Lactococcus) was the core bacteria during anaerobic hydrolysis process, while the denitrifying bacteria (Denitratisoma and unclassified Comamonadaceae) were the core bacterial community during AnHD process, which were responsible for nitrogen removal and anaerobic granular formation.