Role of cycle duration on the formation of quinoline-degraded aerobic granules in the aspect of sludge characteristics, extracellular polymeric substances and microbial communities

Abstract

This study investigated the culture and characteristics of quinoline-degraded aerobic granular sludge (AGS) under 8-h and 12-h cycle duration. According to results, the cultivation of an 8-h cycle duration enhanced the growth of quinoline-degraded AGS, as well as the settleability of sludge and the retention of biomass. Quinoline can be removed from mature AGS at a rate of more than 90%, but it is removed at a rate slightly higher when the AGS are cultured for 12-h. Compared to 12-h cycle duration, 8-h cycle duration result in a greater increase in the production of extracellular polymeric substances, particularly extracellular proteins. In these two systems, Acidovorax and Paracoccus dominated the quinoline degrading bacteria. In addition, analysis by non-metric multidimensional scaling (based on Bray-curtis distance) showed significant differences of community structure between the two reactors. Clostridia and Acidaminobacter are different bacteria with an 8-h cycle duration compared to 12 h. Relative abundance of nitrogen metabolism genes based on PICRUSt2 prediction, which explain the better total nitrogen removal for an 8-h cycle duration compared to a 12-h cycle duration. Finally, the KEGG pathway was analyzed in order to confirm the results of the microbial analysis.