AHL-mediated quorum sensing regulates the variations of microbial community and sludge properties of aerobic granular sludge under low organic loading

Han Chen,Ang Li,Chongwei Cui,Fang Ma,Di Cui,Heping Zhao,Qilin Wang,Bingjie Ni,Jixian Yang

doi:10.1016/j.envint.2019.104946

Abstract

Aerobic granular sludge (AGS) is promising in wastewater treatment. However, the formation and existence of AGS under low organic loading rate (OLR) is still not fully understood due to a knowledge gap in the variations and correlations of N-acyl-homoserine lactones (AHLs), the microbial community, extracellular polymeric substances (EPS) and other physiochemical granule properties. This study comprehensively investigated the AHL-mediated quorum sensing (QS) and microbial community characters in the AGS fed with ammonium-rich wastewater under a low OLR of 0.15 kg COD (m3 d)−1. The results showed that the AGS appeared within 90 days, and the size of mature granules was over 700 μm with strong settleability and ammonium removal performance. More tightly-bound extracellular polysaccharide and tightly-bound extracelluar protein were produced in the larger AGS. C10-HSL and C12-HSL gradually became dominant in sludge, and short-chain AHLs dominated in water. EPS producers and autotrophic nitrifiers were successfully retained in the AGS under low OLR. AHL-mediated QS utilized C10-HSL, C12-HSL and 3OC6-HSL as the critical AHLs to regulate the TB-EPS in aerobic granulation, and autotrophic nitrifiers may perform interspecific communication with C10-HSL. The correlations of bacterial genera with AGS properties and AHLs were complex due to the dynamic fluctuations of microbial composition and other variable factors in the mixed-culture system. These findings confirmed the participation of AHL-mediated QS in the regulation of microbial community characters and AGS properties under low OLR, which may provide guidance for the operation of AGS systems under low OLR from a microbiological viewpoint.

Highlights

Aerobic granular sludge (AGS) is a promising technology for wastewater treatment due to its excellent settling property, small footprint demand and low operation costs (Nancharaiah and Reddy, 2018; van Loosdrecht and Brdjanovic, 2014)
The TB-extracellular polymeric substances (EPS) concentrations were calculated as the sum of the tightly-bound PN (TB-PN) and tightlybound PS (TB-PS) concentrations, and the contents of loosely-bound EPS (LB-EPS) were the sum of the loosely-bound PN (LB-PN) and loosely-bound PS (LB-PS)
N-decanoyl homoserine lactone (C10-HSL) and N-dodecanoyl homoserine lactone (C12-HSL) gradually became dominant in the sludge phase, and short-chain N-acyl-homoserine lactones (AHL) dominated in the water phase under low organic loading rate (OLR)

Summary

Introduction

Aerobic granular sludge (AGS) is a promising technology for wastewater treatment due to its excellent settling property, small footprint demand and low operation costs (Nancharaiah and Reddy, 2018; van Loosdrecht and Brdjanovic, 2014). As a key influencing factor, the organic loading rate (OLR) has been proven to affect the formation and characteristics of AGS (Ni et al, 2009; Wan et al, 2016; Zhang et al, 2018a). Several types of practical industrial wastewater, such as fertilizer production wastewater and synthetic ammonia industry wastewater, usually contain low COD and high ammonium concentrations (Keluskar et al, 2013; Yu et al, 2012; Zhang et al, 2012), which result in low OLRs and high ammonium loading rates (ALRs). The feasibility and granulation process of AGS under low OLR, such as 0.15 kg COD (m3 d)−1, are rarely reported in ammonium-rich wastewater

Methods

Results

Conclusion