Related Experiment Video
Updated: Jun 2, 2026

Extraction of Structural Extracellular Polymeric Substances from Aerobic Granular Sludge
Published on: September 26, 2016
Exogenous floc-granule replacement regulates particle-size distribution and signaling-associated ecological responses
Xin Wang1, Yuan Huang1, Jie Xu1
1Key Laboratory of Northwest Water Resource, Environment, and Ecology, MOE, School of Environmental and Municipal Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China; Xi'an Key Laboratory of Intelligent Equipment Technology for Environmental Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, China.
Abstract:
Aerobic granular sludge (AGS) operation remains constrained by excessive granule enlargement, particle-size redistribution, and structural instability. In this study, exogenous floc-granule replacement was evaluated as a chemical-free, in situ particle-size management strategy for AGS. A conventional granulation reactor (R1) and an exogenous floc-granule replacement reactor (R2) were operated in parallel to compare granulation dynamics, reactor performance, extracellular polymeric substances (EPS), extracellular acyl-homoserine lactones (AHLs), respiration, bacterial partitioning, metagenomic functional gene profiles, and microbial co-occurrence patterns. During the first replacement window, R2 maintained smaller and more uniform granules than R1, with mean particle size of 220 μm on Day 83 compared with 378 μm in R1. R2 also maintained comparable chemical oxygen demand and NH4+-N removal performance and showed lower nitrite accumulation during rapid granulation. Particle-size regulation was accompanied by lower extracellular AHL accumulation, altered EPS composition, and distinct respiratory allocation, reflecting higher autotrophic-to-heterotrophic respiration ratio in R2 than in R1 on Day 82 (0.10 vs. 0.07). Comparative characterization indicated that exogenous flocs represented a distinct biomass fraction with smaller particle size, lower protein-to-polysaccharide ratio, and lower extracellular AHL accumulation than endogenous flocs and mature granules. Metagenomic and co-occurrence network analyses showed higher abundance of quorum quenching (QQ)-related genes and greater representation of QQ- or combined quorum sensing /QQ-associated taxa in R2. Overall, exogenous floc-granule replacement represents a tunable structure-based strategy for regulating AGS particle-size distribution, but its effectiveness should be further evaluated according to application scenario.
Related Concept Videos
Gene Regulation in Microbial Communities: Quorum Sensing
Coagulation
Microbial Wastewater Treatment
Biofilms
Bacterial Signaling
Microbial Bioremediation of Hydrocarbons

