Effects of N-Acyl homoserine lactones (AHLs) on aerobic sludge granulation during the treatment of phenolic wastewater

This study examines the role of N-Acyl homoserine lactones (AHLs) in aerobic granular sludge (AGS) for the treatment of phenolic wastewaters. AGS was successfully formed with phenol removal efficiency of 99.7%. AHLs content displayed an initial rise followed by a decline, both C4-HSL and 3-oxo-C10-HSL are critical AHLs to regulate the concentration and composition of EPS, showing the highest concentrations in large granules. The content of EPS constantly increased to 149.4 mg/gVSS, and PN was predominantly found in small and large granules. Luteococcus was dominant genus constituting up to 54.9% after the granulation process, and exhibited a strong association with C4-HSL. The synthesis and dynamics of AHLs were mainly governed by AHLs-producing bacterial strains of Rhodobacter and Pseudomonas, and AHLs-quenching strains of Flavobacterium and Comamonas. This regulation occurred within the purview of the AHLs synthetic genes (lasI and bjaI), sensing genes (sdiA, cciR and bjaR1), and degradation genes (pvdQ).