The effect of quorum sensing on performance of salt-tolerance aerobic granular sludge: linking extracellular polymeric substances and microbial community

Aerobic granular sludge (AGS) technology is generally negatively affected by the salinity in high saline organic wastewater. The effect of salinity on organic pollutants removal of AGS was studied in three parallel sequencing batch reactors. The results indicated that the performance of reactors operating at relative low salinity (1%) remained stable. However, at medium salinity (2%) and higher salinity (4%) conditions, the organic pollutants removal efficiencies deteriorated from 93.7 +/- 3.0 to 71.6 +/- 6.8 and 53.6 +/- 5.4%, respectively. The addition of a mixture of acyl-homoserine lactone (AHL) mediated quorum sensing (QS) signaling molecules (0.1 mu mol/L of mixed C6-HSL, C8-HSL and 3OC8-HSL) only restored the performance of the 2% salinity reactor back to 86.3 +/- 6.2% due to the changing of hydrophobic extracellular polymeric substance ratio from 64 +/- 3 to 71 +/- 4%. Addition of the AHL had no effect on the pollution removal efficiency at the 4% salinity conditions. Microbial community analysis showed that Dyella (32.3%) species were the dominant member of the community and its occurrence was positively correlated with organic pollutants removal efficiency at relative high salinity (2% and 4%), while Mangrovibacter showed the opposite trend. Higher abundances of hdtS and acylase genes, the synthesis and degradation genes of AHL, were found after adding AHLs to reactors at 2% salinity, which indicated that AHL mediated QS was the primary QS system in salt-tolerant AGS.