Effects of extracellular polymeric substances (EPS) and N-acyl-L-homoserine lactones (AHLs) on the activity of anammox biomass

This study investigated the effect of N-acyl-L-homoserine lactones (AHLs) and EPS on anammox activity, and identified the relationship between AHLs and EPS. The effects of AHLs and different EPS fractions (loosely bound (LB) and tightly bound (TB) EPS) from denitrification sludge (DS) and perchlorate reducing sludge (PRS) on anammox activity were conducted by batch experiments. Compared with the control experiment, the nitrogen removal rate was increased by 82.0%, 73.9% and 73.0%, respectively, when adding DS-EPS (integral DS EPS), PRS-EPS (integral PRS EPS) and DS-LB in anammox biomass. EPS fractions of DS and PRS contained the same kinds of AHLs, including C4-HSL, C6-HSL and C8-HSL, as identified by HPLC-MS. C4-HSL and C6-HSL at 0.1 mg L−1 concentration effectively improved the nitrogen removal rate by induceing the expression of anammox active genes during the anammox process. This study provides a new idea for efficient nitrogen removal from anammox bacteria.