Two birds with one stone: Simultaneous improvement of biofilm formation and nitrogen transformation in MBBR treating high ammonia nitrogen wastewater via exogenous N-acyl homoserine lactones

Abstract

Moving bed biofilm reactor (MBBR) is facing the challenges of slow start-up and poor treatment performance when treating high ammonia nitrogen wastewater, especially at low temperature. Exogenous N-acyl homoserine lactones (AHLs) were proposed to improve the biofilm formation and pollutant removal simultaneously for the first time. The effects of 100 nM exogenous C6-HSL and C8-HSL on the distribution of AHLs, reactor performance, biofilm characteristics and microbial community structure were systematically investigated in six lab-scale MBBRs treating wastewater with 200 mg/L ammonia nitrogen at 25 °C and 5 °C. Results showed that exogenous AHLs exhibited more significant influences during the stable operation period rather than the start-up of MBBR. Biofilm growth and EPS secretion were significantly promoted by C8-HSL (p < 0.05) while inhibited by C6-HSL at 25 °C, however, the results were opposite at 5 °C. Denitrogenation-related enzyme activities and function genes, and abundances of bacteria possessing quorum sensing and pollutants degradation ability, were heightened by exogenous AHLs (p < 0.05), thus enhancing biofilm formation and pollutants removal at room and low temperature. This study inspired a feasible strategy towards synchronous enhancement of biofilm growth and performance of MBBR treating high ammonia nitrogen wastewater through exogenous AHLs.