Metagenomics-based interpretation of AHL-mediated quorum sensing in anammox biofilm reactors for low-strength wastewater treatment

AbstractAnammox-based nitrogen removal can advance sustainable wastewater treatment, including main-stream wastewater treatment. Two lab-scale anammox biofilm reactors fed with influent ammonia concentrations of 110 mg/L (Anammox-H) and 50 mg/L (Anammox-L) were operated, and nitrogen removal and mechanisms of quorum sensing (QS)/quorum quenching (QQ) were examined. The achieved nitrogen removal rates were 0.65 g N/L·d in Anammox-H and 0.25 g N/L·d in Anammox-L. Candidatus Kuenenia was dominant in both reactors. Higher contents of tight extracellular polymeric substance and hydrophobic amino acid confirmed that dense anammox biofilm developed in Anammox-H. C6-HSL and C8-HSL were detected in Anammox-H and Anammox-L, and high concentration of acyl-homoserine lactones (AHLs) in water and biomass phases of Anammox-H was consist with that more active QS processes existed in Anammox-H. Functional genes including hao, pmoA-amoC, nirK and narGZHY were detected and harbored by Candidatus Kuenenia stuttgartiensis, Nitrosomonas europaea and Lautropia sp. SCN 69-89. These organisms not only involved in nitrogen metabolism, but also in pyruvate, fatty acid and S-Adenosy-L-methionine synthesis (important for AHLs). Influent ammonia concentration influenced the balance between QQ and QS activities, resulting in different anammox activity and biomass morphology.