Operational pattern affects nitritation, microbial community and quorum sensing in nitrifying wastewater treatment systems.

Achievement of nitrite accumulation is critical for the application of advanced nitrogen removal processes. Two lab-scale sequencing batch biofilm reactors (SBBRs) and two sequencing batch reactors (SBRs) were operated under intermittent aeration with different feeding patterns. The nitrite accumulation ratio was 56.6% (pulse feeding) and 68.9% (constant feeding) in SBBRs with nitritation. Nitrate accounted for 98% of the effluent nitrogen in SBRs with complete nitrification. The dominant nitrifier was Nitrosomonas in SBBRs and Nitrospira in SBRs. Four types of acyl homoserine lactones (AHLs) were detected. N‑[(RS)‑3‑Hydroxybutyryl]‑l‑homoserine lactone and N‑octanoyl‑l‑homoserine lactone had a high concentration in the extracellular polymeric substance phase, and had an obvious relationship with nitrite accumulation and ammonia removal. Various microbial communities coexisted in nitrifying systems, with diverse microbial interactions. Microorganisms harboring AHLs-related genes had more interactions with each other, suggesting that nitritation could be regulated by AHLs based quorum sensing.