Upgrading of the symbiosis of Nitrosomanas and anammox bacteria in a novel single-stage partial nitritation-anammox system: Nitrogen removal potential and Microbial characterization

•A single-stage nitritation-anammox system using functional carriers was developed.•Nitrogen removal efficiency was 81.1% at a nitrogen loading of 1.5 kg/m3/d.•Syntrophically structured Nitrosomonas and Candidatus_Kuenenia formed in biofilm.•Two types of filamentous bacteria confer structural integrity to the aggregates.

A novel single-stage partial nitritation-anammox process equipped with porous functional suspended carriers was developed at 25 °C in a CSTR by controlling dissolved oxygen <0.3 mg/L. The nitrogen removal performance was almost unchanged over a nitrogen loading rate ranging from 0.5 to 2.5 kg NH4+-N/m3/d with a high nitrogen removal efficiency of 81.1%. The specific activity of AOB and anammox bacteria was of 3.00 g-N/g-MLVSS/d (the suspended sludge), 3.56 g-N/g-MLVSS/d (the biofilm sludge), respectively. The results of pyrosequencing revealed that Nitrosomonas (5.66%) and Candidatus_Kuenenia (4.95%) were symbiotic in carriers while Nitrosomonas (40.70%) was predominant in the suspended flocs. Besides, two specific types of heterotrophic filamentous bacteria in the suspended flocs (Haliscomenobacter) and the functional carrier biofilm (Longilinea) were shown to confer structural integrity to the aggregates. The novel single-stage partial nitritation-anammox process equipped with functional suspended carriers was shown to have good potential for the nitrogen-rich wastewater treatment.

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