The importance of integrated fixed film activated sludge reactor and intermittent aeration in nitritation-anammox systems: Understanding reactor optimization for lagoon supernatant treatment

A single stage nitritation-anammox process was studied in a continuous flow reactor fed with raw lagoon municipal-sludge supernatant containing 835 +/- 45 mg N L-1 of NH4+-N in the feed. Reactor operation was divided into five periods for a total of 438 days. Application of intermittent aeration with a 105 min aeration phase followed by a 15 min non-aeration phase reduced the aerobic nitritation rate by 13% but enhanced the anammox activity by 1.9 times. Under the dual effect of IFAS and intermittent aeration, the nitrogen removal rate (NRR) was improved from 0.12 +/- 0.012 kg N (m(3)d)(-1) to 0.28 +/- 0.03 kg N (m(3)d)(-1), representing an increased removal of NH4+ from 56 +/- 4.3% to 92.2 +/- 2.1%. The evolution of bacterial activity and communities showed that anammox activity significantly improved with the addition of the non-aeration phase, and the AOB population was largely improved with an increase of suspended biomass concentration in the reactor. Microbial community composition through 16S rRNA gene sequencing analysis showed that Nitrosomonas was the predominant AOB in the flocs phase, while Candidatus Brocadia was the dominant anammox bacteria in the biofilm phase.