Response to high nitrite concentrations of anammox biomass from two SBR fed on synthetic wastewater and landfill leachate

The present work aimed to assess nitrite inhibition on granular anammox biomasses and to verify the following recovering ability. The granular biomass used came from two lab-scale sequencing batch reactors (SBRs) treating synthetic wastewater (SBR-1) and real landfill leachate (SBR-2), with similar nitrogen removal efficiencies (around 85–90%). The specific anammox activity (SAA) was determined by manometric batch tests where different concentrations of nitrite _100 to 500 mg NO2-N/L and exposure times (3–4 h, 24 h) were applied. The biomass from both reactors was consisted of Brocadia enrichments and presented similar behavior under high nitrite exposure, in spite of being adapted to very different matrix of wastewater. Anammox granules from both reactors were proven to be quite tolerant to moderate to high nitrite shocks, as long as the exposure time was limited to 3–4 h (less than 40% activity loss at 500 mg NO2—N/L). The activity loss was substantial after prolonged exposure (24 h) and the IC50 (half maximal inhibitory concentration) for SBR-1 and SBR-2 granules was set at 173 +/-23 mg NO2—N/L and 171 +/- 8mg NO2—N/L, respectively. The biomass recovered the activity with values up to 60–80% of the initial maximum SAA immediately after washing to remove the nitrite.