Long-term operation of a partial nitritation pilot plant treating leachate with extremely high ammonium concentration prior to an anammox process

The goal of this work was to demonstrate the feasibility of treating leachate with high ammonium concentrations using the SBR technology, as a preparative step for the treatment in an anammox reactor. The cycle was based on a step-feed strategy, alternating anoxic and aerobic conditions. Results of the study verified the viability of this process, treating an influent with concentration up to 5000 mg N–NH4+ L−1. An effluent with about 1500–2000 mg N–NH4+ L−1 and 2000–3000 mg N–NO2- L−1 was achieved, presenting a nitrite to ammonium molar ratio close to the 1.32 required by the anammox. Furthermore, taking advantage of the biodegradable organic matter, the operational strategy allowed denitrifying about 200 mg N–NO2- L−1. The extreme operational conditions during the long-term resulted on the selection of a sole AOB phylotype, identified by molecular techniques as Nitrosomonas sp. IWT514.