Is the CANON reactor an alternative for nitrogen removal from pre-treated swine slurry?

The use of the completely autotrophic nitrogen removal over nitrite (CANON) process as a post-treatment for nitrogen removal from anaerobically pre-treated swine slurry is studied in the present work. The ammonium removal, under oxygen-limited conditions, in a system with anammox bacteria mainly in the form of granules and aerobic ammonium oxidizing bacteria mainly as dispersed biomass was researched in an air pulsing sequencing batch reactor operated at room temperature. The achieved nitrogen removal rate was of 0.46 kg N/(m3 d) treating 300 mg NH4+-N/L with values of nitrogen removal efficiencies around 75%.The presence of slowly or non-biodegradable organic matter (from 260 to 45 mg COD/L) did not affect the operation of the process. By means of the FISH technique, Nitrosomonas were detected as the majority of ammonia oxidizing bacteria in the sample, and Candidatus “Brocadia fulgida” and Candidatus “Brocadia anammoxidans” as the anammox bacteria.The comparison of this aerobic process with other post-treatments for effluents from anaerobic digesters showed that the CANON process is a promising alternative to remove nitrogen from effluents generated in pig farms.

► CANON system is a viable alternative for nitrogen removal from pre-treated swine slurry. ► Nitrogen removal rates of 0.46 kg N/(m3 d) were treated working at 20 °C. ► Organic matter in the wastewater did not affect the performance of the CANON reactor. ► Anammox, ammonia oxidizing and heterotrophic bacteria supported the process.