Start-up of the Canon process from activated sludge under salt stress in a sequencing batch biofilm reactor (SBBR)

In this study, a lab-scale sequencing batch biofilm reactor (SBBR) was used to start-up the completely autotrophic nitrogen removal over nitrite (Canon) process from conventional activated sludge under salt stress for 118 days. A persistent, stable partial nitrification was achieved in the SBBR when the salt concentration gradually increased to 6.5 g NaCl L−1. Anaerobic ammonium oxidation (Anammox) bacteria were successfully enriched from the conventional activated sludge in the SBBR after 68 days of operation. Anammox bacterial strains similar to the order Planctomycetales, genus Candidatus brocardia and genus Candidatus kuenenia were confirmed to exist in the internal layer of the biofilm via Fluorescence in Situ Hybridization (FISH) analysis. A maximal total nitrogen (TN) removal rate of 0.072 kg N m−3 d−1 was achieved for the Canon process when the salinity was maintained at a constant 10.0 g NaCl L−1 in the SBBR. This reactor may have applications for the Canon process treatment of salinity wastewaters containing high concentrations of ammonia.