Achieving nitritation and anammox enrichment in a single moving-bed biofilm reactor treating reject water

A biofilm with high nitrifying efficiency was converted into a nitritating and thereafter a nitritating-anammox biofilm in a moving-bed biofilm reactor at 26.5 (+/-0.5)degrees C by means of a combination of intermittent aeration, low dissolved oxygen concentration, low hydraulic retention time, free ammonia and furthermore, also by elevated HCO3- concentration. Nitrite-oxidizing bacteria (NOB) were more effectively suppressed by an enhanced HCO3- concentration range of 1200-2350 mg/L as opposed to free-ammonia-based process control where NOBs recovered from inhibition; the respective total-nitrogen removal rates were 0.3 kgN/(m(3).d) and 0.2 kgN/(m(3).d). The biofilm modification strategies resulted in a shift in bacterial community as the NOB Nitrobacter spp. were replaced with NOB belonging to the genus Nitrospira spp. and were closely related to Candidatus Nitrospira defluvii. A community of anaerobic ammonium-oxidizing microorganisms -uncultured Planctomycetales bacterium clone P4 (closely related to Candidatus Brocadia fulgida) - was developed.