Fast start-up of anammox process with mixed activated sludge and settling option.

In this study, successful start-up of the anaerobic ammonium oxidation (anammox) process in a sequencing batch reactor (SBR) was achieved by seeding mixed activated sludge which included aerobic sludge, anaerobic sludge, simultaneous partial nitrification, anammox and denitrification (SNAD) sludge, and anammox sludge with low activity at a 2200:2100:5:2 volume ratio. On day 15, the effective anammox activity was attained in SBR, with the specific total nitrogen removal rate (SRR) of 0.214 gNg VSSd. The total nitrogen removal rate (NRR) increased to 230 gNm d by gradually reducing the setting time to 10 min. With the nitrogen loading rate (NLR) up to 506 gNm d, the total NRR of the SBR reached 433 gNm d during stationary phase. Candidatus Brocadia was detected as predominant functional microbes in the anammox SBR. The results demonstrated the feasibility of seeding mixed activated sludge to start-up an anammox SBR by settling option.