Effect of Seeding Single/Mixed Sludge on Rapid Start-up of an ANAMMOX Reactor

Abstract

The experiment explored the effect of different seeding sludge on the rapid start-up of an anaerobic ammonium oxidation (ANAMMOX) reactor by seeding a single type of denitrified granular sludge and a mixed sludge composed of denitrified granular sludge and aerobic nitrification sludge (the volume ratio of the mixed sludge was 2:1) in two sequencing batch reactors (SBR), R0 and R1, respectively. The results indicated that R0 was started up successfully on day 64 with a nitrogen removal rate (NRR) of 0.26 kg·(m3·d)-1, while R1 was started up by day 47 with a NRR of 0.30 kg·(m3·d)-1, which was shorter than R0 by 17 d. In the enrichment stage, reddish sludge appeared in R1, and the characteristics of anaerobic ammonium oxidation of the system were more obvious than in R0. After the reactor was started up successfully, the stoichiometric ratio of R0 was 1.20 and 0.34, respectively, and the stoichiometric ratio of R1 was 1.26 and 0.21, which was closer to the theoretical values of 1.32 and 0.26. The mixed liquor suspended solids (MLSS) and mixed liquor volatile suspended solids (MLVSS) of R0 were restored to 51% (4.2 g·L-1) and 38% (2.3 g·L-1)of the initial seeding sludge, respectively, while the MLSS and MLVSS of R1 were restored to 54% (4.4 g·L-1) and 42% (2.6 g·L-1),which was higher than R0. It can be speculated that the proliferation rate of AnAOB in R1 was faster than in R0. Seeding mixed sludge can accelerate the start-up process of anaerobic ammonium oxidation with more stable N-removal performance.