Optimization of two CSTRs using granular sludges dominated by Ca. Jettenia asiatica and Ca. Brocadia sinica

Abstract

Two CSTRs using granules dominated by Ca. Jetteni asiatica (R1) and Ca. Brocadia sinica (R2) were operated depending on influent T-N concentrations and HRT. R1 achieved the highest NRR of 1.64 kgN/m3/day at HRT 8 h and T-N 600 mg/L, while R2 obtained the highest NRR of 2.05 kgN/m3/day at HRT 4 h and T-N 400 mg/L. The both reactors achieved high performance in high T-N concentration with the increasing of HRT in relatively short time. The sufficient T-N concentration and favorable short HRT were giving significant effects in promoting biomass increment and maintaining high removal in R1 and R2. In R1, granules larger than 2 mm accounted for over 60 %, while in R2 granules in the range of 1-2 mm comprised approximately 60 %. Granules in R1 were relatively harder and denser, and the surface of granules in R1 appeared rough, whereas the surface of granules in R2 seemed smoother. The abundance of anammox bacteria were much improved in both R1 and R2, operating under optimal operational conditions, showed significant improvement. The distribution of Ca. Brocadia sinica increased from 2.6 % to 42.0 % for R1 and from 9.1 %, to 90.5 % for R2, while there was little change in Ca. Jettenia asiatica. In this study, while the optimal HRT and nitrogen concentration as influent varied depending on the dominant anammox bacteria and granule characteristics in the inoculum, Ca. Brocadia sinica appears to play a significant role in nitrogen removal.