High-nitrate wastewater treatment in an expanded granular sludge bed reactor and microbial diversity using 454 pyrosequencing analysis

Denitrification of high concentration of nitrate wastewater was investigated in expanded granular sludge bed (EGSB) reactor with sodium acetate as the carbon source. The optimal parameters were achieved with C/N mole ratio of 2.0, liquid up-flow velocity (Vup) of 3.0 m/h and pH of 6.2–8.2. Complete denitrification can be achieved even with nitrate nitrogen concentration as high as 14000 mg/L. Furthermore, 454-pyrosequencing technology was used to analyze bacterial diversity. Results showed that a total of 5573 sequences were obtained which could be affiliated to 6 phylogenetic groups, including Proteobacteria, Firmicutes, Actinobacteria, Bacteroidetes, Chloroflexi and unclassified phylum. Proteobacteria (84.53%) was the dominant microbial population, followed by Firmicutes (13.24%) and Actinobacteria (0.38%). The dominate phylum was different from that in other anaerobic system.