Effects of different carbon sources and C/N ratios on the simultaneous anammox and denitrification process

The simultaneous anammox and denitrification (SAD) process is an emerging treatment for wastewaters containing nitrogen pollution and organics. However, there is little research on the effect of organic matter types on the SAD process. In this study, two reactors, one with glucose (R1) and the other with acetate (R2), were used to investigate the effects of different carbon sources and C/N ratios on the SAD process. The nitrogen removal performance, functional gene abundance, biomass activity and microbial community structures of the two reactors were analyzed and compared. Results showed that a desirable nitrogen removal efficiency (NRE) was obtained at the C/N ratio of 1.2 in R1, whereas a similar NRE could be achieved at a C/N ratio of 0.8 in R2, which was more susceptible to a high C/N ratio. Moreover, at high C/N ratios, the microbial species diversity of R1 was higher than that of R2. High-throughput sequencing analysis revealed that anammox bacteria predominated at low COD, but denitrifying bacteria grew rapidly at high C/N ratio. Removal of NO3−-N in the glucose-driven reactor appeared to be more depended on other heterotrophic bacteria other than denitrification bacteria. In general, the glucose-driven reactor was more stable and resistant to high C/N ratios during the SAD process than the acetate-driven one. Results of this study provide information for practical treatment of wastewater with high nitrogen contents.