Achieving Deep Nitrogen Removal via Two-stage PN-SAED Process from Low C/N Ratio Waste water
To address the issue of instability and nitrate accumulation in the effluent of the mainstream anaerobic ammonia oxidation(Anammox)process treating municipal wastewater,this study established a two-stage process combining partial nitrification/Anammox with endogenous denitrification(PN-SAED)process for low carbon to nitrogen(C/N)ratio wastewater treatment,and the deep nitrogen removal performance and changes in microbial community structure were evaluated.The results indicated that,with an influent C/N ratio of 2.60±0.11,the PN-SAED process achieved an effluent total inorganic nitrogen(TIN)concentration of(2.6±0.5)mg/L,corresponding to a TIN removal efficiency of(94.6±1.0)％.Nitrogen balance analysis during a typical cycle showed that the contributions of the PN and SAED systems to nitrogen removal were 7.3％and 92.7％,respectively,with the Anammox pathway accounting for the majority of nitrogen removal(82.2％)in the SAED system.High-throughput sequencing data revealed that the addition of hydroxylamine led to a rapid decline in the abundance of nitrite-oxidizing bacteria(Nitrospira,from 3.1％to 0.6％)in the PN system,while enriching ammonia-oxidizing bacteria(Nitrosomonas,from 0.13％to 0.92％),achieving stable partial nitrification.In the SAED system,Candidatus Brocadia(12.3％)and Candidatus Jettenia(2.83％)emerged as the dominant Anammox bacteria,coexisting synergistically with endogenous denitrifying bacteria of Candidatus Competibacter(17.5％)and Denitratisoma(7.15％),thereby accomplishing deep nitrogen removal from municipal wastewater with a low C/N ratio.
partial nitrificationAnammoxendogenous denitrificationdeep nitrogen removalmicrobial community structure
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