Rapid start-up performance of mainstream Anammox in a single-stage fixed-bed biofilm reactor
Mainstream anaerobic ammonium oxidation(Anammox)is a hotspot and difficulty issue for nitrogen removal from municipal wastewater.In this study,a single-stage fixed-bed biofilm reactor(SFBR)was used to treat simulated municipal wastewater.By switching from intermittent operation and controlling low-oxygen(DO:0.4-0.7mg/L),mainstream Anammox was successfully started up after 65 days,and the system achieved removal efficiencies of ammonia nitrogen and total nitrogen up to 98.8％and 92.6％,respectively.At this moment,the biofilm structure was dense and appeared red.Microbial activity test showed that the activity of Anammox bacteria(SAA)was the highest among all the functional bacteria.High-throughput sequencing confirmed that the co-existence of Anammox genus(Candidatus Brocadia),partial denitrification genus(Thauera)and nitrifying genus(Nitrospira),but ammonia oxidizing bacteria was not detected.Further analysis of the amoA functional gene amplicon indicated that Nitrospira was actually complete ammonia oxidizing(Comammox)bacteria.Therefore,the system achieved nitrogen removal from municipal wastewater through the coupled pathway of complete nitrification/partial denitrification/Anammox within an oxygen-stratified biofilm.These study findings provided a new process idea for the rapid realization of mainstream Anammox.
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