Study On CANON Process Startupand Its Influencing Factors

Completely Autotrophic Nitrogen Removal Over Nitrite（CANON）is a new type of biological nitrogen removal process.Compared with the traditional biological nitrogen removal process,it has the advantages of saving aeration and eliminating the need to add exogenous organic carbon.However,the CANON process starts slowly and it is difficult to operate stably under low-temperature and low-matrix conditions,which restrict the industrial application of the CANON process.The CANON process is currently mainly applied to the treatment of high ammonia nitrogen wastewater such as landfill leachate and sludge digestion,and there is less research on the treatment of low ammonia nitrogen wastewater,and the actual wastewater temperature is low,so the research of CANON process in low matrix and low temperature wastewater is imperative.In this paper,firstly,Anaerobic ammonium oxidation（Anammox）granular sludge and short-range nitrifying flocculant were separately cultured,and then the pre-cultured sludge was inoculated to start the Sequencing Batch Reactor（SBR）.The CANON process was operated to investigate the nitrogen removal performance.The composition and abundance of microbial community structure during the two sludge culture enrichment processes and the start-up operation of the CANON system were analyzed.The conclusions were as follows:（1）The Anammox sludge enrichment experiment was started quickly within 30days.The removal rates of ammonia nitrogen,nitrite and total nitrogen were 86.25%,96.09%and 88.01%,respectively,and the average particle size was 67.2μm.After the addition of COD,substance replacement（from nitrite to nitrate）,system recovery,reduction of HRT,etc.,after 418 d operation,the stable TN removal rate was above90%,and the average particle size reached 492.5μm.High-throughput sequencing results showed that the dominant Anammox genus was Candidatus Brocadia.（2）Ammonia oxidizing bacteria（AOB）flocculating sludge enrichment experiment was successfully started within 52 days.After 82 days operation,the average ammonia nitrogen removal rate reached 56.01%,and the average effluent ammonia nitrogen and nitrite were about 80 mg/L and 70 mg/L;the average effluent nitrate concentration was lower than 15 mg/L,which could meet the needs of the Anammox process.High-throughput sequencing results showed that the dominant AOB genus was Nitrosomonas,and the dominant genus of NOB（Nitrite oxidizing bacteria）was Nitrospira.（3）The CANON process was started with Anammox granular sludge and AOB floc sludge as the inoculated sludge.The average TN removal rate reached 78.72%at19 d,and the CANON process was quickly started.The reactor temperature gradually decreased from 25℃ to 17℃.At 17℃,the TN removal efficiency of the reactor decreased from 78.72%to 18.97%.Many adjustment method was adopted to increase the nitrogen removal performance,including reducing the TN volume load,adjusting the aeration amount,adding Anammox granular sludge and changing the operation cycle.Finally,the TN removal rate increased to 64.15%,under 100 mg NH₄⁺-N/L,0.097 kg/m³·d,17℃.The optimization operation cycle was anaerobic（135min）-aerobic（505 min）-anaerobic（35 min）.High-throughput sequencing results showed that the dominant bacteria in the CANON system were:Proteobacteria,Planctomycetes,Bacteroidetes,Chloroflexi,Acidobacteria,Firmicutes and Actinobacteria.The dominant genus Anammox was Candidatus Brocadia,the dominant genus of AOB was Nitrosomonas,and the dominant genus of NOB was Nitrospira.