Study On The Conversion Characteristics Of Ammonia Nitrogen In Anammox Reactor In The Absence Of Nitrite

Anammox process can generate nitrogen by the reaction of ammonia nitrogen and nitrite under anaerobic inorganic conditions,and has a low sludge yield and wide application prospects.Studies have found that sulfate seems to be an electron acceptor in the anammox process to oxidize ammonia to generate nitrogen under anaerobic conditions,but there is still a lack of in-depth research on this phenomenon.The subject used a UASB reactor to start the anammox process,and studied nitrogen removal of the anammox in the presence of sulfate while continuously reducing the supply of nitrte;after the reactor is interrupted and the anammox activity is restored,the reaction to sulfate and sulfate and ammonia nitrogen conversion pathway;using high-throughput sequencing technology to analyze the microbial structure of the inoculated sludge,the sludge after starting anammox,and the sludge lacking nitrite,and the mechanism of reactor denitrification was explored.The results of the study are as follows:（1）Inoculating a small amount of sludge with anammox activity helps the reactor to start up quickly under the condition of higher substrate concentration,and the total nitrogen removal load reaches 0.338kg N/（m3·d）on the 30th day of operation.The reactor stagnates for 117 days at room temperature,and the ammonia and nitros nitrogen removal load can be restored to the level before the shutdown after 11 days of restarting.After restarting the anammox reactor,excessive removal of ammonia nitrogen and excessive production of nitrate nitrogen occurred during stable operation.△NO₂^--N/△NH₄⁺-N was 1.2,and△NO₃^--N/△NH₄⁺-N was 0.31.（2）When the influent NO₂^--N/NH₄⁺-N is 0.5,the ammonia nitrogen that is excessively removed by the reactor accounts for 47.84%of the total ammonia nitrogen removal,and the ratio of△NO₂^--N/△NH₄⁺-N is 0.69.When the concentrations of ammonia nitrogen and nitros nitrogen in the influent water are 150 and 0 mg/L,respectively,the ammonia nitrogen is continuously and stably removed,and the total nitrogen removal load can reach 64.32 mg N/（L·d）,and the nitrous nitrogen concentration in the effluent is lower than 1 mg/L,nitrate The nitrogen concentration is about 12mg/L.（3）After conventional deoxygenation treatment,in a completely closed serum bottle,ammonia nitrogen can only be converted to 3.65 mg/L without adding nitrite,and the conversion of ammonia nitrogen is increased to 18.86 mg/L after air injection.In-situ experiments found that ammonia nitrogen can be continuously and stably removed,the ammonia nitrogen conversion rate is 0.471mg NH₄⁺-N/（g VSS·h）,and the nitrate nitrogen generation rate is 0.110mg NO₃^--N/（g VSS·h）.The concentration of sulfate did not change significantly before and after the experiment.（4）Properly increasing the reflux ratio of the reactor is beneficial to increase the conversion of ammonia nitrogen.The suitable reflux ratio in this study is 10.In this study,when nitrous nitrogen is insufficient,the reaction is generally characterized as an acid production process,and bicarbonate mainly acts as a p H buffer and a carbon source.In this study,when the concentration of sodium acetate is lower than 50mg/L,it has no significant effect on the nitrogen conversion of the reactor.When the concentration of sodium acetate reaches 90mg/L,the nitrate concentration in the effluent decreases significantly,the conversion of ammonia nitrogen is basically unchanged,and the total nitrogen removal rate improve.（5）High-throughput sequencing showed that the anammox bacteria enriched in the reactor after startup were Candidatus Brocadia（4.37%）,Candidatus Jettenia（2.03%）,and Candidatus Kuenenia（0.01%）.After prolonged starvation and lack of nitrous nitrogen supply,the anammox bacteria in the reactor evolved into Candidatus Brocadia（0.19%）,Candidatus Kuenenia（0.8%）,unclassified Candidatus Brocadiaceae（10.04%）.Without the nitrite stage,the relative abundance of Nitrosomonas and Nitrospira in the reactor increased.