Study On Ammonia Nitrogen Removal Characteristics Of Anammox System Under Nitrite Nitrogen Supply Deficiency

Anaerobic ammonia oxidation（Anammox）process has attracted more and more attention in wastewater treatment because of its advantages of nitrogen removal.However,anaerobic sulfate reduction ammonia oxidation discovered in recent years can convert part or all ammonia nitrogen（NH₄⁺）into nitrogen（N₂）in waste water with the help of original sulfate in it,which seems providing a new way for low energy consumption and high efficiency nitrogen removal of municipal sewage.However,in the Anammox reactor where ammonium and sulfate are supplied simultaneously for a long time,they are often removed asynchronously,and enen NH₄⁺is removed in excess,and no removal of SO₄^2-.To explore these phenomena,the return sludge from the common sewage treatment plant was inoculated into a upflow anaerobic sludge bed reactor.Firstly,the rapid start-up of Anammox in the reaction was studied,the operation process was analyzed by kinetic models,and the high-throughput sequencing technology was used to analyze the microbial community changes in the reactor before and after the start-up.Secondly,in the Anammox reactor containing both NH₄⁺and SO₄^2-wastewater,the removal path of NH₄⁺was studied,and the activity and flora structure of anaerobic ammonia-oxidizing bacteria,ammonia-oxidizing bacteria and Nitrite-oxidizing bacteria in the reactor were analyzed.The main results achieved of this paper are as follows:（1）It took only 40 days to start the reactor successfully,the removal rates of ammonia nitrogen and nitrite nitrogen were maintained above 90%,the maximum total nitrogen removal load was 0.99 kg·N·m^-3·d^-1,the ratio of NH₄⁺:NO₂^-:NO₃^-was1/1.28/0.26,the contribution of denitrification to total nitrogen removal gradually decreased from 83%to 12%during the start-up process in the reactor,and the cell yield of anaerobic ammonia oxidizing bacteria at the end of the activity retardation period reached（1.37～13.75）×10¹⁰ cells/d;Candidiatus Brocadia（25.14%）and Candidiats Jettenia（2.92%）were the main anaerobic ammonia oxidizing bacteria in the reactor at the initial stage of successful start-up.During long-term operation,the abundance of Jettenia gradually increased to 12.67%and became the main dominant bacteria genus.（2）The improved Stover-Kincannon matrix removal model（R²=0.98）and Grau’s second-order kinetic model（R²=0.99）are suitable for predicting the nitrogen removal performance and matrix removal efficiency of Anammox reactor with high prediction accuracy.The correlation coefficient fitted by Monod model is 0.82 which is not suitable for describing the nitrogen removal performance of UASB-anammox reactor under different HRT.（3）When the Anammox system was restarted after stopped for 100 days,the influent wastewater with NH₄⁺-N concentration of 130 mg·L^-1 and natural dissolved oxygen(DO=6±2mg·L^-1)was not effectively utilized,but the average removal rate of NH₄⁺-N was 79 mg·L^-1·d^-1,the maximum TN removal load of the system was 0.07kg·N·m^-3·d^-1,and the average FA of the effluent was 3 mg·L^-1.After HRT was adjusted from 26 h to 16 h,the nitrogen removal efficiency of the system remained unchanged.Batch experiments show that AOB in the reactor uses influent water and trace DO permeated by the reaction device to carry out ammonia oxidation reaction,and cooperates with An AOB to remove NH₄⁺-N from influent water.The activities of AOB and Anammox were 84.66 mg·N·g^-1·VSS^-1·d^-1 and 28.75 mg·N·g^-1·VSS^-1·d^-1,respectively,and no NOB activity was found at all.The activity of Anammox recovered to 90%of the highest level before"shutdown".（4）FISH analysis shows that there are a lot of AOB in the granular sludge in the Anammox reactor with long-term stop of NO₂^-supply,which is mainly distributed outside the An AOB;At the same time,the high-throughput results showed that Candidate Brocadia,Candidate Jettenia,Candidate Kuenenia and Nitrosomonas in the reactor increased a lot after start-up,and the reactor still contained a certain abundance of denitrifying bacteria（Comamonas,Denitratisoma and Pseudomonas）.The pathways involved in NH₄⁺-N transformation include aerobic ammonia oxidation,Anammox and partial denitrification.