Analysis Of Nitrogen Removal Efficiency And Functional Bacteria Interaction Mechanism Of Mainstream Anammox Filter Under Temperature Stress

In recent years,the anammox process has been successfully applied to wastewater treatment with high temperature and high ammonia,such as digestion sludge supernatant and landfill leachate,and has achieved significant results.The mainstream anammox technology surrounding the wastewater treatment at normol and low temperature and low ammonia is becoming one of the focuses of global wastewater treatment research and development.In this paper,the upflow anammox biofilter is taken as the research object,and the enfluence of temperature on the nitrogen removal efficiency of the mainstream anammox filter is investigated.At the same time,modern molecular biology technology was used to study the functional bacteria and functional genes of nitrogen metabolism in the filter at different temperatures,and the systemic research on the interaction mechanism of nitrogen metabolic functional bacteria and the nitrogen transfer pathway in the reactor was carried out.Finally,by optimizing the operating parameters of the reactor,the maximum operating efficiency at each temperature was determined.The main conclusions are as follows:The reactor has a strong resistance to sudden drop in temperature of moderate and normal temperature.Under the conditions of moderate temperature（30±1℃）,the total nitrogen removal efficiency and removal rate reached 85.4%and 0.34 kg N·m^-3·d^-1,respectively.At 25±1℃,the average total nitrogen removal efficiency and average total nitrogen removal rate of the reactor reached 0.35±0.019 kg N·m^-3·d^-1 and 84.8±3.05%.At 20±1℃,the average total nitrogen removal efficiency and average total nitrogen removal rate were 79.6±4.4%and 0.261±0.0215 kg N·m^-3·d^-1,respectively.Under low temperature conditions,the nitrogen removal efficiency of the reactor decreased significantly.At 15±1℃,the average total nitrogen removal efficiency was73.3±3.34%and the average total nitrogen removal rate was 0.248±0.0188 kg N·m^-3·d^-1.At 10±1℃,the removal efficiency of ammonia and nitrite decreased simultaneously,and the average total nitrogen removal efficiency was only 55.6±6.11%,and total nitrogen removal rate was only 0.196±0.027 kg N·m^-3·d^-1。The results of high-throughput sequencing showed that the dominant bacteria in the reactor at various temperatures were Chloroflexi,Planctomycetes,Proteobacteria,and Chlorobibi.Only Candidatus Brocadia and Candidatus Jettenia were detected in the reactor.The former exists mainly in biofilm samples,while the latter exists in both sludge samples and biofilm samples.Nitrosomonadales is the only ammonia oxidizing bacteria（AOB）,which is mainly distributed in sludge samples,and has been enriched to some extent during the cooling process.Nitrospira was the only nitrite oxidizing bacteria（NOB）detected,mainly distributed in sludge samples.There are many kinds of denitrification bacteria in the reactor,mainly Pseudomonas.Pseudomonas tends to exist as granular sludge.The relative abundance of Pseudomonas in sludge samples increases with decreasing temperature,while the relative abundance of Pseudomonas in biofilm samples is the opposite.The q PCR results showed that the nitrogen-metabolizing bacteria in the reactor were mainly anammox bacteria（AMX）,Nitrospira,short-cut denitrification bacteria（nar G）,and ammonia oxidizing bacteria（AOB）.The relative abundance of AMX and Nitrospira decreased significantly with decreasing temperature,the relative abundance of nar G increased with decreasing temperature,and relative abundance of AOB remained basically stable at various temperatures.Based on the results of high-throughput and q PCR analysis,a conceptual model for the interaction of nitrogen removal functional bacteria in the reactor was proposed,and various nitrogen transformation pathways were clarified.The calculation results of nitrogen balance show that the contribution of AMX to ammonia removal gradually decreases with decreasing temperature,while the contribution of AOB to ammonia removal gradually increases with decreasing temperature.During the cooling process,the contribution of AMX and NOB to the removal of nitrite gradually increased,while the contribution of AOB and short-cut denitrification bacteria to the removal of nitrite gradually decreased with decreasing temperature.The contribution of AMX to the removal of nitrate is relatively stable throughout the cooling process,the contribution of NOB gradually decreases with decreasing temperature,and the contribution of short-cut denitrification bacteria gradually increases with decreasing temperature.The anammox filter has a specific proportional relationship between the demand for nitrite and ammonia at a specific temperature.Influent according to the specific substrate ratio can ensure that the reactor has a high nitrogen removal capacity at each temperature.When the temperature of the filter are 10±1℃,15±1℃,20±1℃,25±1℃,and 30±1℃,respectively,and the corresponding substrate ratios are 0.59,0.804,0.915,0.999,and 1.061,respectively,the anammox filter can achieve the maximum operating efficiency and ensure that the effluent meets Standard A of the first classd in“Discharge standard of pollutants for municipal wastewater treatment plant”（GB18918-2002）.