Start-up And Influential Factors Of Completely Autotrophic Nitrogen Removal Over Nitrite In Membrane Bioreactor

Compared with conventional nitrification/denitrification process,single-stage autotrophic nitrogen removal process(CANON)is one of the most economical,low energy consumption and high efficiency denitrification ways which based on the shortcut nitrification and anaerobic ammonia oxidation coupled could reduce the occupied area,save 100% organic carbon source and 60% aeration.At the same time,this process of sludge production was only about 10% of the conventional denitrification process.The development of this process will greatly reduce the cost of low C/N ratio wastewater treatment.This project is combining the CANON process and sequencing batch membrane bioreactor(SBMBR),and with the method of inoculating the anaerobic ammonia oxidation sludge to start the CANON process.Then research the C/N ratio and low intensity ultrasound influence on SBMBR-CANON process,study the sludge characteristics of extracellular polymeric substance(EPS)in the reactor,and using macro genome sequencing methods test the microbial characteristics direct at different conditions.Firstly,the study inoculate normal activated sludge from municipal sewage plant to SBMBR to realize shortcut nitrification,and reinoculates small amounts of anaerobic ammonia oxidation sludge to complete quick start CANON process.The results shows that when controls the temperature in 28-30 ℃,pH is about 8.0,the reactor is intermittent operation and run cycle of 8 hours,the inflow ammonia nitrogen concentration is 300-400mg/L,under the condition of limited oxygen,the reactor run 40 days to achieve the shortcut nitrification.And then control the inflow ammonia nitrogen concentration is 200-300 mg/L,dissolved oxygen is 0.1-0.15mg/L,the reactor start the CANON process in 60 th day.The total nitrogen removal rate reached 79%,total nitrogen removal load is 0.1 kg-N/m3/d.In the reactor load lifting stage,total nitrogen removal rate reached more than 86%,and total nitrogen removal load reached 0.28 kgN/(m3·d).When the inflow ammonia nitrogen is 420 mg/L,C/N ratio is 0.8,adding COD is helpful to improve the CANON process treatment effect.It improves the reacror’s total nitrogenremoval rate from about 65% to more than 75%,and improves the reacror’s total nitrogen removal load from about 0.24 kg-N/m3/d up to around 0.30 kgN/(m3·d),and COD removal rate is more than 90%.The heterotrophic denitrifying bacteria and anaerobic ammonia oxidation bacteria and anaerobic ammonia oxidation bacteria is collaborative competition relationship,but heterotrophic denitrifying bacteria at a disadvantage position.When the C/N ratio is 1,the reactor’s total nitrogen removal rate decline to 60%,and the total nitrogen removal load down to 0.24 kgN/(m3·d)below,and COD removal rate is more than 95%.The heterotrophic denitrifying bacteria and anaerobic ammonia oxidation bacteria and anaerobic ammonia oxidation bacteria is collaborative competition relationship,but heterotrophic denitrifying bacteria in a dominant position.Then the experiment used the genome sequencing technology to test the microbial community.The results show that when the CANON process started,firstly the anaerobic ammonia oxidation bacteria Candidatus Anammoxoglobus is 33.77% of the total bacteria number,secondly aerobic oxidation bacteria Nitrosomonas is accounted for 7.12%.It all belong to the reactor advantage bacterium.At the same time there are also a small amounts of nitrite oxidizing bacteria Nitrospira,accounted for 0.24%.When the reactor operation 31 days after adding COD,the anaerobic ammonia oxidation bacteria Candidatus Anammoxoglobus is reduce to 13.67%,the aerobic oxidation bacteria Nitrosomonas is reduce to 2.67%,the heterotrophic denitrifying bacteria Thauera increased to 12.33%,and Armatimonadetes_gp5increased to 12.87%.The experiment using the change of content and composition of EPS to analyze the SBMBR-CANON process sludge when adding COD or not.When go through the extraction method optimization of Tightly Bound EPS(TB-EPS),the study determine the best TB-EPS extraction method is heat extraction and the condition is: 80℃,45 min.The results shows that when reactor don’t add COD,content of total EPS is higher than adding COD(content of Soluble Microbial Products(SMP)is the highist),and the highest EPS component content is DNA.When the C/N ratio is 0.5,0.8,1,the reactor’s total EPS content gradually decrease,content of SMP and Loosely Bound EPS(LB-EPS)decrease to the lowest,but the content ofTB-EPS increased to the highest.The protein of EPS components decreased in SMP and LB-EPS but it gradually increased in TB-EPS.The polysaccharide of EPS components changed a little in SMP,LB-EPS and TB-EPS.The DNA of EPS components rapidly decreased in SMP,LB-EPS and TB-EPS.The change of reactor sludge EPS account for that when reactor adding the COD,the activity and to some extent content of sludge increased.Finally,the study using low intensity ultrasound to deal with the sludge of SBMBR-CANON process,and then using the orthogonal experiment to analyze the effects on microorganisms under different conditions of the low intensity ultrasound(ultrasonic power,ultrasonic time,the sludge concentration and dissolved oxygen).Results shows that the low intensity ultrasound can improve the activity of microorganisms and the optimal ultrasonic conditions as follows: the ultrasonic time is 6 min,ultrasonic is 60 W power,sludge concentration is 3000 mg/L,the DO is 0.15 mg/L.When put the ultraphonic sludge in reactor.Result show that ammonia nitrogen removal rate increased 16.53% than before and TN removal rate increased about 11.45% than before.