Research On The Performance And Pathway Of Anammox Bacteria Degrade NO And N₂H₄

Compared with the traditional biological denitrification method,the new biological nitrogen removal process with ANAMMOX process as the core has the advantages of high efficiency,economy and small amount of sludge.NO and N2H4 are intermediates in the ANAMMOX process,which are important for the stable operation of the ANAMMOX process,and they are also closely related to human life.Although it has proven that ANAMMOX bacteria has ability to produce and convert NO and N2H4 in its body.However,it is still unclear that ANAMMOX system can directly convert and use NO and N2H4 came from the external environment.In this paper,In this paper,The changes of the denitrification performance caused by the addition of N2H4 and NO and the conversion performance of the two substances in ANAMMOX system was studied,and based on this study,the existing ANAMMOX bacteria preservation and recovery methods have been further improved.The results are as follows:(1)The degradation performance of NO in ANAMMOX system was studied.It was found that ANAMMOX system can simultaneously degrade NH4+ in water and NO in gas by standard ANAMMOX process,and it will not accumulate NO3-in the process.Those factors including the concentration of NO into the system(NOin).the residence time of NO in system(GRT)and sludge concentration(MLSS)will affect degradation performance of NO in ANAMMOX system.When NOin increases from 200ppm to 1500ppm,The absorption rate of NO decreased from 90%to 35%,when GRT increased from 1.5s to 6s,The absorption rate of NO increased from 14%to 50%,When the MLSS in ANAMMOX system increased from 2197mg/L to 8126mg/L,the absorption rate of NO was increased from 35.1%To 69.7%,but the spectific NO absorption capacity(SNC)decreased from 46.52 ppm/gVSS to 24.34 ppm/gVSS.(2)The effect of N2H4 addition on the denitrification performance of ANAMMOX system was studied.The results shown that hydrazine addition has improved the specific anammox activity by 42%,which is mainly reflected in the following three aspects:i)hydrazine addition can easily be degraded by anammox bacteria and the maximum specific substrate uptake rate and half-saturation constant of N2H4 was 151.86mgN/gVSS/d and 15.99 mgN/L,respectively.Those extra electrons released from the degradation of hydrazine addition could strengthen normal anammox process and improve the conversation rate of ammonia and nitrite simultaneously,which can increase specific anammox activity by 10%.ii)hydrazine addition could react with nitrite to generate azide.it has additionally accelerate the degradation of nitrite and increase maximum specific substrate uptake rate of nitrite from 145.86mgN/gVSS/d to 212.02mgN/gVSS/d as well as half-saturation constant of nitrite from 10.67mgN/L to 13.86mgN/L.which can increase specific anammox activity(SAA)by about 20%.iii)hydrazine addition avoid accumulation and even promote degradation of nitrate in anammox system because the activity of Nar was selectively inhibited by adize generated from the biological reaction of hydrazine addition and nitrite.which can increase specific anammox activity(SAA)by about 12%.Based on the above findings,this paper proposed the converted mechanism of N2H4 addition in ANAMMOX bacteria.(3)The effect of gas phase conditions on the performance of anaerobic ammonium oxidation(ANAMMOX)bacteria under short-term preservation was studied.Under the conditions of normal temperature(14±0.5)? and low temperature(4±0.5)?,ANAMMOX bacteria were preserved in the four gas phase conditions(10000ppm NO,1000ppmNO,nitrogen and air)for 28days and the recovery experiments of ANAMMOX bacteria preserved under normal temperature condition was studied.The results showed that the activities of the ANAMMOX bacteria preserved in 1000ppmNO and nitrogen conditions were higher than that of the bacteria preserved in the air at the corresponding temperature.The retention rates of ANAMMOX bacteria were 23.40%,86.22%,61.54%and 46.47%,respectively,underthe four kinds of preservation(normal temperature condition),However,Under low temperature conditions,the retention rates were 36.53%,47.12%,53.53%and 42.95%,respectively;The results demonstrated that preservation in oxygen-free environment was beneficial to maintain color and settleability of bacteria while biomass decreased and in high concentrations of NO Can reduce the loss of biomass during preservation.The time uesd in restoring the activity to more than 90%could be saved by 40%when adding trace amounts of N2H4 to ANAMMOX system Continuously during the recovering avtivity of ANAMMOX bacteria.