Stable Operation Strategy Of Partial Nitrosation In SBR And Experimental Study On The Effect Of Fulcrum Acid On It

At present,the combined process of biological process,membrane treatment and advanced oxidation treatment is generally used todenitrogenate landfill leachate in China.In the process of biological treatment,Partial nitrification-Anammox combined process has the potential to become a new biological nitrogen removal technology to replace the traditional nitrification and denitrification because of its advantages such as energy saving,low economic cost and reduction of floor space.In order to ensure the denitrification efficiency of the combined process,it is necessary to strictly control the NO₂^--N/NH₄⁺-N ratio of the water produced by partial nitrosation process to be 1.32:1,so as to meet the inlet requirements of ANAMMOX for denitrification.However,this processhas the shortcomings of long start-up time and it isdifficult for a single factor to achieve long-term andhigh-efficiency inhibition of NOB bacterial activity.At the same time,the refractory organic fulvic acid contained in the landfill leachate may also affect the operation effect of some nitrosation processes.In this experiment,artificially simulated two-stage anaerobic effluent of landfill leachate was used as the inlet water matrix.Under the premise of maintaining the temperature at 30±2℃and p H at 8.0±0.2,the concentration of dissolved oxygen（DO）,the duration of aeration and the inlet were adjusted.The three parameters of ammonia nitrogen concentration in water determine the cultivation strategy to achieve rapid start and stable operation of partial nitrosation under medium temperature conditions.After the system was operating stably for a period of time,fulvic acid was gradually added to the feed water matrix,and the effect of fulvic acid on partial nitrosation efficiency and the corresponding process optimization research were carried out.The main findings are as follows:（1）Under the optimal conditions of other conditions,the DO concentration of 0.5mg/L inhibits the oxidation kinetics of NH₄⁺-N and NO₂^--N;and when the DO concentration is1.0mg/L,the ratio of ammonia oxidation rate The accumulation rate of nitrate nitrogen increased to 0.563mg N/mg MLSS·d and 0.168mg N/mg MLSS·d,respectively.While maintaining thehigher activity of AOB bacteria,it effectively inhibited the activity of NOB bacteria.（2）When the DO concentration in the reactor is 1.0mg/L,changing the aeration time by the‘p H final value method’has a significant impact on the nitrosation performance.When the aeration time is 3.6hours,the p H value reaches the lowest value of 6.8 in the cycle,and then the system is filled with water for 10minutes,stirred for 60minutes under anoxic condition,aerated for 216minutes,sedimented for 10minutes,drained for 10minutes,and left for54minutes.It runs for 50days and produces nearly 1.1:1 of NO₂^--N/NH₄⁺-N,which successfully realizes the rapid start of part of the nitrosation process;When the influent ammonia nitrogen concentration increased to 300mg/L,the ammonia nitrogen removal rate and nitrite nitrogen accumulation rate reached 60%and 87%,respectively,and the effluent NO₂^--N/NH₄⁺-N increased to 1.25:1.The stability of partial nitrification process was guaranteed（3）The concentration of fulvic acid will affect the extracellular polymer Subtance（EPS）content of activated sludge.When 60mg/L fulvic acid was added,the ratio of protein to polysaccharide content（PN/PS）reached thehighest value of 7.07,and the sedimentation performance of the granular sludge was good;then gradually increasing the concentration of fulvic acid to 180mg/L,the reaction The EPS in thedevice first increases and thendecreases,and the PN/PS graduallydecreases.The sludge aggregation effect becomes worse,causing the sludge todisintegrate,and the stability of some nitrosated granular sludge isdestroyed.（4）Fulvic acidhas a significant effect on some nitrosation efficiency.When the concentration of fulvic acid is 60mg/L,AOB bacteria is thedominant strain,and the nitrite nitrogen/ammonia nitrogen of the effluent is maintained at around 1.19:1,and the reactor can still maintain a relativelyhigh level of partial nitrification efficiency;continue to increase the fulvic acid When the acid concentration reaches 120mg/L and 180mg/L,the NO₂^--N/NH₄⁺-N in the effluentdrops to 0.71:1 and 0.38:1,respectively,and the activity of NOB bacteria is restored.The reproduction ofheterotrophic bacteria leads to thedisintegration and loss of sludge,which is part of the system.Nitrification efficiency,sludge activity,ammonia oxidation rate,etc.are all suppressed.After the addition of fulvic acid was stopped,the operating efficiency and granular sludge activity of part of the nitrosative process were restored,but it could not be restored to the state before the addition in a short time.（5）Changing the stop-exposure ratio underhigh-frequency exposure can improve the partial nitrosation performancedestroyed by fulvic acid.In thehypoxia time of 2～4min,the longer thehypoxia time,the greater the inhibition of NOB bacteria,the better the sludge sedimentation,and the better the improvement of partial nitrosation efficiency.