Study On The Rapid Start-up Of PN-A Process And The Regulation Mechanism Of The Main Intermediates On The Proces

Partial Nitritation-Anammox（PN-A）,as a cost-effective and environmental friendly biological nitrogen removal technology,is the research hotspot in wastewater nitrogen removal.It has been widely used in the sidesteam high ammonium-nitrogen wastewater treatment.Single-stage PN-A process is the most widely employed due to its advantages of little land occupation,low equipment investment and convenient operation.However,the extention and application of single-stage PN-A process still needs a long way to go.In this study,rapid start-up strategy and nitrogen removal performance were explored;N₂O emission reduction strategy was analyzed in the single-stage biofilm PN-A process.The enhancement of PN-A process by adding NH₂OH and N₂H₄ was studied,while interaction relationship and synergistic balance relationship between nitrogen cycle functional bacterium was further analyzed.It is expected to provide theoretical and technical support for the extention and application of single-stage PN-A process.The main conclusions are stated below.（1）The rapid start-up strategy of PN-A process was exployed in a sequencing batch biofilm reactor（SBBR）.Aeration strategy was regulated by adding full aeration,pre non-aeration and post non-aeration under conditions of fixed aeration rate,temperature of 30℃,initial p H of8.0±0.2,influent contration of 100 mg NH₄⁺-N·L^-1.As a result,the PN-A process was successfully started within 31days with average ammonia removal efficiency（ARE）,total nitrogen removal efficiency（TNRE）and TNRR of 98.5±1.5%,89.5±1.6%and 0.146±0.095kg N·m^-3·d^-1.The balance among functional bacterias were perfectly matained through employing starvation aeration.The TNRR was promoted to 0.258±0.13 0.258±0.13 kg N·m^-3·d^-1 by employing 1-hour pre non aeration and 1-hour post non aeration,promoting aeration and shortening cycle time.The abundances of AOB,An AOB and NOB are 1.6%,19.3%and 0.3%.（2）The results of performance and bacterial activities showed that a certain time starvation was beneficial to maintain the balance between functional bacteria and maintain the stability of the process performance.NO accumulation gradually decreased,indicating that NO produced by AOB may participate in Anammox metabolism to induce Anammox as well as an indicator for synergy between AOB and An AOB.Under certain conditions,the symbiosis between An AOB and AOB is beneficial to the start-up of Anammox process.The N₂O production of PN-A process in this study during stable stage accounted for 0.51%of the total influent nitrogen.（3）In order to study the rapid recovery strategy of p N-A process performance degradation caused by over-aeration,NH₂OH was added to the continuous aeration SBBR single-stage PN-A system.Meanwhile,the effect of NH₂OH on PN-A process metabolism was studied and the role of intermediate NO among functional bacteria was analyzed.By adding 10 mg N·L-1NH₂OH at intervals（once every other cycle）,the PN-A process was completely recovered within 5 days,and NOB was effectively inhibited.△NO₃^--N/△NH₄⁺-N decreased from 28.5%to less than 11.0%.Adding NH₂OH can promote the production of NO and N₂O,and reduce the generation of NO₃^-.During the cycle of adding 10 mg N·L^-1NH₂OH,the△NO₃^--N/△NH₄⁺-N was less than 9%,lower than theretical value of 11%.The results showed that the intermediate NO played an important role in the correlation and regulation of functional bacteria in PN-A process.This study advanced the understanding of the metabolism versatility of NH₂OH and NO as well as their function in interaction between AOB and An AOB,and the potential application of NH₂OH dosing in ammonium-contained wastewater treatment.（4）In single-stage PN-A process,the replacement of reflux pump leads to a large amount of NO₃^-accumulation.This study investigated the enhancement of PN-A process by N₂H₄(10mg·L^-1)dosing.After 20-days dosing,the activity of An AOB and TNRE increased by about 16.3%and 16.5%,respectively.The inhibition effect of N₂H₄ on NOB is reversible.Auxiliary control strategy is needed to maintain the performance after N₂H₄ dosing being stopped.In addition,the addition of N₂H₄ can reduce the accumulation of NO₂^-,NO and N₂O,which is conducive to the N₂O emission control in PN-A process.（5）The mechanism of biochemical reaction of NH2OH and N2H4 on PN-A process was explained based on mathematical model.A mathematical model of single-stage PN-A biofilm containing intermediates including NH₂OH,NO and N₂H₄ of AOB and An AOB was established.By fitting the experimental data,the obtained model could accurately simulate the nitrogen transformation rule of continuous aeration single-stage PN-A process.The simulation results show that the added NH₂OH can be turned into NO by AOB,which can provide Anammox with a matrix of ammonia nitrogen oxides,thus promoting the metabolic rate of Anammox and reducing the generation of NO₃^-.The addition of hydroxyl ammonia can reduce the formation of NO₃^-.