| Nitrogen pollution has brought great harm to humans and the environment.The partial nitrification/anaerobic ammonia oxidation process is one of the wastewater denitrification treatment processes,including AOB-led ammonia oxidation process and An AOB-led Anammox process,which has low treatment cost,high nitrogen removal efficiency,and broad application prospects.In the process of nitrogen removal,the microorganisms are fixed by immobilization technology,which can effectively prevent the loss of bacteria,improve the impact resistance,and have the advantages of high efficiency and easy reaction control.In this paper,the start-up and operation of the partial nitrification and Anammox process were tested separately,in order to provide some theoretical support for the application of the integrated technology.The main conclusions of the experiment are as follows:?1?Different carrier materials were selected to prepare six kinds of nitrified sludge immobilizing particles,including waterborne polyurethane?WPU?,polyvinyl alcohol?PVA?,sodium alginate?SA?,polyethylene glycol?PEG?,polyacrylamide?PAM?,etc.The characteristics of six kinds of immobilized particles are characterized.The results showed that WPU immobilized particles have excellent mechanical strength and extremely high stability.The effective diffusion coefficient?De?value of ammonia nitrogen in WPU immobilized particles is 0.313×10-9 m2/s,indicating that WPU immobilized particles can maintain good permeability in the reaction,and can provide a certain buffer for the bacteria to resist the influence of the external environment,and ensure the activity of microorganisms.?2?After the nitrified sludge-immobilized particles were successfully prepared,the influencing factors of the partial nitrification process were explored through batch test.First,the influent concentration of NH4+-N was gradually changed,and a stable nitrogen removal process was achieved at the influent concentration of 100 mg·L-1.Secondly,the influence of aeration mode on the reaction process was compared.Under aerobic 10 min/anaerobic 20min intermittent aeration,excellent results were achieved.The batch test results at six different salinities(0,5,10,20,30,50 g·L-1)show that the immobilized particles can gradually adapt to the salt environment,and the high salt inhibited the activity of AOB and NOB.But at a salinity of 10 g·L-1,the ammonia removal rate??A?can reach more than 55%,and the nitrite accumulation rate?NAR?can reach 90%.Finally,the optimal aeration time of the partial nitrification reaction was determined under different influent NH4+-N concentrations and salinity.The experiment found that the reaction effect was the best when the aeration time was8 h.?3?The optimal reaction conditions were selected to start the continuous flow UASB partial nitrification reactor.Under the operating conditions of influent NH4+-N concentration of 100 mg·L-1,intermittent aeration time of aerobic 10 min/anaerobic 20 min and aeration time of 8 h,the UASB reactor was successfully started.During the initial operation,the nitrogen removal effect of the system was unstable.On the 15th day,10 g·L-1 NaCl was added to the reactor.After domestication culture,the NAR gradually increased from the 20th day and reached 81.03%.The start of the reactor is successfully realized.Matrix kinetic analysis was performed on the immobilized particles.The Haldane model was used to describe the kinetic characteristics of the particles,and the measured experimental data were linearly fitted to obtain the maximum ammonia reaction rate?SAA-NH4+-N?of the immobilized particles of1.98 kg·?kg·d?-1,the half-rate constant for ammonia is 1.60 mmol·L-1,and the half-inhibition constant for ammonia is 468 mmol·L-1,indicating that the particles have a greater affinity for the matrix and are conducive to the reaction.?4?The effect of adding salinity on the stability of anammox process was studied and microbial analysis was carried out.The salinity gradually increased from 0 g·L-1 to 10 g·L-1,and the system can achieve good removal rate of NH4+-N and NO2--N through short-term salinity domestication,and the ratio of the removal rate of NH4+-N and NO2--N and the generation rate of NO3--N is very close to its theoretical value?1:1.32:0.26?,and a stable Anammox process is realized.When the salinity increased from 10 g·L-1 to 15 g·L-1,the Anammox process was significantly inhibited,and the cell metabolic function was disturbed.From the analysis of the results of the microbial community structure,it can be seen that the Planctomycetes belonging to AnAOB are 31.2%and 10.7%at 10 g·L-1 and 15 g·L-1 salinity,respectively.At the genus level,the abundance of Candidatus Brocadia reached 20.6%at a salinity of 10 g·L-1.The abundance of 15 g·L-1 salinity is less than 1%,which indicates that the better microbial activity can be maintained under the salinity of 10 g·L-1. |
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