Study On A Dynamic Membrane Sequence Batch Reactor(DM-SBR)Applied In A Single-stage Partial Nitritation And Anammox Process

In recent year,shigh-strength ammonia wastewater including anaerobic fermentation liquid and landfill leachate comes from a wide range of sources and has complex components.It is difficult to achieve high ammonia wastewater treatment which will cost a lot.Therefore,it is urgent to develop a stable and efficient treatment process to solve this problem.Compared with traditional nitrification and denitrification,anaerobic ammonia-oxidation（anammox）has the advantages of no additional organic carbon source,less oxygen demand,less excess sludge and low operating cost.The single-stage partial nitritation and anammox process（PN/A）based on anammox process is derived,which requires a small footprint and produces few by-products.In this process,aerobic ammonia-oxidizing bacteria（AOB）and anaerobic ammonia-oxidizing bacteria（AnAOB）can be enriched in a single unit with multi-substrate and multi-culture,which requires high control of operating conditions.In addition,AOB and AnAOB are both autotrophic bacteria,sensitive to the environment with a long doubling time and washed out with effluent easily.Therefore,it is of great significance to study how to start and optimize the one-stage PN/A reactor.In this study,the SBR equipped with dynamic membrane based on the one-stage PN/A was operated,which reactor biomass retention by dynamic membrane.The performance of the reactor,kinetics of nitrogen removal and characteristics of microbial community at different NLR were discussed during the whole operation.The conclusions of the study are as follows:（1）The reactor operated steadily for 380 days with the HRT of 24h,the ammiona concentration from 100 to 400mg/L and the nitrogen load（NLR）increased from 0.1 to0.4kgN/m3/d,and the nitrogen removal efficiency（NRE）reached up to 70.5±7.1%.The dissolved oxygen（DO）in the reactor was stable,and the concentration of dissolved oxygen was 0.20±0.05mg/L in the settlement phase.With the increase of NLR,free ammonia（FA）increased to 80mg/L,which had an adverse effect to Anammox process.（2）AOR,NOR and NRR increased with the increase of load.The ratio of NO₃^--N/ΔNH₄⁺-N was in the range of 0.1～0.3,which was close to the PN/A process.The contribution rate of nitrogen removal was the highest in the aeration stage of SBR cycle,and the ratio of contribution rate of nitrogen removal between aeration stage and standing stage was 2.15:1.（3）The dynamic membrane can effectively intercept the biomass in the reactor,and the effluent turbidity was kept around 10NTU.When the transmembrane pressure jumped to-45kpa after 20 days,the membrane was cleaned or replaced directly.The average diameter of sludge particles in the cake layer（93.30μm）was smaller than that of suspended sludge（139.20μm）,which was benificial to the interception of dynamic film.The figures of SEM showed the durability of membrane material and surface morphology of the dynamic membrane.The results of FTIR indicated that self-generate organisms in the surface of membrane material in addition to some matters intercepted by dynamic membrane from the reactor caused membrane fouling.（4）With the increase of the NLR,the reaction potential of AOB,AnAOB and NOB increased accordingly.In the activity test,the specific activity of AOB（SAOA）increased from 7.29 to 17.92gN/gVSS/d and the activity of NOB（SNOA）increased from 0.69 to2.77 gN/gVSS/d with the increase from 0.1 to 0.25 kgN/m3/d.However,,the activity of AnAOB（SAA）increased from 0.39 to 2.72 gN/gVSS/d with the NLR increased from 0.1to 0.2 kgN/m3/d,but when the NLR further increased to 0.25 kgN/m3/d,the SAA decreased to 1.55 gN/gVSS/d,which was mainly due to the inhibition of free ammonia and the presence the rapid increase of NOB activity.（5）The analysis of the distribution of sludge aggregates by using FISH technology first proved the existence of AOB and AnAOB,and the AOB was always distributed on the edge of the particles wrapped with internal clusters of AnAOB.The main phylum in the one-stage PN/A system were Bacteroidetes（20.3%）,Planctomycetes（23.87%）,Proteobacteria（15.8%）and Chloroflexi（21.59%）.Moreover,the enrichment of functional bacteria involved in the process of nitrogen removal in the reactor ensured the stable operation of one-stage PN/A process at the microbial level.Among which the genus were mainly Candidatus Jettenia（11.06%）related to AnAOB and Candidatus Brocadia（1.59%）with relative abundance of 12.65%and the genus related to AOB was Nitrosomonas with a relative abundance of 2.76%.