Simultaneous Aerobic Oxidation,Shortcut Nitrification-Denitrification Coupled With Anaerobic Ammonia Oxidation(ANAMMOX)By SBBR Treating High Ammonium And Low C/N Ratio Wastewater

Organic carbon and nitrogen removals by conventional biological nitrogen removal process removing were limited severely due to high ammonia and insufficient C/N ratio of high ammonia and low C/N ratio wastewater leading to effluent TN exceeding the standard.Its effective treatment has been a research hotspot and difficulty in the field of domestic and abroad wastewater treatment.Thus,it is important to develop a novel process removing organics and nitrogen to treat high ammonia and low C/N ratio wastewater.Sequencing batch biofilm reactor(SBBR)integrates advantages of SBR and biofilm process have been widely applied to treat high ammonium and low C/N ratio wastewater.However,there were few studies on new treatment process and related mechanism for treating high ammonium and low C/N ratio wastewaters by SBBR process.In this study,a novel single-reactor process coupling simultaneous aerobic oxidation,partial shortcut nitrification-denitrification and Anaerobic Ammonia Oxidation(ANAMMOX)was developed to achieve simultaneous efficient removal of COD,NH4+-N and TN using a SBBR reactor with polyurethane as the carriers treating treat high ammonium and low C/N ratio wastewaters.Furthermore,the mechanism of simultaneous removal of nitrogen and carbon was also explored.The findings will provide theoretical basis for process design and technical application for enhanced treatment of high ammonium and low C/N ratio wastewater.The main results were achieved as follows:(1)The experiment was continuously operated for more than 140 runs.And the removal capacity of nitrogen and COD for treating high ammonia and low C/N ratio wastewater by PU-SBBR system was investigated under different operating stages(R1-R4).The results demonstrated that,NH4+-N and COD was removed by complete nitrification and denitrification due to low ammonium loading and long HRT in R1 stage.The average removal efficiency of COD,NH4+-N,TN was 98.7%,89.5% and 38.1%,respectively.And nitrite accumulation ratio was only lower than 5%.In R2 stage,nitrite accumulation rate increased to92.3% with the increase of ammonia nitrogen loading and aeration rate,removal efficiency of COD,NH4+-N,TN was averagely 93%,98% and 65%,respectively.On the basis of R2 stage achieving shortcut nitrification denitrification in the system,in R3 stage pale red biofilm was observed by controlling C/N of 3 and maintaining DO of 1.3 mg/L.90.7% of NH4+-N removal and 87.5% of nitrite accumulation ratio was achieved.Meanwhile,COD removal efficiency was 94% and the best TN removal efficiency was further increased to 85.6%.Nitrogen and COD mass balance and chemometrics showed that 53.6% of TN was removed by shortcut nitrification-denitrification and 41.2% was contributed by ANAMMOX path.Around 71.9%of COD were removed by aerobic biodegradation and the rest were contributed by denitrification.It indicated that aerobic biodegradation,shortcut nitrification denitrification and ANAMMOX were simultaneously coupled in the system.In R4 stage,however,removal efficiency of NH4+-N and TN removal was decreased from 89% and 84.6% to 79% and 74%,respectively due to reducing ANAMMOX as the aeration rate was further increased.Optimum process parameters for coupling of aerobic biodegradation,shortcut nitrification-denitrification and ANAMMOX were C/N of 3,influent ammonia loading of0.188 kg/(m3 d),COD loading of 0.563 kg/(m3 d),aeration rate of 200 mL/min and DO of 1.3mg/L.(2)PU-sponge carrier has high porosity and specific surface area and Rq was 41.31 nm.Hydroxyl,amine and imine groups and other active groups in PU sponge favored that microorganisms were more easily attached rapidly enriched in the biofilm.Appearance and SEM Obseration found that the colors of biofilm in PU-sponge carrier at different stages R1-R4 were light yellow,yellowish-brown,shallow red and yellowish-brown,respectively.In R3,achieving the highest removal efficiency of TN,SEM showed that the structures ofbiofilm were compact and the majority of microorganisms were cocci and filamentous bacterium.3D-EEM and FT-IR analysis found that the presence of a relatively high tryptophan protein-like substances and suitable amount of humic-like substances were able to promote the aerobic degradation,shortcut nitrification denitrification coupling ANAMMOX in the system.Oxygen microelectrode measurement showed that anaerobic zone accounted for 58.1% in the biofilm at aeration rate of 200mL/min with bulk DO concentration in liquid phase of 1.3 mg/L,whereas unfavorable achievement of simultaneous aerobic biodegradation,shortcut nitrification-denitrification coupling ANAMMOX was at too high or too low oxygen in anaerobic microzones.The dense or loose structure of biofilm had isolated holes or holes through the outside,helping to promote the oxygen and mass transfer in biofilm.Oxygen transfer kinetic studies showed that the oxygen transfer coefficients was 3.3×10-5 m2/d.(3)High-throughput sequencing results showed that the most abundant phylum and class was Proteobacteria and ?-Proteobacteria,respectively in PU-SBBR system treating high ammonium and low C/N ratio.Ammonia oxidizing bacteria(AOB)and nitrite oxidizing bacteria(NOB)and their abundance were closely related to the treatment efficiency of.the system.Nitrosomonas and Nitrospira were the main genera of AOB and NOB,respectively.A large number of Brocadiaceae families and Candidatus Anammoxoglobus strains,belonging to anaerobic ammonia oxidizing bacteria were detected in R3 stage indicating occurring ANAMMOX but it was distinctly decrease in R4 stage.28 kinds of denitrifying bacteria in the system were detected in four stages,accounting for more than 30% of total bacteria.Furthermore,dominant denitrifying bacterial genera included Thauera,Comamonas,Thermomonas,Azospira and Dechloromonas.From RDA analysis,the influent ammonia nitrogen load and C/N ratio are important driving factors for simultaneous aerobic oxidation,shortcut nitrification-denitrification coupled with anaerobic ammonia oxidation(ANAMMOX).(4)Biokinetic analysis suggested that the modified Stover-Kincannon model was more suitable for predicting ammonium nitrogen removal and TN removal,while Monod-biological contact oxidation model was applicable for predicting COD removal.According to the results of model optimum,the maximum ammonium removal rate was 10.2459 kg/(m3 d),TN removal rate was 0.1345 kg/(m3 d),and the maximum removal rate in unit area of carrier is0.0084 g/(m2 d).It showed that the PU-SBBR system had a great potential for treating high ammonium and low C/N ratio wastewater.(5)Simultaneous coupling of aerobic oxidation,shortcut nitrification,denitrification and ANAMMOX in the single PU-SBBR system treating high ammonia and low C/N ratio wastewater through the process control and optimization,achieving efficiently simultaneous removals of NH4+-N,COD and TN.The process will break through the bottlenecks of ANAMMOX-based process for treating wastewater of C/N ratio and further improve wastewater treatment efficiency of simultaneous nitrogen and COD removal and have wide application prospects.