Start Up And Operation Performance Of SNAD Process Based On SBBR

Simultaneous Nitrification,Anammox and Denitrification（SNAD）has the advantages of high nitrogen removal efficiency,low carbon source and low sludge yield.The nitrification and denitrification processes of SNAD are related to the release of N₂O.Therefore,understanding the N₂O production mechanism and release characteristics of the SNAD process in nitrogenous wastewater can also help to understand it’s performance.Therefore,this study used an SBBR reactor to successfully operate the SNAD process at a high oxygen concentration throughout the aerobic under the two operating modes i.e.An/O/A（anaerobic/aerobic/anoxic）and O/A（aerobic/anoxic）conditions.The effects of different carbon to nitrogen ratio（COD/N）of 0,1and 2 on the denitrification efficiency of SNAD reactor and the characteristics of N₂O production and release were studied,and the microbial population structure in the reactor was analyzed.The major findings of the study are as follows:（1）After the 116d culture,the SBBR reactor reached to stable operation.The removal rates of NH₄⁺-N and TN reached 98%and 90%respectively,The corresponding total nitrogen volume load and total nitrogen removal load were 0.27±0.01 kg N m^-3 d^-1 and 0.25±0.01 kg N m^-3 d^-1 respectively.（2）Based on the stable operation of the SNAD reactor,the effects of different COD concentrations on the nitrogen removal in the reactor were investigated in the An/O/A and O/A modes.The experimental results show that in the An/O/A mode,when the influent COD/N=2is lower than COD/N=0 and 1,the removal rate of NH₄⁺-N and TN are lower.In the O/A mode,as the influent COD concentration increases,denitrification converts more nitrite and nitrate nitrogen into N₂,resulting in high ammonia nitrogen and total nitrogen removal rates.（3）For the N₂O production in the SNAD process,the N₂O production and release in case of COD/N 1 and 2 were investigated based on the stable operation during the An/O/A mode.The results showed that the influent COD concentration increased,the N₂O production and release factor were also increased,and the total N₂O production with influent COD/N of 1 and2 was 27.72 mg·L^-1 and 42.91 mg·L^-1 respectively.Its release factor（N₂O release/ammonia nitrogen removal total）was found 20%and 30%respectively.（4）Microbial flora structure identification of biofilm samples in SBBR.The results showed that the dominant bacteria in the system were Proteobacteria（58.6%）;the main genus was Nitrosomonas（7.3%）Thauera（7.05%）,Saccharibacteria_genera_incertae_sedis（6.21%）,Candidatus Kuenenia（1.1%）.