Study On Nitritation Performance Of Zeolite SBR In Treating Low C/N Ammonium Wastewater And The Nitrogen Removal Of Coupled Anammox

Among ammonia wastewater,achieving low-carbon and efficient nitrogen removal from low C/N ammonia wastewater is still a focus and a huge challenge in wastewater treatment field.Compared with traditional nitrification and denitrification process,partial nitritation and anammox process（PN-ANAMMOX）has the advantages of low oxygen and alkalinity consumption,no extra carbon source and less greenhouse gases N₂O production,which ensures it a bright prospect in application in treating low C/N ammonia wastewater.However,it is still essential and difficult to seek efficient and stable means to achieve nitritation for the application of PN-ANAMMOX.Based on aforementioned problems,sequencing batch reactor filled with zeolite（ZSBR）was used in this study to start up nitritation and the stability of ZSBR in treating low C/N ammonia wastewater was investigated.Finally,ZSBR（PN）and up-flow blanket filter bed（UBF）（ANAMMOX）was combined for the disposal of synthetic wastewater.The obtained results were expected to provide theoretical guidance for the actual application of the combined process.Nitritation was achieved successfully in ZSBR after only 14 cycles of operation with nitrite accumulation rate（NAR）stabilizing at over 97%.After the successful establishment of nitritation in ZSBR,the operating characteristics of ZSBR under different influent C/N（COD/NH₄⁺-N）and different kinds of organics were investigated in focus.The results showed that,NAR remained at a high level during the whole test,but nitrite production rate（NPR）was affected after adding organics.As influent C/N ratio increased from 0 to 1.5,NPR declined from 0.43±0.07 kg NO₂^--N/（m³·day）to 0.05±0.04 kg NO₂^--N/（m³·day）;with the same influent C/N,NPR in ZSBR was 0.30±0.03 kg NO₂^--N/（m³·day）,0.27±0.02 kg NO₂^--N/（m³·day）and0.24±0.01 kg NO₂^--N/（m³·day）under the conditions of glucose,enthanol and sodium acetate as carbon source,respectively.High-throughput sequencing analysis results further presented that Nitrosomonas had a high relative abundance in ZSBR,which was in favor of nitritation.However,the addition of organics caused a lower relative abundance of Nitrosomonas,leading to the deterioration of nitritation.Meanwhile,Thauera,a common genus of denitrifying bacteria,appeared in ZSBR.The mechanisms of the realization of nitritation and the influence of organics on nitritation performance in ZSBR could be concluded as follows:the nitrite accumulation was realized in ZSBR mainly attributed to the inhibitory effect of free ammonia on nitrite-oxidizing bacteria（NOB）.But NPR in ZSBR would change due to the addition of organics in influent.On the one hand,adding organics favors the rapid proliferation of heterotrophs,which would compete with nitrifiers for dissolved oxygen,ultimately slowing down the rate of nitrification.On the other hand,denitrification process was carried out by heterotrophs in the presence of organics in ZSBR,which would exhaust the generated nitrite.Finally,the coupling process of ZSBR（PN）-UBF（ANAMMOX）was carried out for the treatment of low C/N synthetic ammonia wastewater.It was found that with influent 300 mg/L NH₄⁺-N and 150 mg/L COD,the lowest effluent NH₄⁺-N concentration of 0.02 mg/L was obtained,and the average ammonia removal efficiency（ARE）and ammonia removal rate（ARR）was 98.7±1.2%and 0.59±0.02 kg N/（m³·day）,with a maximum of 99.9%and 0.62kg N/（m³·day）.Meanwhile,the combined process showed excellent total nitrogen removal performance with nitrogen removal efficiency（NRE）and nitrogen removal rate（NRR）of 88.9±1.7%and 0.53±0.02 kg N/（m³·day）.The combined ZSBR（PN）-UBF（ANAMMOX）process was feasible for efficient low C/N ammonia wastewater（C/N=0.5） treatment.