Study On Denitrification Performance Of SBR System Enriched By Thauera

At present,the nitrogen pollution in domestic sewage is mainly removed by the activated sludge technique,and the microorganism is the main body of the biological denitrification process.Thauera has excellent denitrification ability,and N₂O has attracted much attention as a greenhouse gas.Therefore,it is very meaningful to study the effect of this genus on the production of N₂O.In recent years,simultaneous nitrification and denitrification(SND)has become a research hotspot because nitrification and denitrification can occur simultaneously in the same reactor and under the same conditions.In this experiment,a series of nitrogen removal studies were carried out in SBR reactor:Firstly,the denitrification sludge system dominated by Thauera was cultured under anoxic condition,and monitoring the sludge activity and N₂O production;After successful cultivation,change the operation and cultivation conditions to induce it into the SND system(SBR1^#).Retake sludge from sewage plant for SND cultivation(SBR2^#),compared with SBR1^#system.The SND effect of the two reactors under different influent ammonia nitrogen and different influent organic carbon source concentration was investigated.Through experiments,comes to the conclusions as follows:(1)The NOx-N removal rate and COD removal rate stabilized at 100%and 87.05%after the denitrification SBR reactor was operated for 20 days.During the enrichment culture of Thauera,the denitrification activity of the sludge was enhanced and the conversion of N₂O decreased by 97.5%.The results of 16S r RNA high-throughput gene sequencing showed that Thauera was the dominant denitrification bacteria in denitrification system,which increased from 24.03%to 76.4%.(2)According to the change of nitrogen removal in SND system,the whole process aeration of SBR1^#sludge system can be divided into D1 stage(Day 5?35),D2 stage(Day 35?60)and D3 stage(Day 60?90).The TN removal rate and SND efficiency in the D1 stage were the highest,at about 84%.The whole process aeration of SBR2^#sludge system can be divided into D1 stage(Day 5?30)and D2 stage(Day 30?90).The average SND efficiency was 79.08%and 74.85%respectively.It shows that the higher Thauera content in the system is beneficial to the denitrification effect.Therefore,the sludge dominated by Thauera can be added into the reactor to achieve better SND efficiency.(3)Monitoring the water quality change in typical period,the SBR1^#sludge system has the best SND denitrification effect at D1 stage,and the effluent is only NO₂^--N.The removal rate of TN in D2 and D3 stage has decreased,and the effluent is NO₃^--N.The removal rate of TN in SBR2^#D2 stage was slightly lower than that in D1 stage,the effluent is NO₃^--N.There is no significant difference in denitrification effect between SBR1^#D3 and SBR2^#D2 stage,which indicates that Thauera may be eliminated under full aerobic conditionsthe sludge system and will eventually show similar denitrification effect after long-term operation of the two reactors under the same conditions.(4)After 1 cycle of influent ammonia nitrogen at 35mg/L,the NH₄⁺-N removal rate of the two reactors was 100%,and the SND efficiency was 72.73%and 71.58%respectively;After 1 cycle of influent ammonia nitrogen at 100mg/L,the NH₄⁺-N removal rate was 80.13%and 80.69%respectively,the SND efficiency of the system was above 95%.In addition,the TN removal rate and SND efficiency of SBR1^# were 2.40%and 1.70%lower than that of SBR2^#,which shows that the impact load resistance of SBR1^#is weaker than that of SBR2^#.(5)Under different influent COD concentrations,the TN removal rate and SND efficiency of SBR1^#and SBR2^#both increased with the increase of influent COD concentration.The TN removal rate and SND efficiency of SBR1^#D1 stage are higher than those of D3 sludge system,and the denitrification of SBR1^#D1 sludge system is better than that of SBR2^#D1 and D2 sludge system,which indicates that Thauera can improve the denitrification efficiency of the system.However,the denitrification effect of SBR2^#D2 is slightly higher than that of SBR1^#D3,which indicates that the impact load resistance of SBR1^#is weaker than that of SBR2^#.(6)The highest proportion of the two reactors in genus level was the Candidatus?Competibacter,which become predominant within the the sludge system.After the sludge system of SBR1^#was induced from denitrification to SND,Thauera was gradually eliminated.It shows that the change of conditions and long-term operation will have a significant impact on the structure of activated sludge microorganism community.