Study On The Start-up Of Simultaneous Anammox And Denitrification Process And Treatment Efficiency For Breeding Wastewater

The development of aquaculture produces a large number of breeding wastewater.The disadvantages of traditional biological treatment of breeding wastewater,such as high energy consumption and sludge yield,are gradually exposed.It is a trend to study thealternativetechnologyoftraditionalbiologicalmethod.Simultaneous Anammox and denitrification（SAD）,which combines Anammox with denitrification,has the advantages of high treatment efficiency and low energy consumption,and can achieve the purpose of simultaneous nitrogen and carbon removal.During the operation of sad process,certain impact resistance is required,such as the change of COD concentration in the influent,the change of temperature in differeent seasons,and the instability of NO₂^--N/NH₄⁺-N caused by different reaeration degrees of front reactor.Therefore,it has important practical value to study the influence of these factors on SAD to enhance the stable operation of SAD.In view of these problems,this paper studies the start-up of Anammox and SAD process and the impact resistance of SAD process.The main conclusions are as follows:（1）The denitrification characteristics and microbial community changes during the start-up of Anammox were studied.After increasing the influent concentration of NH₄⁺-N and NO₂^--N,the Anammox was started successfully.The average removal rates of NH₄⁺-N,NO₂^--N and TN were 97.6%,94.1%and 85.6%respectively,and the TN volume removal load was 1.11kg·（m³·d）^-1.ΔNO₂^--N/ΔNH₄⁺-N和NO₃^--N/ΔNH₄⁺-N are slightly lower than the theoretical values of 1.32 and 0.26.During the start-up process,the Anammox activity of the sludge increased gradually,and the Anammox activity of the lower sludge was higher than that of the upper sludge.After the successful start-up,the diversity and richness of microorganisms in the reactor decreased,and An AOB were enriched.Candidatus Kuenenia replaced Candidatus Brocadia as the main An AOB.（2）The start-up of SAD process was studied by increasing COD concentration of influent water With the increase of COD concentration in the influent,the effluent of NH₄⁺-N and NO₂^--N was stable,and the average removal rate of TN was more than 98%;the removal rate of TN gradually increased.When the COD concentration in the influent was 330mg·L^-1,the average removal rate of TN was 95.6%,which was 6.8%higher than the TN removal rate of Anammox theory.After SAD was started,the activity of Anammox decreased slightly,the denitrification activity of sludge increased significantly,and the denitrification activity of upper sludge was higher.The main functional microorganisms related to nitrogen and carbon removal were Anammox,denitrification and anaerobic fermentation bacteria.The abundance of An AOB decreased after the start-up of SAD while and the anaerobic fermentation bacteria and denitrifying bacteria increased significantly.（3）The effect of NO₂^--N/NH₄⁺-N on SAD process was studied.After the fluctuation of influent substrate NO₂^--N/NH₄⁺-N,the average removal rate of NH₄⁺-N in SAD reactor decreased from 98.1%to 93%,while the average removal rate of NO₂^--N before and after the fluctuation of substrate was both higher than 98%.In the fluctuation of substrate,COD removal rate and TN volume removal load are relatively stable,and the nitragen and carbon removal effect of SAD process has good impact resistance to the fluctuation of influent NO₂^--N/NH₄⁺-N.The results of batch test showed that the degradation of NO₂^--N and NH₄⁺-N decreased linearly in 0～10h,and tended to be stable slowly after 10h.The concentration of NO₃^--N increased first and then decreased in the reaction,and reached the maximum value in 10～12h.With the increase of NO₂^--N/NH₄⁺-N in the raw water,the maximum value of NO₃^--N increased gradually.After 24 hours of reaction,the change rules ofΔNO₂^--N/ΔNH₄⁺-N,COD removal rate and denitrification contribution rate are the same,the overall trend of which were gradually increasing with the increase of NO₂^--N/NH₄⁺-N in the raw water.（4）The effect of seasonal temperature change on the nitrogen and carbon removal efficiency of SAD and the recovery performance of SAD after low temperature operation were studied.The temperature range of SAD reaction was 10.1℃～31.8℃.In the process of temperature change from summer to winter,when the reaction temperature is higher than 15℃,SAD can keep a good effect of nitrogen and carbon removal.The average removal rate of three nitrogen can keep above 93%,and the average removal rate of COD is more than 80%.When the reaction temperature is lower than 15℃,the average removal rate of NH₄⁺-N and NO₂^--N were below 80%.15℃is the critical temperature for the nitrogen removal effect of SAD.After a long time of low temperature suppression,the removal rate of NH₄⁺-N improved after the temperature increased,but it was still lower than that in summer and autumn.After the recovery,the removal effect of TN basically reached the level of summer and autumn,and the removal effect of COD remained good.From June 19 to November 21,the abundance of An AOB in SAD reactor was 8.8%～11.7%,and the nitrogen removal effect of SAD was good.At this stage,Candidatus Kuenenia replaced Candidatus Brocadia as the main An AOB.From November 21 to December 30,denitrifying bacteria became the most abundant functional bacteria,the main denitrifying bacteria were Thauera and Hydrophaga.From December 30 to January 21 of the following year,after 22 days of temperature rise recovery,the abundance of An AOB recovered from 4.2%to 6.6%.In the process of seasonal temperature change,the high abundance of anaerobic fermentation bacteria and denitrifying bacteria in the reactor makes SAD keep a great removal of COD.Compared with the single Anammox process,SAD process is more suitable for the adverse effects of low temperature and has good impact resistance.It is feasible to apply SAD process to the treatment of breeding wastewater,which can not only obtain good nitrogen and carbon removal,but also reduce the operation cost.The results of this paper show that the law of pollutant removal in the process of Anammox and SAD start-up is closely related to the characteristics of microbial community.The influent NO₂^--N/NH₄⁺-N and seasonal temperature change are important factors of the nitrogen and carbon removal efficiency and microbial community.The analysis shows that it is feasible to apply SAD to the treatment of breeding wastewater,which can not only remove pollutants better,but also reduce the operation cost.