| Deammonification process is a promising technology for nitrogen removal,which brings municipal wastewater treatment plants(WWTP)closer to energy autarky.However,compared to the widely application of ammonium-rich wastewater treatment,mainstream deammonification process is still difficult to maintain stability.The Instability of long-term partial nitritation process because of the difficulty of inhibiting NOB is still a major problem,hindering the application of deammonification process in municipal wastewater treatment.Besides,many existing WWTP use A/O,A2/O,or other plug-flow processes,if mainstream one-stage deammonification can be achieved by slightly modifying existing plug-flow installations,the great advantages of cost cannot be ignored.In this study,a plug-flow reactor designed with reference to A/O reactor was used,filled with fixed carriers and using deammonification process.And this reactor was named one-stage deammonification plug-flow fixed bed biofilm reactor.In this study,this reactor was used to explore the start-up and stable operation strategies.To explore the microbial mechanism to maintain stable performance of the deammonification process,spatial variations of bacterial community structures were investigated.Finally,real domestic sewage after high rate activated sludge process pretreatment was treated by the deammonification plug-flow fixed bed biofilm reactor to evaluate nitrogen removal performances.The deammonification process was started-up successfully after 110 days of operation,and 98.8% of ammonium removal efficiency,90.6% of total nitrogen removal efficiency and 124.6 g N/(m~3·d)of nitrogen removal rate were obtained on 110 d.Through analysis of nitrogen removal performances and adjustment measures,it was revealed that high temperature(30°C),appropriate influent COD concentration(70 mg/L),intermittent aeration,residual ammonia in the reactor,low DO concentration,and total aeration control based on effluent nitrogen concentration contributed to the stability of deammonification system.Further studies indicated that incapable of precise control of aeration limited the highest performance.Thus,due to the instability of aeration rate,the ammonium removal efficiency and the total nitrogen removal efficiency fluctuated from 86.8% to 100% and from 76.4% to 91.6%,respectively.High-throughput sequencing analysis revealed the spatial variations of community structures.Proteobacteria,Bacteroidetes and Chloroflexi were dominated in the front of reactor,and Planctomycetes,Proteobacteria,Chloroflexi and Uncultured phylum OD1 were dominated in the end of reactor.Anammox bacteria were always dominated by Candidatus Jettenia while Candidatus Brocadia abundance increased along with plug-flow distance.The abundance of AOB dominated by Nitrosomonadales was surprisingly low in the front of reactor.The abundance of NOB dominated by Nitrospira increased along with plug-flow distance.This study shows that spatial variations of bacterial community structures in the plug-flow system contribute to maintaining stable deammonification due to efficiency NOB inhibition.In order to investigate the feasibility of the one-stage deammonification plug-flow fixed biofilm reactor invented in this study for the treatment of actual domestic sewage,real domestic sewage after high rate activated sludge process pretreatment was treated by the deammonification reactor.The results showed that the pre-treated domestic sewage with average COD concentration of 81.6 mg/L and average ammonium concentration of 44.9 mg/L were obtained after pretreatment.And after the deammonification reactor treatment,the average effluent COD concentration,ammonium concentration,total nitrogen concentration,and nitrogen removal rate were 28.5 mg/L,3.7 mg/L,7.9 mg/L and 149.9 g N/(m~3·d),respectively.These results indicated that the system composed of a high rate activated sludge reactor and a one-stage deammonification plug-flow fixed bed biofilm reactor was able to treat real domestic sewage and maintain stable operation. |
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