Nitrogen Removal Performance of Continuous Anoxic/Oxic System Using Activated Sludge and Sludge Biofilms

Nitrogen is the most important component for living beings while the excessive discharge of organic and inorganic nitrogen may create severe environmental problems.In this study,a continuous anoxic/oxic(A/O)reactor adopting activated sludge and sludge biofilms in the anoxic and oxic zones was applied for total nitrogen(TN)and chemical oxygen demand(COD)removal,and the efficiencies of nitrification and denitrification were compared as well.Results showed that when using activated sludge,the effluent concentrations of NH_(4)^(+)-N,NO_(3)^(-)-N,NO_(2)^(-)-N,TN and COD were inconsistent and fluctuated greatly,and the removal efficiencies of corresponding nitrification,denitrification and TN were also unstable;the obtained average COD removal efficiency was 85%.While using sludge biofilms,the acquired effluent concentrations of NH^(+)_(4)-N,NO^(-)_(3)-N,NO_(2)^(-)-N,TN and COD became stable and constant.The nitrification,denitrification,TN and COD removal efficiencies were 96%,84%and 65%and 94%,respectively.Bacterial community analysis of sludge biofilms indicated that the genus Arcobacter was the major denitrifiers in the anoxic zone with relative abundance of 76.1%,and in the oxic zone the abundances of Acinetobacter,Hydrogenophaga and Nitrospira responsible for complete nitrification were 20.05%,7.6%and 3.7%respectively.The high abundance of nitrifying bacteria and denitrifiers were related with the high and stable nitrogen and COD removal.

In situ electron-induced reduction of NOx via CNTs activated by DBD at low temperature

In this study,a new in situ electron-induced process is presented with carbon nanotubes(CNTs)as a reduction agent activated by dielectric barrier discharge(DBD)for nitrogen oxide(NOx)abatement at low temperature(<407 K).Compared with a single DBD system and a DBD system with activated carbon(DBD-AC),a DBD system with carbon nanotubes(DBD-CNT)showed a significant promotion of NOx removal efficiency and N2 selectivity.Although the 02 content was 10%,the NOv conversion and N2 selectivity in the DBD-CNT system still reached 64.9%and 81.9%at a specific input energy(SIE)of 1424 J^L,and these values decreased to 16.8%,31.9%and 43.2%,62.3%in the single DBD system and the DBD-AC system,respectively.X-ray photoelectron spectroscopy(XPS)and scanning electron microscopy(SEM)were utilized to investigate surface changes in the CNTs after activation by DBD to explore the NO.t reduction abatement mechanism of this new process.Furthermore,the outlet gas components were also observed via Fourier transform infrared spectroscopy(FTIR)to help reveal the NOr reduction mechanism.Experimental results verified that carbon atoms excited by DBD and the structure of CNTs contributed to the synergistic activity of the DBD-CNT system.The new deNOx process was accomplished through in situ heterogenetic reduction reactions between the NOx and carbon atoms activated by the plasma on the CNTs.In addition,further results indicated that the new deNOv process exhibited acceptable S02 tolerance and water resistance.