The Enhancement By Electrical/Magnetic Field And Multi-species Coupling Of ANAMMOX Technology For Autotrophic Nitrogen Removal

The ANarobic AMMonium OXidizing(ANAMMOX) was verified to have the potential to convert ammonium with nitrite as electron acceptor to N₂ under anoxic condition.Although this novel nitrogen removal technology has been investigated for more than ten years,the stringent metabolism conditions and extremely slow growth rate of the ANAMMOX bacteria have restricted its application to pilot-scale plants.To solve these problems,the thesis work was systematically performed with the ANAMMOX consortium,including the corresponding characteristics to shorten the start-up period of ANAMMOX process in via of enhancing the ANAMMOX bacteria activity by electric and magnetic field,as well as the basic mechanisms of multi-species coupling processes based on ANAMMOX to enlarge the application scale of ANAMMOX process. Some innovative findings have been made as follows:(1) The magnetic field was useful for fast start-up of ANAMMOX process since it was proved as a convenient approach to enhance anaerobic ammonium oxidizing activity.A maximum 50%increase was obtained at the value of 75.0 mT.AnANAMMOX reactor with magnetic field of 60.0 mT was operated in laboratory-scale.The results demonstrated that a significant 30%increase in maximum nitrogen removal rate and an approximate 1/4 saving in cultivation time were achieved by using the magnetic system.Microbiological community analysis indicated that the strains belonging to genus Planctomycetes sp.were highly enriched. Plactomycetes sp.approximately accounted for 60%and 80%of the bacteria in the no-magnetic ANAMMOX biofilm and magnetic ANAMMOX biofilm,respectively.(2) The electric field was useful to enhance anaerobic ammonium oxidizing activity of ANAMMOX consortium,and further to shorten the start-up of ANAMMOX process.The highest activity was achieved at electrode voltage of -0.05 V_SCE with 20%increasement. When electrode voltage of -0.05 V_SCE Was supplied,approximate 1/5 saving in the start-up time of ANAMMOX process compared with control experiment.Moreover,the TN removal efficiency could reach 99.8%to compete the nitrogen elimination.Microbiological community analysis validated that the Planctomycetes sp.were highly enriched,and the diversity of bacterial community structure dramatically changed when voltage of -0.05～-2.2 V_SCE was supplied.Some Pseudomonas sp.were enriched for the autotrophic denitrification in biofilm-electrode ANAMMOX reactor.(3) Urea nitrogen removal was realized in the ANAMMOX reactor via the combined process of urea hydrolysis by Bacillus sp.LST-1 and ammonium oxidizing by ANAMMOX bacteria.The pure ANAMMOX bacteria were obtained by percoll density-gradient centrifugation and found to be of incapable to hydrolyze urea.Bacteria spread plate and streak, and comparative analysis of partial 16S rRNA sequence indicated that the ureolytic bacteria belonging to Bacillus sp.Form field application view,this autotrophic and anoxic combined process is used to widen the application of ANAMMOX technology.(4) The simultaneous NH₄⁺-N and SO₄^2- removal was achieved in an anaerobic,autotrophic reactor,consisted of NH₄⁺-N oxidization with SO₄^2- deoxidization,and subsequently traditional anammox process.Microbiological community analysis revealed that a new organism belonging to Planctomycetales was strongly enriched.The new species,named Anammoxoglobus sulfate,was so considered to play a critical role in the NH₄⁺-N oxidization with SO₄^2- deoxidization to NO₂^--N.Afterwards,the Planctomycetes sp.existing in the bacteria community performed the anammox process.The new anaerobic ammonium and sulfate process can offer a great future potential to widen the application of ANAMMOX technology.(5) The ANAMMOX consortium was found to adapt to the wastewater containing dissolved oxygen(DO).Batch tests indicated the maximum aerobic ammonium oxidizing activity of the consortium was 1.38 mmolNH₄⁺-N/(gVSS·day),which played key roles in the oxygen consumption process;the maximum anaerobic ammonium oxidizing activity was slightly decreased after long-term oxygen exposure,but only from 21.23 mmolNH₄⁺-N/(gVSS·day) to 20.23 mmolNH₄⁺-N/(gVSS·day).Microbiological community analysis identified two strains similar to Nitrosomonas eutropha() were responsible for oxygen consumption,which were able to exist in the autotrophic anaerobic condition for long periods and protect Planctomycetes sp.from the influence of oxygen.The possibility of DO adaptation in cultivation anammox consortium will lead to substantial savings of energy and resource to the treatment of high-ammonium wastewater.(6) Additional salinity can be served as a positive monitoring strategy for the successful start-up of CANON process.Batch tests indicated that 10 gNaCl/L was a preferable definite level to stand out ammonium oxidizing activity and ANAMMOX activity,and selectively suppress nitrite oxidizing activity.Reactor operation showed that the nitrogen removal rate was increased from 0.4 kg N/(m³Â·day)to 0.6 kg N/(m³Â·day) after salinity addition,with the increased TN removal percent from 54%to 80%.Microbiological community analysis revealed that Nitrospira sp.were specialized nitrite oxidizers existed in oxygen-limited condition,which were eliminated under salinity exposure.Moreover,Planctomycetes sp.and Nitrosomonas sp.could be highly enriched.Salinity-contained high ammonium wastewater will be considered as suitable influent for CANON process in industrial application.