Realization Of Feammox And Study On The Effect Of Added Nitrate

Excessive nitrogen in aquatic systems can lead to acidification and eutrophication.Nitrogen removal from wastewater is of great significance for protecting water resources.A variety of nitrogen removal technologies have emerged in engineering,and anaerobic ammonia oxidation technology（Anammox）with NO₂^-as electron acceptor is widely concerned.However,NO₂^-is easily oxidized,difficult to obtain in practical engineering,and Anammox bacteria are very sensitive to environmental requirements.Industrial wastewater often contains large amounts of iron ions,affecting the operation of Anammox process.In recent years,Feammox process,which uses Fe³⁺instead of NO₂^-as electron acceptor,is considered to be a green and efficient new nitrogen removal process,which has practical engineering significance.However,due to the lack of research on Feammox,the reaction pathway is not clear,and the denitrification rate needs to be improved.Therefore,this thesis domesticated Anammox sludge,analyzed the potential of Feammox occurrence and started operation,and the effect of extra addition of nitrate on the denitrification effect of Feammox was explored to find the optimization method.It was found that the rapid start-up of Anammox could be achieved by continuously reducing hydraulic retention time（HRT）and increasing nitrogen load in SBR reactor with secondary sludge as inoculum.The results showed that the removal rate of NH₄⁺was 91.6%on the 90_thday,the color of sludge became red and granular gradually,and the number of spherical bacteria increased under electron microscope.The 16Sr RNA microbial detection showed that the functional bacteria of Anammox were successfully enriched.When exploring the occurrence potential of Feammox based on the Anammox system,it was found that the addition of Fe³⁺could cause extra nitrogen loss and improve the system stability.When the Fe³⁺concentration was 0.08 m M/L,the nitrogen removal rate was the highest and the nitrogen ratio error was the smallest.When the concentration of Fe³⁺was 0.16m M/L,the sludge settleability in the reactor was the best.The experiment proved that Fe³⁺could be used as the electron acceptor of NH₄⁺,and had a positive effect on Anammox,indicating that the occurrence of Feammox was possible.Feammox was started by inoculating Anammox sludge.It was found that when the influent Fe³⁺concentration increased to 30mg/L,the system could achieve stable nitrogen removal,and the addition of NO₂^-promoted the operation of Feammox.Through grouping experiments,it was proved that Feammox was a biological reaction,which was a new way for denitrification with NH₄⁺and Fe³⁺as reactants,and Feammox occurs with Anammox and NDFO simultaneously.Microbial detection found that although the Anammox bacteria in the system gradually replaced by Feammox bacteria,there is still a certain proportion.When further exploring the optimization effect of nitrate on Feammox,it was found that adding an appropriate amount of nitrate can effectively improve the denitrification capacity of the system and promote the enrichment of functional bacteria of Feammox and NDFO.And when the temperature was 30℃,p H was 6.5 and there was no organic matter added,it was the optimal process operation condition in the optimization system.The research conclusion provided a practical and theoretical basis for the optimization of Feammox.