Study On Reaction Mechanism Of Feammox And The Functional Microbial Community

The discoveriy of Anammox reaction provides a new understanding of nitrogen transformation in nature.With further research,the scholars found that not only NO2-,but also Mn4+,SO₄^2-and organic acid can be used as electron acceptors for the oxidation of NH⁴⁺ in the anaerobic condition by Anammox microorganisms.At present,researchers have found that there was the phenomenon of reaction by Fe³⁺ and NH⁴⁺ in nature which was defined as Ferric ammonium oxidation?Feammox?,but its mechanism reported on the reaction was not uniform and the laboratory study basis of Feammox reaction was not sufficient.In this paper,we using Fe³⁺ as the only electron acceptor for ammonia oxidation,studied the biological conversion process of Fe³⁺ and NH⁴⁺ through long term operation in the anaerobic sequencing batch reactor.By adding additional oxidant NO^3-or O2 to the reactor to made the reaction phenomenon more obvious in the system and explored the reaction mechanism and functional microorganism of Feammox through material transformation of trial batch reactor and isotope tracer technique and macro genome sequencing technology with traditional anammox sludge under anaerobic conditions.The conclusions are as follows:?1?With traditional anammox sludge under anaerobic conditions,the NH⁴⁺ appeared to transformation after the operation of 32 d in sequencing batch reactor,continue to running 24 d with stable removal of NH⁴⁺,the synchronous transformation of NH⁴⁺ and Fe³⁺ was occurs.The average effluent concentration of Fe2+ was as high as 19.58mg·L-1 and the average capacity of NH⁴⁺-N transformation was 3.45mg·L-1 while the average conversion rate was 3.45mg·?L·d?-1 with influent concentration of NH⁴⁺-N and Fe³⁺ were 50.00 mg·L-1 and 30.00 mg·L-1.The reaction product were NO^3-,N2 and Fe2+.?2?Both conversion rate of NH⁴⁺-N after addition of the two oxidants were improved.With NO^3-as an oxidant,the average conversion rate of NH⁴⁺-N was 9.34 mg·?L·d?-1,while the Feammox reaction leads to the average conversion rate of NH⁴⁺-N during 4.55⁹.34 mg·?L·d?-1.With O2 as an oxidant,the average conversion rate of NH⁴⁺-N was 31.58mg·?L·d?-1,in which parts of the transformation of NH⁴⁺-N was caused by the Feammox.?3?Using macro genome sequencing methods measured the strains of microorganisms anaerobic sequencing batch reactor and continuous flow reactor,results show that the advantages of strain in the inoculating anammox sludge was changed after long-term Feammox reaction environment.The proportion of Ignavibacteria in inoculation sludge was 16.72%,while increase to 34.00% after 99 d running in anaerobic sequencing batch reactor and 21.52% after 172 d running in continuous flow reactor which may was the functional microbial of Feammox.At the same time,the Planctomycetes still exists in the system which indicates that there were microorganisms which could carry out Anammox reaction.?4?Through the solid-liquid phase material of import and export,the product and concentration of rection in batch test experiments combined with isotope tracer technique to analysis the mechanism of Feammox rection.We draw a conclusion that the Feammox reaction is Fe³⁺ as the electron acceptor oxidation NH⁴⁺,the reaction products is NO2-and Fe2+.At the same time,the Anammox microorganisms used the NO2-above producted to oxidation NH⁴⁺,the main end product of nitrogen in the system was N2.