The Feasibility Study Of Different Electron Acceptors By Anammox Microorganisms

Recently years, several studies found that anammox microorganism could use NO3-、SO42-、Fe3+and manganic oxide as electron acceptor, also could use Fe2+and differentacids (formic acid, acetic acid and propionic acid) as electron donor. The study of differentelectron acceptors has important scientific significance and application value. Research ofdifferent electron acceptors (NO3-、SO42-、HCO3-) was carried out in an anaerobiccirculating fluidization reactor in which Anammox microorganism acted as an inoculum inan inorganic anaerobic environment.Through a period of more than a year the experimentresults showed that nitrogen loss was bound up with HCO3-. The verification of anaerobicbicarbonate-reducing ammonia oxidation reaction was made in this study, and thesynchronized removal biologic characteristics of HCO3-and NH4+also be studied, finallythe possible reaction mechanism was speculated. The main research results were shown asfollows:(1) In the circulation fluidization reactor, when the influent electron acceptor is NO3-、SO42-、HCO3-, the average conversion rate of NH4+-N reached328.1mg·(L·d)-1、415.7mg·(L·d)-1and434.3mg·(L·d)-1respectively. however, the electron acceptor SO42-or NO3-was not removed, indicating that the system of SO42-or NO3-electron acceptor was notoxidized NH4+, revealing that HCO3-was electron acceptor for the oxidation of ammonia.(2) Biological reaction was achieved between NH4+-N and HCO3--C based on theresults of chemical reaction experiments and biological reaction experiments.(3) The form of alkalinity had no significant effect on the conversion rate of ammonia,when the concentration of HCO3-was insufficient, the conversion rate of ammonianitrogen significantly decreased, indicating that HCO3-played a key role. The ammonianitrogen conversion rate was related to the HCO3--C/NH4+-N ratio in differentHCO3--C/NH4+-N molar ratio of water inflow, and HCO3--C/NH4+-N ratio should begreater than or equal to1.14to make the reaction smoothly.(4) In the circulation fluidization reactor, the average removal rates of HCO3--C andNH4+-N reached514.6mg·(L·d)-1and504.9mg·(L·d)-1, respectively, HCO3--C/NH4+-Nmolar conversion ratio stably kept in1.14.(5) Reaction mechanism was composed of two stages and three basic reactions in thecirculation fluidization reaction system. The first stage was two parallel reactions, namelyredox reaction of NH4+and HCO3-to NO3-, at the same time, and NH4+and HCO3- simultaneously produced intermediate NO2-. The second stage was traditional anammoxreaction of the generated NO2-and NH4+to N2.