Pathway Of Carbon Fixation In An Anaerobic Ammonium Oxidation (Anammox) Process

Nitrite bacteria and anammox bacteria,as the key microorganism of anammox process,are autotrophic microbes;inorganic carbon as carbon source,have certain ability of carbon fixation.The results showed that the carbon fixation capacity of anammox process is not only affected by bacterial metabolism,but also related to the biochemical reaction process.However,up to now,there are few reports about the potential of carbon fixation in anammox process,very little research on the mechanism is involved.In this paper,partial nitrification sludge and anammox sludge were taken as the research objects in the different substrate concentration respectively to established the optimum reaction conditions,adopted ¹³C isotope tracer technique to realized the isotope label of inorganic carbon influent,¹³C isotope abundance analysis were taken with Stable Isotope Mass Spectrometer,combined with microbial molecular techniques,to determine the path of carbon fixation.The main conclusions are as follows:?1?The anammox sludge experimental results showed that nitrogen removal rate was better when the concentration of NH₄⁺-N and NO₂^--N,HCO₃^-,Ca²⁺and Mg²⁺,microbiological agents were 100 mg/L and 125 mg/L,250 mg/L,113.17 mg/L and 101.3 mg/L,1 ml/L respectively,the removal rate of NH₄⁺-N and NO₂^--N were up to over 95%,and the carbon fixation rate associated with nitrogen removal,the more amount of nitrogen removal,the higher rate of carbon fixation,the maximum rate of carbon fixation was up to 12.93%.?2?The partial nitrification sludge experimental results showed that nitrogen removal rate was better when the concentration of NH₄⁺-N,HCO₃^-,Ca²⁺and Mg²⁺,microbial promoters were 15 mg/L,250 mg/L,113 mg/L and 100 mg/L,1 ml/L respectively,the maximum accumulation rate of nitrite was up to 96.95%,had a positive correlation between the nitrogen removal amount and carbon fixation rate,the maximum rate of carbon fixation was up to 5.31%.?3?¹³C isotopic abundance test results showed that the ¹³C abundance of anammox and partial nitrification sludge increased to a certain extent which labeled the ¹³C isotope,compared with the blank samples,the ¹³C abundance of anammox sludge increased from 1.07%to over 1.17%,the ¹³C abundance of partial nitrification sludge increased from 1.06%to over1.27%.And suggested that inorganic carbon influent went to the body of microorganisms.?4?The molecular microbiology research results showed that the functional gene followed the Calvin cycle for carbon fixation existed in anammox sludge and partial nitrification sludge,and the gene abundance on nitrogen had higher level of response than other substrates.