[Influence of preservation temperature on the characteristics of Anammox granular sludge]

To study the effect of preservation temperature on the characteristics of anaerobic ammonium oxidation (Anammox) granules and optimize the preservation temperature of Anammox granules, the Anammox granules were cultivated in an upflow anaerobic sludge bed reactor through adjusting the hydraulic retention times, and the inorganic carbon with KHCO3/NaHCO3 was alternately supplied. Subsequently, the enriched Anammox granules were preserved at -40, 4 and 35 °C, and ambient temperature of (27 ± 4) °C. NaHCO3 can be used as the inorganic carbon for the growth of anaerobic ammonium oxidizing bacterium (AnAOB). The best preservation temperature was 4 °C for maintaining Anammox biomass, Anammox activity, settleability, and the integrity of the Anammox granule and AnAOB cell structure. During the preservation period, the first-order exponential decay model can simulate the decay of Anammox biomass and activity, and the decay coefficients (bAN) of Anammox biomass and activity had positive correlation with the degree of AnAOB cell lysis. Meanwhile, the rate of Anammox biomass decay was larger than that of Anammox activity. The ratio of protein to polysaccharide in extracellular polymeric substances and heme c cannot effectively indicate the changes of Anammox granules settleability and activity, respectively, and the bioactivity has a negative association with the degree of AnAOB cell lysis.