The properties of anaerobic ammonium oxidation (anammox) granules: Roles of ambient temperature, salinity and calcium concentration

In the present study, the effects of temperature, salinity and calcium concentration on the properties of anaerobic ammonium oxidation (anammox) granules were comparatively investigated using four upflow anaerobic sludge blanket (UASB) reactors. The results demonstrated that the metabolic pathway of the anaerobic ammonium oxidizing bacterium (AnAOB) with its inner structure was changed following the addition of salt. The reaction ratios shown a considerable change. Both low ambient temperature and cell lysis reduced the activity, diameter and strength of the granules. A calcium concentration of 152 mg Ca2+ L−1 protected AnAOB from lysis and deformation under salinity stress. The precipitation of calcium improved the strength and density of the anammox granules, resulting in amelioration of settleability but a reduction in the diameter and the ratio of volatile suspended solids to suspended solids. In addition, the precipitation of calcium also reduced the activity of AnAOB.