Characterization of magnetite assisted anammox granules based on in-depth analysis of extracellular polymeric substance (EPS)

Magnetite can be considered as an iron-rich carrier particles that can be ionized into Fe2+ and Fe3+ which im-proves the activity and aggregation of anammox bacteria. Three samples from this carrier assisted granulation reactor with size groups including Flocs, FL (0-300 mu m), Small Granules, SG (300-500 mu m) and Large Granules, LG (500-1000 mu m) were used in this study. It was observed that as the granule size increased, the iron-rich carrier content increased, and their active crystals improved the microbial cell density. Specific anammox ac-tivity (SAA) was 34.63 +/- 5.02, 55.29 +/- 5.14, and 63.81 +/- 7.50 mg-N/g-VSS/d for FL, SG and LG, respectively. In addition, in heme c content of LG was 31.5 % higher than SG and 62.9 % higher than FL. An in-depth study into the extracellular polymeric substances (EPS) showed that the secretion intensity of essential proteins followed the order of FL < SG < LG in loosely bound EPS and FL > SG > LG in tightly bound EPS. Functional group analysis confirmed that the hydrophobic C-N and N-H stretching vibration band had almost 3.5 times higher transmittance intensity in LG than the other sizes and the corresponding ratio of alpha-helix/(beta sheet + random coil) in secondary derivative proteins analysis showed tightness in the protein structures of FL. The relative abundance of Brocadia Sinica increased from 0 % in FL to a high of 20.46 % in LG. This study aims to communicate the essence of in-depth EPS analysis beyond the usual EPS yield and major contents of proteins (PN) and poly-saccharides (PS) analysis.