| Abstract:In order to understand the calcification of granular sludge in papermaking wastewater treatment system, the granular sludge calcification of a recycled papermaking wastewater plant in Shaanxi Province was traching for nearly one year. The morphological structure, inorganic content and type of granulated sludge calcification and the effect of anaerobic treatment were investigated. The results showed that with the deepening of calcification of the sludge, the removal rate of Ca2+ and COD by granular sludge decreased, the content of inorganic components in granular sludge increases, and the color of granular sludge after drying changed from dark to light, in terms of the type of inorganic matter in the granular sludge, CaCO3 mainly existed in the form of calcite and was doped with a small amount of SiO2， in the later stage, CaCO3 coexisted in the form of calcite and aragonite, accompanied by FeCO3 and Fe2O3.The broles and cavities in the structure of the granular sludge were reduced, instead it was covered by deposits of flakes and granular aggregates, and the rod-shaped bacteria and the cocci were reduced. The sub-classification level of methanogens in granular sludge was analyzed by High-throughput sequencing. It was found that the proportion of acetic acid-type methanogens increased gradually with the prolongation of reactor operation time, and the proportion of hydrogen-trophic methanogens decreased significatly. Finally, the existing calcification control measures or methods were reviewed, and a new idea of enriching functional flora to slow down calcification was proposed from the perspective of microorganisms. |
