Characteristics Of Denitrification Anoxic Granular Sludge Cultivated In SBR

Granular sludge due to excellent feature such as good settlement property, high activity, tight structure and microbial species diversity have been become a research focus in recent years. In this study, granular sludge with good setting property was cultivated in SBR fed with acetate and nitrate, physical characteristics of the sludge, such as physiology and settling velocity were studied. EPS content and components change, the relevance of SVI and sludge EPS were discussed in the process, at the same time, the EPS content from different sludge were compared. The results were showed as follows:(1)By shortening the settling time, the granular sludge can be speeded up through effective hydraulic selection. Cultivated after 200 days, the sludge in the reactor was almost granulated. Granular sludge had good settling ability and denitrification. Settling velocity was 12.51m/h-14.33m/h, the VSS/SS ratio was 86.2%-89.7%, the COD removal rate was up to 91.49% and nitrate nitrogen (NO3--N) removal efficiency was up to 98.02% on average.(2) The stirring intensity on the process of granular sludge formation have a major impact. When the stirring speed was 70rpm, the size range of the granular sludge was 2～3mm, the corresponding SVI was 185.7mL/g on average. When the stirring speed was 130rpm, the size range of the granular sludge was 1～2mm, the corresponding SVI was 138.0mL/g.(3)The EPS content change in the process of granulation was comparatively large. With sludge granulation, SVI of the sludge was decreased, while the total amount of EPS was increased and gradually up to 29.365mg/g-VSS; the main group of EPS was polysaccharide, followed by protein, and nucleic acid content at least.(4) EPS content and content of each component of different sludge were different. The total amount of EPS from actual urban sewage was 19.721mg/g-VSS～24.116mg/g-VSS, which polysaccharide was accounted for 45.3%, protein was accounted for 44.9%. While the polysaccharide in the artificial wastewater sludge was as high as 75.2% and protein was accounted for 18.9%.