[Characteristics of autotrophic nitrifying granular sludge in sequencing batch reactor]

The variation of some performances of the sludge during granulation process was investigated by seeding the nitrifying sludge in sequencing batch reactor, the sludge volume index (SVI), extracellular polymeric substances (EPS), specific oxygen uptake rate (SOUR) and ammonia-oxidizing activity were monitored. The experimental results indicated that when the settling time was gradually decreased from 39 min to 10 min, the SVI decreased from the initial 110 mL/g to 2442 mL/g. The protein content in EPS increased from 163 mg/g to 250-270 mg/g, while polysaccharide content in EPS almost remained around 20-30 mg/g. The ratio of protein/ polysaccharide in EPS was about 9-13. The sludge concentration in SBR was 2. 5 g/L and the ratio of VSS/S was 85%-90%. At the initial phase of granulation process, the ammonia-oxidizing activity (SOUR-A) and the nitrite-oxidizing activity (SOUR-N) gradually increased and reached 259 mg/(g x h) and 119 mg/(g x h) at day 17, respectively, they were 2.4 times and 5.3 time of the seeding sludge. The SOUR-A and SOUR-N began to decrease when the granular size increased. The activity of heterotrophic microorganisms (SOUR-H) and the endogenous respiration activity (SOUR-E) was kept at 10 mg/(g x h) during the granulation process.