[Characteristics of granular sludge during start-up of the internal circulation]

The quick start-up of the laboratory scale IC reactor and the characteristics of granular sludge during start-up were studied in this paper. The results showed that the first start-up of IC reactor could be finished in 20 days, while secondary start-up only needed 15 days with COD loading rate of 12-15 kg.(m3.d)-1 and COD removal larger than 85%. During start-up, the characteristics of granular sludge changed greatly: average granular diameter was increased from 0.88 mm to 1.25 mm; average settling velocity was enhanced from 35.4 m.h-1 to 105.17 m.h-1; methanogenic activities of the granular increased up to 4 times as large as the seeded sludge; the main methanobacteria was changed from Methanothrix to Methanococcus and Methanobacterium.