| Granular sludge membrane bioreactor(GMBR), operated with alternating anaerobic-aerobic mode, showed good organics removal and simultaneous nitrification and denitrification(SND) performances during 120 days operation. Moreover, sludge size distribution examination showed that the increase of sludge concentration in GMBR was mostly due to the increase of small granular sludge with diameter between 0.18～0.45 mm and flocculent sludge smaller than 0.18 mm, and most of granular sludge larger than 0.45 mm was stably existed in GMBR, at the end of operation granular sludge with diameter larger than 0.18mm remained 60%～65% in GMBR. Sludge surface negative charge increased with the sludge size distribution variation, and surface charge remained-0.42～-0.80 meq·g-1 after 80 days operation. The increase of sludge surface negative charge was mostly caused by sludge smaller than 0.45 mm, thereinto sludge smaller than 0.18 mm had the greatest effect. Moreover, results revealed that the sludge surface negative charge decreased as the sludge size increased, and a linear correlation can be obtained between sludge surface negative charge and sludge size. Sludge in GMBR had good settleability, and SVI was about 60～90 mＬ/g. Furthermore results showed that sludge surface charge was correlated with SVI, sludge SVI increased with surface negative charge increased. |
