| Aerobic sludge granulation was successfully achieved in this study in a full-scale sequencing batch reactor (SBR) with50,000m3/d for treating a town’s wastewater,30%from domestic and70%from industrial use. Previously, onsite lab-scale and pilot-scale SBR were built up and proved the feasibility of cultivating aerobic granules in this wastewater treatment plant (WWTP). Then, the SBR project was built up and came into operation. After operating for337days, aerobic granules with sludge volume index of47.1mL/g, mean diameter of0.5mm and mean settling velocity of42m/h were obtained. After granulation in SBR, granular sludge was compared with sludges from anaerobic/oxic (A/O,10,000m3/d) and oxidation ditch (OD,50,000m3/d). The result showed that aerobic granular sludge in SBR had more compact structure and better settling ability. Three kinds of sludge all had a high content of protein in extracellular polymeric substance (EPS). X-ray fluorescence (XRF) analysis revealed that metal ions and some inorganics from wastewater precipitated and gathered in granules and acted as core to enhance granulation. Raw wastewater characteristics had a positive effect on the granule formation, but the SBR mode with periodic feast-famine, shorter settling time and no return sludge pump play a crucial role in aerobic granulation. Denaturing gradient gel electrophoresis (DGGE) bacteria analysis indicated that bacterial community composition was different between granular sludge from SBR and floc sludge from a continuous flow reactor (A/O and OD). For example, Flavobacterium sp., uncultured beta proteobacterium, uncultured Aquabacterium sp. and uncultured Leptothrix sp. were just dominated in SBR, whereas uncultured bacteroidets were only found in A/O and OD. |
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