Formation of granular sludge and its mechanism in enhanced process of biological phosphorus removal

The promoting effect on the formation of granular sludge by inoculating activated sludge in the enhanced process of biological phosphorus removal was studied in a laboratory-scale sequencing batch reactor (SBR). The results showed that the activated sludge kept in stabilized flocculent state at biological denitrification stage, and the average SVI was 138.9 ml·g-1, while at biological de-phosphorus one the activated sludge flocs became granular sludge gradually as the performance of P removal became better. The average SVI decreased to 74.1 ml·g-1 and the average diameter of the granules was 0.8 mm. Therefore, the biological phosphorus removal process performed in SBR favored for the formation of granular sludge. Moreover, it was found that a lot of positive charged particles were formed with the release of phosphorus at the anaerobic stage in the biological de-phosphorus process. These particles could serve as the cores of granules to attract the negative charged cells and stimulate the granulation. The granular sludge system of enhancing biological de-phosphorus have an excellent ability for the removal of phosphorus. The average removal rate of P was nearly 100%. © All Rights Reserved.