Understanding the granulation process of activated sludge in a biological phosphorus removal sequencing batch reactor

• Published in: Chemosphere (Oxford) 2012-02, Vol.86 (8), p.767-773
• Main Authors: Wu, Chang-Yong, Peng, Yong-Zhen, Wang, Ran-Deng, Zhou, Yue-Xi
• Format: Article
• Language: English
• Subjects: Activated sludge; Applied sciences; Bacterial Physiological Phenomena; Biological and medical sciences; Biological phosphorus removal; Biological treatment of waters; Bioreactors - microbiology; Biotechnology; Environment and pollution; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Granulation; Industrial applications and implications. Economical aspects; Nitrogen - isolation & purification; Other wastewaters; Phosphorus - isolation & purification; Pollution; Positive charged particle; Sewage - microbiology; Waste Disposal, Fluid - methods; Wastewaters; Water Purification - methods; Water treatment and pollution
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2011.11.002

► Granules were formed easily with the increase of biological P removal ability. ► The positive charged particles can stimulate the granulation in P removal process. ► The granulation process consisted of aggregation, collision and adhesion. The granulation of activated sludge was investigated using two parallel sequencing batch reactors (SBRs) operated in biological nitrogen and phosphorus removal conditions though the reactor configuration and operating parameters did not favor the granulation. Granules were not observed when the SBR was operated in biological nitrogen removal period for 30d. However, aerobic granules were formed naturally without the increase of aeration intensity when enhanced biological phosphorus removal (EBPR) was achieved. It can be detected that plenty of positive charged particles were formed with the release of phosphorus during the anaerobic period of EBPR. The size of the particles was about 5–20μm and their highest positive ζ potential was about 73mV. These positive charged particles can stimulate the granulation. Based on the experimental results, a hypothesis was proposed to interpret the granulation process of activated sludge in the EBPR process in SBR. Dense and compact subgranules were formed stimulated by the positive charged particles. The subgranules grew gradually by collision, adhesion and attached growth of bacteria. Finally, the extrusion and shear of hydrodynamic shear force would help the maturation of granules. Aerobic granular SBR showed excellent biological phosphorus removal ability. The average phosphorus removal efficiency was over 95% and the phosphorus in the effluent was below 0.50mgL−1 during the operation.