Fast granulation under extreme selection and its formation mechanism

Zhang, Xing, Tay, Joo-Hwa and Jiang, Wen-Ju (2013) Fast granulation under extreme selection and its formation mechanism. Fresenius Environmental Bulletin, 22 (5).

Abstract

This study investigated the feasibility of fast granulation by manipulating organic loading rate and hydraulic selection pressure. With high organic loading rate and strong hydraulic selection pressure, such as organic loading rate (OLR) of 24 kg m-3 d-1, cycle time of 30 min, and fixed settling time of 1 min, aerobic granules could be observed obviously, even with naked eyes within 7 h. However, the rapidly formed aerobic granules disintegrated after 2-day operation. In the meantime, aerobic granules formed within 24 h under operational conditions of OLR of 6 or 12 kg m-3 d-1, cycle time of 1 h, fixed settling time of 2 min, stability was successfully maintained and reactor reached the steady state within 12 days. The mixed liquor volatile suspended solids (MLVSS) of aerobic granules reached 6.3 g L-1 at the steady state. This is the shortest time for formation of aerobic granules and achievement of steadily operated aerobic granule reactor in the published literature. Granules formed in this study did not show notable differences in terms of morphology and other main physical characteristics compared with those reported in other researches. The results indicate that in the case of fast granulation under extreme selection pressures, strong hydrodynamic selection pressure plays a key role in the initial stage for granulation while high OLR is important for the subsequent fast biomass accumulation, once granules are formed.

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Contributors

Author: Xing Zhang

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