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Mixing criteria development for aerobic granular sludge reactor operations

Nor Anuar, Aznah and Ujang, Zaini and Loosdrecht, M.C.M van and Krek, M.K. de and Olsson, G. (2008) Mixing criteria development for aerobic granular sludge reactor operations. In: International Conf & Expo on Environmental Management and Technologies 2008 , 2008, PWTC, Kuala Lumpur.

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Abstract

Aerobic granular sludge technology has recently received growing attention by researchers and technology developers, worldwide. It has good settling properties and high capacity for biomass retention. Furthermore, it is suggested that aerobic granules can be established and profitably used in activated sludge plants, provided adequate design specifications and process conditions are applied. In the operation of aerobic granule reactors, either mechanical or aerated mixing has been commonly used to introduce shear effects in the system. Sufficient shear stress is needed for the formation of stable and dense aerobic granules. However, excessive shear stress (due to excessive mixing) might negatively affect the aerobic granules settling characteristics. In pilot or full-scale implementations, as the size of the reactor increases, the effect of the mixing mechanism strategy becomes more significant. Therefore, this study was conducted to explore the influence of mixing conditions (both aerated and mechanical mixing) on the settling characteristics of the aerobic granules. Special attention was given to three parameters that have a strong influence on the aerobic granules settling velocity (?), i.e. (a) the stirrer speed (N), (b) the shear rates (?) and (c) the ratio of blade and vessel diameters (D/Tv) in mechanical mixing operation. For aerated mixing, two parameters have a major influence on the aerobic granules settling velocity (?); (a) the airflow rate (Qair) and (b) the bubble size (r2). Parameters that relate to aerobic granules settling characteristics, such as settling velocities of aerobic granules are compared with activated sludge flocs from sequencing batch reactor system, extended aeration and conventional activated sludge plants. Optimum mixing conditions required for maintaining aerobic granules, defined by high speed settling characteristics (? > 10 mh-1) are highlighted in this study.

Item Type:Conference or Workshop Item (Paper)
Uncontrolled Keywords:Aerobic granules, settling characteristics, settling velocity, mixing operation
Subjects:T Technology > TA Engineering (General). Civil engineering (General)
Divisions:Civil Engineering
ID Code:15921
Deposited By: Siti Khairiyah Nordin
Deposited On:30 Sep 2011 09:54
Last Modified:30 Sep 2011 09:54

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