China
Africa
Explore chapters and articles related to this topic
Aeration
Published in Gaetano Joseph Celenza, Industrial Waste Treatment Process Engineering, 2019
Some general characteristics of diffused aeration can be summarized as follows [2,6,8,9]: Oxygen transfer efficiencies are generally at the low end of the aeration devices, with fine bubble diffusers more efficient than large bubble diffusers.They are commonly employed in plug flow aeration basin configurations.Careful attention to basin design and diffuser placement is required to insure solids dispersion.The ability to vary diffuser air flow provides complete operational flexibility.Major limitations include (a) diffusers, especially fine bubble devices, are prone to plugging problems, (b) they are generally employed in more expensive (long-narrow) basins, and (c) they could potentially require higher installed horsepower if they cannot be designed to accommodate the varying load consistent with a plug flow configuration.Their major advantages include (a) the flexibility to tailor individual diffusers to area oxygen demands, (b) a relatively quiet aeration basin operation is achieved by isolating the blowers, and (c) no icing problems.
Application of real-time nitrogen measurement for intermittent aeration implementation in a biological nitrogen removal system: performances and efficiencies
Published in Environmental Technology, 2019
R. Ferrentino, M. Langone, M. Vian, G. Andreottola
One of the key factors for the control of aeration is maintaining the defined dissolved oxygen (DO) levels in the aeration step for aerobic microorganisms performing organic carbon removal and nitrification. The energy efficiency criteria have gradually led to the replacement of mechanical aerators by diffused aerators, which have a higher oxygen transfer efficiency. Fine-bubble diffusers have been preferred compared to coarse-bubble diffusers, because of high oxygen transfer and energy efficiency. In the last decade, a gas-permeable membrane (often a hollow fiber membrane), immersed in a suspended biomass, used both for biofilm growth on the carrier and for oxygen diffuser supply to the biofilm, has proved to transfer oxygen very efficiently [6,7]. Further, the replacement of existing conventional blower technology with direct-drive, high-speed, turbo blowers is often identified in energy audits as high priority projects for improving the WWTPs energy efficiency [8]. A substantial reduction of oxygen consumption could be obtained by automatically controlling the oxygen required for the aeration, both in continuous aeration systems [9] and in intermittent aeration activated process, where oxic and anoxic periods alternate [10]. These changes favor a significant decrement of the energy consumption and thus of the operational costs of the whole WWTP.
CFD Investigation of the effects of bubble aerator layouts on hydrodynamics of an activated sludge channel reactor
Published in Environmental Technology, 2019
Rainier Hreiz, Olivier Potier, Jim Wicks, Jean-Marc Commenge
As it could be expected, regardless of the aerators layout, 1 mm bubbles generate higher void fractions since fine bubbles rise slower than larger ones. Moreover, given their higher surface to volume ratio, they lead to a much greater interfacial area. So from an oxygenation point of view, fine bubble diffusers are considerably more efficient than coarse bubble aerators.