Eliminating Backflow in Retrofit BNR Systems
Publication: Journal of Environmental Engineering
Volume 122, Issue 10
Abstract
The retrofit of an existing activated sludge system with a biological nitrogen removal system requires the installation of a baffle wall to separate the biological nitrogen removal anoxic and oxic zones. The baffle wall consists of a weir and a submerged orifice. An experimental investigation of the hydraulics of the anoxic/oxic baffle wall is presented. It is shown that backflow from the oxic zone to the anoxic zone can occur if the baffle wall is not designed properly. This backflow will reduce the efficiency of the biological nitrogen removal process. Based on the experimental data, a design procedure that eliminates backflow over the anoxic/oxic baffle wall is developed. The design procedure introduces a backflow parameter that is a dimensionless number dependent on the total discharge, orifice area, tank depth, and oxic zone air concentration. The resulting design offers an economical alternative to designs implementing a valve option.
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Information & Authors
Information
Published In
Journal of Environmental Engineering
Volume 122 • Issue 10 • October 1996
Pages: 950 - 954
Copyright
Copyright © 1996 American Society of Civil Engineers.
History
Published online: Oct 1, 1996
Published in print: Oct 1996
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