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Sustainability 2015, 7(2), 1201-1212; doi:10.3390/su7021201

Oxygen Control and Improved Denitrification Efficiency by Means of a Post-Anoxic Reactor

1,†,* , 2,†
Department of Biotechnologies and Life Sciences, University of Insubria, Via G.B. Vico 46, I-21100 Varese, Italy
Department of Civil Engineering and Computer Science Engineering, University of Rome "Tor Vergata", Via Politecnico 1, I-00133 Roma, Italy
Department of Civil and Environmental Engineering, University of Rome "La Sapienza", Via Eudossiana 18, I-00184 Rome, Italy
These authors contributed equally to this work.
Author to whom correspondence should be addressed.
Academic Editor: Vincenzo Torretta
Received: 17 November 2014 / Accepted: 19 January 2015 / Published: 23 January 2015
(This article belongs to the Special Issue Sustainability of Resources)
View Full-Text   |   Download PDF [1530 KB, uploaded 24 February 2015]   |  


The presence of dissolved oxygen (DO) in biological denitrification reactors determines inhibition effects on the denitrification rate. The article shows the results of an experimental study to control the DO concentration in the pre-denitrification stage by a post-anoxic reactor. The results demonstrate that the post-anoxic reactor is very effective in improving the nitrogen removal efficiency because it causes a considerable reduction of the DO content in the mixed liquor recycle sent to the pre-denitrification reactor. This reduction is influenced by both the retention time and the F:M ratio (referred to the denitrification and the oxidation-nitrification volume). In fact, a retention time and a F:M ratio equal to 1.5 h and 0.130 kgBOD5 kgMLVSS−1·day−1, respectively, allow to limit DO in the post-anoxic reactor at 0.31 mgO2·L−1. Such concentration determines a DO concentration of 0.11 mgO2·L−1 in the pre-denitrification reactor and, consequently, a denitrification efficiency of 91%. Moreover, the contribution of the endogenous denitrification to the whole denitrification efficiency was found negligible. The paper contributes to the progress in nitrogen removal from sewage, a fundamental issue for a sustainable management of water resources. View Full-Text
Keywords: activated sludge; denitrification; nitrogen removal; pre-denitrification; post-denitrification; sewage treatment activated sludge; denitrification; nitrogen removal; pre-denitrification; post-denitrification; sewage treatment

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Urbini, G.; Gavasci, R.; Viotti, P. Oxygen Control and Improved Denitrification Efficiency by Means of a Post-Anoxic Reactor. Sustainability 2015, 7, 1201-1212.

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