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- Title
Minimum COD needs for denitrification: from biological models to experimental set-up.
- Authors
Lahdhiri, Ameni; Lesage, Geoffroy; Hannachi, Ahmed; Heran, Marc
- Abstract
The nitrogen content in treated wastewater is a key issue when considering discharge in sensitive areas or reuse targets as standards are getting increasingly stringent. In this study, a Membrane Biological Reactor (MBR), mainly dedicated to nitrogen removal through a nitrification-denitrification process was investigated in order to identify the minimum amount of organic matter that allows complete denitrification. Thus, the Minimum COD/N Ratio, referred to as MR, was assessed using activated sludge modeling (ASM3). Both lab-scale experiments and modeling results pointed out that endogenous denitrification could have a major role in nitrate removal. This role can be strengthened at high Solid Retention Times (SRT). Furthermore, the dissolved oxygen, provided by mixed liquor recirculation between aerobic and anoxic compartments, hindered the denitrification rate. An analytical expression for an apparent Minimum Ratio (MRA) was developed, taking into account previously described processes. This allowed the influent COD to be adjusted to ensure complete denitrification. MRA depends on main design characteristics and operating parameters, mainly the SRT, the anoxic compartment volume, the dissolved oxygen in the aerobic tank and the recirculation rate. For an SRT ranging from 40 to 60 d, laboratory experiments showed that, contrary to a COD/N ratio of 5, a value of 3.5 led to non-stable nitrate removal performances. This was consistent with the assessed MRA, estimated at approximately 4, for identical operating conditions and design characteristics.
- Subjects
BIOLOGICAL models; DENITRIFICATION; MEMBRANE reactors; BIOLOGICAL membranes; RF values (Chromatography); ORGANIC compounds; ANOXIC zones
- Publication
Desalination & Water Treatment, 2017, Vol 61, p326
- ISSN
1944-3994
- Publication type
Article
- DOI
10.5004/dwt.2017.11130