Elimination of Residual Chemical Oxygen Demand (COD) in a Low-Temperature Post-Denitrifying Moving Bed Biofilm Reactor (MBBR)

Moving bed biofilm reactors (MBBRs) are compact biofilm systems that provide a sustainable solution for biological nitrogen removal. A study was conducted on an innovative post-denitrification method as a polishing step to reduce low nitrate nitrogen concentrations (10 mg/L) to 2.1–4.9 mg/L. The obj...

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Bibliographic Details
Published in:Water (Basel) 2024-07, Vol.16 (13), p.1829
Main Authors: Leonhard, Stephan, Wichern, Marc, Hilliges, Rita
Format: Article
Language:English
Subjects:
Biofilms
Carbon
Chemical oxygen demand
Drinking water
Effluents
Laboratories
Nitrates
Nitrogen
Reactors
Water temperature
Water treatment
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Summary:Moving bed biofilm reactors (MBBRs) are compact biofilm systems that provide a sustainable solution for biological nitrogen removal. A study was conducted on an innovative post-denitrification method as a polishing step to reduce low nitrate nitrogen concentrations (10 mg/L) to 2.1–4.9 mg/L. The objective was to minimize residual chemical oxygen demand (COD) in the effluent caused by the external carbon source required for this final treatment step. Therefore, four continuous flow reactors with varying synthetic loads and hydraulic retention times (HRTs), as well as two carrier sizes, were operated over 335 days. The results showed that an HRT of 2 h is necessary to successfully reduce the residual COD to 5–6 mg/L. Additionally, it was demonstrated that the protected volume of the biofilm carriers has a significant impact on MBBRs compared to the protected surface, which is commonly discussed in the literature. The available protected volume can limit biofilm growth, as demonstrated by measuring the total biofilm solids (TBS) and biofilm thickness on the carrier at varying COD eliminations. When providing sufficient protected volume for the biofilm through the filling ratio and carrier size, a COD elimination rate of 1.4 to 1.45 kg/(m3d) was achieved with a biofilm thickness of only 500 µm.
ISSN:2073-4441
2073-4441
DOI:10.3390/w16131829