Issue 12, 2021

Piloting carbon-lean nitrogen removal for energy-autonomous sewage treatment

Abstract

Energy-autonomous sewage treatment can be achieved if nitrogen (N) removal does not rely on organic carbon (∼chemical oxygen demand, COD), so that a maximum of the COD can be redirected to energy recovery. Shortcut N removal technologies such as partial nitritation/anammox and nitritation/denitritation are therefore essential, enabling carbon- and energy-lean nitrogen removal. In this study, a novel three-reactor pilot design was tested and consisted of a denitrification, an intermittent aeration, and an anammox tank. A vibrating sieve was added for differential sludge retention time (SRT) control. The 13 m3 pilot was operated on pre-treated sewage (A-stage effluent) at 12–24 °C. Selective suppression of unwanted nitrite-oxidizing bacteria over aerobic ammonium-oxidizing bacteria was achieved with strict floccular SRT management combined with innovative aeration control, resulting in a minimal nitrate production ratio of 17 ± 10%. Additionally, anoxic ammonium-oxidizing bacteria (AnAOB) activity could be maintained in the reactor for at least 150 days because of long granular SRT management and the anammox tank. Consequently, the COD/N removal ratio of 2.3 ± 0.7 demonstrated shortcut N removal almost three times lower than the currently applied nitrification/denitrification technology. The effluent total N concentrations of 17 ± 3 mg TN per L (at 21 ± 1 °C) and 17 ± 6 mg TN per L (at 15 ± 1 °C) were however too high for application at the sewage treatment plant Nieuwveer (Breda, The Netherlands). Corresponding N removal efficiencies were 52 ± 12% and 37 ± 21%, respectively. Further development should focus on redirecting more nitrite to AnAOB in the B-stage, exploring effluent-polishing options, or cycling nitrate for increased A-stage denitrification.

Graphical abstract: Piloting carbon-lean nitrogen removal for energy-autonomous sewage treatment

Supplementary files

Article information

Article type
Paper
Submitted
23 juil. 2021
Accepted
27 oct. 2021
First published
29 oct. 2021

Environ. Sci.: Water Res. Technol., 2021,7, 2268-2281

Piloting carbon-lean nitrogen removal for energy-autonomous sewage treatment

M. Van Tendeloo, B. Bundervoet, N. Carlier, W. Van Beeck, H. Mollen, S. Lebeer, J. Colsen and S. E. Vlaeminck, Environ. Sci.: Water Res. Technol., 2021, 7, 2268 DOI: 10.1039/D1EW00525A

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