4.7 Article

Intensified nitrogen removal by endogenous denitrification in a full-scale municipal wastewater treatment plant

Journal

ENVIRONMENTAL RESEARCH
Volume 205, Issue -, Pages -

Publisher

ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.envres.2021.112564

Keywords

Municipal wastewater; Biological nitrogen removal; AAO-AO process; Endogenous denitrification; Denitrifying glycogen-accumulating organisms

Funding

  1. National Major Science and Technology Program for Water Pollution Control and Treatment [2017ZX07102-003]

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In this study, endogenous denitrification (ED) was enhanced in a practical AAO-AO process for the first time, leading to a significant increase in nitrogen removal efficiency (NRE). The findings suggest a novel cost-and energy-efficient strategy to improve NRE by optimizing the ED process.
In this study, for the first time, endogenous denitrification (ED) was enhanced in a practical anaerobic-anoxic-oxic-[post-anoxic]-[post-oxic] (AAO-AO) process, contributing to a remarkable increase in the nitrogen removal efficiency (NRE). The long-term operation (203 days) result showed that the NRE was improved by 7% compared to the theoretical maximum NRE (68-70%) of AAO processes, with the effluent total nitrogen (TN) decreasing from 13.7 (1 d) to 6.1 mg/L (203 d). Approximately 99.4% of the influent COD was transformed to poly-beta-hydroxyalkanoates (PHAs) in the anaerobic zone. The synthesized PHAs were consumed in the following zones and the secondary sedimentation tank accompanied by over 32.5% N-loss, indicating that the ED process could be responsible for the enhanced NRE. 16S rRNA amplicon sequencing results further confirmed that denitrifying glycogen-accumulating organisms, which are capable of ED, were enriched with the relative abundance of 2.10%. Our findings provide a novel cost-and energy-efficient strategy to improve nitrogen removal without external carbon additions but by enhancing ED performance.

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