Hydraulic retention time optimization achieved unexpectedly high nitrogen removal rate in pilot-scale anaerobic/aerobic/anoxic system for low-strength municipal wastewater treatment.

Applications of post-denitrification processes are subjected to low reaction rates caused by a lack of carbon resources. To offer a solution for reaction rate promotion, this research found a pilot-scale anaerobic/aerobic/anoxic bioreactor treating 55-120 m ³ /d low-strength municipal wastewater for 273 days. A short hydraulic retention time (HRT, 5-6 h) and a high nitrogen removal rate (63.2 ± 9.3 g-N/m ³ ·d) were achieved using HRT optimization. The effluent total nitrogen concentration was maintained at 5.8 ± 1.4 mg/L while operating at a high nitrogen loading rate of 86.2 ± 12.8 g-N/m ³ ·d. The short aeration (1.25-1.5 h) minimized the Glycogen loss. The endogenous denitrification rate increased to above 1.0 mg/(g-VSS·h). The functional genus Ca. Competibacter enriched to 2.3 %, guaranteeing the efficient post-denitrification process. Dechloromonas rose to 1.1 %, aiding in the synchronous phosphorus removal. These findings offered fresh insights into AOA processes to achieve energy/cost-saving wastewater treatment.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2023. Published by Elsevier Ltd.)