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ORIGINAL RESEARCH article
Front. Microbiol.
Sec. Microbiotechnology
Volume 16 - 2025 | doi: 10.3389/fmicb.2025.1591974
This article is part of the Research Topic Recent Advances in Agricultural Waste Recycling by Microorganisms and Their Symbiosis View all 10 articles
Microalgae-bacteria symbiosis enhanced nitrogen removal from wastewater in an inversed fluidized bed bioreactor: Performance and Microflora
Provisionally accepted
Xin Zheng 1
Ruoting Liu 2 Kai Li 3 Junhao Sun 2 Kanming Wang 1 Yuanyuan Shao 4
Zhongce Hu 1 Jesse Zhu 2 Zhiyan Pan 1* George Nakhla 2*- 1 Zhejiang University of Technology, Hangzhou, China
- 2 Western University, London, Ontario, Canada
- 3 Wenzhou Ecological and Environmental Monitoring Center of Zhejiang Province, Wenzhou, China
- 4 The University of Nottingham Ningbo (China), Ningbo, Zhejiang Province, China
Conventional wastewater biological nitrogen removal (BNR) processes require a large amount of air and external organic carbon, causing a significant increase in operating costs and potential secondary pollution. Herein, this study investigated the nitrogen removal performance and the underlying mechanisms of a novel simultaneous nitrification and denitrification (SND) coupled with photoautotrophic assimilation system in an inversed fluidized bed bioreactor (IFBBR). Nitrogen removal was achieved through the synergistic interaction of microalgae and bacteria, with microalgae providing O2 for nitrification and microbial biomass decay supplying organic carbon for denitrification. The IFBBR was continuously operated for more than 240 days without aeration and external organic carbon, the total nitrogen (TN) removal efficiency reached over 95%. A novel C-N-O dynamic balance model was constructed, revealing that nitrification and denitrification were the primary pathways for nitrogen removal. The model further quantified the microbial contributions, showing that microalgae generated O2 at a rate of 81.82 mg/L·d, while microbial biomass decay released organic carbon at a rate of 148.66 mg/L·d. Microbial diversity analysis confirmed the majority presence of microalgae (Trebouxiophyceae), nitrifying bacteria (Gordonia and Nitrosomonas) and denitrifying bacteria (Ignavibacterium and Limnobacter). This study successfully achieved enhanced nitrogen removal without the need for aeration or external organic carbon. These advancements provide valuable insights into efficient wastewater nitrogen removal, offering significant benefits in terms of reduced energy consumption, lower operational costs, and decreased CO2 emissions.
Keywords: microalgal-bacterial symbiosis system, Biological nitrogen removal, mass balance, Simultaneous nitrification and denitrification, Syntrophic microbial communities
Received: 11 Mar 2025; Accepted: 02 Apr 2025.
Copyright: © 2025 Zheng, Liu, Li, Sun, Wang, Shao, Hu, Zhu, Pan and Nakhla. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence:
Zhiyan Pan, Zhejiang University of Technology, Hangzhou, China
George Nakhla, Western University, London, N6A 3K7, Ontario, Canada
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