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This is a In Vitro Study study (also classified as: Observational).

August 17, 2025Open Access

Addition of Heterotrophic Nitrification and Aerobic Denitrification Bacterial Agents to Enhance Bio-Nests Treating Low Carbon-to-Nitrogen Ratio Municipal Wastewater

QDQiyu DiaoChinese Academy of Agricultural Sciences CQChengshi QuanJilin University WLWanmeng LiJiangsu University

Key Points

The A+M reactor achieved a median removal efficiency of 82.2% for NH4+-N, highlighting its superior performance compared to other tested reactors.
Incorporating Acinetobacter beijerinckii and Klebsiella variicola into the mixed strains improved total nitrogen removal efficiency significantly.
Observational analysis across different reactor types revealed the A+M configuration increased microbial diversity and biofilm activity effectively.
This approach suggests that using HN-AD bacterial agents can optimize nitrogen removal and reduce dependence on external carbon sources in wastewater treatment.

Abstract

Municipal wastewater with a low carbon-to-nitrogen (C/N) ratio presents challenges for conventional nitrogen removal processes, often requiring costly external carbon sources. This study investigated the enhancement of nitrogen removal in a simultaneous nitrification and denitrification (SND) system by incorporating heterotrophic nitrification and aerobic denitrification (HN-AD) bacterial agents (Klebsiella variicola L3, Acinetobacter beijerinckii W4, and Acinetobacter sp. Z1) with modified basalt fiber carriers. Three reactors were compared: mixed HN-AD strains (M), mixed strains with activated sludge (A+M), and activated sludge alone (A). Results demonstrated that the A+M reactor achieved superior performance, with median removal efficiencies of 82.2% for NH4+-N, 52.9% for total nitrogen (TN), and 51.6% for COD, outperforming the M reactor (75.2%, 43.6%, and 51.6%) and the A reactor (63.2%, 29.3%, and 44.8%). The A+M reactor also exhibited a 40% reduction in COD consumption per unit TN removed (2.55 ± 1.75) compared to the control reactor A (4.25 ± 3.99). Microbial analysis revealed Acinetobacter sp. Z1 (6.1%) and K. variicola L3 (1.1%) as dominant species, with the A+M reactor showing higher microbial diversity (56.4% Proteobacteria, 10.2% Bacteroidota) and biological viability (VSS/SS ratio of 0.70 ± 0.01). Extracellular polymeric substance (EPS) content in A+M reached 242.26 ± 15.52 mg/g-VSS, with a protein-to-polysaccharide ratio of 2.77 ± 0.00, indicating robust biofilm activity. These findings highlight the potential of HN-AD bacterial agents to enhance nitrogen removal in low C/N wastewater treatment, offering a cost-effective and sustainable alternative to traditional methods by reducing reliance on external carbon sources and improving system efficiency.

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