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Updated: Aug 6, 2026

Development of Sulfidogenic Sludge from Marine Sediments and Trichloroethylene Reduction in an Upflow Anaerobic Sludge Blanket Reactor
Published on: October 15, 2015
Carbon conversion in sludge fermentation liquid drives exogenous-to-endogenous transition of partial denitrification
1National Engineering Laboratory for Advanced Municipal Wastewater Treatment and Reuse Technology, Engineering Research Center of Beijing, Beijing University of Technology, Beijing, 100124, PR China.
Abstract:
Traditional biological nitrogen removal processes for wastewater characterized by a low carbon-to-nitrogen (C/N) ratio often rely heavily on external carbon sources, resulting in excessively high operational costs. This study investigated the feasibility of using sludge fermentation liquid (SFL) as an alternative carbon source to drive the endogenous partial denitrification-anammox (EnPDA) process for efficient nitrogen removal. A sequencing batch reactor (SBR) was operated for 285 days, consisting of a partial denitrification (PD) phase (183 days) and a subsequent EnPDA phase (102 days). During the PD phase, exogenous PD (ExPD) shifted to endogenous PD (EnPD). After integrating anammox, the single-stage EnPDA system achieved a total inorganic nitrogen removal efficiency of 95.1 ± 1.2%, and maintained 93.8 ± 1.8% efficiency even under elevated ammonium loading. The batch tests revealed the robustness of EnPDA system and its preference for nitrate as the electron acceptor. Microbial community analysis showed a functional shift from Thauera to the endogenous denitrifier Ca. Competibacter, with Ca. Brocadia (1.04%) as the dominant anammox bacterium. Metagenomic analysis revealed 68.6% increased abundance of denitrification-related (narGHI) genes and 7.8-fold enhancement of anammox-related (hzs/hdh) genes. Furthermore, the genes related to carbon metabolism were also upregulated to sustain endogenous electron supply. This work clarifies the microbial and metabolic mechanisms underlying the transition of ExPD to EnPD. The study validates that SFL-driven EnPDA is a cost-effective strategy for advanced nitrogen removal from low C/N wastewater.
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