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Sulfide-driven mixotrophic partial denitrification: From performance to microbial mechanism.

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Title:	Sulfide-driven mixotrophic partial denitrification: From performance to microbial mechanism.
Authors:	Chen, Zebin¹ (AUTHOR), Kang, Peilun¹ (AUTHOR), Ye, Shengqi¹ (AUTHOR), Xie, Bing¹ (AUTHOR), Xie, Xinyu¹ (AUTHOR), Song, Jingwen¹ (AUTHOR), Ma, Yiting¹ (AUTHOR), Wu, Zixuan¹ (AUTHOR), Cui, Xi¹ (AUTHOR), Zhang, Xiaojing² (AUTHOR), Yu, Guangwei¹ (AUTHOR), Liang, Yuhai¹ (AUTHOR) liangyuhai@scau.edu.cn
Source:	Chemical Engineering Journal. Apr2026, Vol. 534, pN.PAG-N.PAG. 1p.
Subjects:	Denitrification, Nitrites, Nitrate reductase, Genes, Bacteria, Bacterial adaptation, Sludge management
Abstract:	Partial denitrification can provide a continuous supply of nitrite for anammox. To circumvent the bottlenecks of microbial competition and inhibition inherent in integrated one-stage systems, a mixotrophic partial denitrification (S-MPD) system driven by sulfide and acetate was constructed in an independent reactor to achieve decoupled operation from anammox. The regulatory effects of S/C/N ratios, sludge discharge, and long-term acclimation on system performance and microbial mechanisms were investigated. The results demonstrated that at a S/C/N ratio of 0.24:1.31:1, the nitrate removal efficiency reached (97.8 ± 1.1)% with a nitrite accumulation rate of (81.4 ± 2.3)%. When the S/C/N ratio was increased to 0.48:0.88:1, the system recovered stable operation through sludge discharge and long-term acclimation, maintaining a nitrite accumulation rate of (68.6 ± 3.6)%. Microbial analysis revealed that Thauera was the key mixotrophic denitrifier responsible for S-MPD. By dynamically regulating the abundances of narG and soxB genes, Thauera mitigated sulfur stress and optimized electron flow distribution, thereby maintaining efficient nitrite accumulation. This study confirms the stability and regulatory potential of decoupled S-MPD for efficient nitrite accumulation, providing a theoretical basis for the construction and optimization of two-stage S-MPD/anammox processes. [Display omitted] • The independent S-MPD reactor achieved stable nitrite accumulation with mixed electron donors. • Sludge discharge and long-term acclimation restored S-MPD performance after sulfide inhibition. • Thauera emerged as the key bacterium by regulating narG and soxB genes under sulfide stress. [ABSTRACT FROM AUTHOR]
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Database:	Engineering Source

Description
Abstract:	Partial denitrification can provide a continuous supply of nitrite for anammox. To circumvent the bottlenecks of microbial competition and inhibition inherent in integrated one-stage systems, a mixotrophic partial denitrification (S-MPD) system driven by sulfide and acetate was constructed in an independent reactor to achieve decoupled operation from anammox. The regulatory effects of S/C/N ratios, sludge discharge, and long-term acclimation on system performance and microbial mechanisms were investigated. The results demonstrated that at a S/C/N ratio of 0.24:1.31:1, the nitrate removal efficiency reached (97.8 ± 1.1)% with a nitrite accumulation rate of (81.4 ± 2.3)%. When the S/C/N ratio was increased to 0.48:0.88:1, the system recovered stable operation through sludge discharge and long-term acclimation, maintaining a nitrite accumulation rate of (68.6 ± 3.6)%. Microbial analysis revealed that Thauera was the key mixotrophic denitrifier responsible for S-MPD. By dynamically regulating the abundances of narG and soxB genes, Thauera mitigated sulfur stress and optimized electron flow distribution, thereby maintaining efficient nitrite accumulation. This study confirms the stability and regulatory potential of decoupled S-MPD for efficient nitrite accumulation, providing a theoretical basis for the construction and optimization of two-stage S-MPD/anammox processes. [Display omitted] • The independent S-MPD reactor achieved stable nitrite accumulation with mixed electron donors. • Sludge discharge and long-term acclimation restored S-MPD performance after sulfide inhibition. • Thauera emerged as the key bacterium by regulating narG and soxB genes under sulfide stress. [ABSTRACT FROM AUTHOR]
ISSN:	13858947
DOI:	10.1016/j.cej.2026.175104