Mechanism of electro-acclimation shaped microbiota facilitating phosphorus release from iron-containing sludge: microbial reduction and induced dissolution

Xinran Meng; Sijia Chen; Ziwei Liu; Lang Cheng; Yaoyue Hu; Xia Huang

doi:10.1016/j.watres.2025.124197

Mechanism of electro-acclimation shaped microbiota facilitating phosphorus release from iron-containing sludge: microbial reduction and induced dissolution

Water Res. 2025 Jul 10:286:124197. doi: 10.1016/j.watres.2025.124197. Online ahead of print.

Authors

Xinran Meng¹, Sijia Chen¹, Ziwei Liu², Lang Cheng¹, Yaoyue Hu¹, Xia Huang³

Affiliations

¹ State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, 100084, PR China.
² State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, 100084, PR China. Electronic address: ziweiliu@mail.tsinghua.edu.cn.
³ State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, 100084, PR China; Research and Application Center for Membrane Technology, School of Environment, Tsinghua University, Beijing 100084, PR China. Electronic address: xhuang@tsinghua.edu.cn.

PMID: 40652650
DOI: 10.1016/j.watres.2025.124197

Abstract

Iron-based Chemically Enhanced Primary Treatment (Fe-CEPT) can efficiently concentrate phosphorus (P) from municipal wastewater into sludge; however, unfavorable P release efficiency impedes P recovery from Iron-based Chemically Enhanced Primary Sludge (Fe-CEPS). This study developed an electro-digester by applying controlled potentials to bio-electrodes. The electro-acclimated microorganisms on bio-electrodes achieved efficient P release due to microbial Fe(III) reduction and microbial metabolism-induced P-Fe complexes dissolution. In P release potential tests, 53.2 % of total P was released within 60 h after +1.0 V acclimation, 2.2-fold of the control. P fractionation analysis revealed that the proportion of Fe(II)-P, Fe(III)-P, and Reductant-P in Fe-CEPS (substrate) decreased by 9.7 %, 44.8 %, and 37.5 % after P release, respectively, combined with X-ray diffraction analysis, indicating P-release process followed Fe(III)-P and reductant-P first being reduced to Fe(II)-P and then dissolved into P(liquid), while inherent Fe(II)-P directly dissolved into P(liquid). The enhanced electron transfer capacity of electro-acclimated microorganisms, demonstrated by cyclic voltammetry analysis, promoted Fe(III)-P reduction. The lower pH (a minimum of 5.7) in mixed liquor, achieved by the enhanced metabolism of electro-acclimated microorganisms and elevated enzyme activities relating to hydrolysis-acidification, facilitated the dissolution of Fe(II)-P into the liquid phase. These two steps were dominated by enriched iron-reducing bacteria as Deferribacteraceae and fermentative bacteria as Clostridiaceae in electro-acclimation shaped microbiota. Metagenomic analysis showed consistent results as genes encoding cellular respiratory, metabolism and electron transportation upregulated significantly. These findings provided an eco-friendly, cost-effective solution for treating iron-containing chemical sludge and recovering valuable P resources.

Keywords: Acidogenesis; Electro-acclimation; Fe-CEPS; Hydrolysis; Iron reduction; Phosphorus release.