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<p>Vivianite (Fe<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub>·8H<sub>2</sub>O) precipitation during anaerobic digestion offers a promising strategy for phosphorus recovery from wastewater sludge. The efficiency of vivianite formation, however, is strongly influenced by the type and dosage of iron sources. In this study, we evaluated the feasibility of enhancing phosphorus recovery and vivianite yield in anaerobic digestion sludge by supplementing three types of iron species: FeCl₃, amorphous FeOOH, and α-Fe₂O₃, representing soluble Fe(III) ions, poorly crystalline iron oxides, and well-crystalline iron oxides, respectively. Anaerobic batch experiments were conducted at Fe/P molar ratios of 1, 2, and 4, combined with spectroscopic analyses and sequential phosphate extraction. Amorphous FeOOH at an Fe/P molar ratio of 2 exhibited the highest vivianite recovery efficiency (63.14%) by providing bioavailable Fe<sup>2+</sup> and sustaining microbial diversity. In contrast, excessive FeCl₃ dosages caused pH decline, suppressed microbial activity, and inhibited vivianite formation. Furthermore, a strong correlation was observed between Fe-bound phosphorus fractions and the resonance intensity in solid-state <sup>31</sup>P nuclear magnetic resonance (NMR) spectra, indicating that solid-state <sup>31</sup>P NMR could serve as a reliable tool for monitoring vivianite formation. These findings provide practical insights into optimizing iron dosing strategies for sustainable phosphorus recovery in full-scale wastewater treatment applications.</p>

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Enhanced Phosphorus Removal by Vivianite Crystallization: Influence of Iron Sources During Anaerobic Digestion

  • 期刊论文

  • 发表日期：

    2025年12月12日

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  • Yi-Xin Liu,
  • Wei-Hua Li,
  • Qiong-Xia Xia,
  • Zhi-Hao Chen,
  • Ting-Ting Yang

摘要

Vivianite (Fe3(PO4)2·8H2O) precipitation during anaerobic digestion offers a promising strategy for phosphorus recovery from wastewater sludge. The efficiency of vivianite formation, however, is strongly influenced by the type and dosage of iron sources. In this study, we evaluated the feasibility of enhancing phosphorus recovery and vivianite yield in anaerobic digestion sludge by supplementing three types of iron species: FeCl₃, amorphous FeOOH, and α-Fe₂O₃, representing soluble Fe(III) ions, poorly crystalline iron oxides, and well-crystalline iron oxides, respectively. Anaerobic batch experiments were conducted at Fe/P molar ratios of 1, 2, and 4, combined with spectroscopic analyses and sequential phosphate extraction. Amorphous FeOOH at an Fe/P molar ratio of 2 exhibited the highest vivianite recovery efficiency (63.14%) by providing bioavailable Fe2+ and sustaining microbial diversity. In contrast, excessive FeCl₃ dosages caused pH decline, suppressed microbial activity, and inhibited vivianite formation. Furthermore, a strong correlation was observed between Fe-bound phosphorus fractions and the resonance intensity in solid-state 31P nuclear magnetic resonance (NMR) spectra, indicating that solid-state 31P NMR could serve as a reliable tool for monitoring vivianite formation. These findings provide practical insights into optimizing iron dosing strategies for sustainable phosphorus recovery in full-scale wastewater treatment applications.