Fe(III) reduction and vivianite formation in activated sludge

Ru Wang, Philipp Wilfert, Iulian Dugulan, Kees Goubitz, Leon Korving*, Geert Jan Witkamp, Mark C.M. van Loosdrecht

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

46 Scopus citations


Kinetics of iron reduction, formation of vivianite and the microbial community in activated sludge from two sewage treatment plants (STPs) with low (STP Leeuwarden, applying enhanced biological phosphate removal, EBPR) and high (STP Cologne, applying chemical phosphate removal, CPR) iron dosing were studied in anaerobic batch experiments. The iron reduction rate in CPR sludge (2.99 mg-Fe g VS−1 h−1) was 3-times higher compared to EBPR sludge (1.02 mg-Fe g VS−1 h−1) which is probably caused by its 3-times higher iron content. Accordingly, first order rate constants in both sludges are comparable (0.06 ± 0.001 h−1 in EBPR vs 0.05 ± 0.007 h−1 in CPR sludge), thus potential rates in both sludges are comparable. The measured Fe(III) reduction rates suggest that all iron in STP Leeuwarden and STP Cologne can be turned over within 15 h and 44 h respectively. Mössbauer spectroscopy and X-ray diffraction (XRD) indicated vivianite formation within 24 h in both sludges. After 24 h, 53% and 34% of all iron were bound in vivianite in the EBPR and CPR sludge respectively. Next generation sequencing (NGS) showed that the microbial community in the CPR sludge comprised more genera with iron-oxidizing and iron-reducing bacteria. Iron reduction and vivianite formation commence once activated sludge is exposed to oxygen free conditions. Our study reveals that the biogeochemistry of iron in STPs is very dynamic. By understanding the interactions between iron and phosphate crucial processes in modern sewage treatment, such as chemical phosphate removal or phosphate recovery from sewage sludge, can be optimized.

Original languageEnglish (US)
Pages (from-to)126-135
Number of pages10
JournalSeparation and Purification Technology
StatePublished - Aug 1 2019

Bibliographical note

Publisher Copyright:
© 2019


  • Activated sludge
  • Iron reduction
  • Phosphate
  • Sewage
  • Vivianite

ASJC Scopus subject areas

  • Analytical Chemistry
  • Filtration and Separation


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