Degradation of inhibitory substances by heterotrophic microorganisms during bioleaching of heavy metals from anaerobically digested sewage sludge

Xiang Yang Gu, Jonathan W C WONG*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

27 Citations (Scopus)

Abstract

The presence of organic acids was found to be inhibitory to the bioleaching of sewage sludge and the objective of the present study was to elucidate the roles of heterotrophic microorganisms in removing organic acids during the bioleaching of heavy metals from anaerobically digested sewage sludge. Microbiological analysis showed that acetic and propionic acids posed a severe inhibitory effect on iron-oxidizing bacteria as reflected by a sharp decrease in their viable counts in the first 4 d and it only started to increase 2 d after the depletion of both acids. Biodegradation of these inhibitory organic acids was revealed by sharp increases in total fungi and acidophiles between day 3 and day 5 which coincided with degradation of organic acids. This was further confirmed by the increases in total counts of both acetate and propionate degraders in the same period. Two yeast strains Y4 and Y5 with strong ability to degrade acetate and/or propionate were isolated and identified as Pichia sp. and Blastoschizomycetes capitatus, respectively. B. capitatus Y5 was an more important player in removing the inhibitory organic acids during the bioleaching process since it could utilize both acetate and propionate as sole carbon source while Pichia sp. Y4 was an strict acetate degrader. Results from the present study not only provided the evidence for biodegradation of organic acids by heterotrophs, but also disclosed a biological mechanism for the initiation of bioleaching of organic acid-laden sewage sludge.

Original languageEnglish
Pages (from-to)311-318
Number of pages8
JournalChemosphere
Volume69
Issue number2
DOIs
Publication statusPublished - Sep 2007

Scopus Subject Areas

  • Environmental Engineering
  • Environmental Chemistry
  • Chemistry(all)
  • Pollution
  • Health, Toxicology and Mutagenesis

User-Defined Keywords

  • Acidithiobacillus ferrooxidans
  • Bioleaching
  • Heavy metal
  • Organic acid
  • Sewage sludge

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