Identification of inhibitory substances affecting bioleaching of heavy metals from anaerobically digested sewage sludge

Xiangyang Gu, Jonathan W C WONG*

*Corresponding author for this work

Research output: Contribution to journalJournal articlepeer-review

81 Citations (Scopus)


Significant inhibitory effects of the filtrate medium of anaerobically digested sewage sludge on iron oxidation by Acidithiobacillus ferrooxidans ANYL-1 were observed in our preliminary experiments, indicating the presence of inhibitory substances in anaerobically digested sewage sludge. The objectives of the present study were to identify the possible inhibitory substances and to evaluate their impacts on metal solubilization during bioleaching of sewage sludge. The results showed that the concentrations of total reducing sugars, all tested metal ions, and anions were too low to suppress iron oxidation, and only organic acids, especially acetic and propionic acids, were found at concentrations higher than their inhibitory levels. The presence of 10.8 mM acetic acid and 9.88 mM propionic acid in sewage sludge (sludge N) led to long lag periods of 6 and 7 days for solubilization of Cu and Cr, respectively, as compared to a lag period of only 1 day in the control and another sludge (sludge S) with a low level of organic acids. Meanwhile the leaching time for maximum solubilization of Zn also extended to 6 days in the presence of organic acids as compared to 3 days in the control. Acetic and propionic acids posed an unfavorable bioleaching condition for anaerobically digested sewage sludge; therefore, further studies are required to explore the means to remove the inhibitory effects to improve the heavy metal bioleaching efficiency.

Original languageEnglish
Pages (from-to)2934-2939
Number of pages6
JournalEnvironmental Science and Technology
Issue number10
Publication statusPublished - 15 May 2004

Scopus Subject Areas

  • Chemistry(all)
  • Environmental Chemistry


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