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Published on: October 15, 2015
Bioleaching of heavy metals from anaerobically digested sewage sludge
Ashish Pathak1, M G Dastidar, T R Sreekrishnan
1Centre for Energy Studies, Indian Institute of Technology, Hauz Khas, New Delhi, India.
Summary
Optimizing sulfur concentration is key for metal bioleaching from sewage sludge. Indigenous microorganisms effectively solubilize metals like zinc and copper with 2 g L(-1) elemental sulfur, even across a wide pH range.
Area of Science:
- Environmental Microbiology
- Biotechnology
- Waste Management
Background:
- Sewage sludge contains valuable metals but requires efficient extraction methods.
- Bioleaching offers a sustainable approach for metal recovery from waste materials.
Purpose of the Study:
- To investigate the impact of sulfur concentration, initial pH, and sludge solid content on metal bioleaching from anaerobically digested sewage sludge.
- To optimize elemental sulfur dosage for efficient metal solubilization.
Main Methods:
- Experiments were conducted using anaerobically digested sewage sludge from Delhi, India.
- Elemental sulfur concentration was varied from 0-4 g L(-1).
- Changes in pH, sulfate concentration, and oxidation-reduction potential (ORP) were monitored over time.
Main Results:
- 2 g L(-1) of elemental sulfur was found optimal for metal bioleaching, achieving high solubilization rates for Zn (86%), Cu (71.5%), and Mn (70%).
- Bioleaching was effective across a broad range of initial sludge pH values (pH 7 to pH 3).
- Higher sludge solid content (>20 g L(-1)) reduced metal solubilization due to increased buffering capacity.
Conclusions:
- Indigenous sulfur-oxidizing microorganisms can effectively lower pH for significant metal solubilization using 2 g L(-1) elemental sulfur.
- Bioleaching of metals from sewage sludge is feasible over a wide range of initial pH conditions.
- Sludge solid content is a critical factor influencing the efficiency of metal bioleaching.
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