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Two-way Valorization of Blast Furnace Slag: Synthesis of Precipitated Calcium Carbonate and Zeolitic Heavy Metal Adsorbent
Published on: February 21, 2017
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Efficient metal removal from digested sludge and supernatant by nitrification-driven acidifying leaching and
Chenkai Niu1, Tao Liu2, Zheng Kong1
1Australian Centre for Water and Environmental Biotechnology (ACWEB, formerly AWMC), The University of Queensland, St. Lucia, Queensland 4072, Australia.
Water Research
|October 7, 2025
Summary
This study presents a two-step bioprocess for removing heavy metals from sludge. It uses pH shifts during nitrification and denitrification to recover metals and remove nitrogen, offering a sustainable sludge management solution.
Area of Science:
- Environmental Science
- Microbiology
- Chemical Engineering
Background:
- Heavy metal contamination in wastewater sludge poses significant environmental and disposal challenges.
- Effective sludge management strategies are crucial for mitigating the risks associated with heavy metal transfer.
- Current methods for heavy metal removal from sludge often involve harsh chemicals or energy-intensive processes.
Purpose of the Study:
- To develop and evaluate a novel two-step biological process for simultaneous heavy metal and nitrogen removal from digested sludge and supernatant.
- To investigate the efficacy of pH-driven bioleaching and subsequent metal precipitation using a membrane biofilm reactor.
- To explore the role of microbial communities and volatile fatty acids in the treatment process.
Main Methods:
- A two-stage bioprocess was employed: Stage 1 involved acid-tolerant ammonia-oxidizing bacteria (AOB) for sludge acidification and metal solubilization.
- Stage 2 utilized a hydrogen/carbon dioxide (H2/CO2)-based membrane biofilm reactor (MBfR) for denitrification, nitrogen removal, and metal precipitation.
- Microbial community analysis and in situ batch assays were conducted to identify key microorganisms and electron donors.
Main Results:
- The first stage achieved high solubilization efficiencies for Cu (84.1%), Zn (94.5%), Mg (83.9%), and Al (72.3%) at pH ~2.
- The second stage demonstrated over 90% nitrogen removal and precipitation of over 90% of Cu, Zn, and Al at pH >7.
- Volatile fatty acids (VFAs) were identified as secondary electron donors, alongside hydrogen, supporting the biological processes.
Conclusions:
- The proposed two-step biological treatment effectively removes heavy metals from sludge and supernatant without external acids or alkalis.
- This method offers a sustainable and integrated approach to sludge management and resource recovery.
- The findings support the potential of microbial processes in addressing complex environmental pollution issues.
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