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Investigating Ammonium By-product Removal for Ureolytic Bio-cementation Using Meter-scale Experiments
Minyong Lee1, Michael G Gomez2, Alexandra C M San Pablo3
1Department of Civil and Environmental Engineering, University of Washington, Seattle, WA, 98195, USA.
Scientific Reports
|December 5, 2019
Summary
Ureolytic bio-cementation effectively removes ammonium (NH4+) by-products from soils using a rinse solution. Soil engineering properties remain stable during this bio-remediation process, indicating its viability.
Area of Science:
- Geotechnical Engineering
- Environmental Science
- Microbiology
Background:
- Microbially Induced Calcite Precipitation (MICP) enhances soil properties via calcium carbonate precipitation.
- Ureolytic bio-cementation is a key MICP method, but ammonium (NH4+) by-product management is a critical concern.
- Addressing NH4+ fate is essential for the widespread adoption of bio-cementation technologies.
Purpose of the Study:
- To investigate the efficacy of a high pH, high ionic strength rinse solution for removing NH4+ by-products post-MICP treatment.
- To assess the impact of NH4+ removal on the structural integrity of bio-cemented soil.
- To quantify NH4+ removal efficiency and understand the distribution of residual NH4+.
Main Methods:
- Five 3.7-meter soil columns were treated using ureolytic bio-cementation.
- Post-treatment, columns were rinsed with 525 L of a specialized rinse solution.
- Aqueous NH4+ concentrations and soil shear wave velocity (Vs) were monitored throughout the rinsing process.
Main Results:
- Aqueous NH4+ concentrations decreased significantly, from initial levels of 100–500 mM to 0.3–20 mM.
- Shear wave velocity measurements indicated no significant loss of cementation integrity during NH4+ removal.
- Over 97.9% cumulative NH4+ removal was achieved, though significant sorbed NH4+ remained in soil samples.
Conclusions:
- The developed rinsing technique effectively removes NH4+ by-products from bio-cemented soils.
- The structural integrity of the soil remains intact during the NH4+ removal process.
- Site-specific requirements will dictate acceptable NH4+ limits, necessitating further refinement of removal techniques.
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