Investigating Ammonium By-product Removal for Ureolytic Bio-cementation Using Meter-scale Experiments

• Published in: Scientific reports 2019-12, Vol.9 (1), p.18313-15, Article 18313
• Main Authors: Lee, Minyong, Gomez, Michael G., San Pablo, Alexandra C. M., Kolbus, Colin M., Graddy, Charles M. R., DeJong, Jason T., Nelson, Douglas C.
• Format: Article
• Language: English
• Subjects: 631/326/2522; 639/166/986; 704/172/169; Ammonium; Byproducts; Calcite; Calcium carbonate; Chemical precipitation; Humanities and Social Sciences; Investigations; Ionic strength; multidisciplinary; Science; Science (multidisciplinary); Soil columns; Soil properties
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-019-54666-1

Microbially Induced Calcite Precipitation (MICP), or bio-cementation, is a promising bio-mediated technology that can improve the engineering properties of soils through the precipitation of calcium carbonate. Despite significant advances in the technology, concerns regarding the fate of produced NH 4 + by-products have remained largely unaddressed. In this study, five 3.7-meter long soil columns each containing one of three different soils were improved using ureolytic bio-cementation, and post-treatment NH 4 + by-product removal was investigated during the application of 525 L of a high pH and high ionic strength rinse solution. During rinsing, reductions in aqueous NH 4 + were observed in all columns from initial concentrations between ≈100 mM to 500 mM to final values between ≈0.3 mM and 20 mM with higher NH 4 + concentrations observed at distances furthest from the injection well. In addition, soil V s measurements completed during rinse injections suggested that no significant changes in cementation integrity occurred during NH 4 + removal. After rinsing and a 12 hour stop flow period, all column solutions achieved cumulative NH 4 + removals exceeding 97.9%. Soil samples collected following rinsing, however, contained significant sorbed NH 4 + masses that appeared to have a near linear relationship with surrounding aqueous NH 4 + concentrations. While these results suggest that NH 4 + can be successfully removed from bio-cemented soils, acceptable limits for NH 4 + aqueous concentrations and sorbed NH 4 + masses will likely be governed by site-specific requirements and may require further investigation and refinement of the developed techniques.