Biogeochemical Model for Soil Improvement by Denitrification

AbstractA biogeochemical model describing the rate at which calcium carbonate (CaCO3) is precipitated from the pore water and biogas (carbon dioxide and nitrogen gas) is generated by dissimilatory reduction of nitrate (denitrification) through microbially induced desaturation and precipitation (MIDP...

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Bibliographic Details
Published in:Journal of geotechnical and geoenvironmental engineering 2019-11, Vol.145 (11)
Main Authors: O’Donnell, Sean T, Hall, Caitlyn A, Kavazanjian, Edward, Rittmann, Bruce E
Format: Article
Language:English
Subjects:
Acetates
Acetic acid
Batch reactors
Biogas
Biogeochemistry
Calcium
Calcium carbonate
Calcium carbonates
Calcium nitrate
Carbon dioxide
Carbonates
Chemical precipitation
Chemical reactions
Columns (structural)
Continuously stirred tank reactors
Denitrification
Desaturation
Gas production
Growth kinetics
Kinetics
Laboratory tests
Mechanical properties
Microorganisms
Organic chemistry
Pore pressure
Pore water
Pore water pressure
Reaction kinetics
Reactors
Sensitivity analysis
Shear strength
Soil
Soil improvement
Soil mechanics
Soil properties
Soil resistance
Soils
Stiffness
Stoichiometry
Substrates
Technical Papers
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Summary:AbstractA biogeochemical model describing the rate at which calcium carbonate (CaCO3) is precipitated from the pore water and biogas (carbon dioxide and nitrogen gas) is generated by dissimilatory reduction of nitrate (denitrification) through microbially induced desaturation and precipitation (MIDP) has been developed. Both CaCO3 precipitation and desaturation via biogas formation can improve the static and cyclic mechanical properties of granular soil. CaCO3 precipitation can improve the static and cyclic stiffness, shear strength, and volume change characteristics of granular soil. Desaturation via biogenic gas generation suppresses excess pore pressure development and thereby improves the cyclic shear resistance of granular soil. MIDP represents the combined effect of these two mechanisms. Effective implementation of MIDP for ground improvement demands quantitative understanding of the rate at which both mechanisms occur. The biogeochemical model developed herein is an upgrade of the model presented in earlier research; it includes additional features, such as inhibition terms, an expanded number of organic substrates, and a greater number of chemical constituents. It predicts the rate of CaCO3 precipitation and gas production by integrating stoichiometry, thermodynamics, microbial growth kinetics, and chemical reaction kinetics for a continuously stirred batch reactor. The model was calibrated using results from laboratory test columns. Sensitivity analyses conducted using the calibrated model identified a molar ratio for acetate:calcium:nitrate of 0.9∶1.0∶1.0 as the preferred ratio for maximizing CaCO3 precipitation and gas generation while avoiding excess residuals in the modeled batch reactor system.
ISSN:1090-0241
1943-5606
DOI:10.1061/(ASCE)GT.1943-5606.0002126