Multi-phase Biogeochemical Model for Microbially Induced Desaturation and Precipitation

Microbially induced desaturation and precipitation (MIDP) is a biogeotechnical technique that takes advantage of native subsurface denitrifying bacteria to mitigate earthquake-induced soil liquefaction. Our next-generation model considers microbial growth and decay, alternative microbial metabolic processes, gas production, mineral-solids production, alkalinity and pH, microbial inhibition, and desaturation and precipitation in both freshwater and coastal environments that may influence MIDP behaviour. The next-generation model was constructed in Matlab.  The modelling equations (e.g., microbial growth, CaCO₃ precipitation, and biogenic gas evolution) were programmed within the original, publicly available van Turnhout Toolbox, a general-form mechanistic model for environmental systems (van Turnhout et al., 2016).  The van Turnhout Toolbox simulates chemical speciation with ORCHESTRA (Meeussen, 2003), an extensive database of established geochemical equilibria.  The MIDP-specific biogeochemical model components (i.e., stoichiometry, type of inhibition and kinetics, potential chemical species) were specified in an input spreadsheet that the program accesses.  The degree of saturation and percent (by weight) of mineral precipitation were calculated outside of the van Turnhout Toolbox using model results.