Carbonate Mineral Precipitation for Soil Improvement through Microbial Denitrification

Microbially induced calcium carbonate precipitation (MICP) is attracting increasing attention as a sustainable means of soil improvement. Microbial denitrification has the potential to become the preferred method for MICP because denitrification does not produce toxic byproducts, does not require a water-soluble electron donor, can utilize nearly 100% of the electron donor, does not require exogenous organic nitrogen, is thermodynamically more favorable than other processes, readily occurs under anoxic conditions, and potentially has a greater carbonate yield per mole of substrate than other MICP processes. Bench scale bioreactor and column tests using Pseudomonas denitrificans have shown that calcite can be precipitated from calcium-rich pore water using denitrification. Recent experiments at Arizona State University and by others have sought to reduce potential environmental impacts and lower costs associated with denitrification by reducing the total dissolved solids in the reactors and columns and by addressing the loss of free calcium in the form of calcium phosphate precipitate from the pore fluid.