Experimental study on microbial salinity domestication and MICP-treated desert sand in mineralized water environment

To overcome engineering constraints posed by scarce freshwater resources and high transportation costs in desert regions, a microbial sand fixation technology using mineralized water instead of fresh water was proposed. The biomineralization mechanism and sand-fixing efficacy in a mineralized water environment were studied by microbial salinity domestication and culture, combined with microscopic analysis of carbonate precipitation and sand-fixing tests. The results showed that microorganisms gradually adapt to the mineralized water environment through salinity acclimation, and individual bacterial mineralization efficiency was also improved. Bacterial proliferation and urease secretion were inhibited by mineralized water, but urease-specific activity showed a positive response to increasing salinity. In deionized water, carbonate crystals were mainly hexagonal prismatic calcite, whereas in mineralized water, they were mainly coated structures composed of triangular-pyramidal calcite, Mg-calcite, and spherical vaterite, with crystal size decreasing as salinity increased. Sand fixation experiments reveal that the solidification effect in mineralized water environments is weaker than that in deionized water. Still, the calcium ion conversion rate exceeded 90% in both environments when the mixture ratio was 2:1. The MICP-treated samples with three treatment cycles could resist wind erosion at 10 m/s when the mixture ratio was 2:1, and the cementation solution concentration was ≥ 1.5 mol/L. In summary, increasing treatment cycles effectively mitigates the bacteriostatic effect of mineralized water, leading to improved wind erosion resistance.