Calcium Carbonate Precipitation And Biogrouting Experiment Research Induced By Non-Ureaclastic Bacteria Serratia Marcescens

Microbial mineralization phenomenon is widespread in nature, especially in geological diagenesis. Recent studies show that the formation of some rocks, especially carbonate rocks, has an inseparable relationship with microbial activities. Based on microbial mineralization phenomenon, microbial reinforcement technology is using the principle of microbial-induced precipitation of calcium carbonate(MICP), for reinforcement and repair of geotechnical engineering. This is a both economic efficiency and sustainable environmentally friendly method.Existing reaction mechanism of MICP mainly was urea hydrolysis, In this reaction process, the by-products was mainly ammonium ions, it was harmful to the surrounding environment. Therefore, this article conducted Serratia marcescens induced calcium carbonate precipitation research, it was based on the oxidation which substrates was calcium acetate.The main results of the research are as follows:(1) By bacterial enrichment and separation, and calcificationexperiments, a strain was successfully isolated from indigenous microorganisms. The strain could use calcium acetate as carbon source and calcium source inducing calcium carbonate precipitation. And it was identified as Serratia marcescens after DNA sequencing, ribosomal database and BLAST alignments comparisons, the match was up to100%.(2)The single factor experiments had been set to determine the optimum medium composition and culture conditions of Serratia marcescens. It was found that the optimum medium composition was yeast extract concentration 4%(w/v) and sodium acetate concentration of 4%(w/v), and the optimal culture conditions was temperature 30?,shaking speed 120 rpm, the culture initial p H 8 and inoculum size 4%(v/v). The growth curve could completely fitted to the Gom-Rich models.(3) The optimum calcium concentration of calcium carbonate precipitation induced by Serratia marcescens was determined as 0.15mol/L by shake flask experiments, formation of the main mineral were calcite and vaterite of this concentration, the amount of crystalline calcium precipitation reached 859.4 mg per unit concentration of bacteria(OD600 value), and the best conservation period was 9 d. XRD and SEM analysis showed that two forms of mineral calcium carbonate crystals were mainly calcite and vaterite, the composition of crystal wasmainly affected by calcium concentration.(4) Sand column cementation experiments showed that quartz sand after cementation with MICP technology by Serratia marcescens,the average Ca CO3 crystals formation reached 22.16 kg/m3, the porosity was decreased by 91%, and the permeability coefficient was decreased by more than 80%, but strength was insufficient. Therefore, in order to enhance the strength of sand column cementation body, the circulation of injection for cementation solution should be increased and the conservation period should be extended. XRD and SEM results showed that precipitated Ca CO3 crystals were mainly calcite, and these crystals would improve the physical properties of loose media by adhesion on the sand particles surface and filling in particle pore.