Enhancing Staphylococcus succinus tolerance via pre-mineralization for bioflocculation-based oilfield water treatment

Microbially Induced Calcite Precipitation (MICP) is a promising approach for treating high-hardness wastewater, such as oilfield-produced water (PW). However, elevated levels of suspended solids and the biotoxicity of pollutants in PW pose significant challenges to biological treatment. In this study, a pre-mineralization strategy was developed for the ureolytic bacterium Staphylococcus succinus J3. By forming a protective calcium carbonate shell on the bacterial surface, this strategy enhanced the bacterium's environmental resistance and provided nucleation sites for hardness ions. Compared with the unmodified strain, pre-mineralized J3 exhibited higher removal efficiency for hardness ions and improved self-flocculation capability, enabling simultaneous removal of suspended solids and hardness ions from PW. Batch experiments demonstrated that pre-mineralized J3, cultivated with glucose as the carbon source and inoculated at 5 × 10⁷ CFU/mL, achieved removal rates of 98.09 % for suspended solids and 95.41 % for hardness ions. Viability assays confirmed that the mineral shell significantly enhanced bacterial resistance to toxic components. Furthermore, analysis of extracellular polymeric substances (EPS) and microscopic structural characterization revealed that suspended solids were encapsulated and immobilized within the mineral matrix, facilitating their removal. This study presents a novel approach for biologically treating complex wastewater while minimizing biomass contamination, offering a promising solution for pretreatment in water purification processes.