Simultaneous removal of hardness and organic matter from oilfield-produced water by microbially induced calcite precipitation.

Oilfield-produced water (PW), the largest by-product of petroleum extraction, presents significant treatment challenges due to high concentrations of total dissolved solids, heavy metals, and organic compounds. In this study, a ureolytic bacterium Staphylococcus succinus J3, with efficient petroleum degradation and microbially induced calcite precipitation (MICP) capabilities, was screened for simultaneous removal of hardness ions and organic pollutants from PW. Strain J3 showed excellent removal of Ca (95 %), organic contaminants (62 %), and heavy metals (100 % for As and Mn, 94 % for Cu, 71 % for Ba) in high salinity PW under low nutrient conditions. Mechanistic analysis revealed that the bacteria removed organic pollutants through biodegradation, and the biominerals generated by MICP further accelerated the removal of organic contaminants through adsorption. Meanwhile, molecular characterization via FT-ICR MS demonstrated the conversion of large organic molecules into smaller, less toxic compounds, facilitating the downstream treatment of PW. Furthermore, the ammonium by-product (NH-N) from urea hydrolysis was efficiently recovered (83.73 %) as ammonium sulfate for agricultural production through Donnan dialysis (DD). This research presents a promising new approach for the pre-treatment of high-hardness organic wastewater and provides molecular-level insights into the mechanisms of organic matter removal, thus supporting the advancement and optimization of PW recycling technology.