Synergistic remediation of electroplating wastewater contaminated soil and reduction of risk of groundwater contamination by biochar and Pseudomonas hibiscicola strain L1

With the continuous development of electroplating industry, a large amount of electroplating wastewater is generated, which can be harmful to soil and basement. Introducing microorganisms into polluted soil can improve the soil environment, but it has the disadvantages of easy loss and low activity. In this study, the synergistic effect of biochar and strain L1 (BL1) was utilized to effectively reduce the risk of groundwater contamination by Ni(II), Cu(II), Cr(VI), and Zn(II), which are common heavy metals in electroplating wastewater. And the mechanism was found as BL1 was found to increase the porosity and water retention of the soil by specific surface area determination (BET) and scanning electron microscopy (SEM), favored the growth of soil microorganisms. It was found that BL1 could improve soil pH, enzyme activity, total organic carbon and other indicators by measuring soil physical and chemical properties. The results of microbial community analysis showed that BL1 increased the diversity of soil community and enriched microorganisms with nitrification and denitrification functions, thus promoting the removal of NH₄⁺-N and NO₃-N. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) diffraction results showed that -OH, -CH, C=O, Si-O-Si, CO₃²⁻ and PO₄³⁻ of BL1 complexed with heavy metals to form precipitates. Thus, the conversion of heavy metals to the stable state was promoted. These results show that the addition of BL1 can effectively improve the soil environment and promote the self-recovery of soil function.