Abstract: Sediments from urban rivers and nearby water bodies are enriched with heavy metals and persistent organic pollutants. In this study, we investigated the performance and mechanisms of in situ remediation of sediment polluted with Pb and phenanthrene by iron-based biochar combined with bioelectrochemical technology. The results showed that the iron-based biochar can be prepared by impregnation and drying method. The surface iron was mainly composed of Fe₃O₄ and γ-Fe₂O₃, which has magnetic property. The iron-based biochar combined with bioelectrochemical technology (0.2 V) increased removal rate of phenanthrene in sediment by 6.75 times, mainly because that the anode can be used as an electron receptor to strengthen the co-metabolic degradation of phenanthrene in sediment. Addition of glucose further accelerated bioelectrochemical degradation of phenanthrene in sediment, resulting in an  increase of phenanthrene removal rate by 1.09 times. The anodic bioelectrochemical process reduced sediment pH and promoted the transformation of Pb to weakly acid soluble state which was migrated to the cathode and transformed to residual state under the action of electric field force. The results of high-throughput sequencing showed that iron based biochar combined with bioelectrochemistry promoted the growth of Tissierella, Erysipelotrichaceae and Pseudomonas in the sediments, leading to the bioelectrochemical enhanced degradation of phenanthrene and Pb activation.

Key words: iron-based biochar, bioelectrochemistry, polycyclic aromatic hydrocarbon, heavy metal, enhanced removal.