| Summary: | Black odorous sediment pollution in urban areas has received widespread attention, especially pollution caused by acidified volatile sulfide (AVS), phosphorus and heavy metals. In this study, an Fe<sub>3</sub>O<sub>4</sub>@BC composite was fabricated by the coprecipitate method of Fe<sub>3</sub>O<sub>4</sub> and biochar (BC) and was mixed with calcium peroxide (CP) for sediment pollution treatment. The results showed that the AVS removal rate could reach 52.8% in the CP+Fe<sub>3</sub>O<sub>4</sub>@BC system and −18.1% in the control group on the 25th day. AVS was removed in the following three ways: AVS could be oxidized with oxygen produced by CP; H<sub>2</sub>O<sub>2</sub> produced from CP also could be activated by Fe<sup>2+</sup> to generate hydroxyl radicals that have strong oxidation properties to oxidize AVS; AVS could also be removed by bacterial denitrification. As for phosphorus, total phosphorus (TP) content in overlying water remained at 0.1 mg/L after CP and Fe<sub>3</sub>O<sub>4</sub>@BC were added. This is due to the conversion of NH<sub>4</sub>Cl-P and Fe/Al-P into Ca-P in sediments, which inhibited the release of phosphorus. Simultaneously, the release and migration of heavy metal chromium (Cr) were slowed, as demonstrated by the results (the acid extractable and reducible states of Cr in the sediment decreased to 0.58% and 0.97%, respectively). In addition, the results of the high-throughput genetic test showed the total number of microorganisms greatly increased in the CP+Fe<sub>3</sub>O<sub>4</sub>@BC group. The abundance of Sulfurovum increased while that of sulphate-reducing bacteria (SRBs) was inhibited. Furthermore, the abundance of denitrifying bacteria (Dechlorominas, Acinetobacter and Flavobacterium) was increased. In brief, our study showed the synergistic effect of Fe<sub>3</sub>O<sub>4</sub>@BC composites and CP had a remarkable effect on the urban sediment treatment, which provides a new way to remove sediment pollution.
|
|---|