Simultaneous removal of nitrate, oxytetracycline and copper by ferrous-manganese co-driven immobilized bioreactor

The treatment of polluted water contaminated by nitrate, antibiotics, and heavy metals is a difficult problem in the current water treatment process. In this study, MnFe2O4 modified illite was mixed with sodium alginate (SA) to prepare a biological carrier illite@MnFe2O4@SA (IMFSA), which was used to immobilize strain Zoogloea sp. MFQ7 and construct a bioreactor. The bioreactor can use sodium acetate as a carbon source as well as ferrous and manganese ions as additional electron donors to achieve efficient nitrate removal. The denitrification capability of bioreactor was considerably enhanced by the addition of illite@MnFe2O4 (IMF) in comparison to SA biological carrier. The bioreactor was able to achieve a nitrate removal efficiency of 97.2% when hydraulic retention time is 5.0 h, C/N ratio is 2.0, and the concentration of Fe2+ and Mn2+ were 5.0 mg L-1. Furthermore, the bioreactor can achieve efficient removal of oxytetracycline (91.8%) and copper (85.6%) through the adsorption by IMF and biological iron-manganese precipitates. High-throughput sequencing results indicated that Zoogloea was successfully immobilized into the biocarrier. According to the KEGG database, it is suggested that the addition of modified IMF enhances denitrification and stimulates the expression of genes associated with the iron-manganese redox cycle.