Insight into synergies between Acinetobacter sp. AL-6 and pomelo peel biochar in a hybrid process for highly efficient manganese removal

The manganese contamination of groundwater is a global issue that needs to be solved urgently. In this study, a hybrid process between pomelo peel biochar(BC) and Acinetobacter sp. AL-6 (strain AL-6) was established to remove manganese from water. The results showed that microbe-biochar composite had removed 98.19% of manganese (800 mg L-1) within 48 h. Compared with two separate systems (biochar, strain AL-6), the co-system (strain AL6 and BC composite) had an excellent synergy effect onmanganese removal. The average removal rate ofmanganese in the synergistic system was 14.08 mg L-1 h(-1), which was 6.41 times higher than strain AL-6, 3.45 times higher than biochar, and even at 2.24 times their sum. In addition, the scanning electron microscope (SEM) and the bioassay indicated that many strains were attached to biochar and had vigorous biological activity. The FTIR results showed that the functional groups of -OH, C-O, C=O,-CH2, and C-H played a vital role in removing manganese. And the correlation analysis shows that biochar with strains AL-6 has a highly synergistic effect on manganese removal. Meanwhile, the compositematerial can maintain excellentmanganese removal efficiency under different pH conditions. Besides, in the sequence batch reactor (SBR) inoculating with the microbe-biochar composite, more than 96% of manganesewas removed, which far exceeded the treatment efficiency of free bacteria in the SBR. Hence, biocharimmobilized AL-6 has great potential and can be applied to degrade manganese polluted wastewater. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study established a hybrid process using pomelo peel biochar and Acinetobacter sp. AL-6 to remove manganese from water, showing a synergistic effect on manganese removal. The composite material maintained excellent manganese removal efficiency under different pH conditions and outperformed free bacteria in a sequence batch reactor. The results suggest that biochar-immobilized AL-6 has great potential in degrading manganese polluted wastewater.