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 AL-6 and BC composite) had an excellent synergy effect on manganese removal. The average removal rate of manganese 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, CO, CO, CH2, and CH 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 composite material can maintain excellent manganese removal efficiency under different pH conditions. Besides, in the sequence batch reactor (SBR) inoculating with the microbe-biochar composite, more than 96% of manganese was removed, which far exceeded the treatment efficiency of free bacteria in the SBR. Hence, biochar-immobilized AL-6 has great potential and can be applied to degrade manganese polluted wastewater.