Efficient remediation of Mn and NH-N in co-contaminated water and soil by Acinetobacter sp. AL-6 synergized with grapefruit peel biochar: Performance and mechanism.

Electrolysis manganese slag produced in industrial manganese production causes massive leachate containing heavy metal Mn and inorganic NH-N, which causes serious hazard to the water body and soil. A cost-effective alternative to address the multiple pollution is urgently needed. This study investigated the synergy of grapefruit peel biochar (BC) and strain AL-6 to remediate Mn and NH-N in sequencing batch bioreactor (SBR) and soil column. The results showed that, in SBR, under the condition of C/N 5, temperature 30°C, BC and strain AL-6 showed fabulous performance to remove Mn (99.3%) and NH-N (97.7%). The coexisting ions Mg and Ca had no effects on the removal of Mn and COD, however, 23.3% removal efficiency of NH-N was curtailed. Characterization found that the presence of MnCO confirmed the adsorption of Mn by functional groups action, and gas chromatography indicated that BC and strain AL-6 promoted the reduction of NO and organic carbon. In addition, BC and strain AL-6 helped to immobilize 799.41 mg L of Mn and 320 mg L of NH-N after 45 d in the soil column. And the determination of TOC, CEC, pH, Eh, soil enzymatic activity (catalase and urease), and microbial diversity and abundance confirmed that BC and strain AL-6 increased the soil fertility and bioavailability of pollutants. Totally, BC and strain AL-6 possess great potential to remediate Mn and NH-N pollution in water and soil.