Heavy metal contaminated soil remediated by a bioelectrochemical system: Simultaneous promotion of electrochemically active bacteria and bipolar membrane

ABS T R A C T A modified microbial electrolysis desalination cell (BP-C-MEDC) equipped with a bipolar membrane (BPM) and a cation exchange membrane (CEM) was fabricated to efficiently remove heavy metals from polluted soil, compared with microbial electrolysis desalination chemical-production cell and conventional MEDC at various solid-to-liquid (S/L) ratios. At optimal 0.1 g/mL of S/L ratio, the BP-C-MEDC showed the highest current density due to BPM application to alleviate the acidification of the anode chamber and obtain the lowest resistance. Simultaneously, the lowest desalination efficiency (3.88 +/- 1.73%) of the BP-C-MEDC led to less weight loss in the soil at the S/L ratio due to less self-diffusion induced by anion exchange membrane loss. The BP-C-MEDC had negligible organics pollution, where the total organic carbon concentration of the cathode chamber was only 5.2 +/- 0.6 mg/L after 12 h of treatment with the S/L ratio. The lowest pH and the highest current density derived from the direct application of BPM brought about the highest removal efficiencies of Cd (81.10%), Pb (23.05%), and Zn (30.14%) at the S/L ratio of the BP-C-MEDC, along with the lowest energy consumption of metal removal. The results suggest that the proposed system has the potential to efficiently treat heavy metals and inefficiently release organics from the contaminated soil.