Accelerated Pb(II) removal and concurrent bioelectricity production via constructed wetland-microbial fuel cell: Structural orthogonal optimization and microbial response mechanism

Abstract

In this study, a novel constructed wetland-microbial fuel cell (CW-MFC) filled with biomass carbon sources was established to elucidate the impacts of orthogonal configuration of multiple constraints towards wastewater purification and bioelectricity generation under Pb(II) stress. As a result, the optimal structural layouts of CW-MFC were granular activated carbon, Iris pseudacorus and 20 cm of electrode spacing, respectively. The homologous system yielded a favorable Pb(II) removal efficiency of 99.05 %, a maximum output voltage of 394.3 mV and power density of 4468.40 mW/m2, respectively. The migration results highlighted the major contribution of substrate and biomass to Pb(II) adsorption and fixation. Likewise, Pb(II) was immobilized on the cathode via potential binding to O. A visible enrichment of electroactive bacteria (Clostridium, Geobacter, Pseudomonas) and metal-resistant bacteria (Novosphingobium, Aeromonas) was noted. Also, microorganisms modulated the intracellular transport, chemotactic and antioxidant systems by engaging in the metabolic processes of carbohydrate, glutathione, pyruvate, etc. The microbial analysis signified that the genera enriched in disparate regions of CW-MFC-6 regulated the metabolic processes to facilitate their activities and resistance to Pb(II) stress, thereby synergistically enhancing the integrated capability of closed-circuit device. This study was dedicated to elucidating the microbial response mechanism of structural orthogonal optimization of CW-MFC, and providing a theoretical guidance for an effective regulation of Pb(II)-containing wastewater treatment.