Synergistic Remediation of Metal(loid)-Contaminated Groundwater Using Sequential BES–Phytoremediation Approach

Conventional polluted groundwater remediation struggles with persistent metal(loid)s, creating a need for integrated bioelectrochemical systems (BESs) and phytoremediation. The proposed configuration consisted of two sequential BESs, a microbial fuel cell (MFC) followed by a microbial electrolysis cell (MEC), whose treated effluent and exhausted anolyte were subsequently polished in individual subsurface vertical-flow macrophyte mesocosms (VFMMs), planted either with Phragmites australis, Scirpus holoschoenus, or Typha angustifolia. The overall treatment period was 38 days, comprising 8 days of BES treatment followed by 30 days of VFMM treatment. With MFC-MEC pretreatment, an overall 91% metal(loid) removal efficiency (RE) was noted, with REs of >99% for Fe and Cu, and between 71% and 92% for Al, Ni, Zn, Cd, and As, significantly increasing groundwater pH from 2.66 to 4.65, at p < 0.05. Macrophyte mesocosms, notably with P. australis and S. holoschoenus, further reduced residual Cu, Cd, Zn, and As levels below Flemish groundwater sanitation standards, nutrient concentrations and ecotoxicity (as demonstrated by Aliivibrio fischeri bioluminescence assays). Residual Ni was reduced by >99.9% but remained above regulatory thresholds. BES–phytoremediation sequential integration proved to be an effective biotreatment that combines the rapid contaminant removal capacity of BES with the polishing and ecological stabilization functions of constructed wetlands.