Macrophyte-Assisted Vermifiltration for Postanaerobic Polishing of High-Strength Swine Wastewater: Coupled Organic Stabilization, Pathogen Reduction, and Metal Phyto-Stabilization

Intensified pig meat production has increased swine wastewater generation, necessitating advanced treatment. Anaerobic systems effectively reduce organic load and recover energy, but nutrients, pathogens, and trace metals still require removal. The efficacy of macrophyte-assisted vermifiltration (MVF) as a post-anaerobic treatment was evaluated and compared with conventional vermifiltration (VF) across varying hydraulic loads. Anaerobically treated swine wastewater (COD: 2607 ± 475 mg/L) was processed in continuous-flow VF and MVF reactors with Colocasia esculenta . At optimal flow rates (0.0014–0.0029 m 3 /d), MVF achieved over 90% COD and BOD 5 removal, lowering effluent BOD 5 to 17 mg/L. MVF also showed enhanced nitrification and lower residual ammonia than VF. Pathogen removal achieved 2.5–3.5 log reductions in total and thermotolerant coliforms, attributed to synergistic interactions between earthworms and plant roots. Effluent concentrations of major cations (Na, K, Mg, Ca) and trace metals (Fe, Mn, Ni, Cu, Zn) were substantially reduced, with metals primarily accumulating in root tissues (translocation factor <1), thereby confirming phyto-stabilization. Allium cepa assays showed improved root elongation (up to 450% at moderate dilutions) and a higher mitotic index (22.9 ± 9.3%) at 100% effluent, compared with the cytotoxic control (6.6 ± 2.8%). Integrating C. esculenta improves sustainable polishing of swine wastewater through vermifiltration.