Abstract
<title>Abstract</title> <p>The discharge of residual agro-industrial effluents containing potentially toxic elements (PTEs) after conventional biological treatment remains an environmental challenge, since secondary treatment mainly removes organic matter, and not inorganic contaminants. Nature-based polishing technologies utilizing floating aquatic macrophytes are promising alternatives; however, under realistic operating conditions remain limited. This study evaluated the feasibility of using aquatic macrophytes as tertiary polishing systems for dairy effluents previously subjected to secondary treatment, at a pilot scale and under batch-flow conditions. The performance of Pontederia crassipes, Pistia stratiotes, and Salvinia auriculata was compared over 36 days by analyzing water physicochemical parameters, plant growth, nutrient dynamics, and Pb and Cd accumulation. All species improved effluent quality by reducing turbidity, total solids, and chemical oxygen demand, while maintaining dissolved oxygen and pH within environmentally acceptable ranges. P. crassipes and P. stratiotes produced greater biomass and accumulated higher metal concentrations than S. auriculata. The integration of metal data with bioaccumulation and translocation analyses revealed that pH-induced changes in metal speciation influenced bioavailability and uptake, providing mechanistic insights that go beyond conventional removal assessments. Although each treatment utilized a single pilot reactor, repeated temporal monitoring allowed for a robust assessment of treatment dynamics and comparative species performance under consistent operating conditions, substantiating technological viability rather than determining a definitive treatment efficiency. By integrating environmental engineering and plant physiology approaches, our study contributes to the mechanistic understanding of phytoremediation and may inform the optimization and future full-scale implementation of low-cost tertiary polishing systems for agro-industrial effluents.Keywords: effluent polishing; heavy metals; metal bioaccumulation; physicochemical parameters; plant growth.</p>