Synergistic microalgae-duckweed systems for enhanced aquaculture wastewater treatment, biomass recovery, and CO2 sequestration: A novel approach for sustainable resource recovery.

Current aquaculture practices generate nutrient-rich effluents that cause significant environmental pollution. This study presents a novel synergistic microalgae-duckweed system integrating Chlorella sp. and Spirodela polyrhiza for sustainable wastewater treatment, biomass valorization, and carbon sequestration. Over a 15-day treatment period, the system achieved unprecedented removal efficiencies: 91.25% for NO3--N, 98.90% for NH4+-N, 100% for total phosphorus, and a 95% reduction in chemical oxygen demand (COD). Concurrently, the system produced 6.67 g/L of microalgal biomass and 90 g/m2 of duckweed biomass significantly higher than those of standalone systems, which showed enhanced protein and lipid contents suitable for bioenergy or feed applications. The dual system sequestered CO2 at a remarkable rate of 1.65 g/L/day, exceeding standalone treatments. Microbial community analysis revealed enriched functional diversity, promoting optimized nutrient cycling and organic matter degradation. Although the system was tested at a lab scale, it demonstrates promising scalability due to its efficient nutrient removal and biomass production, as well as the robustness of the combined microalgae-duckweed treatment approach. This integrated approach not only addresses water pollution but also advances the circular economy by converting aquaculture waste into high-value biomass and mitigating carbon emissions. These findings position the synergistic microalgae-duckweed system as a scalable and eco-friendly solution for sustainable aquaculture management and environmental conservation.