This study introduces novel functionalized polysaccharide-based bioflocculants derived from the low-cost biomass of Melocactus andinus and Stenocereus griseus. The objective was to develop a high-efficiency, bio-derived alternative for water purification to address the critical needs of decentralized community systems. The key novelty lies in the first-time application of Deep Eutectic Solvents (DES) as green functionalization agents for cactus polysaccharides, yielding performance metrics that benchmark favorably against commercial synthetic flocculants like polyacrylamide (PAM). The methodology involved the extraction of mucilage and cellulose via Microwave-Assisted Extraction (MAE), followed by sequential oxidation (LiCl/NaIO4) and functionalization with DES (aminoguanidine chloride and choline chloride).Characterization via XRD confirmed structural modification with crystallinity index values of 41.2 ± 0.9% (CSg-GndCl) and 45.4 ± 0.1% (MMa-ClC), while FTIR-ATR verified successful functionalization through the emergence of C=N (1668 cm-1) and N-H (1635 cm-1) bands. Comprehensive jar tests demonstrated exceptional efficacy: modified cellulose (CSg-GndCl) achieved a turbidity removal of 99.0 ± 0.3% and reduced colour below 15 PCU at a low dosage of 32 ± 1.1 mg/L (pH 6). Similarly, modified mucilage (MMa-ClC) removed 97.3 ± 0.5% of turbidity at 56 ± 0.8 mg/L (pH 4). While these results confirm a resource-efficient strategy for sustainable water treatment, the study highlights the transition from laboratory optimization to the treatment of complex effluents. Consequently, future research will focus on the long-term stability and removal of emerging pollutants in diverse industrial and municipal matrices to establish a robust basis for industrial scale-up.