Quality of life depend on access to water that is free from contaminants and harmful microorganisms. However, industrialization, population growth, and environmental pollution have severely impacted water quality worldwide. This study presents a novel, biodegradable, and cost-effective ternary bio-nanocomposite composed of macromolecules of cerium-substituted hydroxyapatite (Ce-HAP), chitosan (CS), and bamboo fiber (BF). The Ce-HAP/CS/BF bio-nanocomposite was derived from renewable biogenic sources such as snail shells, CS, and BF. It was designed for applications in both environmental remediation and biomedical fields. The physicochemical characterization of Ce-HAP/CS/BF was performed using FTIR, XRD, HRSEM, TEM, EDX, TGA/DTA, UV-DRS, and XPS, confirming the successful integration of all components along with enhanced crystallinity, porosity, and thermal stability. Photocatalytic studies revealed effective degradation of methylene blue (MB) dye, with hydroxyl radicals (•OH) identified as the primary active species. Antibacterial assays demonstrated strong inhibitory effects against Escherichia coli and Staphylococcus aureus. Cytocompatibility evaluation using MG63 osteoblast-like cells showed over 90 % cell viability at all tested concentrations, confirming excellent biocompatibility. Furthermore, swelling and degradation studies in simulated body fluid indicated suitable water absorption and controlled degradation rates. Overall, the Ce-HAP/CS/BF bio-nanocomposite exhibits great potential as a sustainable material for wastewater treatment and bone tissue engineering, offering a multifunctional approach to address both environmental and healthcare challenges. © 2025 Elsevier B.V., All rights reserved.