In this work, novel Punica granatum peel extract-derived cauliflower-like ZnO decorated with bovine bone-derived hydroxyapatite (ZnO/HAP) composites were successfully synthesized via a facile eco-friendly method. Numerous analytical characterization methods were utilized to investigate the structural, morphological and optical properties of synthesized photocatalysts. Under visible light irradiation, the as-synthesized ZnO/HAP-5 composite demonstrated the highest antibacterial activity against Enterococcus faecalis (E. faecalis) among all the tested products. The exceptional antibacterial performance of synthesized ZnO/HAP-5 composite was also noticed through the K+ and protein leakage, bacterial morphological change and cellular substance alteration. Additionally, catalyst recycling and bacterial regrowth experiments were conducted to determine the practicability of as-synthesized products in photocatalytic disinfection. The photocatalytic improvement of ZnO/HAP-5 composite can be ascribed to the efficient charge carrier separation and high H2O2 generation. Furthermore, the excellent antibiofilm performance of ZnO/HAP-5 composite was verified with microscopic examination, exopolysaccharides reduction and hydrophobicity index decline in E. faecalis biofilm. Finally, the synthesized ZnO/HAP-5 composite was found to inhibit the activity of 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radicals efficiently. This work shed a light on the conversion of agricultural wastes into efficient photocatalytic materials for safe and practical water disinfection applications. © 2021 Elsevier Ltd. All rights reserved.