<p>The development of sustainable antimicrobial materials is essential for next-generation air and water purification systems, particularly in view of the increasing occurrence of multidrug-resistant pathogens. In this work, three-dimensional porous poly(lactic acid) (PLA) fibrous mats were fabricated by coagulation-wet electrospinning, followed by pH-controlled in situ green functionalization with silver (Ag) and silver oxide (Ag₂O) nanoparticles using tannic acid as a natural reducing agent. The influence of pH on nanoparticle nucleation, size, distribution, and composition was systematically investigated. Comprehensive surface and structural analyses (ATR-FTIR, FE-SEM, EDS, XRD, XPS) were performed immediately after functionalization and after 30 days of immersion in water to simulate realistic filtration conditions. The results confirmed successful and stable incorporation of silver species and revealed pH-dependent differences in nanoparticle characteristics. Antibacterial tests against <i>Staphylococcus epidermidis and Escherichia coli</i> showed strong efficacy with significant retention of activity after prolonged water exposure. Uniaxial compression tests performed in aqueous conditions demonstrated that the monoliths possess sufficient mechanical robustness and structural integrity for water filtration applications. Antibacterial water filtration test evidenced a significant removal of <i>S. epidermidis</i> and a complete inactivation of the bacteria on the silver-containing filters. Overall, pH-tailored Ag-functionalized PLA fibrous scaffolds emerge as a sustainable, durable, and effective platform for antimicrobial environmental purification.</p> Graphical Abstract <p></p>