Bacterial deactivation by cell-wall rupturing is widely described. Complete mineralization of both aqueous gram-positive Staphylococcus aureus and gram-negative Klebsiella pneumoniae, leaving no organic species, is described here for the first time. Solar-simulated radiation (with 5% UV), with ZnO nanoparticle photocatalyst, is used. In addition to complete bacterial deactivation ( 100%), their mineralization is achievable with time. Both bacteria, with thick and thin peptidoglycan layers, are mineralized. In thicker walled S. aureus, 72% mineralization is achievable, while in thinner walled K. pneumoniae, mineralization is 85%. Anthocyanin-sensitized ZnO shows higher catalytic efficiency under purely visible light, while pristine ZnO particles are more effective under simulated solar radiation. The results show the feasibility of using direct solar radiation in photocatalytic water disinfection without the need to use other more costly and hazardous methods. The study is especially useful to many societies having limited access to safe drinking water. © 2020, The Minerals, Metals & Materials Society.