The antibacterial activity of natural zeolitized tuffs containing 2.60 wt.% Cu2+, 1.47 Zn2+ or 0.52 Ni2+ were tested. Antibacterial activities of the zeolites against Escherichia coil and Staphylococcus aureus were tested after 1 h and 24 h of exposure to 1 g of the zeolite in 100 mL of three different media, namely Luria Bertani, synthetic wastewater and secondary effluent wastewater. The antibacterial activities of the zeolites in Luria Bertani medium were significantly lower than those in the other media and negatively correlated with the chemical oxygen demand of the media. The Ni-loaded zeolite showed high leaching of Ni2+ (3.44-9.13 wt.% of the Ni2+ loaded) and weak antibacterial activity in the effluent water. Since Cu-loaded zeolite did not leach Cu2+ and the leaching of Zn2+ from Zn-loaded zeolite was low (1.07-1.61 wt.% of the Zn2+ loaded), the strong antibacterial activity classified the Cu- and Zn-loaded zeolite as promising antibacterial materials for disinfection of secondary effluent water. (C) 2011 Elsevier B.V. All rights reserved.