Comparison and determination of probable toxicity of ZnO nanoparticle by four current bacteria in wastewater sludge

Toxicity investigating is necessary before furthermore progressing the nanotechnology industry. This study investigates the toxicity of ZnO nanoparticle (NP) with using available bacteria in sludge wastewater. The stock NPs suspensions (10g/L) were diluted with Mueller-Hinton Agar medium to achieve the 5-6000mg/l NPs concentrations. Each concentration was prepared in triplicate and The refined bacteria cultured on these media and growth inhibition percent of bacteria determined by comparing these cultured media with blank samples. These data analyzed using Probit analysis in SPSS ver 16. 0 software and 50% effective concentration (EC50)، no observed effect concentration (NOEC) and 100% growth inhibition of NPs determined. The Nano ZnO EC50 was 181. 7، 656. 4، 93. 9، and 935. 8 mg/l for E. coli، B. subtilis، S. aureus، and P. aeruginosa respectively. Also it was revealed that nano ZnO have a high toxicity level as NOEC calculation showed the least particle of this nanoparticle is toxic to all tested bacteria species، so the NOEC calculated zero for these bacteria. The 100% growth inhibition showed at 2813 mg/l of nano ZnO concentrations، 100% growth inhibition occurred for all bacteria. The results of this study are shown، S. aureus for determining of nano ZnO toxicity and P. aeruginosa for antibacterial applications، between four tested bacteria، are proper indicators.