Nowadays, water resources are suffering from the release of waste products from commercial and industrial sectors besides untreated domestic sewage and chemical pollutants those leaked into fresh water resources which considered as a horribly detrimental thing to both the human community and the ecosystem, including animals and plants. In this regard, the major water contaminants are heavy metal ions, organics (e.g., dyes), and oils which can disqualify any water stream for drinking. In that context, we have done studies to evaluate the effectiveness of the anti-bacterial action that mediated by ZnO nanoparticles which have been extracted using a green synthesis method which involves utilization of artemisia plant. The activity has been evaluated against a diversity of bacteria which exist in the water resources. Our research has been conducted against gram-positive bacteria, such as S. aureus and gram-negative bacteria, such as E.coli and Klebsiella pneumoniae. The bacterial strains have been isolated and identified by means of many biochemical tests. The effectiveness of ZnO nanoparticles has been determined through measurement of mean inhibition zone value against each type of bacteria, which appeared to be 20 mm against S. aureus, 22 mm against Klebsiella pneumoniae and 24 mm against E.coli, therefore, those values indicate effectiveness of ZnO nanoparticles as an anti-bacterial.