This study investigates the application of 8% and 10% manganese-doped copper (II) oxide nanoparticles (MDCN) for treatment of contaminated water infested with Salmonella specie, Staphylococcus aureus, lead and cadmium ions. 8% and 10% Mn-doped CuO nanoparticles were synthesized using the co-precipitation method, and their physicochemical properties were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR). The antibacterial activity of both nanoparticles was evaluated using a turbidimetric assay. The average crystallites size (D) of the synthesized 8% and 10% Mn-doped CuO NP was 31.86nm and 15.10nm respectively. The antibacterial assay revealed that both 8% and 10%-Mn–CuO NP reduced the growth of salmonella specie and Staphylococcus aureus in a manner that connote a decrease in activity after the peak is reached. 8%Mn-CuO NP was more effective in reducing salmonella specie at 20mg, 40mg, and 100mg, while 10%Mn-CuO NP was more effective for staphylococus aureus at 20mg, 40mg, 60mg, 80mg and 100mg. The adsorption process of Cd(II) and Pb(II) ions on 8%-Mn-CuO NP and 10%Mn-CuO NP was normal, favorable and occurred via physiosorption. The 10%Mn-CuO removed more Pb(II) ions from the contaminated water (110.068mg/g) than 8%Mn-CuO NP (92.712mg/g). Likewise, 10%Mn-CuO also slightly removed more Cd(II) ions from the contaminated water (58.183mg/g) than 8%Mn-CuO (55.62302mg/g).