BACKGROUND AND OBJECTIVE: Iron oxide nanoparticles at low concentrations can act as a source of iron ions required microorganisms but high concentrations can cause stress and cell damage in bacterial cells are reduced cell growth. The effect of iron oxide nanoparticles were studied remove coliform bacteria from contaminated water.

METHODS: In this experimental-laboratory study synthetic municipal wastewater by adding 5 mL to 60 liters of water in urban distribution network was built. Every time in half a liter of synthetic samples 100, 250, 500, 1000, 2000, 4000 and 6000 ppm of iron oxide nanoparticles were added at the time of zero, 20, 40, 60, 80 and 100 minute samples and with method 15-tube was tested.

FINDINGS: With increasing concentrations of iron oxide nanoparticles from 100 ppm to 6000 ppm the most likely number of coliforms per 100 ml (MPN) average removal rate from 70 percent to 82 percent synthesized samples. (Number of MPN) and removal efficiency at 0, 20, 40, 60, 80 and 100 minutes, was (660.52) 0% (330.42) 48.83, (317.00) 53.75, (200.14) 68.48, (161.66) 73.96 and (128.04) 80.16 respectively. Significant differences between time and removal of coliform bacteria (P=000.0) was observed. Maximum efficiency in the contact time of 100 minutes and 6000 mg/L concentration of iron oxide nanoparticles to 100 percent.

CONCLUSION: The results showed that with increasing contact time and increasing concentrations of nanoparticles, remove the MPN samples is increasing.