Background and aims: Silver is the metal as a safe and effective antibacterial agent which can be raised more than 650 types of microorganisms such as bacteria and virus. Common indicator used to assess water quality and compliance with standards to determine the presence of total coli forms and fecal coli forms are bacteria. The aim of this study was to evaluate the effect of nanosilver on inactivation the coli forms and fecal coli forms from drinking water.

Methods: This bench-scale experimental study was carried out in a batch system on artificially contaminated water samples prepared by adding 10 ml effluent to 90 liters of distilled water. In each run, the nanosilver (30-180 μgL) was added to 6 containers of contaminated water and then a sample was taken every 20 minutes for a 100-minute period. The samples were tested by
15-tube series method based on the instruction no. 9221-B of 21th edition of standard method book on water and wastewater experiments (21st edition).

Results: Results revealed that the coli forms and fecal coli forms inactivation significantly increased with increasing the contact time of nonosilver (P=0.001), but there was no significant correlation between the nanosilver concentrations and coli forms and fecal coli forms inactivation (P=0.13). The maximum coli forms and fecal coli forms inactivation (76.2, 65%) was achieved within 100 minutes contact time for 180 μgL of silver.

Conclusion: Based on the current results, it can be concluded nanosilver treatment is effective in coli forms and fecal coli forms inactivation from contaminated water and advice as a new method for water disinfection.