Effect of silver nanoparticles on the inactivation of heterotrophic bacteria in water contaminated

Common methods for water disinfection are using chlorine which can efficiently control microbial agents. Researches in recent decades have shown a relationship between the disinfection of water and disinfection by-products. Nanotechnology in the last decades has provided opportunities for discovering the bactericide property of metal nanoparticles. Among all anti-microbial nanoparticles, silver is the most applicable one. Therefore, the aim of this study was to evaluate the effect of nanosilver on inactivating of the heterotrophic bacteria in contaminated waters.
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-1) was added to 6 containers of contaminated water and then a sample was taken every 20 minutes for a 100-minute period. Numbers of heterotrophic plate count (HPC) were determined for all samples according to the standard methods book instructions (21st edition).
Results revealed that the heterotrophic bacteria inactivation significantly increased with increasing the contact time of nonosilver (P=0.001), but there was no significant correlation between the nanosilver concentrations and heterotrophic bacteria inactivation (P=0.13). The maximum heterotrophic bacteria inactivation (83.6%) was achieved within 100 minutes of contact time for 180 μgL-1 of nanosilver.
Nanosilver treatment is effective in heterotrophic bacteria inactivation in contaminated water and can be advised as a new method for water disinfection.