Developing a socially-embedded point-of-use water treatment strategy incorporating silver nanoparticles and microwave radiation
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Providing safe drinking water is a multifaceted problem that goes beyond a treatment device and deserves a holistic approach with respect to sanitation, handling, education, and customs of the target community. Socially-embedded point-of-use treatment strategies based on familiar components are more likely to receive prolonged use from the residents. Microwave ovens are a globally diffused, socially accepted technology that are enticing options for foundations of irradiation-based treatment. Taking advantage of the exceptional qualities of certain materials at the nano-scale allows one to utilize the low-energy radiation of microwave rays. This study focused on silver nanoparticles under the hypothesis that increased temperature from microwave exposure would result in increased ion dissolution and heat shock, thus enhancing antimicrobial potency. Using Escherichia coli (K12) as a model microorganism, 1 mL samples containing up to 1 mg/L of suspended silver nanoparticles were irradiated in a microwave reactor (2,450 MHz; 70 W) for 60 and 90 s. A clear synergistic effect between microwave radiation and silver nanoparticles was observed as microbial inactivation increased with additional microwave exposure and higher concentrations of silver. A maximum of 4.7 log₁₀ reduction was achieved after 90 s of irradiation, indicating rapid inactivation as typical batch studies involving silver nanoparticles take on the order of hours to achieve such inactivation. These results are promising for the development of nanomaterials capable of utilizing microwave radiation; however, efficiency will need to be increased in order to treat larger volumes of water. Incorporating various nanomaterials with several stress-inducing mechanisms has the potential to enable irradiation-based disinfection with the globally-diffused microwave oven for treatment at the household level.