(337a) Ambient-Air Plasmas for Frugal and Sustainable Water Disinfection in the Developing World

Ambient-condition air plasmas have been shown to decontaminate water and aqueous solutions through the production of reactive oxygen and nitrogen species (RONS) that are toxic to bacteria and other microorganisms. One method of creating air plasma at ambient conditions is the “dielectric barrier discharge” (DBD) technique, which creates a small, confined plasma region near a pair of electrodes separated by a dielectric layer such as glass or ceramic; RONS diffuse away from the plasma region and into a contaminated aqueous volume. We have previously shown that DBD-based devices can disinfect water in two distinct “modes”: a high-power, nitrogen oxides-rich discharge creates a persistent antimicrobial effect in water that can last at least one week [1], while a low-power, ozone-rich mode can rapidly decontaminate aqueous solution [2].

We describe a design and configuration of air plasma reactors for the novel application of water disinfection in low-resource settings, including the developing world. Ambient-air plasma is a promising method for low-resource sanitation because it requires only electricity and air to create a disinfectant. The plasma reactors used in this study are assembled from inexpensive materials including ceramic tubes and steel rods, and comparatively low-cost energy sources and power supplies like solar-energy rechargeable lead-acid batteries and neon-sign transformers are used to ignite the plasma. In this study, we compare the gas- and liquid-phase RONS chemistry created by these “frugal” devices to the chemistry observed by using more expensive and precisely tunable laboratory devices. In addition, we show how the disinfection efficacy, using E. coli as a model bacterium, depends on transformer voltage, dissipated power, air flow rate through the reactors, and reactor configuration. Our preliminary results indicate that the concentrations of some reactive species can differ dramatically based on the reactor geometry and material and the power source. However, the chemistry measured here agrees reasonably well with the established laboratory-scale plasma chemistry in some important aspects, including the ozone-nitrogen oxide “mode transition”. Therefore, air plasma treatment remains a promising strategy for inexpensive and effective water disinfection.

References:

[1]         M. J. Traylor, M. J. Pavlovich, S. Karim, P. Hait, Y. Sakiyama, D. S. Clark, D. B. Graves, Journal of Physics D: Applied Physics 2011, 44, 472001.

[2]         M. J. Pavlovich, H.-W. Chang, Y. Sakiyama, D. S. Clark, D. B. Graves, Journal of Physics D: Applied Physics 2013, 46, 145202.