Use of Plasma-Shell Technology for Concurrent Control of Chemical and Microbial Contaminants

Abstract

Abstract An emerging treatment system, based on using Plasma-Shells as a high surface area source of Ultraviolet (UV) light, holds promise for addressing some of the key microbial and chemical water quality issues faced by small water systems. Plasma-Shells are hollow dielectric gas encapsulating shells that can be energized to emit light over a broad range of wavelengths. When the shells are coated with titanium dioxide and energized, advanced oxidation reactions can occur in tandem with disinfection. By optimizing the wavelength characteristics, it is possible to achieve pathogen inactivation (~250 nm) and also promote photocatalytic reactions through excitation of titanium dioxide (~350 nm). From a water treatment perspective, the net effect of these reactions is disinfection and photocatalytic mineralization of waterborne contaminants. A key advantage of titanium dioxide coated Plasma-Shells over more traditional UV light sources is that all components are rugged, inert, and safe. The ceramic based shell material and the encapsulated gas (neon and/or xenon) are inert and, therefore, do not impact water quality. The system is highly water efficient and does not generate a waste stream or process residuals. In addition, there are no consumable chemicals that need to be stored on-site. The shells can be regenerated on-site through an off-line thermal system. The high surface area of the Plasma-Shells allows for a relatively small technology footprint, compared to more traditional disinfection or oxidation systems. The size of the Plasma-Shells and the process design configuration can be tailored to provide reaction conditions that are appropriate to address a broad spectrum of chemical and microbial waterborne contaminants. Key elements of the technology include:Simple construction, rugged design, and scalable to meet site specific constraints.Modular process configuration that can be adapted to meet specific treatment requirements.Reliable source of UV light that is devoid of mercury or other potential environmental contaminants.High surface area to volume ratio that can provide efficient contact time for inactivating or mineralizing microbial and chemical waterborne contaminants.Efficient activation of titanium dioxide due to its direct contact with the UV light source.Use of a thin film of titanium dioxide obviates the need for post-treatment filtration and accomplishes the photocatalytic reaction in a single-step.