(128d) Plasma-Based Water Treatment: Targeted Application and Guidelines for Process Scale-up

Electrical discharge plasma is an effective and versatile advanced oxidation process due to the formation of reactive species such as hydroxyl radicals. The technology requires no chemical additions, can degrade a broad range of contaminants, and produces no residual waste. Despite promising results of bench-scale studies and evident potential advantages of plasma water treatment, the technology has not been used in practice. A major obstacle hindering the development of plasma reactors is associated with the absence of general principles to guide the design of new reactors with higher efficiency. In an attempt to improve the feasibility of plasma-based water treatment technology and develop basic guidelines for reactor design and optimization, we have determined that the size of the contact area between the plasma and the treated solution is the single most important factor affecting the plasma reactor performance. Building on this knowledge, we have modified the traditional gas-discharge plasma reactor to maximize this contact area, which resulted in the development of the foaming plasma reactor. The foaming electrical discharge plasma reactor rapidly and efficiently degrades many chemicals including pharmaceuticals, personal care products, disinfection byproducts, and several perfluoroalkyl acids (PFAAs). Of all the compounds evaluated, perfluorooctanoic acid and perfluorooctanesulfonic acid were degraded the fastest. Experiments conducted with groundwater containing PFAAs demonstrated that co-contaminants do not appear to influence the efficiency of the reactor.

We have determined the efficacy of the plasma process for treatment of a wide range of different compounds of environmental importance and used the results of this investigation to construct a model to predict the approximate treatability of any compound based on just a few of the compoundâ??s physical properties. We have determined design guidelines for plasma reactor scale up as well as the efficiency and relative competitiveness of the scaled up process for selected compounds.