Evaluation of the biocidal efficacy of titanium dioxide coatings for water purification

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The World Heath Organization estimates that over half the world's population water supplies are contaminated with microorganisms, many of which are often pathogenic- underscoring the need for cost effective and non-toxic strategies for the treatment of large volumes of water. A breakthrough water treatment strategy that has gained widespread acceptance is the dispersant into water supplies of a nano-photocatalysts. When photocatalysts are exposed to photons in the UV or visible light range, highly reactive oxygen radicals are generated that decompose and disintegrate organic molecules and microbes, transforming them into water and CO2. A promising and widely used photocatalyst is titanium dioxide (TiO2), which is non-toxic, insoluble in water and resistant to most chemicals, such as acids, bases or solvents and relatively inexpensive. Unfortunately, the nanoparticles cannot be easily removed from the treated water. The potential long-term consequences to human health of ingesting the nanoparticles are a major concern since multiple adverse effects have been noted with cell lines and test organisms. A novel strategy proposed by Simulant Inc. is to immobilize Ti02 crystals on adhesive surfaces as a more viable and safe alternative to achieve economical and effective treatment of water. A modified Thermal Spray process is being engineering to achieve high concentrations of the biocidal, anatase form of TiO2. The grant proposal aims to evaluate the biocidal activities of the engineered TiO2 coating using gram-negative, gram-positive and spore forming bacteria. The data generated will play a critical role in the engineering of water treatment plants employing immobilized TiO2 photocatalytic cells.