AWWA ACE63058

Although the current market for nanomaterials is small and their concentration may not be high enough in the environment to cause human health or environmental problems, this market is increasing rapidly and the discharge of nanomaterials into the environment in the near future could be significant as manufacturing costs decrease and new applications are discovered. The accumulation of nanomaterials in cells may have significant environmental and human impacts. At present, however, very little is known about the fate, transport, transformation, and toxicity of these man-made nanomaterials in the environment. The objectives of this research project are to: characterize the fundamental properties of nanomaterials in aquatic environments; examine the interactions between nanomaterials and toxic organic pollutants and pathogens (viruses); evaluate the removal efficiency of nanomaterials by drinking water unit processes; and, test the toxicity of nanomaterials in drinking water using the cell culture model system of the epithelium. This study considers the physical, chemical, and biological implications of nanomaterial fate and toxicity in systems that will provide insight into the potential for nanomaterials to be present and to cause health concern in treated drinking water. Characterization of commercial metal oxide nanoparticles (powder or liquid suspensions) by scanning electron microscopy or by dynamic light scatter after placing these particles in water indicates that these nanomaterials are aggregated when purchased and remain aggregated in solution. Attempts to disaggregate the nanomaterials in water using sonication, pH adjustment, solvent addition, or surfactant addition had minimal effect on mean particle sizes. As a consequence, the metal oxide nanoparticle aggregates range in size from 500 to 10,000 nm in diameter at concentrations of 10 mg/L of nanoparticles. Thus fate and transport of metal oxide nanoparticles may actually depend more on aggregation kinetics than behavior of discrete nanoparticles in water. To address the fate of discrete nanoparticles our team has synthesized metal oxides with mean particle diameters of ~ 10 nm, which are not initially aggregated and will be used in future tests. Experiments have been conducted that simulate drinking water treatment (jar tests with coagulation, flocculation, sedimentation, and filtration). Both metal coagulants (alum, ferric) and salt (MgCl₂) have been used to destabilize or otherwise aggregate metal oxide nanoparticles. Experiments have included titanium, iron, and aluminum oxide nanoparticles, and cadmium quantum dots. Overall, coagulation and sedimentation alone remove 40 to 60 percent of these nanoparticles, and filtration (0.45 µm or 3 µm pore diameter) removes an additional 50 to 80 percent. Ten to 30 percent of some initial nanoparticles remain, however, after this simulated water treatment test. Trans-Epithelial Electrical Resistance (TEER) measurements have been made using Caco2 BBe (human intestinal cells) grown and maintained with Dulbecco's Modified Eagle Medium (DMEM) media supplemented with 10 percent fetal bovine serum, penicillin/ streptomycin/ fungizone, and transferrin. Extensive optimization of growth conditions were undertaken. Preliminary experiments indicate a decrease of 10 to 50 percent in TEER within 1 hour after application of metal oxide nanoparticles. Spectroscopic investigations of the cells are underway to determine the mechanism for change in TEER. Includes 57 references, figure.