AWWA ACE63058

Although the current market for nanomaterials is small and their concentration may notbe high enough in the environment to cause human health or environmental problems,this market is increasing rapidly and the discharge of nanomaterials into the environmentin the near future could be significant as manufacturing costs decrease and newapplications are discovered. The accumulation of nanomaterials in cells may havesignificant environmental and human impacts. At present, however, very little is knownabout the fate, transport, transformation, and toxicity of these man-made nanomaterials inthe environment. The objectives of this research project are to: characterize thefundamental properties of nanomaterials in aquatic environments; examine theinteractions 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 modelsystem of the epithelium. This study considers the physical, chemical, and biologicalimplications of nanomaterial fate and toxicity in systems that will provide insight into thepotential for nanomaterials to be present and to cause health concern in treated drinkingwater.Characterization of commercial metal oxide nanoparticles (powder or liquid suspensions)by scanning electron microscopy or by dynamic light scatter after placing these particlesin water indicates that these nanomaterials are aggregated when purchased and remainaggregated in solution. Attempts to disaggregate the nanomaterials in water usingsonication, pH adjustment, solvent addition, or surfactant addition had minimal effect onmean particle sizes. As a consequence, the metal oxide nanoparticle aggregates range insize 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 onaggregation kinetics than behavior of discrete nanoparticles in water. To address the fateof discrete nanoparticles our team has synthesized metal oxides with mean particlediameters 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 withcoagulation, flocculation, sedimentation, and filtration). Both metal coagulants (alum,ferric) and salt (MgCl₂) have been used to destabilize or otherwise aggregate metal oxidenanoparticles. Experiments have included titanium, iron, and aluminum oxidenanoparticles, and cadmium quantum dots. Overall, coagulation and sedimentation aloneremove 40 to 60 percent of these nanoparticles, and filtration (0.45 µm or 3 µm porediameter) removes an additional 50 to 80 percent. Ten to 30 percent of some initialnanoparticles remain, however, after this simulated water treatment test.Trans-Epithelial Electrical Resistance (TEER) measurements have been made usingCaco2 BBe (human intestinal cells) grown and maintained with Dulbecco's ModifiedEagle Medium (DMEM) media supplemented with 10 percent fetal bovine serum,penicillin/ streptomycin/ fungizone, and transferrin. Extensive optimization of growthconditions were undertaken. Preliminary experiments indicate a decrease of 10 to 50percent in TEER within 1 hour after application of metal oxide nanoparticles.Spectroscopic investigations of the cells are underway to determine the mechanism forchange in TEER. Includes 57 references, figure.

Product Details

Edition:

Vol. - No.

Published:

06/01/2006

Number of Pages:

8

File Size:

1 file , 320 KB