| 英文摘要: | 1438619 (Smith). In the U.S. and other developed nations, high quality drinking water is typically provided through centralized water treatment and distributions systems. In the developing world, these systems are often unreliable, unable to meet the demand for treated water, or simply do not exist. As a result, 3-4 billion people do not receive reliable, high-quality water delivered to their households. The World Health Organization has indicated that one possible solution to this problem is to decentralize water treatment so that people treat their water right before they consume it in their homes. Designing such "point-of-use" water treatment technologies is a challenging problem, as they must be low cost, technologically effective, simple to use, and socially acceptable. For this study, a porous ceramic tablet infused with nanoscale patches of silver and/or copper is proposed for point-of-use water treatment. The ceramic tablet is most applicable to developing-world water treatment and further, it addresses the three elements of the Triple Bottom Line: social, economic, and environmental sustainability. The ceramic tablet will be simple and inexpensive to manufacture. For use, the tablet would be placed into a 10-20-L household water storage container, where it gradually would release ionic silver and/or copper into the water. The tablet design is such that silver/copper concentrations in the drinking water will be sufficient to disinfect waterborne pathogens while not exceeding the drinking water standards of 0.1 mg/L (silver) or 1.0 mg/L (copper).
In this research, multiple tablets will be fabricated using different raw materials, including two clay types, sawdust with varying particle sizes, silver and copper nitrate at different concentrations, and with and without the use of different reducing and capping agents. During firing, ionic silver and copper will be reduced to zero-valent metallic oxidation states, forming "nanopatches" throughout the porous ceramic. The tablets will be characterized using transmission electron microscopy to determine nanopatch morphology and size distribution and using mercury porosimetry to evaluate ceramic pore-size distribution. Through simulation and fundamental experiments on porous media diffusion, sorption to ceramic pore walls, and oxidation kinetics, the relative importance of these transport processes will be determined and the tablet design will in turn be optimized. Disinfection kinetics will be quantified for viral, bacterial, and protozoan pathogens for a range of water chemistries and turbidities. Both short- (24-hr) and long-term (6-month) performance tests will be conducted. A field test of this technology will be performed in conjunction with the University of Venda (UNIVEN) and three rural communities located in Limpopo Province, South Africa. Local potters working at a previously established ceramic filter factory in Ha-Mashamba, S. Africa will be taught to produce ceramic tablets. These tablets will then be field tested in two nearby rural S. African communities. The tablets will be evaluated as stand-alone water purifiers, and in combination with more conventional ceramic water filters. Field work will leverage resources of a recently awarded Research Experiences for Undergraduates Site Program called "Water, Society, and Health." A life-cycle analysis of this technology will be performed with consideration of economic, environmental, and social factors. Its performance in these categories will be compared to centralized water-treatment and distribution systems and other point-of-use water treatment technologies. Existing point-of-use water treatment technologies have either a relatively high entry-level price point (> $30) or are depleted after a single use (Aquatabs, Pur sachets, etc.). By comparison, the ceramic tablet water purifier is a potentially disruptive technology that that likely could be sold for $5 or $6 while lasting for 6 months without any special action by the end user. |