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Overview of conventional and nano-base water treatment technologies
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Lack of access to clean water and sanitation in developing countries remains a high development priority. Despite numerous intervention strategies and large public and private investments, many challenges continue to impede water and sanitation projects, in particular those establishing centralized water systems. Funding, governance, trained engineers, skilled labor, and access to appropriate technologies are commonly recognized obstacles to establishing regional and national-scale water systems. The difficulty and lack of success in overcoming obstacles to regional and national water supplies has led, in part, to increased interest in point-of-use (POU) water treatment methods at the household and community level. Advocates of community and household level POU water treatment methods suggest that these approaches avoid many of the barriers associated with large-scale water supply projects because they are relatively inexpensive, can be purchased by the unit, and/or constructed using readily available materials. For these reasons, POU technologies avoid the need for large capital investments, management systems, and governance structures. They also allow community or individual ownership and involvement in decisions, maintenance, and other aspects of the water treatment. While there appear to be advantages to POU approaches, experts also point out that many POU technologies rely heavily on international aid agencies and non-governmental organizations for subsidization and distribution. Many products have components that need to be frequently replaced in order for water to be effectively treated, and some components can not be made locally in developing countries, leaving users vulnerable to disruptions in distribution. Nanotechnology is increasingly being identified as an area of science and technology that could play a role in addressing some of the short-comings of conventional POU devices. Proponents suggest that nanotechnology-based materials could lead to cheaper, more durable, and more efficient water treatment technologies that meet the needs of developing countries. Several water treatment methods and devices that incorporate nanoscale materials are already commercially available, and others are being developed. These nanotechnology-based products include water filters, filtration membranes, catalysts, and nanoparticles for groundwater remediation. While there is growing interest in these nanotechnology-based POU products, various stakeholders are also raising questions about possible implications of products containing nanoscale materials, including potential environmental and human health risks, as well as socio-economic and ownership issues. This paper draws on a broad range of disparate information sources and synthesizes information about relevant attributes of conventional and nanotechnology-based water treatment devices including: contaminant removal; amount of water treated; cost; ease of use; and other considerations. The first section describes a range of well-known and field-tested conventional POU approaches to removing contaminants from water. The information provided draws on technical papers and peer-reviewed literature, as well as manufacturers’ specifications and patent filings. The second section provides examples of available nanotechnologies that could be used to enhance existing or develop new POU water treatment technologies. Since these products are still very new or not yet on the market, much of the information is obtained from materials provided by the manufacturers, as well as limited scientific publications. In many cases, independent verification of the performance of these products is not yet available. The paper does not include information about potential environmental or human health risks because little, if any, data about these issues is available in the context of specific water treatment devices. The data provided is taken from numerous sources that report on studies that were conducted under different conditions using a variety of methodologies, techniques, and approaches. Therefore, the data reported in this paper should be interpreted with consideration that direct comparison of data is not always possible; however, the data should provide an overview of the relative effectiveness of the technologies described. The paper demonstrates that many conventional technologies exist that effectively remove bacteria, viruses, coliforms, turbidity, and other contaminants from water, and that are affordable and can be produced locally. However, a review of the literature suggests that several technical challenges remain with regards to the cost and effectiveness of removal of certain contaminants in a manner that meets the needs of people in developing countries. http://kenbah.gbaopan.com/files/b91e7bf3f5354606aac54f016eb6c456.gbp |
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