Water Purification

Water purification or the removal of water contaminants is an important field of application of nanotechnologies. Water purification is necessary when water is contaminated, for example, after accidental or illegal discharge of waste water and toxic substances into inland water reaching groundwater, or also into the open sea. New ways of protecting the public in case of an emergency are being developed, both in terms of early warning systems (e.g., sensors) and concerning purification. The second and most important challenge is to provide potable water to people in developing (and developed) countries: in 2002 more than 1 billion people in the developing world were without a reliable water supply and 2.6 billion had no access to adequate sanitation. New methods employing nanotechnologies could complement or replace conventional water-treatment technologies to remediate and purify water more effectively—concerning the removal of contaminations or desalinization. Questions of risk assessment concerning the toxicity of nanomaterials used and questions of social sustainability must not be left aside in the process.

Devices for water treatment that incorporate nanotechnological elements are already available on the market and others are in different stages of development. These nanoenabled technologies mainly rely on different types of membranes and filters that contain carbon nanotubes, magnetic nanoparticles, nanopo-rous ceramics, titanium dioxide nanoparticles for the catalytic degradation of pollutants, and other materials and processes. Also, nanosensors are used to detect and identify pollutants. Conventional (non-nano) technologies (operating on the microscale) for water treatment include filtration (ceramic filters, biosand filters, fiber and fabric, charcoal filters, and others), ultraviolet radiation, chemical treatment, and desalination. Thus, the purification technologies must aim at removing most biological (like bacteria), organic (like insecticides) and inorganic (like metals) pollutants. The nanoenabled technologies are hoped to be less costly, more durable and more efficient, thus better meeting the needs of developing countries, especially when used on community and household levels (and not large-scale projects).

Prominent among the various applications of nanotechnology which can support the United Nations (UN) Millennium Development Goals (MDG), therefore, is water treatment and remediation, including desalinization. In 2000, the member states of the UN committed themselves to achieve the eight MDGs by 2015; and water treatment is especially important for the MDGs eradicate extreme hunger and poverty, reduce child mortality, improve maternal health, and ensure environmental [Page 794]sustainability. Especially in the developing world, and with increasing pressure of scarcity, there is a need for water purification—not only to make it possible for everybody to have access to water that is not contaminated, but also to do something to prevent future wars that are likely to be battles for water.

Thus, the discussion around water purification is part of a larger theme that is sometimes summarized as “nanotechnology and the poor.” In this context, a possible “nanodivide” that would see the benefits of nanotechnology only with the wealthy is contrasted with benefits for the poor and for developing countries, and water remediation is a major issue there.

Though everybody wishes that water purification and access to potable water for developing countries will be improved, there are also some open questions to be considered over

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