Nanotechnology for domestic water purification - Nanotechnology in Eco-efficient Construction - page 362

Bank, 2005). Lack of drinking water and sanitation kills about 4,500 chil-
dren a day. Many children are missing school because neither their homes
nor schools have adequate drinking water and sanitation facilities. Sustain-
able water management is therefore a critical aspect in addressing poverty,
equity and related issues. The UN Millennium Development Goal of ensur-
ing environmental sustainability commits governments to 'reduce by half
the proportion of people without sustainable access to safe drinking water'
by 2015, a goal closely linked with the separate goal of access to sanitation
and basic hygiene education.
Different countries and regions face different environmental, social and
economic conditions and have different needs with regard to water use,
water quality, access to technology, fi eld conditions, and the types of tech-
nologies that may be appropriate in different circumstances. Water treat-
ment technologies include fi ltration using membranes, chemical treatment,
heat and ultraviolet treatment and distillation. They seek to remove solid
and other contaminants, or to neutralize them, and many treatments have
a long history of use in systems for producing water for domestic, industrial
and agricultural use (OECD, 2011). Most current approaches are materials
intensive, have a large ecological footprint and are not in a position to
comply with the increasing water quality standards of developing industrial-
ized nations. The conventional methods of disinfection such as chlorination
and ozonation can produce harmful byproducts due to reactions with
various constituents of wastewater, which may call for a tradeoff between
optimum disinfection and harmful byproduct formation.
The possibility of having ready access to safe drinking water is becoming
increasingly rare because of over-exploitation of existing water resources,
alarming effects of global warming (causing highly uneven rainfall patterns
in particular places, which in turn disturbs the tendency for water harvest-
ing), increasing levels of contamination as a result of rapid industrialization,
leaky water distribution systems and deterioration of water quality upon
ageing (though water has been treated at the point of entry, POE). On the
other hand, funding, governance, trained engineers and skilled labour are
commonly recognized obstacles to establishing regional and national-scale
water treatment systems.
The diffi culty 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
(Hillie et al. , 2007b). Community and household level POU water treatment
methods 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, manage-
ment systems and governance structures.

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