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| − | Water is life. To secure a high standard of living for all people, we must secure a renewable supply of water for drinking, cleaning, cooking, irrigation, heating and cooling. | + | {{:Water}} {{more|Water}} |
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| − | In the USA in 2006, the average water use per person per day was 575 litres. Compare this with 149 litres in the UK and 4 litres in Mozambique. Peter Gleick has said that 50 litres of water is sufficient for a person[http://en.wikipedia.org/wiki/Water_resources#Uses_of_fresh_water], though this does not take into account non-residential uses of water.
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| − | The intelligent use of mankind's water resources is not just an environmental issue; it is a public health issue. Drinking contaminated water is one of the most common causes of cholera, typhoid, diarrhoea, hepatitis A, dysentery and river blindness.
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| − | Suspended particles can be removed from water by passing them through a [http://en.wikipedia.org/wiki/Slow_sand_filter slow sand filter] with layers of gravel and sand. This is within the reach of all the World's people, as it requires no input of energy and no technological sophistication. A slow sand filter makes water safer for drinking, but does not fully remove all microscopic pathogens. UV light can kill water-borne pathogens. As [[LEDs]] get cheaper and more energy-efficient, the use of UV-emitting LEDs to sterilize water becomes more and more attractive. It would be a relatively simple matter to fit homes with the means to catch rainwater, pass it through a slow sand filter and sterilize it with UV light. In many temperate and tropical climates, this would provide the inhabitants of the home with an abundance of water. This decentralization of water-production would eliminate the need for complicated municipal water-distribution systems and would make individuals more independent and resilient in the case of [[disasters]].
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| − | Using composting toilets rather than flush toilets would save 26.7%[http://www.epa.gov/watersense/pubs/indoor.html] of water use in the home. Composting toilets can also be used as a source of fertilizer to grow food and electrodes could even harvest electricity from the bacteria they contain (see [[Fundamental resources/Energy|Energy]])
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| − | Passive means of cooling and heating building would also lighten the demand on our water supplies.
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| − | The [http://challenge.bfi.org/application_summary/385 Watermill] is an invention that condenses water from the air. This water is clean and ready to drink.
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| − | Nanofilters are an effective way of filtering out both suspended particles (which cause unpleasant tastes, smells and discoloration) and pathogens. The Tata Swach is a device that uses nanofilters to give very pure water. It retails for only $21. However, like other filters, it eventually clogs with impurities. <br> Filters made of [[carbon nanotubes]], small enough to let water molecules pass though, while blocking salt particles, impurites and pathogens, have recently reduced the price of desalination of sea water by 75% [http://www.technologyreview.com/read_article.aspx?ch=nanotech&sc=&id=16977&pg=1]. As 97% of the world's water is in the oceans, and unsalted water is needed for most human purposes, a practical method of desalination is a huge key to making Spaceship Earth work for all its inhabitants. IBM are conducting research into nanofiltration-based desalination [http://www.inhabitat.com/2010/04/07/ibm-saudi-researchers-team-up-on-solar-powered-desalination-technology/]. Filtration using nanotubes that are too small to become clogged is being investigated [http://cleantechnica.com/2008/09/15/carbon-nanotubes-might-be-used-in-future-water-filters/].
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Latest revision as of 18:38, 28 December 2012
With world population growing, demand for food (and hence
water for farming 
) expected to grow by 70%
[1], rivers becoming polluted and one in eight people already without clean drinking water
[2], some have warned that we are heading for a 'peak water' crisis with people lacking the necessary water to survive, and wars breaking out over the access to water supplies
[3]. Already, about half of all infectious disease is caused by contaminated drinking water.
A grim picture, indeed. But fortunately, an entirely avoidable one. Water is one of the most abundant resources available to us on this blue planet. The only problem we may face is synthetic scarcity; this article aims to show that there is no real shortage of water, nor of techniques to purify and manage it. If we simply apply the water-management techniques — many of which are extremely simple, low-tech, low-cost things — we have all the water we could ever need. 
