Poring over water solutions

There is a desperate need for drinkable water in Third World countries, of course – and people in tropical countries require about five litres per day. The needs in Europe are less – but is still necessary to maintain sound health and optimum working efficiency, especially in hot weather. The solution in many offices is pure water from a dispenser –but the raw material comes in large plastic bottles, which are both quite expensive and heavy to carry, especially if they have to be brought upstairs. The Challenge Our challenge is to come up with a sound and practical solution for supplying top quality drinking water. Purity should be as high as possible, while cost should be minimal. The technology to produce it should work on the small scale – suitable for the office – and on the large scale, supplying drinking water when conventional sources are unavailable. It should work where there are rivers, or by the sea, or even in the middle of a desert where rain is rare. Our solution is based on an old idea that has saved many lives down the years in hostile environments, and is scalable. It does not rely on filtration: there are ways of filtering even pond water, to make it drinkable. However high-performance filters that are used to process murky water inevitably become clogged, so their replacement is a significant cost. The solution offered below solves the problem elegantly and at low cost. Once you see it, you may consider it obvious. But many of the tweaks that turn it into cost effective equipment are innovative enough to be protected by patents. For those without access to the web, the solution will be described fully in our August issue. Let us know if you have a better way to make things flow! Solution The solution to last month's challenge – on a cheap supply of pure water – comes from Australia, where lack of water is a problem over much of the country. The base principle is to condense water out of the air. Even the Sahara Desert manages to have a relative humidity of around 25%. In fact, an old survival trick is to dig a hole, suspend a piece of plastic over it, with a stone to weigh down the centre, and collect the water that condenses on the underside during the night in a cup placed beneath the plastic. Insects and other creatures making use of the same 'watering hole' should be removed before drinking. However, the machines developed by Envirosource in Australia are more sophisticated than that. Hitesh Gohel, the company's UK sales representative, says the smallest solutions (from around £800) make up to 24 litres per day of what he describes as absolutely pure, distilled water – usually more than enough for a British office, since average use in the UK is only 15 litres per week. Water is sucked in at the rear of the machine and condenses on a chilled surface. To prevent biological organisms taking up residence, the water is constantly circulated, filtered and sterilised by an ultraviolet lamp. The company also produces industrial-scale units, producing up to 5,000 litres per day. A commercial greenhouse-scale unit in the offing will produce 200,000 litres per day.