THE GUNK from a truck鈥檚 tailpipe might not seem very attractive to drink. But a British defence lab may ask parched soldiers of the future to do just that, using a gadget it is developing that harvests water from the exhaust of jeeps, trucks and tanks, then filters it until it is drinkable.
The idea comes from Mel Scott and his team at the defence research company Qinetiq in Gosport, Hampshire. Instead of arranging for thousands of bottles of water to be supplied in areas where the pumping, treatment and supply of water has been disrupted by conflict or drought, troops will produce their own water as they motor around.
The combustion products of diesel are made up mainly of carbon dioxide and large amounts of admittedly filthy water. By wrapping a small refrigerating device around a truck鈥檚 tailpipe, Scott and his team believe it can not only condense out water from the exhaust when the engine is running but also condense water from the ambient air in the pipe.
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In tests on a prototype water-harvesting system mounted on the back of a truck, 5.1 litres of diesel burnt by the engine, produced 4.5 litres of a water-rich gunky black condensate. Some of this was then poured into a soldier鈥檚 water bottle, through an activated carbon filter in its neck that removes particles larger than 2 micrometres across. The water that emerged from the filter was clear but undrinkable, as its pH was 4.5.
鈥淪ome soft drinks are considerably more acidic than that,鈥� Qinetiq鈥檚 Vince Watson points out. But the water would need to be further purified to meet drinking water purity standards, which require a neutral pH. The water would also face a battery of other tests, for example to confirm that dissolved solids have been successfully removed. Qinetiq is now analysing the recovered water to assess what other steps will be needed in the field to make it drinkable.
Qinetiq thinks aid organisations operating in drought-stricken areas will find its idea useful. But the International Committee of the Red Cross (ICRC) is sceptical. 鈥淔or personal use, maybe this would work, but we need quantity 鈥� tens to hundreds of thousands of litres a day. And it sounds complicated,鈥� warns Ricardo Conti, head of water engineering at the ICRC.