The invention represents a breakthough for membrane technology and ready meal packaging, though whether consumers can be persuaded to rehydrate their chicken and rice ready meals in this manner is debatable.
UK-based New Scientist magazine reports that the ration comes in a pouch containing a filter, which, according to the US Combat Feeding Directorate, is capable of removing 99.9 per cent of bacteria and most toxic chemicals from the water used to rehydrate it.
The pouch relies on osmosis to filter the water or urine. When two solutions of different concentrations are separated by a semipermeable membrane, with gaps that allow only water molecules to pass through, the water is drawn to the more concentrated side.
According to the New Scientist report, the membranes are made of thin sheets of a cellulose-based plastic, with gaps between the fibres that are just 0.5 nanometres across, too small for bacteria to pass through.
The aim of the concept is to reduce the amount of water soldiers need to carry. However Hydration Technology, the company that makes the membrane, says soldiers should only use urine in an emergency because the membrane is too coarse to filter out urea.