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Purifying water

Product analysis: Cellopore sachets

The market
The main market for the Cellopore sachets is in disasters and emergencies. The sachets are sold to governments or relief agencies, which distribute them to the end-users. There is a huge potential market:

Technical specification
There are a range of Cellopore sachets designed to meet a variety of needs.

Product function
Cellulose naturally attracts water. The lower part of the sachet is usually filled with sugar. When placed in water, this becomes wet and creates an osmotic gradient that draws water into the sachet in the same way that a tree sucks water from the ground.

The membrane (made from cellulose film called cellophane) does not have holes in it. Instead it has a matrix of long-chain molecules, which create a barrier to all molecules larger than 0.002Ám (about 6,000 daltons). Pyrogens are 20,000 daltons; viruses about 60,000; and most bacteria are larger than 2,000,000 daltons. Thus all microbiological contamination is prevented, even from the smallest viruses. Because external pressure is not applied, sediment never 'clogs' the membrane, unlike with standard filters.

The Cellopore sachets are made from cellulose film (cellophane), which is made from wood pulp from renewable plantation forests.

The sachets are manufactured in hygienic factory conditions and are packed for easy transportation. If necessary, instructions can be printed in the appropriate language.

The sachets are simple and safe to use. No fuel is needed to get clean water or a rehydrated food product (in the case of the duplo sachet), so there is no danger from boiling, heat or smoke inhalation. There are no added chemicals. The sachets work well even with silted or muddy water. Using them gives a significantly reduced rate of reinfection.

The sachets have been designed to be easy to use and require no special equipment.

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Practical Action - Technology challenging povertyEuropean Commission - Department for International Development

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