Science News

Sweet solution to water purification

Sun, 22nd May 2011

Chris Smith

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Scientists have developed a sugar-fuelled chemical filter to clean up contaminated water.

Provision of clean water is viewed as the leading challenge in the TapTwenty First Century, with still over half of the world's population living in unsanitary conditions. The problem is further intensified by the fact that, apart from just sewage which can be filtered out, water sources are also frequently contaminated by persistent organic pollutants such as trichloroethylene and trichlorophenol, which are known to be carcinogenic.

Now a team from the University of Kentucky in the US led by Dibakar Bhattacharyya, writing in PNAS, may have the answer in an ingeniuous, low-cost multi-membrane glucose-powered filter that can chemically degrade toxins.

The filter consists of an upper membrane into which is impregnated an enzyme called glucose oxidase. This breaks up glucose molecules to yield hydrogen peroxide, oxygen and gluconic acid. The hydrogen peroxide then passes into a second, lower-layer membrane into which are embedded iron oxide nanoparticles.

These catalyse the decomposition of the peroxide to produce a highly reactive chemical called a hydroxyl radical, which can attack and neutralise toxins present in the water.

As a demonstration of the effectiveness of the technology, the team added a solution of glucose and TCP to the top layer of the membrane, successfully breaking down initially 100% and then about 70% of the TCP passing through.

In a further test on a genuine groundwater sample containing trichloroethylene, over 70% of the chemical pollutant was successfully degraded. With further optimisation, such a system could be used to cheaply detoxify drinking water for the half of the world who currently have no access to safe water supplies.

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Interesting, although I'm not convinced that it is any better than the standard sand, micro-porous, & charcoal filter systems.

What is the actual contamination problem with 3rd world water supplies?

Chemicals?  Biologicals?  Both?

I can imagine some little bugs encountering it...  sugar + protein  =  excellent growth medium!!!

I'm trying to figure out why water contamination is so much different between the USA and the 3rd world.

I think part of it is different sanitary water system and waste standards.

Here, municipal systems filter and chlorinate the fresh water, and treat the waste water.

Rural water is predominantly well water & septic systems.  I'm not sure about all the standards, but fresh water and waste water has to be kept separate.  Wells are licensed, and must include about 20 feet of casing which in effect isolates surface water (potential for contamination) from deep water (generally sterile, or free from "human" bacteria).  And the casing is grouted in place to prevent water from traveling down the outside of the casing.

Septic systems use a tank for biologic degradation, and liquid waste is disposed undergound.  Solid waste settles to the bottom of the tank.

So...  the best approach is likely to convince the 3rd world countries to start making clean wells and sanitary septic systems for their rural populations, and to filter and treat the urban water, and build waste treatment facilities. 

Yes, it is probably a tall order, but preventing contamination would be a big step. CliffordK, Mon, 23rd May 2011

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