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How is water filtered in Egypt?

The technology uses pervaporation, a technique by which the water is first filtered through the membrane to remove larger particles and then heated until it vaporises. The vapour is then condensed to get rid of small impurities, and clean water is collected.

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Researchers at Alexandria University in Egypt have unveiled a cost-effective desalination technology which can filter highly salty water in minutes. The technology is based on membranes containing cellulose acetate powder, produced in Egypt. The powder, in combination with other components, binds the salt particles as they pass through, making the technique useful for desalinating seawater. "The membrane we fabricated can easily be made in any laboratory using cheap ingredients, which makes it an excellent option for developing countries," says Ahmed El-Shafei, an associate professor of agricultural and biosystems engineering in Alexandria University, and an author of the study. The technology uses pervaporation, a technique by which the water is first filtered through the membrane to remove larger particles and then heated until it vaporises. The vapour is then condensed to get rid of small impurities, and clean water is collected. According to the research paper, published in Water Science and Technology last month, this method can be used to desalinate water which contains different types of contamination, such as salt, sewage and dirt. This kind of water is difficult to clean quickly using existing procedures. The membrane technology in combination with vaporisation can be applied in remote settings, as it requires only the membranes for the filtering process, and fire to vaporise the filtered water, the researchers say. "Using pervaporation eliminates the need for electricity that is used in classic desalination processes, thus cutting costs significantly," says El-Shafei. Pervaporation is used to separate organic liquids, like alcohols, and is one of the more common systems used in sewage treatment to separate water from organic solvents. The technology has been around since the mid-90s, Helmy El-Zanfaly, a professor of water contamination at Egypt's National Research Center. But, he says, "What is new is making the membrane locally, using materials abundant in Egypt and developing countries." El-Zanfaly adds that existing pervaporation membranes are fabricated using complicated procedures, making them unsuitable for cheap production. "The technology implemented in the study is much better than reverse osmosis, the technology currently used in Egypt and most of the countries in the Middle East and North Africa," El-Zanfaly says. "It can effectively desalinate water with high concentration of salt like that of the Red Sea, where desalination costs more and yields less." The technology can be adapted for commercial use by fabricating larger sheets of the membrane and cutting these into suitable swathes, according to El-Shafei. The next step for the team is to establish a small desalination unit as a pilot project for the technology. More information: "Desalination of simulated seawater by purge-air pervaporation using an innovative fabricated membrane" Water Science & Technology Vol 72 No 5 pp 785–793 IWA Publishing 2015 DOI: 10.2166/wst.2015.277

This article was originally published on SciDev.Net. Read the original article.

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Why we should not drink water immediately after running?

However, drinking ice-cold water right after exercising may cause the digestive system and the internal organs to receive a shock, causing chronic pain in the stomach.

July 10, 2016 05:00 pm | Updated 05:00 pm IST

It is said that we should not drink water just after strenuous exercise. Is there any scientific basis to it?

Archit Chandak, New Delhi

There is no scientific contemplation behind this belief that we should not drink water just after strenuous exercise. During a workout, the body loses a lot of fluids through sweating and leads to dehydration. So, it is imperative that we consume an adequate amount of water to replenish the lost fluids in the body after the vigorous exercises. In the case of those doing longer workouts of an hour or more, some carbohydrate containing drink may be more beneficial. However, drinking ice-cold water right after exercising may cause the digestive system and the internal organs to receive a shock, causing chronic pain in the stomach. This is so because the warm temperature of our body after exercising cannot quickly absorb ice-cold water and causes the digestive system to have a hard time.

Astha Khandelwal, Delhi.

This week’s questions

Is there really any relationship between or side effects of eating fish, milk and eggs together?

Rayis ul Bashir

If we look at the spark that comes while welding, our vision gets blurred. Why?

T.S. Sujith Martin, Tirunelveli, Tamil Nadu

Some people say, “Menstruating women should not touch holy things, should not go to temples.” Is there any scientific basis to this?

Sujitha, Chennai

Why can't some people recollect easily something that they studied thoroughly a long time before?

Hemalochani Janaarthanum

Readers may send their questions/answers to questioncorner@thehindu.co.in

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