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Tuesday, January 18, 2022

How to filter water so that it is not dangerous

Strictly speaking, you cannot call clean drinking water. From the point of view of a chemist, pure water is a distillate free from all impurities and microorganisms. For a microbiologist, clean water is an ideal environment for bacteria. For us, pure water is a liquid enriched with minerals, which can be drunk daily without risk to health.

To date, there is no single universal method for purifying fresh water – its choice depends on the composition of the water, the requirements for it and the scope of its further use. For example, there are ozone, osmotic, filtration and ionic purification systems, each of which has its own pros and cons.

The most promising so far is the nanofiltration technology. This method will effectively eliminate even halogen organic and chlorine-containing impurities in water without the use of aggressive reagents. Nanofiltration is used in Holland, USA and France. This method is one of the most expensive, so it is not widely used. Even in countries where nanofiltration technology is used, they do it only for purifying water with a special purpose.

Water filtration methods of the future

Nanofiber

Korean researchers have unveiled a new technology that makes seawater drinkable in minutes. The scientists used a membrane distillation process, which allowed them to achieve 99.9% purification of water from salt. They are confident that a solution will ease the drinking water crisis exacerbated by climate change.

A new study details a method for purifying seawater using a nanofiber membrane as a salt filter. Although scientists had already used membrane distillation before, they faced a problem that slowed down the process. If the membrane became too wet or flooded with water, it could no longer separate the salt.

Therefore, scientists had to wait for the membrane to dry, or come up with additional solutions, for example, using pressurized air to release trapped water from the pores.

Latest desalination plants

Researchers at the Dalian Maritime University in China have developed a new desalination plant that can float on the surface of seawater, efficiently absorb solar energy, and use that heat to evaporate water.

The block itself consists of three layers: the main part is polyethylene foam, which helps it float and acts as a heat insulator. Outside, the foam is wrapped in special paper – an absorbent material used in disposable diapers. It draws water up to the surface.

It is important to note that the device avoids one major mistake – contamination due to the accumulation of salts on the surface. Over time, this reduces its effectiveness.

During testing, the team found that no salt layer had formed. This indicates that special pores on the block’s coating drain the salt and dump it back into the seawater. Another benefit, the team said, is that the paper material can be reused more than 30 times.

Palladium Gold Nanoparticle Catalyst

Chemists at Cardiff University have created a catalyst for instant water disinfection based on palladium and gold particles.

The authors of the work found that during the synthesis of H2O2, many other molecules containing oxygen arise, which interact tens and hundreds of millions of times more actively with microbes than peroxide and chlorine.

Such a level of bactericidal activity of these compounds, as noted by Hutchins and his colleagues, allows for almost instant water purification from microbes, spores and other organic contaminants that can negatively affect human health.

Flexible membrane

Chemists at the University of California, Berkeley have found a way to make it easier to remove toxic metals such as mercury and boron from water.

The new membrane-based method removes nearly 100% of toxic metals and recovers valuable metals for later use or disposal. According to the authors, the membrane is easy to integrate into current water treatment systems.

During the development process, chemists at the University of California at Berkeley synthesized flexible polymer membranes with nanoparticles that can be tuned to absorb specific metal ions, such as gold or uranium.

The membrane can be tuned to a specific type of particles that it will absorb.

Wood filters

Scientists at the Massachusetts Institute of Technology used the sapwood of non-flowering trees to create a filter for drinking water from natural materials.

They made new xylem filters that filter out pathogens such as E. coli and rotavirus. Laboratory tests have confirmed that their development removes bacteria from contaminated springs and groundwater. Scientists have also developed simple methods to extend the shelf life of filters. As a result, wood discs can purify water for at least two years.

Consequences of water scarcity

Lack of clean water forces people to use unsafe water for drinking, which carries an increased risk of harm to health. Consumption of polluted fresh water leads to a deterioration in living conditions, the development of serious diseases – up to and including death.

Due to water scarcity, there is a practice of storing water in homes, which can significantly increase the risk of contamination and create an environment conducive to the growth of harmful bacteria. Hygiene is also a serious problem: people cannot properly wash themselves, wash clothes and keep their homes clean.

If no measures are taken, then by 2030 almost 5 billion people will remain without satisfactory water treatment – about 67% of the world’s population.

Today for every inhabitant of the Earth there is about 750 m³ of fresh water per year, by 2050 this amount will decrease to 450 m³. Up to 80% of the countries of the world will find themselves in a zone that, according to the UN classification, is categorized below the water scarcity line.

In Africa alone, by 2020, due to climate change, between 75 and 250 million people will find themselves in such a situation. Lack of water in desert and semi-desert regions will cause intensive migration of the population.

Most of India is already suffering from the lack of drinking water.

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