In our previous Short Term Pure Drinking Water Solutions article we mentioned the MadiDrop, which uses silver nanoparticles to kill bacteria. But nanotechnology — that is, the engineering of really, really small objects and structures, smaller than the width of a human hair — has a lot more potential to help clean up the world’s drinking water. Researchers at India’s D.J. Sanghvi College of Engineering say that filters fashioned from carbon nanotubes and alumina fibers, for example, could be capable of removing not just sediment and bacteria, but even traces of toxic elements such as arsenic.


Researchers in India are investigating the use of several nanotechnology approaches to water purification. Water purification using nanotechnology exploits nanoscopic materials such as carbon nanotubes and alumina fibers for nanofiltration.

The impurities that nanotechnology can tackle depend on the stage of purification of water to which the technique is applied, the team adds. It can be used for removal of sediments, chemical effluents, charged particles, bacteria and other pathogens. They explain that toxic trace elements such as arsenic, and viscous liquid impurities such as oil can also be removed using nanotechnology.

“The main advantages of using nanofilters, as opposed to conventional systems, are that less pressure is required to pass water across the filter, they are more efficient, and they have incredibly large surface areas and can be more easily cleaned by back-flushing compared with conventional methods,” the team says.


What Is Nanotechnology?

Nanotechnology refers to a broad range of tools, techniques and applications that simply involve particles on the approximate size scale of a few to hundreds of nanometers in diameter. Particles of this size have some unique physicochemical and surface properties that lend themselves to novel uses. Indeed, advocates of nanotechnology suggest that this area of research could contribute to solutions for some of the major problems we face on the global scale such as ensuring a supply of safe drinking water for a growing population, as well as addressing issues in medicine, energy, and agriculture.


 Using Nanotechnology to Purify Water

“The potential impact areas for nanotechnology in water applications are divided into three categories, i.e., treatment and remediation, sensing and detection, and pollution prevention”. “Within the category of treatment and remediation, nanotechnology has the potential to contribute to long-term water quality, availability, and viability of water resources, such as through the use of advanced filtration materials that enable greater water reuse, recycling, and desalinization. Within the category of sensing and detection, of particular interest is the development of new and enhanced sensors to detect biological and chemical contaminants at very low concentration levels in the environment, including water.”

Cloete is Head of the Microbiology Department at the University of Pretoria in South Africa and Chairperson of the university’s School of Biological Sciences. Together with Associate Professor Jacques Theron and J.A. Walker he published the review article, titled “Nanotechnology and Water Treatment: Applications and Emerging Opportunities”, in the February 2008 issue of Critical Reviews in Microbiology.

Read more: Nanotechnology and water treatment

By dipping plain cotton cloth in a high-tech broth full of silver nanowires and carbon nanotubes, Stanford researchers have developed a new high-speed, low-cost filter that could easily be implemented to purify water in the developing world.

Instead of physically trapping bacteria as most existing filters do, the new filter lets them flow on through with the water. But by the time the pathogens have passed through, they have also passed on, because the device kills them with an electrical field that runs through the highly conductive “nano-coated” cotton.