A novel point-of-use water treatment method by antimicrobial nanosilver textile material. J Water Health. 2014 Dec;12(4):670-7. doi: 10.2166/wh.2014.197.

Liu H1, Tang X2, Liu Q3. Author information: 1Key Laboratory of Natural Medicine and Immuno-Engineering of Henan Province, Henan University, Kaifeng, Henan 475004, China E-mail: hjliu@henu.edu.cn; AGplus Technologies Pte Ltd, 10 Jalan Besar #10-06 Sim Lim Tower, Singapore 208787.
2AGplus Technologies Pte Ltd, 10 Jalan Besar #10-06 Sim Lim Tower, Singapore 208787.
3School of Architecture and the Built Environment, Singapore Polytechnic, 500 Dover Road, Singapore 139651.

Pathogenic bacteria are one of the main reasons for worldwide water-borne disease causing a big threat to public health, hence there is an urgent need to develop cost-effective water treatment technologies. Nano-materials in point-of-use systems have recently attracted considerable research and commercial interests as they can overcome the drawbacks of traditional water treatment techniques. We have developed a new point-of-use water disinfection kit with nanosilver textile material. The silver nanoparticles were in-situ generated and immobilized onto cotton textile, followed by fixing to a plastic tube to make a water disinfection kit. By soaking and stirring the kit in water, pathogenic bacteria have been killed within minutes. The silver leaching from the kit was insignificant, with values <100 ppb – the current US EPA and WHO limit for silver level in drinking water. Herein, the nanosilver textile water disinfection kit could be a new, efficient and cost-effective point-of-use water treatment method for rural areas and emergency preparedness.

Porous Ceramic Tablet Embedded with Silver Nanopatches for Low-Cost Point-of-Use Water Purification. Environ. Sci. Technol., November 11, 2014

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Beeta Ehdaie , Carly Krause , and James A. Smith *

Department of Civil and Environmental Engineering, University of Virginia, Charlottesville, Virginia 22904,

Email: *J. A. Smith. E-mail: jas9e@virginia.edu.

This work describes a novel method to embed silver in ceramic porous media in the form of metallic silver nanopatches. This method has been applied to develop a new POU technology, a silver-infused ceramic tablet that provides long-term water disinfection. The tablet is fabricated using clay, water, sawdust, and silver nitrate. When dropped into a household water storage container, the ceramic tablet releases silver ions at a controlled rate that in turn disinfect microbial pathogens. Characterization of the silver-embedded ceramic media was performed using transmission electron microscopy. Spherical-shaped patches of metallic silver were observed at 1–6 nm diameters and confirmed to be silver with energy dispersive spectroscopy. Disinfection experiments in a 10 L water volume demonstrated a 3 log reduction of Escherichia coli within 8 h while silver levels remained below the World Health Organization drinking water standard (0.1 mg/L). Silver release rate varied with clay mineralogy, sawdust particle size, and initial silver mass. Silver release was repeatable for daily 10 L volumes for 154 days. Results suggest the ceramic tablet can be used to treat a range of water volumes. This technology shows great potential to be a low-cost, simple-to-use water treatment method to provide microbiologically safe drinking water at the household level.

Researchers create novel water purifying filter – Source: SciDevNet, Aug 25, 2014

[CAPE TOWN] A team of researchers have developed a membrane-based water filter that can provide up to 300 litres of clean drinking water.

The WHO says about 780 million people worldwide, especially those in Sub-Saharan Africa, lack access to improved water source.

The researchers from the Swiss Federal Institute of Technology in Zurich (ETHZ) in Switzerland announced last month (22 July) that DrinkPure filter, which they have developed, is based on a simple screw-top design that fits onto any plastic bottle.

• Link to video of DrinkPure

Wendelin Stark, a professor of functional materials engineering at ETHZ, who helped create the innovation, says: “It requires no manual, no electricity, and no additional tools or training needs. You simply screw it on, and you drink [the water].”

The researchers say they used a novel porous polymer membrane developed though  nanotechnology, thus making  DrinkPure allow the filtration of particles as small as 90 nanometres, including bacteria and protozoa, at rate of up to one litre a  minute.

They add that the innovation which weighs less than 100 grams, with a target cost of less than US$20 a filter, has two pre-filtration components — a capture filter that separates large particles and an activated charcoal layer that removes odour and chemical contaminants.

“One DrinkPure water filter provides enough drinking water for one person for one year, after which the membrane and activated carbon can be replaced over and over again,” explains Jeremy Nussbaumer, leader of the project and a research assistant, in a release.

In order to fund the tools to manufacture the filters, the researchers launched a crowdfunding campaign last month (17 July) with a goal of raising US$40,000 by this week (26 August), but have as of today raised more than US$71,000.

Nussbaumer says they plan to have the first filters completed and sent to project supporters for distribution by January 2015 in Sub-Saharan Africa.

Nussbaumer adds that Water & pH soluces, a Swiss NGO that works to provide sustainable, affordable access to safe water and sanitation to communities in Sub-Saharan Africa, plans to distribute DrinkPure for testing in five villages in Mali.

Stark tells SciDev.Net: “The aim is to develop partnerships with partners and local companies who can develop the membranes themselves”.

The researchers say DrinkPure water filter could be used as part of relief efforts following natural disasters, such as tsunamis. “We would like to see these membranes and filters used …in places experiencing environmental issues,” says Christop Kellenberger, a member of the DrinkPure research team.

Nonhlanhla Kalebaila, a research manager of drinking water treatment and quality at the South Africa-based Water Research Commission, says the use of small-scale water purification systems in Africa is increasing rapidly. “Water quality and supply in Africa as a whole is a very touchy subject and has been the topic of strikes and protests in South Africa in the last few years,” she says.

But Kalebaila adds that independent research is needed to ensure the accuracy of water filtration devices and the safety of water that flows from such tools.

Plasma-treated CNTs key to safer drinking water | Source: The Engineer – Aug 2013 |

An international team of researchers has developed a method of water purification that uses membranes enhanced by plasma-treated carbon nanotubes.

The team – led by Associate Professor Hui Ying Yang from Singapore University of Technology and Design – showed in their study that the new method removed contaminants and brine from water. The team included Dr Zhaojun Han and Professor Kostya (Ken) Ostrikov from CSIRO’s Plasma Nanoscience Laboratories.

The study, published in Nature Communications, is said to pave the way for the next generation of portable water purification devices, which could provide relief to the 780 million people around the world without access to clean water.

According to Dr Han, these membranes could be integrated into portable water purification devices the size of a tea pot that would be rechargeable, inexpensive and more effective than many existing filtration methods. Contaminated water would go in one end, and clean drinkable water would come out the other.

‘Small portable purification devices are increasingly recognised as the best way to meet the needs of clean water and sanitation in developing countries and in remote locations, minimising the risk of many serious diseases,’ Han said in a statement.

‘The large industrialised purification plants we see in other parts of the world are just not practical – they consume a large amount of energy and have high labour costs, making them very expensive to run.’

Dr Han acknowledged that some smaller portable devices do already exist. However, because they rely on reverse osmosis and thermal processes, they are able to remove salt ions but are unable to filter out organic contaminants from the briny water found in some rivers and lakes.

‘For people in remote locations, briny water can sometimes be the only available water source,’ he said. ‘That’s why it’s important to not only be able to remove salts from water, but to also be able to put it through a process of purification.’

‘Our study showed that carbon nanotube membranes were able to filter out ions of vastly different sizes – meaning they were able to remove salt, along with other impurities,’ he said.

According to Prof Ostrikov, the other downside of existing portable devices is that they require a continuous power supply to operate their thermal processes. ‘On the other hand, the new membranes could be operated as a rechargeable device.’

Prof Ostrikov attributes the success of the new membranes to the unique properties of plasma treated carbon nanotubes.

‘Firstly, ultra long nanotubes have a very large surface area that is ideal for filtration. Secondly, nanotubes are easy to modify, which allows us to tailor their surface properties through localised nanoscale plasma treatment,’ he said.

Now that the researchers have proven the effectiveness of the method, they plan to extend their research to investigate the filtration properties of other nanomaterials. They will begin by looking at graphene, which has similar properties to carbon nanotubes, but could be made considerably denser and stronger.

The study ‘Carbon nanotube membranes with ultrahigh specific capacity for water desalination and purification’ is a collaborative work between Singapore University of Technology and Design, CSIRO, Massachusetts Institute of Technology (MIT), the University of Sydney, and Hong Kong Polytechnic University.

Biopolymer-reinforced synthetic granular nanocomposites for affordable point-of-use water purification. Proc Natl Acad Sci U S A. 2013 May 21;110(21):8459-64.

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Sankar MU, Aigal S, Maliyekkal SM, Chaudhary A, Anshup, Kumar AA, Chaudhari K, Pradeep T. Unit of Nanoscience and Thematic Unit of Excellence, Department of Chemistry, Indian Institute of Technology Madras, Chennai 600 036, India.

Abstract - Creation of affordable materials for constant release of silver ions in water is one of the most promising ways to provide microbially safe drinking water for all. Combining the capacity of diverse nanocomposites to scavenge toxic species such as arsenic, lead, and other contaminants along with the above capability can result in affordable, all-inclusive drinking water purifiers that can function without electricity. The critical problem in achieving this is the synthesis of stable materials that can release silver ions continuously in the presence of complex species usually present in drinking water that deposit and cause scaling on nanomaterial surfaces.

Here we show that such constant release materials can be synthesized in a simple and effective fashion in water itself without the use of electrical power. The nanocomposite exhibits river sand-like properties, such as higher shear strength in loose and wet forms. These materials have been used to develop an affordable water purifier to deliver clean drinking water at US $2.5/y per family. The ability to prepare nanostructured compositions at near ambient temperature has wide relevance for adsorption-based water purification.

Biopolymer-reinforced synthetic granular nanocomposites for affordable point-of-use water purification. Proceedings of the NAS, May 2013.

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Mohan Udhaya Sankar, et al.

Creation of affordable materials for constant release of silver ions in water is one of the most promising ways to provide microbially safe drinking water for all. Combining the capacity of diverse nanocomposites to scavenge toxic species such as arsenic, lead, and other contaminants along with the above capability can result in affordable, all-inclusive drinking water purifiers that can function without electricity.

The critical problem in achieving this is the synthesis of stable materials that can release silver ions continuously in the presence of complex species usually present in drinking water that deposit and cause scaling on nanomaterial surfaces. Here we show that such constant release materials can be synthesized in a simple and effective fashion in water itself without the use of electrical power. The nanocomposite exhibits river sand-like properties, such as higher shear strength in loose and wet forms.

These materials have been used to develop an affordable water purifier to deliver clean drinking water at US $2.5/y per family. The ability to prepare nanostructured compositions at near ambient temperature has wide relevance for adsorption-based water purification.

Water nanofilter ‘could cut diarrhoea-related deaths’ | Source: Scidev.net, June 2013

Speed read

• The device emits silver ions to kill water-based microbes
• It may be able to provide safe drinking water to families in rural areas for US$2.50 a year
• The units are being installed in water treatment plants in the Indian state of West Bengal

Indian scientists have developed a cheap filter that can rid drinking water of the bacterial and viral contaminants responsible for hundreds of thousands of diarrhoea-related deaths in developing countries each year.

They say that their device can deliver safe drinking water to families in rural areas for just US$2.50 a year, including both the cost of the device and running costs. Their work was published online in Proceedings of the National Academy of Sciences last month (6 May).

The team, from the Indian Institute of Technology Madras (IITM), used a mixture of nanoparticles to form a ‘nanocomposite’ that releases a steady stream of silver ions that kills water-based microbes.

This technique was already known as a promising way to provide safe drinking water, but it has proved a challenge to find an effective material to enable this.

“We had to find a material that was easily available, cheap, environmentally friendly and that maintained a sustained release of silver ions that could keep its concentration in water at less than 50 parts per billion, which is the WHO permissible level for silver [nanoparticles] in water,” Thalappil Pradeep, an author of the paper and a professor in IITM’s chemistry department, tells SciDev.Net.

He says they chose a nanocomposite material called aluminium oxy-hydroxide-chitosan because both its structure and the diameter of the silver nanoparticles embedded in the material created optimal conditions for controlling the release of silver ions in temperatures ranging from five to 35 degrees Celsius.

Pradeep says that the silver nanoparticles are small enough to be highly active and therefore to easily release ions into the water, but large enough to be kept confined within the nanocomposite matrix, which acts as a cage to ensure limited interaction of the silver nanoparticles with water.

The nanomaterial is held in a sieve through which water is passed. The device can be reactivated — when the silver nanoparticles get coated with other impurities present in water and the release of ions stops — by boiling the device or treating it with lemon juice. Each unit is expected to last around six years.

The system can be set up in community water treatment plants. Alternatively, families can buy the device, in which case the sieve is attached to the lid of a bucket-like container.

Currently, the researchers are installing the devices in community water treatment plants in the state of West Bengal. However, they are still looking for companies that can mass-manufacture the devices for household water filtration.

Amitabha Sengupta, a former scientist at the West Bengal State Water Investigation Department, who is now retired, says that such a low-cost filter is urgently needed to bring safe drinking water to the poor due to the huge number of deaths from waterborne intestinal diseases in India.

But he adds that more work needs to be done on low-cost methods of removing chemical contaminants such as arsenic from drinking water.

Link to paper’s abstract