By substituting a single atom in a molecule widely used to purify water, researchers at Sandia National Laboratories in the USA have created a far more effective decontaminant with a shelf- life superior to products currently on the market.
Sandia has applied for a patent on the material, which removes bacterial, viral and other organic and inorganic contaminants from river water destined for human consumption, and from wastewater treatment plants prior to returning water to the environment.
"Human consumption of 'challenged' water is increasing worldwide as preferred supplies become more scarce," said Sandia principal investigator May Nyman. "Technological advances like this may help solve problems faced by water treatment facilities in both developed and developing countries."
The study was published in June 2009 in the journal Environmental Science & Technology. Sandia is working with a major producer of water treatment chemicals to explore the commercial potential of the compound.
The water-treatment reagent, known as a coagulant, is made by substituting an atom of gallium in the centre of an aluminium oxide cluster - itself a commonly used coagulant in water purification, says Nyman.
The substitution is not performed atom by atom using nanoscopic tweezers but rather uses a simple chemical process of dissolving aluminium salts in water, gallium salts into a sodium hydroxide solution and then slowly adding the sodium hydroxide solution to the aluminium solution while heating.
"The substitution of a single gallium atom in that compound makes a big difference," said Nyman. "It greatly improves the stability and effectiveness of the reagent. We've done side-by-side tests with a variety of commercially available products. For almost every case, ours performs best under a wide range of conditions."
Wide-ranging conditions are inevitable, she said, when dealing with a natural water source such as a river. "You get seasonal and even daily fluctuations in pH, temperature, turbidity and water chemistry. And a river in central New Mexico has very different conditions than say, a river in Ohio."
The Sandia coagulant attracts and binds contaminants so well because it maintains its electrostatic charge more reliably than conventional coagulants made without gallium, itself a harmless addition (Fig. 1).
The new material also resists converting to larger, less-reactive aggregates before it is used. This means it maintains a longer shelf life, avoiding the problem faced by related commercially available products that aggregate over time.
"The chemical substitution (of a gallium atom for an aluminum atom) has been studied by Sandia's collaborators at the University of California at Davis, but nobody has ever put this knowledge to use in an application such as removing water contaminants like microorganisms," said Nyman.
Desalination
Researchers at Ben-Gurion University of the Negev in Israel are developing technology to scale up a novel method for achieving very high recoveries in desalination by reverse osmosis to be used in a Jordanian desalinisation plant. The team, lead by Jack Gilron of the Zuckerberg Institute for Water Research (ZIWR) and Eli Korin of the Department of Chemical Engineering, has developed a method of exploiting the finite kinetics of membrane fouling processes by periodically changing the conditions leading to membrane fouling before it can occur. The team was recently awarded grants from the NATO Science for Peace programme and the Middle East Desalination Research Centre (MEDRC).
Working in collaboration with colleagues from University of Colorado and the Hashemite University of Jordan, the group will be developing technology and setting up pilot facilities to produce about 120m3/day at desalination sites in Israel and in Jordan. Gilron explains that the process will be tuned to reduce brine volumes to 33-50 per cent of those generated in conventional reverse osmosis. This greatly reduces the environmental burden and improves the economics of the inland desalination process.
Related to the above development, BGN Technologies - the University's technology transfer company and the Ashkelon Technology Incubator Cleantech Group have established a new company, ROTEC (Reverse Osmosis Technologies) to commercialise the technology. Israel's national water company, Mekorot, selected ROTEC as one of a handful of promising companies in which it invests R&D funding to help promote novel water treatment technologies worldwide and in Israel.
Clearing algal toxins
Novel bacterial strains capable of neutralising toxins produced by blue-green algae have been identified by researchers at Robert Gordon's University, Aberdeen, Scotland. Aakash Welgama presented the group's findings during the Society for General Microbiology's recent meeting at Heriot-Watt University, Edinburgh.
Blooms of blue green algae (cyanobacteria) are found in both fresh and salt water throughout the world. They produce toxins called microcystins which are released into the water and are easily ingested by animals and humans by drinking, swimming or bathing in contaminated water.
Once in the body the toxins attack liver cells causing acute and chronic poisoning. Conventional methods for water treatment such as sedimentation, sand filtration, flocculation and chlorination do not remove microcystins.
The researchers at Robert Gordon's University have identified more than 10 bacterial strains capable of metabolising microcystins, breaking them down into harmless non-toxic materials.
The bacteria, Arthrobacter sp, Brevibacterium sp and Rhodococcus sp were able to break down six commonly occurring microcystins. Six of the strains were incubated in river water with variants of the toxin to simulate natural conditions; all six strains were able to degrade the microcystins.
Complex industrial wastewaters
In Singapore, Nanyang Technological University's Nanyang Environment and Water Research Institute (NTU-NEWRI) and Sembcorp Industries (Sembcorp) have signed an agreement to jointly explore the application of a new system for the treatment of complex industrial wastewater.
Under the agreement, Sembcorp and NTU-NEWRI will work together over the next three years to explore a novel treatment technology aimed at removing recalcitrant organic matter from wastewater. These recalcitrant organic substances are characterised by poor biodegradability and by their difficulty of removal though the biological wastewater treatment process.
Elaborating on the technology to be explored, NTU's associate professor Volodymyr Ivanov, the principal investigator who leads the NTU team for the research collaboration, said, "NTU team has developed an innovative patented process, which is well suited for the treatment of industrial wastewater. This process models nature's way of cleaning the water. It is likely that this technology can be more competitive than other technologies. We are happy to collaborate with Sembcorp and develop this test bed and explore the technology further."
Remarking on the project, Ng Wun Jern, professor and executive director of NTU-NEWRI, said: "Launched in 2008, NEWRI provides a clearly defined window through which industry and research partners can access NTU's comprehensive EWT capabilities. This partnership with Sembcorp is a good demonstration of NEWRI's goal of translating cutting-edge new water technology research and bringing it to an industry eager to benefit society and lead in an expanding market."
