Water. Desalination + reuse
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RESEARCH | 28 | Desalination & Water Reuse | May-June 2016 Record droughts are on the rise Oil and gas operations in the US produce about 3.3 million Ml of wastewater a year. Its high salinity and organic contaminants make treatment difficult and expensive using conventional techniques. Some oil and gas wastewater is currently being treated and reused in the field, but that treatment process typically requires multiple steps and energy from diesel generators. University of Colorado Boulder associate professor of environmental and sustainability engineering and senior author of the paper Zhiyong Jason Ren said: "Right now oil and gas companies have to spend energy to treat the wastewater. We are able to treat it without energy consumption; rather we extract energy out of it." … moRE bugS Researchers at Australia's national science agency, the Commonwealth Scientific and Industrial Research Organisation claim to have found a means to end the need for desalinated water in a crucial copper mining process. The scientists have discovered a bacterium that can tolerate high salinity and acidic conditions making it potentially useful in leaching copper minerals from ore – a process that currently requires high volumes of fresh water. Some 5% of the copper mined worldwide is mined using bacterial leaching from low-grade ore The salt-and-acid-tolerant bacteria were found in drains on farmland near Merredin and Beacon in Western Australia. It has yet to be shown to be capable of bioleaching copper but Rea said the bacteria had already been shown to withstand high sulphate concentrations – a prerequisite for the leaching process which is based on oxidation of sulphides to sulphates. Meanwhile research findings by the US Geological Survey (USGS) have indicated that bacteria in produced water could improve the way that fluid from shale gas operations is handled and reused. The study found that bacteria could be useful in breaking down contaminants in produced water. The findings could have "important implications" for energy companies, according to the USGS report. bubblES Researchers at Murdoch University, Australia, have designed a small-scale greenhouse that deploys desalination technology based on an "unexplained" bubble formation phenomenon to bring food production to remote regions with high-salinity groundwater. The so-called bubble greenhouse uses a novel humidification- dehumidification process powered by solar or wind generation. A regenerative blower pushes air through sinter discs in a column evaporator filled with saline water to generate a stream of fine bubbles. The bubbles saturate with fresh water which is released in a multi-stage condenser to collect fresh water to humidify the greenhouse The researchers said the large air/water interface created by the fine bubble column was enhanced by the use of saline rather than freshwater in the humidification step. He said saline water maintained the air/water interface by inhibiting coalescence of the bubbles by "a still unexplained property." According to the Murdoch team, the project is poised for scaling-up with industry partners. mAgnESium flARE A researcher at Birmingham's Aston University in the UK has proposed a new solar energy-driven process to treat effluent brine from desalination plants and remove dissolved carbon dioxide from the oceans. Philip Davies, of Aston's School of Engineering and Applied Science, has devised a system that harnesses solar energy to convert magnesium chloride in waste brine to magnesium oxide, which is discharged to the ocean. The alkaline oxide would combine with carbon dioxide to form magnesium bicarbonate, thereby removing the carbon dioxide from the seawater. This approach would, according to Davies, increase the energy requirement of a plant by 50 % . But he has calculated that this increase would be offset by the carbon dioxide absorption capacity which he claims could open the way to double the current global desalination capacity. Davies said: "Not much energy is needed to decompose magnesium chloride in brine to magnesium oxide, which makes the use of solar energy potentially very attractive." He added: "Lowering the energy required to dewater brine prior to decomposition would be a major environmental benefit. If we could find better ways to dewater the brine this would become very energy efficient as a means of avoiding carbon dioxide." EnCoRE The perennial quest for lower carbon methods for producing clean water has fired remarkable innovation. In developing answers to questions about where new water sources can be found and how it can be best treated, research communities worldwide are making significant advances in materials and methods. We are seeing exploitation of renewable energy and recycling rising up the agenda and that growing will is driving investment and invention. Whether the emerging technologies will ever see commercial life is, in most of the instances highlighted here, an unanswered question. But the range of possibilities is intriguing and encouraging. There have been moments of great promise and others of disappointment in technologies that have emerged in recent years. There will be more of both. But seeing as climate change isn't going away there remains ample time, incentive and even an imperative to keep innovating.