Water. Desalination + reuse
Issue link: https://fhpublishing.uberflip.com/i/513849
RESEARCH | 28 | Desalination & Water Reuse | May-June 2015 A novel method for making ceramic reverse osmosis membranes with sub- nonometre pores by using DNA as a former overcomes the poor reproducibility encountered in conventional manufacturing methods according to the developer of the technology, Cerahelix. In a paper presented at the recent AMTA and AWWA conference in Orlando, USA, Tyler J Kirkman, explained Cerahelix's process as "manipulating DNA as a generic - not genetic - material to produce a pore structure that is unique in nanofitration membranes." The process exploits DNA's property of aligning in a silica or titanium oxide sol gel to form columns. Once true, the gel is fred to form a ceramic membrane on an alumina support while the DNA is burnt off to leave Ceramic membrane made using DNA A UK academic has proposed a new solar energy-driven process to convert brine produced by desalination plants. The process also removes carbon dioxide dissolved in the oceans to reduce its damaging environmental impacts according to the researcher at Birmingham's Aston University. Philip Davies, of Aston's School of Engineering and Applied Science, has devised a system that uses desalination as a sink, rather than a source of carbon dioxide, to curb ocean acidity created by carbon dioxide. Davies's model harnesses solar energy to convert magnesium chloride in waste brine to magnesium oxide, which is discharged to the ocean. Due to its alkaline nature, this subsequently neutralises ocean acidity and gradually removes carbon dioxide through the conversion of magnesium oxide to bicarbonate, similar to ocean liming. 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. His process would result in 0.4% of carbon dioxide emissions being absorbed which 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 beneft. If we could fnd better ways to dewater the brine this would become very energy effcient as a means of avoiding carbon dioxide." Davies noted that rapid advances in desalination technology were making the dewatering of waste brine easier citing "improved membranes for membrane distillation and electrodialysis". Solar model cuts brine and carbon Municipal demand drives Indian water treatment market pores with diameters of less than 1 nm. "The combination of sub-nanometre pores in a hydrophilic material means that molecules can be separated by size, chemical properties and charge-charge interaction, " said Kirkman. He claimed that the membrane had an "inherent resistance to fouling from organics." Adapting the process from silica to titanium oxide to increase chemical and hydrothermal resistance required modifcation to overcome cracking which increased the pore size. Tests on the titanium product "imply" that the technology could overcome the high sulphate concentrations found in produced water waste, according to Kirkman. Urban population growth in India will increase revenue from municipal water and wastewater treatment including desalination by 57% according to a recent report by market analyst Frost and Sullivan (F&S). More than 20 cities expected to expand greatly by 2032 generating intense water stress according to the report. Major coastal cities including Chennai, Mumbai, Kolkata, Surat and Vizag, offered "high potential" for desalination plants to meet water demand the report predicted. The Indian Municipal Water and Wastewater Treatment Market, earned revenue of INR 31,260 million (US$ 494 million) in 2013 and F&S has estimated this will increase 57% to INR 49,000 million (US$ 775 million) by 2018 fuelled by rising population and urbanization. Observations in the report included: a forecast increase in the adoption of membrane technologies, customer price sensitivity is high with municipal projects usually awarded to the lowest bidder, there is currently "very limited" penetration of recycle and reuse systems, and government policies, such as the National Water Mission, support the growth of the water and wastewater treatment market. F&S energy and environment industry analyst Nideshna Naidu said: "Of the 32 major cities in India, 22 are facing water shortages." Growth will be tempered by the lack of proper planning and funds for infrastructure according to the report. "With water being highly subsidized in India, most municipal corporations are unable to recover the cost of water supply," said the analyst. "Recycled and reused water for various non-potable municipal applications, is very limited," said Naidu. Indian municipalities, the report said, are unable to generate sustained revenues due to low water tariffs, poor meter connections, and a high share of non- revenue water supply. Naidu said desalination and wastewater recycling and reuse have the potential to meet growing water demand. While desalination has strong potential, wastewater has only recently gained currency in India. It has, according to F&S, "tremendous potential" with only 30% of the wastewater currently being treated.