Using microbes and wastewater to desalinate water
DAVID JONES
bioelectrochemical systems are a with up to 35 grams of salt per liUnlikely as it may seem, microbes very versatile type of technology for ter, which is roughly the equivalent and wastewater are key compowastewater treatment,” says Rene´ of seawater. nents of a new technology capable Rozendal, a research fellow at the The new MDC actually solves of desalinating water without any University of Queensland’s (Austramany problems at once, explains Xia additional energy. In a paper relia) Advanced Water Management Huang, who was Cao’s Ph.D. advisor cently published in ES&T (2009, Center. Lars Angenent of Cornell when the research was conducted. DOI 10.1021/es901950j), a team of University’s Department of Biological She says that Cao’s invention grew researchers explains how this new and Environmental Engineertechnology can remove the ing lauds MDCs for making salts from waters with a wide “smart use” of ion exchange range of salinities, including membranes. ocean water. However, the high cost of The technology is based ion exchange membranes also on microbial fuel cells makes the MDC comparatively (MFCs), which use microorexpensive. The MDC’s potenganisms as catalysts to contial to use sewage and other vert chemical energy to wastewater as a low-cost fuel electrical energy. The pacould help reduce its price and per’s authors, including increase its efficiency, accordBruce Logan of Pennsylvania ing to the authors. State University and Xiaoxin The technology’s ability to Cao of Tsinghua University simultaneously generate (China), are among the Penn State researchers are already at work on the next electricity, desalinate water, small group of researchers generation of MDCs, which will be based on air and clean wastewater fits worldwide trying to improve cathodes. with the general trend in MFCssor bioelectrochemiMFCs, says Bert Hamelers of out of a discussion about how to cal systems, as they are beginning Wageningen University’s (The decrease internal membrane resisto be calledsand extend their Netherlands) environmental techtance during one of the group’s utility. As it happens, says Logan, nology department, a leading weekly meetings in September 2008. he and Cao independently conMFC research group. Cao suddenly realized that by using ceived of the same innovation last Industries that must continually two membranes and putting salty year: a technology they call a mireuse process water may find the water between them, MFCs could crobial desalination cell (MDC). MDC particularly attractive, Hameldesalinate water, she recalls. Developing new technologies to ers adds. Angenent, Hamelers, and Logan says that a similar idea improve the energy efficiency of Rozendal agree that the technology came to him one month later, water desalination is one of this could have utility for desalinating when he was sitting on a plane century’s grand engineering chalirrigation water. Huang says that it catching up on his reading. “It hit lenges, according to the National could also prove useful for treating me that we could...modify elecAcademy of Engineering. The MDC brackish water in some areas of trodialysis [a conventional techrequires no external energy source. China. nology for desalinating water] and The main difference between this Although bioelectrochemical sysessentially do the same thing [by] technology and a conventional tems cost more than other wastewausing the MFC as the integrated MFC is that the MDC uses two ter treatment systems, they also power source.” When Logan vismembranes rather than one (or “offer many more opportunities for ited Tsinghua University a few none). Salty water is placed beproduct formation that can potenweeks later, he heard Cao make a tween an anion exchange memtially offset these higher costs,” Ropresentation about the MDC conbrane and a cation exchange zendal says. Such systems have cept. “So, we decided to collabomembrane. When bacteria on the already been proven capable of genrate,” says Logan. MDC’s anode produce current and erating electricity, methane, hydroResearchers from other groups protons, the salty water’s anions gen, hydrogen peroxidesand now that are actively trying to improve migrate through the membrane to desalinated water, he points out. MFCs’ commercial viability agree the anode, and the cations are “What will the future bring?” he asks. that the new work represents an imdrawn to the cathode. In addition portant step forward. “This technolto producing power, the MDC can —KELLYN BETTS ogy yet again demonstrates that remove 90% of the salt from water 10.1021/es902384g
2009 American Chemical Society
Published on Web 08/12/2009
September 15, 2009 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 6895
