Drinking-water analysis turns up even more toxic compounds

Drinking-water analysis turns up even more toxic compounds

The chronic presence of genotoxic compounds at low levels in U.S. drinking water presents conflicting goals for some water utilities.

Catherine M. Cooney

For the first time, researchers have published a study that quantifies the levels of iodo-acid disinfection byproducts (DBPs) in drinking water and that includes a toxicity analysis for each compound. In a collaborative study, analytical chemists, analytical biologists, engineers, and toxicologists analyzed water samples from 22 U.S. cities and 1 Canadian city. The findings could present a conflict for water utilities seeking the best technique for disinfecting drinking water, the authors note.

Six-year occurrence study finds relatively low levels of highly toxic byproducts in U.S. drinking water.

Susan Richardson, with the U.S. EPA’s National Exposure Research Laboratory, and Michael Plewa of the College of Agricultural, Consumer, and Environmental Studies at the University of Illinois Urbana−Champaign were interested in growing evidence showing that the formation of iodinated DBPs in drinking water may be higher when utilities use chloramines, rather than chlorine, ozone, or chlorine dioxide, as a disinfectant. Many U.S. utilities have switched from chlorine to chloramines to meet EPA Stage 1 and Stage 2 DBP rules designed to reduce DBP formation, Richardson says.

DBPs are created when the compounds used for disinfecting drinking water react with natural organic matter, bromide, or iodide. Research shows that iodoacetic acid is highly cytotoxic and more genotoxic in mammalian cells than bromoacetic acid, which is the most genotoxic of the haloacetic acids (HAAs) regulated in the U.S. Iodoacetic acid also has been shown to cause developmental abnormalities in mouse embryos.

In new research published in ES&T (10.1021/es801169k), Plewa, Richardson, and colleagues set out to develop an analytical method to quantify five iodo-acids in drinking water, measure the concentrations of iodo-acids in several water samples treated with chloramination as a disinfectant, and investigate the mammalian cell toxicity of seven synthesized iodo-acids and six iodo-trihalomethanes (iodo-THMs). The researchers found that five iodo-acids and two iodo-THMs were present in the water samples. The levels for these same chemicals were highest at treatment plants with relatively short free-chlorine contact times and were lowest at a chlorine-only plant with long free-chlorine contact times. Of the 13 compounds measured, 7 were genotoxic, they report. In general, compounds that contain an iodo-group have enhanced cytotoxicity and genotoxicity as compared with their brominated and chlorinated analogs.

“Iodo-acid DBPs are going to become very important in the near future,” Plewa predicts. “Fifty percent of the U.S. population lives within 50 miles of a coast.” The paper notes that urban areas with high levels of iodide in their source waters, including many coastal cities, had higher levels of the iodo-acids. This is likely due to the intrusion of seawater into natural source waters, Plewa says. “As people draw down water sources to meet population growth, more and more seawater gets into the water source,” he says. Other U.S. regions also have high iodide levels as a result of salt deposits left from ancient seas.

The collaborators say that they built on a nationwide DBP occurrence study (Environ. Sci. Technol. 2006, 40, 7175−7185) in which iodo-acids were identified for the first time as DBPs in drinking water disinfected with chloramines. The results also support research published in 1999 detailing just how iodo-organic compounds form during disinfection of iodide-containing natural waters. Urs von Gunten, a chemist at the Swiss Federal Institute of Aquatic Science and Technology (Eawag) and coauthor of the 1999 ES&T paper (33, 4040−4045), says he marvels at how far the researchers have come. “In our paper we developed the basic knowledge of the kinetics of this process,” he says. “But at that point, no one was talking about other iodo-organic compounds and the toxicity” of these DBPs, von Gunten says.

The paper includes a simple engineering solution for water utilities, Plewa adds. Once you know the relative toxicity and occurrence of these DBPs, “you can sit down and then you can modify your approach, so you can produce very good water . . . that is less toxic and includes fewer DBPs,” he says.

Despite the presence of the genotoxic compounds, the researchers say that they aren’t worried about the safety of any treated drinking water in the U.S. They note that if the plants studied had used only chlorine they would likely have exceeded the EPA standard for THMs and HAAs. Plewa notes that this raises competing issues for water utilities—how can they meet current EPA standards and produce drinking water free of potentially hazardous byproducts while simultaneously keeping it hygienically safe?


It is rather to teach a man fishing than to give him fish.

环境工程:2人   从事污水处理微生物技术、污染环境修复技术研究,部分研究和清华大学进行合作。

市政工程:2人  从事催化氧化技术、膜分离技术研究,和武汉大学进行合作。








确定重大专项的基本原则:一是紧密结合经济社会发展的重大需求,培育能形成具有核心自主知识产权、对企业自主创新能力的提高具有重大推动作用的战略性产业;二是突出对产业竞争力整体提升具有全局性影响、带动性强的关键共性技术;三是解决制约经济社会发展的重大瓶颈问题;四是体现军民结合、寓军于民,对保障国 家安全和增强综合国力具有重大战略意义;五是切合我国国情,国力能够承受。



Tracking airborne Legionella downwind

The deadly bacteria can linger in biological treatment ponds and elsewhere—but how far can pathogenic strains of legionellae travel in air? New research in ES&T revisits the debate.

Naomi Lubick

An outbreak in Norway of legionellosis, or Legionnaires’ disease, killed 10 people and made more than 50 people sick in 2005. An epidemiological study pegged the source of the infectious Legionella bacteria to an air scrubber at a wood-processing plant, about 10 kilometers away from where the outbreak took place. The facility also houses aeration ponds that are known to harbor all sorts of microbes, some of which may be pathogenic—including strains of Legionella bacteria.

Now, research published in ES&T (DOI 10.1021/es800306m ) revisits the debate over how far Legionella can travel. New modeling and measurements taken at the site confirm that the bacteria can travel by air at least 200 meters downwind of the ponds; however, some controversy still exists.

In 2006, lead author Janet-Martha Blatny of the Norwegian Defence Research Establishment , with co-workers from the company Borregaard, the Norwegian Institute of Public Health, and life sciences company Telelab AS, modeled the wood-processing plant’s air space, using computational fluid dynamics and weather data. They looked at wind flow and other factors to figure out exactly where to place air monitors at various heights and locations around the buildings to capture Legionella aloft.

The researchers found that they could accurately predict the airborne path of aerosolized Legionella within the plant’s footprint, and their monitors captured several different species, depending on weather conditions and each monitor’s height. They also found that the bugs traveled 200 meters downwind, in this case remaining within the compound, where workers might inhale the bacteria.

But Blatny and colleagues needed to determine whether the captured bacteria were viable and infectious. They used real-time polymerase chain reaction and other techniques to examine the bugs. But the serotype of Legionella pneumophila trapped by the monitors turned out not to be the type most likely to cause infections.

Legionellae are ubiquitous in surface waters and are sometimes even found in groundwater. But the most likely sources of human exposure are cooling towers and water distribution systems (including showers and air conditioners), in addition to treatment ponds for industrial sites. The disease is passed not from person to person but only through direct inhalation of viable cells from the environment. Thousands of people get sick from legionellae every year, but those most susceptible tend to be elderly or immune-compromised patients.

None of the sources of the bug can be ruled out, says Jeroen den Boer, a legionellosis specialist at the Regional Public Health Laboratory Kennemerland (The Netherlands). But other research has placed Legionella bugs too far from their source, he says, including the epidemiological studies of the outbreak in Norway. “The way to prove that this person got Legionella from that facility is the way that Janet did it in her article: through air sampling,” den Boer states. “If you have an outbreak, you should look in the vicinity of the thing” that is suspected to be the source.

Lloyd Larsen, a microbiologist at the U.S. Army’s Life Sciences Test Facility at Dugway Proving Ground, says that although the researchers were successful in designing a sampling regime that could capture Legionella, they did not sufficiently validate their model. The experiment failed “to demonstrate the outside limits,” he explains, by sampling beyond the predicted legionellae boundaries.

The monitoring techniques the team used are not groundbreaking, comments Torbjörn Tjärnhage of the Swedish Defence Research Agency. However, the way the researchers put together known technology and modeling yielded useful results, he says, and confirms that air transport is possible. More studies are needed, he adds, particularly in different industries that use such treatment ponds. The team also needs to compare the airborne strains with those present in the ponds, Tjärnhage comments.

The new research “would be far more convincing if [DNA comparisons] would have been included,” den Boer agrees, and he questions whether the researchers tested correctly for various strains that they caught in their air monitors.

However, den Boer says he “was happy to read” the results, which could bolster the idea that airborne Legionella stays relatively close to home. “It is an old discussion which we had in the 1980s and 1990s,” he comments. “Legionella is a bacteria that needs water,” and that’s hard to find kilometers away from its source.

Producing usable materials from e-waste

New technologies being developed in China and Eastern Europe may create usable materials from e-waste.

Kellyn Betts

With the February 2009 deadline for the U.S. switch to digital television signals fast approaching, consumers are expected to inundate the country’s landfills and electronics recycling centers with millions of obsolete TVs. Although the federal government has yet to invest substantially in technologies for recycling old electronics, a small but vocal group of academic researchers, industry scientists, and environmental organizations is trying to change the status quo. The group hopes to persuade policy makers to initiate funding to cope with what the Electronics TakeBack Coalition, an environmental group, calls “the fastest growing waste stream in the U.S.”

A significant proportion of e-waste, like discarded TVs, ends up in developing countries, where it is burned, releasing toxic dioxins into the air.

In the meantime, other countries are conducting important research into new technologies for recycling electronic waste or “e-waste”. Three papers recently published in ES&T and Energy & Fuels discuss solutions being researched in China and Eastern Europe.

Developing such technologies is challenging because of the toxicity of many electronics components. According to the Silicon Valley Toxics Coalition, an environmental group, just one computer can contain hundreds of chemicals, including lead, mercury, cadmium, brominated flame retardants (BFRs), and polyvinyl chloride. Many of these chemicals are known to cause cancer, respiratory illness, and reproductive problems. And burning e-waste can produce harmful dioxins.

Much of the research into improving e-waste recycling focuses on technologies capable of capturing or creating usable materials from the printed circuit boards (PCBs) used in electronics. PCBs are by weight the most valuable component of waste electronics, says Renee St. Denis, director of Hewlett-Packard’s (HP’s) Product Take Back operations, which recycles more electronics than any other company operating in the U.S., according to the U.S. EPA.

Because the components of PCBs vary widely, a major challenge for recyclers is separating the semiconductor chips, metals, wires, and plastics into usable materials. The standard procedure is to use magnetic and eddy current processing to separate the magnetic fraction (iron and steel) and aluminum, says the University of Cambridge’s (U.K.) Derek Fray, a professor of materials chemistry who is also developing technologies for recycling PCBs.

For the past 5 years, researchers at China’s Shanghai Jiao Tong University’s School of Environmental Science and Engineering have been investigating how to improve the efficiencies of technologies capable of such separation. The average metal content of PCBs is 28% (by weight), mainly, copper, lead, and tin, points out Zhenming Xu, the corresponding author of the ES&T papers discussed in this article.

“One metric ton of PCBs contains more than 10 times the concentration of precious metals contained in content-rich minerals. Therefore, from the recovery of valuable materials and waste-management viewpoints, recycling of PCBs is significant,” Xu says. St. Denis adds, “Recycling can play a positive role in addressing climate change by conserving resources such as precious metals contained in electronics and displacing the energy impacts associated with mining or otherwise producing necessary raw materials.”

Xu and his colleagues are focusing on how a technology known as corona electrostatic separation, which is widely used in the mining industry, can be used for separating waste PCBs (Environ. Sci. Technol. 2007, 41, 1995−2000; 2008, 42, 624−628). The technology separates materials on the basis of the particles’ ability to conduct electricity. Particles that conduct electricity are charged by electrostatic induction and attracted to an electrode. What Xu calls “ion bombardment” of the second electrode then pins the nonconductive particles to the surface of a rotating roll electrode.

“The extreme difference in the electric conductivity or specific electric resistance between metals and nonmetals supplies an excellent condition for the successful implementation of a corona electrostatic separation in recycling of [e-]waste,” Xu says.

The latest incarnation of the technology, which is used with a two-step separation process, is discussed in one of Xu’s new papers. Tests by Xu’s team show that it can improve production speeds by 50%, compared with conventional electrostatic separation, while significantly reducing the percentage of PCBs that cannot be recycled.

“The important thing is to get a clean separation between the metallic and nonmetallic components for subsequent processing,” Fray says. “The work by [Xu’s team] seems to achieve that goal and is probably a significant advance,” he says.

Once the metals are separated from the nonmetals, the conventional approach is to send the waste metals to a copper-smelting operation equipped with environmental controls to capture emissions such as SO2, according to St. Denis. There are currently four such smelters in the world, she says. “[Smelting] enables the copper and the precious metals to be recovered, but m
any other metals are lost to the slag phase, which is discarded,” Fray adds.

The second paper by Xu’s team shows how the nonmetal portions of waste PCBs can be used to produce what they call a “kind of nonmetallic plate.” They contend that this plate’s chemical composition and mechanical performance are preferable to those of wood and that the material could be used for products such as sewer grates, park benches, and fences. “We strongly believe that [the] nonmetallic plate[s] have [a] potential market in [the] building industry,” Xu says. He says that he signed a contract on the recycling of waste PCBs with Shanghai Xin Jinqiao Industrial Waste Management Co., Ltd., in May and that “we will produce large-scale prototypes using a high-quality compression machine…in the near future.”

The presence of BFRs, such as tetrabromobisphenol A (TBBPA, the main flame retardant used in PCBs), in this nonmetal plate is a cause for concern, according to Pat Costner, science adviser to the International POPs Elimination Network, a nonprofit environmental group. TBBPA’s use is not banned or restricted in any country—although Norway has been considering such a ban—but the chemical could end up in the nonmetal plate, together with any dioxin-like compounds that previous research has shown can form during e-waste processing, she notes.

Xu concurs that further studies are needed to investigate the presence of BFRs in his group’s nonmetallic plate. He also points out that they “may be considered as a flame retardant for the nonmetallic plate.”

Because BFRs cannot be removed from the plastics portions of electronics products, this “presents a significant recycling and reuse challenge,” St. Denis says. In her testimony at a hearing on e-waste held in late April by the U.S. House of Representatives’ Committee on Science and Technology, she urged Congress to support research on reuse opportunities for plastics containing banned or restricted chemicals, such as PBDE flame retardants. Although she says that HP has pledged to stop using BFRs in its products by 2009, she points out that bromine is contained in the vast majority of e-waste that is currently being recycled.

The third recent paper to discuss a technique for processing waste PCBs was written by a team of researchers from Romania and Turkey led by Cornelia Vasile of Romania’s national Petru Poni Institute of Macromolecular Chemistry. They used pyrolysis to produce a fuel oil from the waste and succeeded in removing “almost all of the hazardous toxic components” in their attempts to render it suitable for use by the petrochemical industry. “The process might be cost-effective if it could be integrated in a petrochemical plant using the existent installations and equipment,” Vasile contends. But the team has yet to approach companies to gauge their interest in the process, she adds.

“The yields do not seem very high, and it is probably cheaper to prepare these oils, etc., by more conventional routes,” Fray says. Eric Williams of Arizona State University’s Department of Civil and Environmental Engineering agrees. However, the technique does address the problems posed by BFRs in waste PCBs, says Williams.

In the long run, “green” design and engineering focused on designing electronics products for recyclability and reducing their use of toxic materials should solve many of the problems currently associated with e-waste, argues Ted Smith, chair of the nonprofit Electronics TakeBack Coalition. In fact, he is convinced that forward-looking companies like HP are already beginning to make important headway in tackling these issues. However, Smith stresses that such innovative design cannot help companies—or governments—cope with the e-waste problems they are facing right now.






      英文综述,特别是那种invited paper 或是发表在高if期刊上的,往往都是本领域的牛人们写的。对此要精读,要分析其文章的构架,特别要关于作者对各个方向的优缺点的评价以及对缺点的改进和展望。通过精读一篇好的英文综述,所获得的不只是对本领域现在发展状况的了解,同时也可以学会很多地道的英文表达。


      1.本领域核心期刊的文献。不同的研究方向有不同的核心期刊,这里也不能一概唯if论了。比如说陶瓷类的核心期刊美陶的if也不过1.5几,但上面的文章特别是feature artical还是值得仔细阅读的。当然,首先你要了解所研究的核心期刊有哪些,这个就要靠学长、老板或者网上战友的互相帮助了。

      2.本领域牛人或者主要课题组的文献。每个领域都有几个所谓的领军人物,他们所从事的方向往往代表目前的发展主流。因此阅读这些组里的文献就可以把握目前的研究重点。这里有人可能要问,我怎么知道谁是牛人呢?这里我个人有两个小方法。第一是在ISI检索本领域的关键词,不要太多,这样你会查到很多文献,而后利用ISI的refine功能,就可以看到哪位作者发表的论文数量比较多,原则上一般发表论文数量较多的人和课题组就是这行里比较主要的了。还有一个方法,就是首先要了解本领域有哪些比较规模大型的国际会议,而后登陆会议主办者的网站一般都能看到关于会议的invited speaker的名字,做为邀请报告的报告人一般来说都是在该行有头有脸的人物了,呵呵