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Purely, Water

Purely, Water

Purely, Water (continued)

By Jackie Powder

The School's Rolf Halden, PhD, PE, has developed a diagnostic tool, now under patent, that's aimed at identifying and deploying the most effective remediation technology available for treating tainted groundwater.

The EHS assistant professor describes the In Situ Microcosm Array (ISMA) as a "miniature underground lab" that would allow investigators to conduct onsite tests to compare cleanup strategies—in situ (in the soil)—for a contaminated aquifer. Measuring about 3 feet in length and 4 inches in diameter, the ISMA is designed to fit into any of the hundreds of thousands of monitoring wells that perforate the subsurface at contaminated sites across the United States.

"Having this tool could accelerate cleanup and potentially will turn more contaminated aquifers into safe drinking water resources," Halden says. "The unique thing is that during testing we don't remove the microbes and contaminants from where they're living." That's important, he explains, since removing a sample from its natural environment immediately changes both water chemistry and microbial activity, which in turn triggers "bottle effects" that are known to limit the value of lab results for predicting treatment effectiveness in field situations.

Halden's lab designed the ISMA with funding from NIH. Its prototype was built by the Instrument Development Group with the University's Department of Physics and Astronomy. Soon to undergo field-testing, the ISMA technology is sponsored by the Maryland Technology Development Corporation's (TEDCO) TechStart program and marketed by Hopkins' Technology Transfer Office.

From an economic standpoint, use of the ISMA could result in significant savings in the costly work of remediation. Currently, a chemical identified as effective in the cleanup process must be introduced into the subsurface via injection in a monitoring well for assessment. But the introduction of any substance at a monitoring station limits that station's usefulness for further testing and regulatory compliance monitoring.

In contrast, the ISMA technology does not compromise the monitoring area—which costs between $5,000 and $1 million to put in place—because all testing takes place within the device and no chemicals or bacteria are released.

Says Halden, "The device allows you to move around and test chemical treatments in different places without disturbing anything."


Appearing somewhat out of place in a 21st century research lab at the Bloomberg School, about a dozen pots made of terracotta clay and sawdust sit stacked against a wall. Some day, they may save lives in Central America.

The bucket-shaped pots—actually ceramic water purifiers—are the work of Potters for Peace. The nonprofit organization coordinates a global network of potters who provide rudimentary water treatment to communities in developing countries that lack potable water. The School's Center for Water and Health is evaluating the effectiveness of the ceramic filter system and other simple methods being used to treat water in the home. These low-tech methods are known as "point-of-use systems," and include everything from simple filtration devices to chemical disinfection solutions that are mixed with contaminated water.

Increasingly, point-of-use systems are gaining credibility as effective alternatives to centralized water treatment and distribution systems—particularly in isolated, rural communities and villages, where people rely on polluted sources or unsafe wells for water. Around the world, some 4,500 children die each day from unsafe water and lack of basic sanitation facilities.

"We're good at building big water plants. We've done that and in many cases it hasn't worked," says Charles O'Melia, PhD, professor emeritus and recently retired chair of the Johns Hopkins Department of Geography and Environmental Engineering (DoGEE). "The resources are not there to keep them up. They cost money to maintain and in many cases they haven't lasted very long."

Potters for Peace products were first used on a large scale in 1998 following Hurricane Mitch in Nicaragua. In the aftermath, local relief agencies distributed more than 5,000 filtration units. Since then, marginalized communities throughout the world with unsanitary water have used the pots. However, the system—along with other point-of-use treatments—has not undergone extensive scientific testing.

That's why the pots are sitting in a research facility at the School.

"We can use our sophisticated technology to evaluate a simple system in a lab-based environment," explains Schwab. "What do they really remove? What claims are being made?"

The pots are made from clay and sawdust, and the firing process burns fine pores over the entire surface, creating a completely porous vessel. Villagers can pour their unclean water through the filter—which will strain potentially deadly, diarrhea-causing bacteria like E. coli, Vibrio cholerae and Shigella—and collect the cleansed water in a storage container underneath.

"When constructed properly, they do a good job at removing bacteria," Schwab says. But the pot filters fail to strain viruses, including rotavirus, hepatitis A virus and norovirus; "They go straight through because they're much smaller," he notes. The filters can also clog and are relatively fragile. "But you can't not do a treatment process because it doesn't treat everything," Schwab says. "Maybe supplying a small community with a small-scale system is an approach worth evaluating."

Schwab, PhD, MS, says lab tests have confirmed that the filters are more effective at killing bacteria when they are dipped in colloidal silver after firing. A chemical interaction between the filter and the silver creates a germ-killing biocide.

Following evaluations in the lab, researchers plan to do field tests in Central America as well as epidemiological and cohort studies.

"We don't know very much about long-term use," says Schwab. "After a year, how many people are still using them? How many are still working?"

How Does Your Garden Grow?

In the hills of South Africa's KwaZulu-Natal province, elderly women walk more than the length of a football field to the nearest stream to fill up buckets of water. Then they heft the 60-pound buckets atop their heads and struggle to make the uphill trip back home. The water is crucial for their community vegetable gardens; the spinach, carrots, tomatoes, cabbage and onions they grow provide the main source of food for their fellow villagers.

Many of these women have lost sons and daughters to AIDS. They are left to care for their sick and dying children, raise their grandchildren, run households—all while making the exhausting trip for water each day.

Learning of the women's plight, a contingent of Johns Hopkins students set out to ease their water-toting burden—by organizing a project to build a simple watering system for the community gardens in the villages of Inchanga and Maphaphateni.

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