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Purely, Water

Purely, Water

Purely, Water

From polymer membranes and in situ testing to simple pumps and clay pots, researchers are working across the technology spectrum to improve water quality

By Jackie Powder

For the lucky, water is a healer, a cooler, a clear-as-glass bonding of hydrogen and oxygen. It's there for the taking—from the tap, from the hose, from ubiquitous plastic bottles—a seemingly infinite supply to cleanse, quench and refresh.

The unlucky—the 1.2 billion people who lack access to safe drinking water—may walk miles to get water of any kind, water that may be laced with deadly contaminants.

From a public health perspective, clean safe water is the ultimate preventive. It's a defense against illness, including waterborne diarrheal-related diseases that claim the lives of 1.8 million people each year, most of them children under 5. "There still are not a lot of places on this planet where you can open up a tap and drink the water," says John Groopman, PhD, chair of the Department of Environmental Health Sciences (EHS) at the Bloomberg School.

Places like slums on the outskirts of Lima, Peru, where nearly a million squatters live in ramshackle structures perched high above the city, cut off from the municipal water and sewer system. Where up to 40 families might rely on a single hose to collect several days worth of water that they store at home in unprotected buckets. Where children play near pits of untreated waste.

"What we take for granted here, water coming to us 24/7, is a constant struggle for these people," says EHS associate professor Kellogg Schwab, director of the School's Center for Water and Health. Last year he traveled to Lima's peri-urban settlements to assess water quality as part of a collaborative research project with the School's Department of International Health and found that more than 20 percent of diarrheal illnesses in children are caused by norovirus. He and his team evaluated the feasibility of a relatively simple solution: a chlorine-based disinfectant, and narrow-necked water storage containers to prevent recontamination, which are now being widely used to prevent diarrheal sicknesses in children. In addition, doctoral candidate Sharon Nappier trained Peruvian technicians to test and monitor water quality at a molecular biology lab established by International Health faculty.

The School's activities in Peru—from identifying the norovirus to recommending practical solutions to defend against it to starting a local training program—provide a glimpse into the world of water and public health.

"The issues of water and sanitation are as big as virtually anything else in the public health field, whether it's malaria or other infectious diseases," says M. Gordon "Reds" Wolman, PhD, the B. Howell Griswold Jr. Professor of Geography and International Affairs at Johns Hopkins.

Researchers with the Johns Hopkins Center for Water and Health—which is based at the School and draws on collaborators from other Hopkins divisions as well—are working at high and low ends of the technology spectrum to improve water quality and access for people in the United States... and around the world.


Can polio and hepatitis A viruses concealed in untreated water squeeze through the 0.001-micron-sized pores of the tightly packed polymer membranes? What about salts and organic matter? The pathogens Giardia, E. coli and cryptosporidium?

In a water research lab at the School, investigations revolve around such questions, as scientists delve deeply into the workings of today's fastest growing water treatment technology: membrane filtration.

"I can easily tell you that this will become the conventional treatment of the future. There's no question in my mind," says EHS adjunct associate professor Joseph Jacangelo, PhD, REHS, who heads the School's membrane filtration research lab. There, investigators work to discover the mechanisms by which membranes remove contaminants, and evaluate different types of membranes for potential use in water treatment systems.

Their work comes at a time when water experts are sounding alarms about deteriorating water treatment and distribution infrastructure ("We have thousands of miles of pipes, some of which are 100 years old, that are not adequately maintained," Schwab notes), and warning that municipalities must develop improved disinfection technologies. Recent waterborne disease outbreaks traced to chlorine-resistant contaminants have highlighted weaknesses in the standard chemical disinfection process in use since the early 20th century.

Over the past two decades, advances in the efficiency and effectiveness of membrane filtration technology have moved steadily from lab concepts to demonstration-scale trials to full-scale water and wastewater treatment plants, says Jacangelo, national technical director with MWH, an environmental engineering company. As a replacement for an aging water plant or an additional treatment step in an existing plant, say water treatment experts, membrane filtration technology may help to prevent another disaster like the 1993 cryptosporidium outbreak in Milwaukee that killed more than 100 people and sickened 400,000.

"From a practical perspective, we look at how well membranes can work to better protect public health," Jacangelo says of his research.

The basics of membrane filtration involve pushing untreated water through tens of thousands of tube-shaped, organic polymer films with small pores on the surface. The system acts as a sieve, excluding microorganisms that are too big to squeeze through the pores, and allowing the filtered water to flow through the membrane.

When the technology came into use in the mid-1980s, a new system typically treated fewer than 1 million gallons of water a day. Today, Minneapolis Water Works has a plant that can treat over 65 million gallons of water with membranes that can that trap pathogens as small as the 0.025-micron viruses.

"The technology is expanding dramatically," in terms of interest from public water utilities, says Schwab. "Manufacturers claim certain capabilities and we evaluate different fiber matrixes in the lab to test for microbial removal and develop tests that utilities could put in place for selection purposes."

"The choice of membrane system," he says, "depends on what you're trying to remove." Microfiltration and ultrafiltration systems, for instance, use membranes with pore sizes of 0.1 and .01 microns, respectively, and apply 15 to 30 pounds of pressure per square inch to strain out microorganisms such as the parasite Giardia, as well as norovirus and enterovirus. A nanofiltration system, which relies on both size-exclusion and contaminant charge as mechanisms of removal, stops divalent ion salts, such as calcium. And reverse osmosis technology, which is used to desalinate seawater, employs very thin films and high pressure to remove all types of salts.

Thanks to tougher water quality regulations, and the fact that membrane filtration systems produce higher water quality at less cost than conventional treatments, Jacangelo expects the demand for membrane filtration systems to continue to grow.

"Almost any new water treatment plant today will consider membranes of some sort," he says. "A 20-million-gallon-a-day plant is now commonplace, whereas 20 years ago, it was really just a dream."

What Lurks Beneath?

When it comes to restoring polluted groundwater, the process begins by selecting the most effective method for destroying the offending chemical contaminants.

It's a complex and costly environmental challenge in the United States, where approximately 400,000 contaminated underground sites have been identified by the Environmental Protection Agency. The estimated cleanup costs in the coming decade alone? Between $500 billion and $1 trillion.

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