stanford medicine


Priming the pumps - Debugging Dhaka's water

Special Report

Priming the pumps

Debugging Dhaka’s water

A flimsy municipal pipe carries water from a polluted lake to this compound’s washing area, where residents clean their dishes and clothes.

Amy Pickering, PhD, stood at the edge of the river, the water blackened by waste and debris, as the ferryman beckoned to her from his fragile wooden skiff, the only means to the other side. It was February 2011, the start of Pickering’s first visit to Dhaka, Bangladesh, and she was getting her first good look at the challenge ahead: Flimsy pipes sucked in foul river water, which would be dispensed through communal pumps for slum dwellers to drink.

Pickering, a postdoctoral researcher in civil and environmental engineering at Stanford, would spend the next few weeks in Dhaka, a city with the distinction of being the most densely populated and — because of its poor infrastructure, inadequate health care and polluted environment — ranked by The Economist as least livable in the world. She was there to lay the groundwork for a project proposing a simple, low-cost method for purifying Dhaka’s contaminated water supplies and improving the health of the city’s estimated 10 million residents. The method, an ingenious chlorination system, is a radical departure from previous approaches to providing clean water. If the method is proven in Dhaka, she and her colleagues would like to see it applied across the developing world.

Slum dwellers use aluminum pots knows as kolshis and plastic bottles to gather their water.
Collecting water
Slum dwellers use aluminum pots knows as kolshis and plastic bottles to gather their water.

The project grew out of the despair of an American doctor working in Bangladesh. Stephen Luby, MD, now a professor of medicine at Stanford and principal investigator for the project, had spent eight years in Dhaka as the director for the U.S. Centers for Disease Control and Prevention in Bangladesh before coming to Stanford in September 2012. While in Dhaka, he also worked with the International Center for Diarrheal Disease Research, whose Dhaka hospital admits more than 100,000 people every year for diarrhea, much of it caused by drinking contaminated water. He estimates fewer than 20 percent of people in Bangladesh have access to water that is free of contamination.

As an infectious disease specialist, Luby was acutely aware of the many waterborne risks to local health, including cholera and typhoid, as well as diarrheal diseases caused by microbes such as rotavirus, E. coli and shigella. Rotavirus, which causes severe, watery diarrhea, is one of the biggest threats, responsible for the death every year of more than 15,000 children under the age of 5 in Bangladesh, according to a 2008 study in the journal Vaccine. More than half a million children worldwide die each year of rotavirus infection, which is one of the primary causes of diarrhea in young people. Those who are infected shed the virus in their feces. It then spreads through hand-to-mouth contact with contaminated material or through drinking tainted water.

“If you talk to people in these communities, almost all of them will be able to tell you about somebody they know who has died of diarrhea,” particularly infants and young children, Luby says. “So mothers are very familiar with the problem.”

Finding a solution became a nagging issue for Luby. So he turned his attention to Dhaka’s water supply and began pondering new ways to clean it up. Unlike developed countries, which rely on large water-treatment plants to purify water, developing nations for the most part put the onus on residents to boil, filter or chlorinate their home water supplies. But fewer than 10 percent are willing or able to take these steps, even if the water they drink could put them — or their children — at risk for serious illness and death, Luby says.

“You’re asking poor people to set up a water treatment plant in their home. Many people don’t,” says Luby, who is also a fellow at Stanford’s Woods Institute for the Environment. He reached the conclusion that clean water would never reach those at highest risk of diarrhea and other serious, water-related ailments without an entirely new approach.

Three years ago, before he came to Stanford, he met Pickering, then a Stanford graduate student, at a scientific meeting in Berkeley. He had reviewed one of her papers and was impressed with her thoroughness and careful scientific reasoning. He saw her again in 2010, at the American Society of Tropical Medicine and Hygiene conference in Atlanta, and talked with her about the water issues in Dhaka, asking if she might come up with a fresh approach — some mid-level solution between a costly treatment plant and a home purification system, which he viewed as a failed strategy.

So Pickering headed to the burgeoning South Asian city on a scouting mission, stepping gingerly into that shaky-looking skiff to arrive at Korail, one of the nearly 5,000 slums scattered around the city. About 40 percent of Dhaka’s people — an estimated 4 million residents — are wedged into these slum neighborhoods, where families live chockablock in single-room tin shacks. Pickering says she loves to travel and has worked in slums in both India and Africa, but had never encountered a place like Dhaka. Its slums, 33 times more densely populated than San Francisco, are a chaotic environment where people compete for every inch of space, dodging rickshaws, bicycles or other obstacles on pockmarked roads.

“I have to say Dhaka is the most intense place I’ve ever worked,” says Pickering, who has visited the city several times. “Living and working there requires a sense of internal calm and focus.”

Air pollution has draped a layer of soot over the city, while rains routinely flood the many homes perched unsteadily along the city’s vast network of waterways.

“There’s open sewage everywhere,” she says. “There’s not a well-functioning sewer system to remove feces from the communities. The kids are playing in it, and it’s very unsafe.”

Water supplies are conveyed through these neighborhoods via PVC pipes resembling backyard garden hoses, which are often cracked and leaky, and exposed to runoff from pit latrines, holes in the ground that serve as communal toilets. Because the city’s water flow is intermittent, it creates a negative pressure in the pipes, which then suck in the surrounding sewage. Tests done by Stanford and the diarrheal research center showed that 80 percent of water samples were contaminated with bacteria from human waste, Luby says.

Chlorination at the pump

In the latest prototype of the Stanford team’s chlorine doser, tiny amounts of bleach flow through a pressure stabilizer and a dose regulator and are then injected into the water stream.

Chart Labels:

The chlorine reservoir holds ordinary bleach.

An air tube helps balance the pressure.

The chlorine travels through a pressure stabilizer.

The chlorine travels through a regulator to control the flow, just a few drops per liter of water.

Water flows through a restriction to create the Venturi effect, which reduces fluid pressure and draws in the chlorine.

Water exits the pump safely chlorinated.


Chlorination at the pump

On her scouting mission, Pickering made a key observation. Most slum dwellers, she noticed, were collecting water at communal hand pumps, which were shared by 10 to 50 families. Women typically rose early, at 4 or 5 a.m., squatting in their colorful salwar kameez (loose-fitting pants and long tunics) to collect the water in plastic buckets or metal vases known as kolshis for use and storage at home.

Slum dwellers use aluminum pots knows as kolshis and plastic bottles to gather their water.
The pump at work
A hand pump with a Stanford prototype device delivers chlorinated water for drinking and washing.

Pickering had a thought: What if she and her colleagues could find a way to infuse chlorine into the water at these shared sites? A few drops of the chemical, which kills viruses and bacteria and most diarrhea-causing pathogens, would purify the water and spare residents the trouble of doing it themselves. If successful, it would be the first automated chlorine disinfection system for use in low-income areas.

The beauty of the approach is that it doesn’t require people to change their behavior — one of the major impediments to many current water-purification programs, says Jenna Davis, PhD, an associate professor of civil and environmental engineering and a member of the project team. Studies show that when people are given the tools to purify water at home, they are initially enthusiastic and rates of diarrhea decline, she says. But once researchers leave, old habits set in, and progress stops.

For instance, Shaila Arman, a scientist at the diarrheal research center and a Dhaka resident, was involved in one community water-chlorination project that failed because people could not adapt to a new, seemingly complex technology, especially since they didn’t consider water contamination a serious health threat. She says most people were less concerned with pathogens in the water than with its smell and appearance. Moreover, taking on a new habit, she says, is hard when people are struggling to get by day to day.

“People are worried a lot about the demands of life, so they are not as concerned about diarrhea, which in the scheme of things is not perceived as so serious,” Arman says.

Before Pickering left Bangladesh, she visited a hardware store and spent $30 on what would become a crucial piece of research equipment for the project: a bright green, 70-pound iron pump, just like those used in the slums. With a colleague’s help, she stuffed the 2-foot pump into her hard-shell suitcase and padded it with her T-shirts and socks. “I was lucky the guy who checked me didn’t bother to weigh it,” she says with a smile. “I was pretty excited about it. I was also worried that it wouldn’t arrive, as our luggage flying to Bangladesh is often lost.”

But arrive it did, and the rusty pump now sits on a makeshift wooden platform in the environmental engineering lab in Stanford’s Y2E2 environment and energy research building, an anomaly among the pristine, sophisticated equipment on neighborhing lab benches. Pickering says she was hoping to find an off-the-shelf device that could easily attach to the pump and dispense an appropriate amount of chlorine into the water, but it was not to be.

“I found there was no technology out there that took into account that there was no access to electricity,” she says. “It would also have to work with a non-continuous water supply and be able to use liquid chlorine, which can be bought very cheaply in Dhaka in the form of household bleach.”

Fortunately, a dedicated group of Stanford students in civil and environmental engineering soon came together, willing to spend countless hours in the lab — and in the field in Dhaka — designing and testing different prototypes. Graduate student Yoshika Crider cobbled together the first in 2011 in a pink bathtub in the Dhaka apartment she shared with two other students. She used pieces of plastic to fashion a rectangular mixing chamber, connected by a hose to a mesh bag of bleach powder. The device, designed with the same principles as a pool chlorinator, was held together by duct tape, “the roughest of prototypes,” she says.

Crider and a few other students later proposed it as a project for a class, Engineers for a Sustainable World, and the effort gathered steam. The team since has gone through at least 20 other iterations, all stowed in a bucket in the lab that graduate student Keegan Cooke calls “the prototype graveyard.” Some of the prototypes weren’t durable enough for use in the field, had trouble with leaky valves or had backflow problems that caused the pipes to rust, among other issues.

One of the biggest challenges was to find a way to dose the right amount of chlorine, as the water pressure is highly variable in Dhaka. The students relied on principles of fluid dynamics to get the pump to draw in just the right amount, or about 0.5 to 1.5 parts per million, the acceptable range. Getting it right took many months and the help of an outside consultant who used customized software to create various fluid simulations.

The real testing began in the summer of 2012, when Crider brought one of the prototypes to Dhaka for a field trial at 10 different pump locations. In the first few days, she says, some residents complained of the chlorine taste, but then their complaints subsided. Some were particularly excited about the project, including one middle-aged mother who had plucked a leech out of the pump the week before.

“She seemed to think there was a difference in the water — that fewer people were getting sick,” Crider says. “She is going to be a champion in the community for the system.”

All of the residents, Crider says, were gracious and welcoming. On her last day there, a snack shop owner insisted on treating her to a lunch of fried potato and vegetable wraps, as a thank you for her help, she says. She says it’s gratifying to see residents already benefiting from the project.

“We’ve already chlorinated people’s water, which is the coolest thing. People are already affected by this technology. It’s good work,” says Crider, who left the device in place. Cooke is working to further optimize the technology, spending most days and many nights in the lab tweaking the design. He manufactured the latest prototype in his garage at home, using his own 3-D printer.

The current prototype, made of the same plastic used in Legos, resembles a kitchen funnel and has a silicone seal that secures it to the mouth of the pump. A slender tube connects the device to a reservoir, which holds about 5 liters of chlorine.

The device regulates the flow of the water, which otherwise pours out or sprays in bursts. After much trial and error, the students introduced the Venturi effect, a principle of fluid dynamics, to induce a low-pressure zone in the flowing water that draws in the chlorine. The device is designed to draw in chlorine according to the rate of flow; this ensures that the water is infused with just the right proportion of chlorine. The students also adapted a regulator used in medical IVs as another way to control the chlorine dose. Whoever manages the system can turn a dial to set the dose so it remains in a consistent, safe range. Ultimately the system will be enclosed so no one can tamper with it, Cooke says.

Cooke was an entrepreneur before he came to Stanford, having created his own company, Keego Technologies, which sells microbial fuel cell kits to schools, where they are used to teach students how microbes in the soil can generate electricity. As one of the few in the group with business experience, he is working on various business models that could help sustain the project over the long haul, a key to its success.

“In the water sanitation field, that’s the hard part,” says civil and environmental engineering faculty member Davis. “We have plenty of technology. We just haven’t figured out how to deploy it on a sustainable basis.”

One approach is to engage existing community-based organizations, which manage a variety of community projects, such as construction of new latrines or pipes, in collecting fees from landlords and other users to maintain the system, Cooke says. The community groups could hire residents for a small fee to periodically refill the chlorine reservoirs and make sure the devices are working properly. Landlords would have an incentive to contribute, as they could advertise their rental units as having clean water supplies. Another alternative could involve local entrepreneurs to maintain the devices, as there are many in Dhaka eager for a steady source of income, he says. He believes the device could be mass-produced for as little as $15 each.

Team members, including Cooke, Crider and Pickering, plan to go back to Bangladesh this summer to test the prototype and lay the groundwork for larger studies on its feasibility and health benefits. Pickering says they’ll select 160 test sites, randomly assigning half to receive the chlorine doser, and compare rates of diarrhea and weight gain among the young children in the two groups.

 Luby ultimately hopes to see the technology applied in communities across South Asia and Africa, where climate change, population growth and poor management practices have made clean water supplies — and water generally — an increasingly scarce commodity.

“Water is a very important resource that is not being well-managed, at the risk of all humanity,” he says. For instance, in South Asia, agricultural interests are depleting the underground aquifers, so while crops are flourishing amid a green revolution, that productivity can’t be sustained, he says. At the same time, surface water is being used as a garbage dump for sewage and industrial waste, compromising water quality and the entire ecosystem, he says.

Luby says he came to Stanford in September because of its collaborative, entrepreneurial spirit — something highly visible in this particular global initiative.

“I spent 17 years working for the U.S. government, and I never had anyone say, ‘Maybe I should create a startup and make this go farther,’ he says. “The fact is that we have been pushing ways of how we can get it out there. It’s very exciting to work with people at Stanford who have that vision.”

The project already is attracting some attention. The team won a $15,000 award in a U.S. Environmental Protection Agency student design competition for sustainability, and in April it won the 2013 American Society of Civil Engineers Sustainable Development Award, which came with a $1,000 prize. And last year the project won first prize, a $20,000 award, in the Social Entrepreneurship Challenge of the Business Association of Stanford Entrepreneurial Students. The project also is supported by grants from the U.S. Agency for International Development and the World Bank, which is funding the health impact evaluation.

As for Pickering, she says she realizes there is still a lot of work to be done to validate the technology and its financial viability. But she has high hopes this will be one of the paths to improved health for a large swath of people for whom clean water now is just a pipe dream.

“My biggest hope for the project is to develop a financially sustainable strategy for disinfecting water that can be adopted and scaled up in low-income, urban communities around the world to improve health,” she says.


E-mail Ruthann Richter


Coming to a sprinkler near you in America, reused water on tap

Not only developing countries such as Bangladesh struggle with their water supplies. In the United States, population pressures, growing energy costs and climate change uncertainties threaten a future of municipal water shortages, particularly in the arid West. Water reuse — the use of treated wastewater — will likely be key to meeting future water needs.

According to the most recent data available from the U.S. Environmental Protection Agency, Americans use 1.7 billion gallons of reused water every day. While that’s a lot of water, it’s less than 1 percent of U.S. daily water use.

Stanford civil and environmental engineering professor Richard Luthy, PhD, is leading the charge to increase water reuse. Luthy is the director of ReNUWIt, a $20 million National Science Foundation multi-institutional research center focused on ensuring that communities have dependable water supplies and designing systems to manage and reuse that water. Water treatment as we know it is energy-intensive and resource-inefficient. “We need to be thinking differently,” says Luthy, the Silas H. Palmer Professor of Civil Engineering and a senior fellow at the Woods Institute for the Environment.

As part of their work for the center, Luthy and his colleagues are planning a test-bed facility on Stanford’s campus — the first of its kind in the United States — where researchers from around the world will experiment with technologies including some that have the potential to reclaim water while producing clean energy.

Luthy and other Stanford experts say that reused water can be as safe as what flows today from the kitchen faucet — a 2012 report by the National Research Council pronounced reclaimed water safe as ordinary drinking water. But they warn that unless chemical waste is curbed, the safety of any type of water will be in jeopardy.

Even with today’s technology, reused water compares well with drinking water. Regarding pathogens, the research council’s report states, “Although there is a great degree of uncertainty, the risk from potable reuse does not appear to be any higher, and may be orders of magnitude lower, than currently experienced in at least some current (and approved) drinking water treatment systems.” Part of the reason for this is that many municipal water supplies contain “de facto” reused water — for example, river water that receives discharge from sewage treatment plants.

The report says that tests “have documented the presence of wastewater-derived contaminants in watersheds throughout the country” and that, according to a recent study of drinking water supplies, “one or more prescription drugs was detected in approximately 25 percent of samples collected at the intakes of drinking water treatment plants in 25 states and Puerto Rico.”

So in simple terms, ordinary drinking water already contains reused water to some extent, as well as some of the chemicals it carries. Which brings us to what professor of medicine Stephen Luby, MD, says is the real issue. It’s not contaminants in reused water, it’s the massive quantity of chemicals we manufacture and release into the environment at large. “Where is this stuff going to go?” asks Luby, an expert on waterborne illness and a senior fellow at Woods and at the Freeman Spogli Institute for International Studies.

“We live in this environment. We can’t escape it,” says Luby. “We are a chemical world. I know the toxicologists say it’s all in the dose, but it does concern me.”

Craig Criddle, PhD, a professor of civil and environmental engineering and a senior fellow at Woods, echoes Luby’s concern, saying more focus should be given to green chemistry and replacing chemicals that are nearly impossible to remove completely from water sources.

The national Safe Drinking Water Act sets maximum exposure levels for many chemicals in municipal drinking water, but does not establish standards for many applications of recycled water, such as toilet flushing, cooling and irrigation, where water of lesser quality may be suitable and less expensive to produce. It also does not set standards for unregulated chemicals, trace amounts of which are sometimes present in reused water.

That means water treatment strategies should be robust, says Luthy. He calls for the use of multiple treatment methods, careful monitoring for equipment malfunction and operator error, and better federal water reuse regulations to rectify non-uniform state rules.

Today only a few municipal systems — including areas of Southern California and Texas — replenish their reservoirs or groundwater basins with treated wastewater, and only about one-tenth of 1 percent of municipal wastewater nationally is recycled into local drinking supplies.

But that will increase, Luthy says.

“Locally sourced water supplies — from water reuse, stormwater capture and better groundwater management — are the future,” he says. — Rob Jordan






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