Making drinking water safe at the source

Researchers with the Stanford Woods Institute's Program on Water, Health and Development are finding affordable, sustainable solutions to the challenge of providing safe drinking water to nearly 1 billion people in city slums.

To the first-time visitor, Dhaka, Bangladesh, can seem the embodiment of chaos. It is among the world's most densely populated cities, a riotous cacophony of sound, smell and colour. Millions of people throng slums where the only access to drinking water for most is through public taps or hand pumps. What comes out is usually contaminated with human waste.

The same story plays out around the world. Almost a billion people, one in every eight, live in an urban slum. ''For many of them, finding a safe water source is impossible,'' says Jenna Davis, an associate professor of civil and environmental engineering and the Higgins-Magid senior fellow at the Stanford Woods Institute for the Environment.

Davis advises a Stanford team developing a low-cost chlorination device for urban slums.

Unlike decades worth of proposed solutions before it, the device would disinfect water at the point of collection and require no behaviour change from residents.

Davis and other members of the Lotus Water Project – a joint effort led by the Stanford Woods Institute's Program on Water, Health and Development – envision a device that has no moving parts, requires no electricity and would sell for $20 or less. ''This makes it sustainable and scalable in low- and middle-income countries,'' Davis said.

Once attached to a pump, the device would dose water with a precise amount of chlorine each time someone used the pump. The chlorine residual would last long enough to protect against recontamination during transport and storage. This novel approach overcomes the challenges and high costs of city-wide water treatment while removing the burden of having to treat water in people's homes.

During World Water Week in Stockholm last year, the project won a $15,000 prize and international recognition as part of the Reed Elsevier Environmental Challenge. The competition was established to contribute to the Water for Life Decade, an international initiative to hold countries accountable for their commitments to the United Nations Millennium Development Goal of halving the number of people without sustainable access to safe drinking water and basic sanitation. The Lotus Water Project was chosen for being ''replicable, scalable, sustainable and innovative.''

Challenging a paradigm
''For decades, there's been the paradigm of point-of-use household treatment,'' said Yoshika Crider, Dhaka-based project manager for Lotus Water and a former Stanford civil and environmental engineering graduate student. ''Numerous studies have shown that uptake under this approach – requiring household members to treat their water with filters or chlorine tablets, for example – is really low.''

Perhaps the most recent such study, a March 2015 paper, was co-authored by several Lotus Water Project team members. The study finds that household use of chlorine tablets decreases by 50 per cent after behavioural promotion visits end.

Caption: Valeria Bauza field tests an early prototype of the Lotus Water filtration technology. (Photo: Amy Pickering)

The issue could not be more pressing; Globally, diarrhoea caused by waterborne pathogens is the second leading killer of children under age 5, according to the World Health Organization.

Lotus Water co-adviser Stephen Luby, a professor of medicine, helped kick-start the project because of his interest in water's contribution to health. ''I've worked on water and health issues for more than 20 years,'' said Luby, a senior fellow at the Stanford Woods Institute and the Freeman Spogli Institute for International Studies. ''Most of those efforts asked people to treat water in their own homes. This project is radically different.''

The Lotus Water Project's service model relies on monthly payments from landlords, who typically own shared water points in Dhaka. The team's research indicates that slum residents are willing to pay higher rents in exchange for higher-quality water. Linking the device's lease to service payments would hold landlords accountable to their tenants. ''They have an incentive to improve their tenants' quality of life,'' said Amy Pickering, an engineering research associate with the Stanford Program on Water, Health and Development. On average, a 1- to 2-percent rent increase would be sufficient to cover device maintenance, according to Pickering.

An iterative process
Lotus Water Project team members, in collaboration with international and local agencies as well as private companies, have designed, built and installed 40 prototype water disinfection devices at test sites.

When they've perfected the chlorinator – hopefully by the end of 2015, they plan to install more than 150 devices that will serve about 10,000 people. The team continues to refine its design while considering other similar devices, evaluating health impacts of access to chlorinated water amid other health hazards present in the slums, and testing the viability of potential business models such as different packages of chlorine refill and hand pump maintenance services.

Lotus Water engineers go into Dhaka's labyrinthine slums every day to test their devices, hold focus group discussions with landlords and residents, and analyze data. Their iterative process has depended as much on human interaction as technology, namely a 3D printer.

After installing and monitoring a disinfection device, team members such as Frederick Goddard, a graduate student in civil and environmental engineering, alter components overnight to improve their function. They start with a sketch, then create a precise 3D rendering with a digital computer program and, finally, print the new piece in thousands of plastic layers.

''The 3D printer drives our work,'' Goddard said. ''That's how we do all our prototyping. It's really cool to design something, print it and attach it to a handpump the next day.''

Of course, things don't always go according to plan. Goddard and his fellow team members frequently must fix the temperamental printer. To deal with Dhaka's intermittent power supply, they invested in a backup battery. To get around a lack of local supplies, they import many of the parts and materials they need on a regular basis. Each time he flies to Dhaka, Goddard's checked baggage includes about 60 pounds of plastic for the 3D printer and, sometimes, the newly repaired printer itself.

Challenges multiply in the field. Vandalism, though infrequent, is a threat to the chlorination devices. Iron in rusty municipal pipes can clog the equipment. Water pressure and demand can vary wildly. Blistering heat, monsoon rains, soaking humidity, curious crowds of onlookers and frequent illness can complicate things.

Goddard had to sit out days of field testing last summer when he developed typhoid that came with a 105-degree fever, loss of appetite and numbing insomnia. ''It was just miserable,'' he said. ''But we are in this because we totally believe in the work we're doing. It's not just about creating a technology that disinfects water. It's about changing people's lives.''

The Lotus Water Project has received support from Stanford Woods Institute for the Environment, Stanford's Center for Innovation in Global Health, the U.S. Environmental Protection Agency, the World Bank, and the Abdul Latif Jameel Poverty Action Lab.