While most people in the developed world have safe drinking water continuously supplied to their homes, more than half of the world's population is exposed to water contaminated with pathogenic organisms that make this most basic resource a potentially deadly health hazard. Children, the elderly, and people with weak immune systems are particularly at risk. In India alone, some 300,000 children (mostly infants) die every year from diarrheal diseases spread through untreated water. Unstable political situations often exacerbate the clean water shortage, and massive outbreaks of diseases such as cholera, typhoid, and dysentery are not uncommon. When Rwandan refugees fled to Zaire in the summer of 1994, a shortage of disinfected water spurred outbreaks of cholera and dysentery that killed at a rate of 20-35 refugees per 1000 per day. According to the World Health Organization, by mid-July 1996, the latest wave of cholera had killed 94 people in Chad and 1,193 in Nigeria.
Environmental physicist Ashok Gadgil and colleagues at Lawrence Berkeley National Laboratory are working to develop a simple and effective device that, along with a basic health education program, can greatly reduce people's risk of becoming infected through the water they drink. The device, named UV Waterworks, is a grocery bag-sized stainless steel box containing a low-pressure mercury vapor lamp like those used in the fluorescent lighting found in most office buildings. In the device, named UV Waterworks, the lamp lacks the phosphor coating that keeps other fluorescent lights from emitting ultraviolet radiation. The result is that 70% of the light emitted from the lamp is UV-C radiation with a wavelength of around 254 nanometers (nm). At this wavelength, UV light has germicidal properties, and, at proper intensities, can render bacteria, viruses, and other pathogens harmless by inactivating their DNA.
The simplicity of the device is one of its strongest attributes. Because its major components are common and inexpensive, UV Waterworks is cheap to build and easy to maintain. The UV lamp, which will burn for about 8,000 hours, must be replaced yearly, but otherwise the device requires almost no maintenance. Water flows through the device by gravity, and electricity is used only to generate the UV light. With a total power demand of just 40 watts, UV Waterworks can operate connected to a car battery or a two-square-meter photovoltaic panel, and can disinfect 15 liters (4 gallons) of water per minute. WaterHealth International, the company that will manufacture UV Waterworks, estimates that when used to supply a community of 1,500-2,000 people, the total cost of disinfected drinking water would be about fifteen cents per person annually. This makes it affordable even by developing world standards.
Disinfection and the Developing World
For Gadgil, who lost five of his cousins in India to diarrheal disease, the objective was to build a device that would be inexpensive and easy to operate, making it practical for use in the developing world. Though many different disinfection schemes have been proposed and used in industrialized nations, none have been developed that meet the requirements of the world's poorest populations. UV waterworks may change that. "The technology is not new, Gadgil said, "however no one had yet pulled this technology for poor communities in the developing world because they weren't seen as a lucrative market."
For nearly a century, it appeared that the disinfection capability of ultraviolet light was an interesting phenomenon without an important practical application. Low-pressure mercury vapor lamps were first developed around 1835, and the biocidal properties of UV light were discovered in the early 1900s. For a brief period it seemed that UV light would become a popular means of disinfecting water in the industrialized world, but the discovery was followed closely by the advent of chlorination, which soon became the standard means of guaranteeing a safe water supply. However, while chlorine effectively controls waterborne disease in the developed world, many developing countries lack the capital, personnel, and distribution systems to implement widespread chlorination. As a result, diseases that have been practically eliminated in countries such as the United States continue to prey on the populations of nonindustrialized countries.
Chlorination lends itself well to use in large water distribution systems where one or two trained technicians can continually monitor and adjust the chlorine level. In the rural developing world, however, the main source of water for villages is often surface waters or a central hand pump that supplies the villagers with untreated groundwater. A typical chlorination system for a village of 1,000-2,000 people would cost around $2000 (four times the cost of UV Waterworks) in addition to the cost of a continuous supply of chlorine. The chlorine required by such a system may not be readily available in parts of the developing world, and, in areas where it is, there usually is no one in the community with the expertise to control the chlorine level. If chlorine levels fall too low, pathogens can survive treatment. If the levels are too high, chlorine will ruin the taste of the water, and, if the water is high in organic compounds (which is common in untreated water), such compounds can react with the chlorine to produce by-products such as trihalomethanes, which have been shown to be carcinogenic. Other disinfection options, including use of ozone and chlorine dioxide, have been used to some degree in the developed world, but they are also unfeasible for use in the developing world for reasons similar to chlorine.
Currently, the primary means of disinfecting water in rural populations is to boil it over a fire fueled by wood or dung. This chore is usually delegated to women, who often suffer negative health consequences. Studies in a rural district of Kenya showed that 70% of the water used was gathered by women who normally would collect 20-25 kilograms and carry it an average of 3.5 kilometers to their homes three times each day. In order to ensure that the water is safe to drink, the women must further labor to collect wood or dung, which are often scarce, for a fire. The process of boiling the water often takes place in huts with poor ventilation, exposing the women to harmful air pollutants.
Even if precautions such as boiling are taken, water can easily become recontaminated before it is consumed. As a result unsanitary drinking water remains a leading cause of death for children in the developing world. In 1993, 3.8 million children under the age of five died from diarrheal disease, according to UNICEF. High infant mortality further degrades the lives of women, as many in the developing world become caught in an unhealthy cycle of pregnancy and loss of children trying to ensure that at least a few children survive to care for their aging parents.
Fitting the Solution to the Problem
Unlike chlorine, which remains in solution while water is transported and stored, killing most organisms that might enter the water after treatment, UV light has no residual disinfecting power.
This drawback to the UV method is a problem in the developing world, where water is often carried from the source for several kilometers in open containers. However, Gadgil maintains that providing education with the device can not only minimize the risk of recontamination, but also can ensure that the device does not fall into disuse. Gadgil plans to enlist the help of volunteer organizations to familiarize villagers with UV Waterworks and teach them such things as how to dispose of human and animal wastes and what containers to use to best protect water from becoming recontaminated. "Our goal," Gadgil said, "is to ensure a safe level [of contaminants] at the cistern and the cup. This will require providing an elementary education in health and hygiene."
A good thing in a small package. A relatively small UV light device may make a big difference in the safety of water in developing countries.
Photo: EEG, Inc.
"The cost of providing training and education will be included in the selling price of the device," says Elwyn Ewalb, president of WaterHealth International. Ewalb says such education is vital to ensure that the device will be used appropriately. "A number of donor organizations are working with placement of chlorination devices [in the developing world]," says Ewalb, "but lack of training and the high maintenance required discourages their use.. . . [As a result,] many good experiments fall apart."
Another drawback to the UV disinfection method is that UV light, like most other disinfection methods, does not completely rid water of viable Giardia or Cryptosporidia, parasitic protozoans that, outside of a host, form cysts that are extremely resistant to disinfection. These cysts can survive dormant for months in most environments and become active upon entering a host. Symptoms of infection for both parasites include nausea and diarrhea which can be fatal in individuals with weak immune systems. However, these pathogens can be removed by slow sand filtration (a process of letting water seep slowly through a vessel containing a fine-grain medium) and other methods that are not beyond the reach of developing-world communities.
Filtration is also a solution to the problem of using UV disinfection in turbid water. Since the effectiveness of UV Waterworks depends on the light's ability to penetrate the water and reach all organisms present in a sample, any cloudiness or particles in the water that can shield pathogens from UV radiation will compromise the device's ability to disinfect. Filtering the water before treatment can reduce the turbidity of the influent and optimize the effect of the UV radiation.
Gadgil decided not to make such a filter part of the initial design of UV Waterworks, however, because keeping the device simple and cost-efficient were the main priorities. To explain this rationale, Gadgil cites a 1993 World Bank report: "In most developing countries the imperative is to get from 'bad' quality (say, more than 1,000 fecal coliforms per 100 milliliters) to 'moderate' quality (less than 10 fecal coliforms per 100 milliliters), not necessarily to meet the stringent quality standards of industrial countries." Gadgil said that he adopted this strategy while designing UV Waterworks. The idea was to create a device with attributes that would allow it to be used by millions of people throughout the developing world, not to create one that would necessarily destroy all pathogens. Gadgil argues that such a device will save many more lives over the long term than would a more effective device with a prohibitive price tag. "Any additions to the device, such as filters," adds Gadgil, "can be offered separately by the manufacturer."
UV Waterworks contains some important innovations and improvements over other UV devices. Most importantly, unlike Gadgil's model, UV devices in the past have required regular cleaning. In these older units, the ultraviolet lamps were encased in quartz glass sleeves and submerged in the water to be disinfected. This design allows films of organic materials or salts to become deposited on the glass, reducing the effectiveness of the device. These films have to be removed periodically by soaking the tubes in a sodium hydrosulfite or citric acid solution. In the UV Waterworks design, the light source is located above the water, where the bulbs will not be effected by dissolved materials in the water.
Making UV Waterworks a Reality
UV Waterworks is a device that is not only well-suited for use in the communities that need it most, but also one that lends itself to mass production and easy adaptation for use in other fields. According to Ewalb, the UV Waterworks device can be used in at least 17 other applications besides sterilizing drinking water, including serum purification and fruit juice processing. The ability to sell the device in other markets may be necessary to offset the cost of manufacturing UV Waterworks. "The developing world," admits Ewalb, "is not the sure-fire kind of market that most companies look for."
Another factor that will figure prominently in putting UV Waterworks to use in the developing world, says Ewalb, is the amount of assistance offered by relief agencies. When WaterHealth International begins mass-producing the device, it will sell (complete with an educational program) for about $500, a significant investment for most rural villages. However, Ewalb says that he envisions a scheme in which donor agencies will grant low-interest loans to groups of villagers to purchase the device. Once trained, these people can set up a small utility business, selling the purified water to other villagers, with a portion of the profits going toward repayment of the loan. Such a business, which would eventually profit the local owners, says Ewalb, would ensure that the device is maintained and that it does not fall into disuse.
In the coming weeks, WaterHealth International will add the final touches to the design that will be used for production, a slight variation from Gadgil's design, for which the company has purchased patent rights. The company will also soon solidify an agreement with the manufacturing company that will produce the device for distribution. The next step will be to develop the accompanying education program.
A South African Learning Experience
The answer to the question of how to best introduce UV Waterworks to people in the developing world should come during a series of tests in rural South Africa slated to begin later this year. An earlier prototype of UV Waterworks, with a much greater flow capacity than the current design, has already been field-tested in India. Based on the feedback from these trials, which took place during 1994 and 1995, Gadgil says he redesigned the device for lower flow. The new design should provide an adequate water supply with less waste and be more cost-effective. Proof of this will come from South Africa, but the primary aim of the upcoming tests will be to develop an education program tailored to meet the needs of developing countries.
The South African tests will take place in 16 villages over the course of two years and will be implemented in three stages. The first stage will involve two villages, the second will involve four, and the final stage will involve ten. In each successive stage, improvements suggested during the previous stage will be implemented and tested. WaterHealth International will provide the water purifiers for these tests and funding is expected from the U.S. Department of Energy and Eskom, a South African utility company.
The South African Center for Essential Community Services (SACECS), will provide the information and instruction that will accompany the device. SACECS is a joint collaboration between Eskom and the Electric Power Research Institute located in Palo Alto, California. According to Cynthia Motau, director of SACECS, the educational effort could involve the use of posters, videos, role playing, participatory shows, and workbooks. Beyond simply teaching people how to use and maintain the device and how to protect the effluent from recontamination, SACECS also plans to provide lessons in basic health protection. "Regardless of the efficacy of the technology," writes Motau, "user education is essential, and we have seen it [to be] prudent that this process be backed up by a programme of public health education."
Once the devices are installed in South Africa, they should significantly reduce the incidence of waterborne diseases in many rural communities. These communities, which comprise mostly black families, have long been excluded from the developments in sanitation afforded to the white-dominated cities. According to I. E. Haffejee, a professor of pediatric and child health at the University of Natal in Durban, South Africa, the infant mortality rate for South African blacks is ten times that of whites, and diarrhea is responsible for 20% of the deaths among black children under the age of five. By preventing many of these deaths, UV Waterworks may be a step toward correcting decades of social injustice. "Unless they improve [the lives of] a lot of the blacks in South Africa," says Gadgil, "democracy is going to be quite unstable because of disparity of the standard of living. One of the first steps in improving [the] standard of living is to provide clean water."
However, both Gadgil and Ewalb are looking past the South African tests to the time when the final product will be marketed throughout the developing world. For Gadgil, whose research team worked many nights and weekends perfecting UV Waterworks, that time will be particularly satisfying. "I incubated the samples [from the initial test of UV Waterworks] at home," Gadgil recalls. "It was really exciting in the morning to find that the outlet water was completely free of E. coli. The first thing I did was I told my two daughters." Some might say that was an appropriate reaction to a device with the potential for saving the lives of millions of children throughout the world.
Christopher G. Reuther
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Last Update: August 5, 1997