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a s h o k  g a d g i l


Photograph of Ashok Gadgil

Ashok Gadgil is a senior staff scientist in the Environmental Energy Technologies Division of the U.S. Department of Energy's Lawrence Berkeley National Lab. Gadgil's invention, the UV Waterworks, received Discover Magazine's 1996 Award for Technological Innovation (Environment Category) and Popular Science Magazine's 1996 Best of What's New Award.


Scientist Ashok Gadgil talks about the UV Waterworks, his breakthrough invention for disinfecting drinking water affordably using ultraviolet light.


Q: Where did you get your education?

A: I was born in Bombay and did my undergraduate studies in India. I later came to the University of California at Berkeley for my Ph.D. studies, and received my doctorate in physics in 1979.


Q: When did you begin to get interested in the concept of disinfecting water?

A: Sometime during my doctoral studies I came to the alarming realization that people in India would never reach a level of material well-being even one-fifth that enjoyed by an average American no matter how hard they tried. Why not? Because the earth wouldn't bear it if a large percentage of the world's population lived at the American standards of consumption and waste. It would just get crushed. That was a bitter surprise to me.


Q: How did it change your outlook?

A: I began to think of ways to improve energy efficiency and deliver a better life -- not by the standard energy-intensive or resource-demanding methods, but by trying to figure out ways of doing things better. In other words, I tried to answer the question: how could we provide a better standard of living without running up against the limits of what the Earth could support?


Q: Which led to thinking about water disinfection?

A: Not directly. The thought of using UV light to disinfect water germinated in my mind when I was working for a non-profit group in India during the years 1983-88. When I returned to the United States the idea was still in the back of my mind, and I was busy sending literature about the concept back to various colleagues in India to see if this was likely to be appropriate. During that period of time, it always remained on the back burner for me.


Q: What made it a matter of pressing importance for you?

A: I started looking seriously at the possibility of UV disinfection after the outbreak of Bengal cholera in 1993. It was a mutant strain that spread rapidly throughout India and neighboring countries, and did not respond to standard cholera vaccines. A huge number of people suffered from it; I would estimate that some 10,000 died.


Q: That gave you the impetus. How did you get started?

A: There was no funding for this investigation, and I didn't really have much spare time myself. So I made a deal with a graduate student in mechanical engineering that I would be his thesis adviser (he was studying solar thermal disinfection methods) if he could take a couple of months off and work with me to examine the economics and technology of UV disinfection.

When we discovered that it was possible to disinfect water for a couple of cents per metric ton we got very excited. This was certainly something that developing country populations at the lower end of the economic ladder could afford.


Q: How did you arrive at the revolutionary design concept?

A: The engineering design was actually a product of the constraints and criteria we had to work with. First, based on my experience in India, I knew that the unit must handle water that is not pressurized or dependent on complicated pressurizing devices. That is, we were dealing with gravity fed water from surface sources such as lakes, ponds, and streams using buckets or pots.

Then, too, I knew that the treatment had to be very quick. People are simply not going to wait around if it takes 15 minutes to disinfect their water. That means that there has to be a fairy high flow rate. At present the unit handles four gallons a minute -- twice as fast as the flow from an average U.S. bathtub faucet.


Q: Why had no one ever thought of using UV light before?

A: They had, but there was always a major problem: fouling by bio-film or chemical deposits on the quartz tube that encloses the lamp. You see, the UV lamp cannot be directly in contact with the water because the wall temperature of the lamp -- which controls the vapor pressure of mercury plasma -- will drop and consequently the lamp won't work well.

Typically people solved this problem by enclosing the lamp inside a quartz tube, using an air gap to separate the lamp from the water. There have been some attempts to use teflon for the same purpose. But in every case there is some solid surface that separates the water from the lamp.


Q: And that causes the bio-film?

A: In a way. When the lamp is off, the water grows stagnant and the bio-film grows. When you turn the lamp on the organisms die but they do not detach from the solid surface. They provide "micro-shadows" for the next layer to grow and take hold.

We considered a lot of alternate designs, but then settled on simply suspending the lamp above the surface of the water. With the lamp suspended in that way, there is no longer any surface on which any fouling can take place.


Q: Were there problems putting the lamp above the surface of the water that you hadn't foreseen?

A: Yes. When you immerse the lamp directly in the water, the amount of UV light that you can direct into the water is far greater than when the lamp is placed above the water. In the latter case, a lot of the light moves upward, away from the water.


Q: How did you solve that problem?

A: We just put a polished aluminum reflector above the lamp. It reflects 70 percent of the UV light back towards the water.


Q: Were you surprised with the end product in terms of the simplicity of its construction?

A: I must say, I wasn't surprised. Simplicity was always one of our most important design considerations. We did not want any moving parts. We wanted the design to be robust and rugged and easy to build. And, one of the major goals was the appropriateness or suitability for developing countries to either manufacture or operate this device.


Q: What do you mean by appropriateness and suitability in this context?

A: We wanted very long maintenance intervals for the device; we didn't want the villagers to do complicated or expensive maintenance. For example, we didn't want them to open up the device and have to clean quartz tubes in acid. That is unrealistic; they don't have enough technical resources or the time to bother with additional burdens of doing all that. So simplicity was part of the design goal. What was surprising was that we could succeed in meeting all of our goals -- no pressurized source, rapid disinfection, robust design and minimal maintenance.


Q: Former Secretary of Energy Hazel O'Leary made several promises concerning the UV Waterworks. What happened to those promises?

A: The US Department of Energy provided us with some funding for undertaking a field test of the UV waterworks in South Africa but there is some misunderstanding between what we asked for and what they thought we asked for. We got a significantly smaller fraction than what we thought we needed. But we have had one field site in operation since August of 1997. And now we have funding from DOE for a second field test site in South Africa and NRDC is supporting our efforts there.


Q: What is the importance of these field tests?

A: We've got to get feedback from the consumers and users to see how the units might fare or fail in the field owing to the way the users tweak it, or may want to use it. But, remember, the key point is this: we are not testing whether the unit disinfects water. We know it does. It has been tested in five different countries, in 11 different tests, in 8 different laboratories.

What we don't know, and what we can't find out in the laboratory, are the additional enhancements, the additional tweaking or modification of the device to make it more user friendly. Only field tests will give us that information. Unfortunately, there is no money to do that kind of research coming out of DOE.


Q: How do you see the world using the UV Waterworks in the future?

A: The best vision I have of how things may work is a two-pronged approach: First, private micro enterprises, maybe operated by low income families or women who are able to take water of questionable quality, process it through UV Waterworks, and offer it for sale to the community living nearby. These consumers would purchase the water in 5 gallon containers for their daily family use.

I see this as a wholly sustainable operation: it would not be running on charity. If someone's livelihood depends on the unit, he or she will make sure the unit works fine -- and will also make the effort to educate the community about the importance of using only safe drinking water, particularly for their children's health. And because it's so inexpensive, a very large fraction of the people would be able to afford safe drinking water.


Q: And what's the other approach?

A: Using the UV Waterworks to provide safe drinking water in places where water is normally provided to communities: railway stations, bus stops, public drinking fountains, restaurants and hotels, schools and the like. These institutionally-supported installations would also be feasible uses of the units.


Q: Are there any other potential uses?

A: Because it only demands 40 watts of energy, the unit works in practically any situation where renewable energy technologies such as wind turbines or solar panels could charge a battery that would power this device. That would make drinking water feasible even in places where maintaining long support chains of chlorine bleach is unthinkable.

And, then, you could also scale it down to reach people who get piped water of questionable quality. Many people in the developing world get contaminated drinking water piped into their home. With a small under-the-sink unit, they would be able to easily disinfect their drinking water.


Q: Has this invention changed your life?

A: So far, all I have got is a number of honors and awards but the difference will come when it actually makes a difference to the real world. That hasn't happened yet because the device started coming off the production line only last year. But it will. It will take some time before that happens. Only then will I be able to say: "Yes! I really feel great about having participated in making a real difference in the world." Until that time, it is almost embarrassing to get all these pats on the back when we haven't really delivered on the amazing promise of this device.


NRDC is currently supporting field trials of the UV Waterworks in South Africa. For more information, please contact Ashok Gadgil at ajgadgil@lbl.gov, or visit the WaterHealth International website. And for additional information on NRDC Online, see Lighting the Way to Clean Water and Purification with Ultraviolet Light.


  Published by the Natural Resources Defense Council -- contact us at nrdcinfo@nrdc.org