Providing clean water for the world

If I were a religious person looking for something to prove the existence of god, I would not waste my time with things like the bacterial flagellum or the blood clotting mechanism or other esoteric phenomena that few other than biologists really understand. I would instead point to the properties of water.

Water is amazing. Not only is it abundant, its properties seem to be perfectly designed for nourishing life. Just the very fact that as its temperature drops below 4oC it stops contracting and begins to expand as it begins to form ice is what prevents our oceans and lakes from freezing solid in winter.

Of course, the idea that water was designed to facilitate life is fallacious thinking, similar to fine-tuning arguments. But the fact that it is essential for our survival is also the reason that it can be deadly. Water-borne diseases due to the consumption of impure water is likely the most common cause of disease in the world so I was interested in this documentary about Dean Kamen’s invention for a water purification device called Slingshot (also the name of the documentary) that can extract pure water from the filthiest source.

SLINGSHOT | Paul Lazarus from Focus Forward Films on Vimeo.

Jason Dorrier has an interview with Paul Lazarus, the maker of the documentary. One question that I could not find the answer to is how all the stuff extracted from the dirty water is periodically taken out of the device and disposed of.

Kamen’s idea is to be able to make it cheaply and reliably enough that it can be provided to communities all over the world. He has partnered with, of all entities, Coco-Cola that has the resources in distribution and marketing and has a self-interest in it because it has received great criticism around the globe for depleting drinking water supplies to make its drinks.

Kamen, most famous for his invention of the Segway, has been working on this device for about fifteen years. He appeared on The Colbert Report back in 2008 demonstrating an earlier version of the same device.

(This clip aired on March 20, 2008. To get suggestions on how to view clips of The Daily Show and The Colbert Report outside the US, please see this earlier post. If the videos autoplay, please see here for a diagnosis and possible solutions.)


  1. lorn says

    I did some work for one of Dean Kamen’s relatives and they gushed over how creative and inventive he is, to which I agree. Then they talked about how he was going to save everyone and provide devices that would change the world, and I smiled.

    I’m not a big Dean Kamen fan. He invented a two-wheeled device to carry a person that you need to plug in and costs several thousand dollars. I took one look and figured we already have a two-wheeled marvel of efficiency that sells for a few hundred called the bicycle. He is a bright guy and he makes a lot of money but to me his inventions are more novelty than practical solution. They are wondrous technological marvels but inappropriate use of technology.

    We already know how to save water and how to provide safe drinking water. We, the human race, just doesn’t do it consistency and for all groups. Simply segregating the sewage from the drinking water supply, inculcate the use of very basic filtration (pouring the water through a cloth), and solar treatment of biologically contaminated water and the majority of the problem goes away. All of these solutions are low-tech, low-cost, reliable, and sustainable indefinitely within the remote communities using only locally sourced materials and skills.

    I don’t begrudge Mister Kaman his success and if this water treatment system helps people who would otherwise do without clean water more power to him. I am interested in how his device works. It obviously, according to his naming of the process, uses a vacuum so we know a vacuum pump is involved. We also know it uses filters of a type that can be cleaned and reused. We also can reliably assume it uses some form of power, likely electricity and a motor to run the vacuum pump, valves and controls. With the proper selection of bearings, seals, materials, and wear surfaces the mechanism might be made to run for a long time. 250,000 hours is about the upper limit for MTBF. So roughly 28 years running 24/7 but this assumes only the best materials, manufacturing, and quality control methods available. This is the sort of precise manufacturing under carefully controlled conditions you might use for manned spaceflight or military satellites. It doesn’t come cheap.

    To keep the price reasonable I figure he has had to settle on a 100,000 hour MTBF rating. So about half still operable after 11 years. Of course Dean Kamen is a smart guy and perhaps he has some fancy tricks up his sleeve to increase reliability.

    I also note that while he is quick to point out the water used to produce bottled water is more than just what goes to fill the bottle he wasn’t very forthcoming about how much water or energy was used to manufacture his device. Stainless steels and Teflon seals are a product of heavy industry that uses a lot of water and energy. It was a bit one-sided to leave those numbers out.

    Good luck to him and his process but to my way of thinking there are already known reliable ways of getting clean water to nearly everyone. Perhaps there is some narrow subset of people for which his device is the most practical solution but I have a hard time imagining the special circumstances that would force that conclusion.

  2. Rob Grigjanis says

    Most convincing argument I’ve seen for the existence of god: The boiling point of ethanol is less than that of water, and greater than that of methanol.

  3. Paulo Borges says

    Let me rain just a bit on your parade.
    I know a bit of Africa, I lived and worked there for a long time and learned something very important.
    Leaders don’t care with anything that does not bring money to them or to the groups that prop them. You can get cell phone coverage in most of Africa, even in the middle of the savanna, because there is money to be made from it. Water, electricity or even basic medical care will not make them richer. Even in many cases, roads are built not to serve the population but big economic groups.
    The solution of charities or NGOs is just a drop in the ocean, there are billions of people in need of the basics and not just in Africa.

  4. sc_770d159609e0f8deaa72849e3731a29d says

    If I were a religious person looking for something to prove the existence of god, I would not waste my time with things like the bacterial flagellum or the blood clotting mechanism or other esoteric phenomena that few other than biologists really understand. I would instead point to the properties of water.

    You’re not the only one:


    If I were called in
    To construct a religion
    I should make use of water.

    Going to church
    Would entail a fording
    To dry, different clothes;

    My liturgy would employ
    Images of sousing,
    A furious devout drench,

    And I should raise in the east
    A glass of water
    Where any-angled light
    Would congregate endlessly.

    -Philip Larkin

  5. dmcclean says

    I’ll defend Kamen a little bit.

    If he were more famous for his extensive involvement with/founding role in FIRST and less famous for the underwhelming Segway, people would probably have a better opinion of him.

  6. lorn says

    Rob Grigjanis @ #2:

    I suspect that the key technology being exploited is that boiling for distillation can be accomplished by raising temperature or lowering pressure. Not a whole lot new there because this has been known for hundreds of years. But Kamen has found a way to make such a system small, light, compact, and both relatively energy efficient and able to operate without non-renewable filters or chemicals. That isn’t an insignificant problem to overcome or easy accomplishment.

    The fact that many contaminates have a lower vapor pressure than water does, as you point out, add some complication but this is easy enough, conceptually, to overcome by discarding the extracts bracketing, both before and after, the vaporization point of pure water. This is commonly done in fractioning columns.

  7. Jim B says

    Before the Segway, Kamen was already rich for inventing a number of medical devices. From wikipedia:

    Kamen was already a successful and wealthy inventor, after inventing the first drug infusion pump and starting a company, AutoSyringe, to market and manufacture the pump.[9] His company DEKA also holds patents for the technology used in portable dialysis machines, an insulin pump (based on the drug infusion pump technology),[10] and an all-terrain electric wheelchair known as the iBOT, using many of the same gyroscopic balancing technologies that later made their way into the Segway.

  8. says

    Don’t sailboaters already have a hand-pumped water purifier system that’s low-weight and fairly reliable? Ah, yes, a bit of googling shows there are reverse osmosis systems that produce 1gal desalinized drinking water/hr. Not cheap, though -- $2k and up. So Kamen has to invent something cheap and simple, rather than fancy and expensive -- that’ll be a bit of a role-reversal for him.

  9. lorn says

    The reverse osmosis systems, some so small they will fit in your hand, issued by the military to fliers as part of their survival kit, are quite functional but they are expensive, require chemical treatment to keep working for long, and subject to failure if exposed certain chemicals or oil. The smaller units also require a significant investment in effort to produce even small amounts of fresh water from saltwater.

    The smallest sells for just this side of $1200:

    Larger, higher capacity systems are more expensive, but in terms of $/gal, cheaper.

    Of course, Katadyn is considered to be the gold standard for such systems and other companies provide larger systems for far less money.

    The difficulty with the RO systems is that the membrane is delicate. The membrane needs cleaning. Salt and minerals tent to plug and tear holes in the membranes. The various chemicals necessary to remove those salts and maintain output volume mean life-cycle costs are high and no mater how well treated the membranes wear out.

    Kaman, using a vacuum distillation system, has avoided the need for a delicate membrane and associated chemical treatments. From an engineering point of view a wise step if the goal is to lower operation costs and complication by avoiding expendables.

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