Water, Water, Everywhere, Nor any Drop to Drink


BISHOP-172Those of us living in the developed world take clean water for granted.  If you are in Boston or NY or almost anywhere else in the US, if you wanted a glass of clean water all you would need to do is get up, walk a few steps and drink your fill.  Most of us would view this as a pretty unremarkable thing to do.  Unfortunately, to many people around the world, this simple, commonplace act is an impossible dream.

In many parts of the world, enough clean drinking water is an unimaginable luxury. Estimates are that water borne illnesses kill 3 million people a year and make many more ill.  The toll among babies and children is particularly brutal as they are more at risk than adults.  In a lot of places in the world, someone’s source of drinking water is downstream from someone else’s toilet.  A clean, simple and inexpensive way to purify water would save the lives of millions of children per year. If you think of all the things one could do to alleviate misery in the under-developed world, providing enough clean water would be pretty close to the top of the list.

In the US we mostly purify drinking water by dumping tons of chemicals into it to chlorinate it.  A lot of folks wonder if this is the healthiest way to purify water but it does work and most of us in the US have never known or heard of anyone dying from contaminated water.  Clearly, this approach isn’t going to work in the under-developed parts of the world that don’t have water purification plants and are unlikely to get them anytime soon.

Folks at BU are working hard to solve the problem.  A team consisting of Ted Moustakas and his collaborators Roberto Paiella, Luca Dal Negro and Enrico Bellotti are working on a technology that promises to be a breakthrough in purifying water.  They are building deep UV lasers.

It has been known for some time that UV light in the C band (200-290nm) will kill micro-organisms.  The light in this band causes the DNA in these guys to fall apart and it can’t be repaired by the organism.  The UV light is preferentially absorbed by the DNA making the process quite efficient from an optical point of view.

The conventional way of producing UV-C light requires the use of Mercury based lamps.  However, these lamps have a lot of drawbacks:  they are electrically inefficient, have toxic Mercury vapor in them at high pressures, are fragile and are expensive.  Solid-state sources are needed.

Ted and his co-workers are developing UV LEDs based on the Nitride semiconductors.  They are depositing epitaxial films to build solid-state UV-C light sources that will be electrically efficient, environmentally safe, mechanically robust and easy to use in an under-developed country.  They are building devices that will make it easy and inexpensive to purify a glass of contaminated water before you drink it.  Their work has the potential to save the lives of millions of adults and children around the world.  If there was ever a reason to get out of bed in the morning, the chance to do this kind of research is it.  We should all be proud of their work and what they are trying to accomplish.  I know I am.


Dave B.