Custom Made UV Sterilizer

mud_muncher · 2018-11-24T00:42:46.000Z

Been looking at these for a while for hiking Trips Store bought ones go for over $100 and was wondering if UV IS UV. Would a highish powered UV LED do the same thing if it is run off a USB powerbank? Can be pretty simple just to drop in a 1 liter water container .

WillyD · 2018-11-24T00:47:02.000Z

Interesting. I have a full house UV purifier as we are on well water, but I’ve never seen small portable ones. I just did a Google search and found them as low as $30.

EasyB · 2018-11-24T00:47:53.000Z

No, for sterilization you need around 265nm, which is shorter wavelength than the typical 365nm LED. I think 265nm LEDs exist but are either very expensive and/or low efficiency and low lifetime.

mattheww1950 · 2018-11-25T01:07:04.000Z

These devices would be difficult to built, and just about impossible to have a long lifetime. Remember how UV sterilization works? It breaks the chemical bonds of organic compounds. All organic compound bonds are covalent bonds. That means the UV photon has to be of higher energy than the bond energy in the organic compounds being disrupted. The bad news is that silicon chemical bonds have very similar bond energies to carbon bond energies, so it would be very difficult to construct such an LED from any silicon based material. A 265nm photon is about 4.8 ev, and that is actually higher than the bond energy of all covalent chemical bonds. Consequently an LED with a 265nm output will tend towards self destruction. Mercury vapor devices put most of their energy into photons that are slightly higher than 4.8 ev. The electric excitation of mercury atoms can elevate their energy states so that when they drop back to ground state, they put the energy they give up into a 4.9 ev photon. Since there are no mercury bonds involved, this isn’t a problem, but ultimately it actually does damage the SiO2 bonds (glass), and that is one of the reasons Mercury Vapor UV sources don’t have an especially long life. The compounds that result from the disruption of the chemical bonds in the glass are not particularly transparent to photons of this energy.

SIGShooter · 2018-11-24T03:00:11.000Z

For something as critical as water purification I think it’s better to just buy one that’s commercially built and has been tested far more than any self-built one will ever be. I have 2 of the Steripen Classic models which we took on vacation to the Amazon and Africa a few years back. Although I can’t prove that they did what they’re supposed to do none of us (family of 5) got ill from drinking the water.

The American Red Cross Ultralight Purifier from Steripen is around half the price of the other models but can only treat around 20 liters on a single charge. The Classic’s can treat around 100 liters using 4 NiMh batteries before they have to be recharged/replaced with another set. I’m leery of built in batteries because they can’t be replaced with a charged set (and 20 liters isn’t much for 4 or 5 people) and when the battery goes bad the unit has to be replaced.

I see that Amazon is selling the Classic right now for $68 but that’s in the USA.

gravelmonkey · 2018-11-24T23:54:08.000Z

You’d need to use a filter anyway - bacteria can hide in opaque particles, so just use cheap chlorine tabs once you’ve filtered. Much more reliable.