How Clean Can UV?

“UV radiation affects microorganisms by altering the DNA in the cells and impeding reproduction. UV treatment does not remove organisms from the water, it merely inactivates them.” – Water Research Center

For the longest time this summer I worked on a machine that performed¬†persulfate-ultraviolet oxidation, but I really had no idea what it was. Looking at the machine, I could see that an oxygen tank and a beaker of persulfate solution were combining with my water samples and traveling through various tiny twisted tubes into a swirl of madness that then shot out in all directions and ended up in a scramble of numbers on the computer screen. So I asked around. Ten weeks of “asking around” later, and still all I knew was that somehow the glowing blue light was breaking down the carbon in my water samples and measuring its concentration.

On the left, persulfate-ultraviolet oxidation. On the right, SteriPEN technology. SteriPEN image found here.

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Ozonation

Most sources on the internet state that ozonation water treatment dates back to the 1800s. The truth is that ozonation could only take place once electricity was discovered, so ozonation as a water treatment method wasn’t studied until the 1840s. The most basic ozonation system includes a transformer, circuit, and water. Take caution if you purchase or own such devices as ozone causes lung damage, and beware that water and electricity are a deadly combination.

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The inside of an ozone generator. Photo from CureZone.

 

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Salt Water to Water

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Graphic from Lumen Learning.

This isn’t my most favorite method of purifying water, but it works. People complain that this method uses too much energy to be efficient, but in places like California where there is never-ending drought but a continuous supply of salt water, DIY desalination might start to become more commonplace. To paraphrase the method from WikiHow, I rewrote the steps to making your own water from salt water:

  1. Pour your salt water into a bowl.
  2. Place a cup in the bowl.
  3. Thoroughly cover the bowl with plastic wrap.
  4. Place the setup in a sunny spot.

This method takes an estimated three to four hours to produce about a quarter of a liter of water. Here is a video of the DIY salt water purifier in action.