“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.
It was the very last day of my internship. My shimmering new scientific poster which shone in all its glorious colors had attracted absolutely no visitors, but was beautiful nonetheless. It was then that my mentor Dr. Charles Driscoll asked if I had any questions about my summer research. Guess what I asked: How does the persulfate-ultraviolet oxidation method work? To which he answered simply: It breaks down the bonds between the carbon based molecules and measures the concentration of the dissolved organic carbon. Dr. Driscoll went on to explain that ultraviolet is so good at breaking down molecules that he installed it at his own house to clean incoming water. Genius!
After a little behind the scenes research I found the SteriPEN technology which was created for hikers who like to clean their own water. Portable UV water purifiers like this one cost around 45 dollars. The SteriPEN is very handy because once you press the ON button, the LED stays on long enough to disinfect the water. Once the light goes off, it is safe to remove the lamp. According to the SafariQuip website, “In clear water the SteriPEN will destroy over 99.9999% of bacteria, 99.99% of viruses and 99.9% of protozoa”. If you are still unsure, the Water Research Center claims that Class A UV treatment will “inactivate and/or remove microorganisms, including bacteria, viruses, Cryptosporidium oocyst and Giardia cysts”. Removing these kinds of harmful bacteria and viruses is standard when it comes to any reliable water treatment method. UV treatment is not intended to purify raw sewage, wastewater, or turbid water. However, if you have evidently dirty streamwater there is a filter attachment that you can use on the SteriPEN bottle. Larger UV systems like my professor’s perform the same task but produce more water and can be upwards of 500 dollars. Do you know of anyone who uses UV to clean their water? Let me know if you liked this article! I hope to cover more about treatment with light later on 🙂 From, Jess
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