How do UVs work?

From large industries to simple household equipment, UV has been used in water treatment. But what does an ultraviolet lamp really do?

We all know that light has different spectra that are invisible to us, these range from infrared light to gamma rays. Within these spectra of light there is a range called UV which, just last century, was discovered to be for batteries what radioactivity is for us. Since it destroys the genetic information of: microorganisms, bacteria and some viruses. Then

microorganisms that are exposed to a frequency of light, with a certain intensity and in a specific time, become sterilized and in some cases even roasted. And here is a fact that we must keep in mind. UV rays from a STERILIZER, what they do is prevent bacteria and viruses from reproducing, very different from a UV biocide, whose purpose is to kill said microorganisms.

What bacteria and viruses do UV affect?

Usually it depends on the equipment, the size and the brand. But good brands usually have a visible catalog of all the microorganisms that affect their equipment. Trojan and Sterilight have them on their pages.

Interesting Fact: UV tends to work where chlorine doesn't. There are some bacteria that are immune to chlorine because they have a shell that inhibits the oxidative effect of chlorine.

UV limitations

One of the limitations of UV is that it only acts on what passes through the chamber, and if there is recontamination at the outlet, the UV no longer works. Unlike chlorine, which, being in contact with water all the time, does not have this limitation.

To exemplify this, we attended a laboratory that complained about our uv sterilizer not working. It had a valve connected to a PVC tube that led to an outlet from where he took his samples (it should be noted that the valve and the PVC tube were after the UV equipment). The valve was large and had air inlets, PVC is not recommended because it is porous, it allows bacteria to fixate there and reproduce. When taking the water samples, they presented microorganisms because both the tube and the valve were contaminated and the UV was before them.

Likewise, using UV equipment for water that is going to be stored in a water tank or dairy that is exposed to bacteria and viruses is wasteful. Other limitations of this equipment are that the bulb or ballast can be damaged, or the frequency at which the bulb radiates may be wrong, which is why we always recommend the advice of one of our engineers when installing them.

When to decide between UV and Osmosis?

They are for very different uses, UV is to sterilize and osmosis is to concentrate the solids in a reject stream and have less conductivity. The case where it is necessary to evaluate which one to use is for domestic use. But this is very simple, if the water analysis complies with NOM 127, only one UV is needed, which is also usually cheaper. If not, it is recommended to install an osmosis equipment.

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Join the discussion 9 Comments

  • DEPURAGUA says:

    IN PURIFIED WATER, HOW LONG LIFE CAN A UV LAMP LAST? WHAT MAINTENANCE IS NECESSARY TO GIVE IT AFTER ONE YEAR OF CONTINUOUS OPERATION? THANKS

    • raul perez says:

      Hello Depuragua,
      You are right, manufacturers recommend changing the bulbs or lamps after one year of operation, since the light intensity begins to decrease from this time, it could last a little longer, but without the same results. The continuous range that you mention is correct too, since connecting and disconnecting the UV equipment can damage the bulbs and lower their life time, in addition to that it can allow microorganisms to pass through during this disconnection period. Thanks for the observation and participation.

  • DEPURAGUA says:

    Thanks for your comments

  • agua polar says:

    Because the water changes flavor after packaging, after 15 days of packaging. thanks

    • Carbotecnia says:

      Hello Polar Water,
      What flavor do you perceive after 15 days?
      You would have to check by means of a water and bacteriological analysis, the taste may be the presence of inert bacteria (which have already gone through the UV and do not reproduce, but generate an odor over time).
      What bottling companies do in this case, inject ozone directly into the container and cover immediately, to leave a residual that keeps the product in good condition until consumption.

      Cheers

  • Ismael says:

    Good afternoon: A system with a UV Lamp, would it be better to place it after the water tank? And the best option would be for the lamp to remain on 24 hours a day.

    • Carbotecnia says:

      Hello Ismael, yes the most recommended is that it is after the water tank, I include the closest thing to the point of use and always keep it on, so as not to subtract hours from the life of the bulb and that it lets any microorganism pass. Regards.

  • Angela Vega says:

    Hello, I have a question….
    How long should the water to be purified be left in contact with the UV Light?

    • Carbotecnia says:

      Hi Angela,

      By design, the lamp has the inlet and outlet diameters so that the water has an adequate contact time with the light to do its job, it is not necessary to manually leave the water to remain in the chamber for a certain time. For example, if the UV is specified at 1 gallon per minute, due to the dimensions and diameters of connections, they should not let more water pass in that time. (Each manufacturer designs their equipment based on flow, radiation intensity, exposure time that is normally between 10 and 20 seconds) I hope it will be useful for you.
      Regards.

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