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.
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.