Most people are familiar with the term “Ultraviolet (UV)”. Do you know what it is? I looked it up, and this is what I got:
“Ultraviolet (UV) light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than soft X-rays. It is so named because the spectrum consists of electromagnetic waves with frequencies higher than those that humans identify as the color violet (purple).”
Did you understand that? (Me too!!) Let’s just say it’s electromagnetic radiation, and to put it more simply, UV light as found in nature is part of the radiation received by the Earth from the Sun. By choosing to live in such a sunny place, most of us have experienced the effects of solar UV through sunburn or maybe even skin cancer.
Although the UV spectrum has many other effects, including both beneficial and damaging changes to human health, we are interested in manmade UV and its relationship with water purification. We are going to look at what UV can do for us, what its limitations are, and what maintenance is required.
There are lots of UV systems installed in Mexico. We see that UV on the label, and we immediately think “purified drinking water.” Let’s take a good look at what you’re getting when you purchase a UV unit.
A typical UV unit consists of a UV lamp housed inside a quartz lens. Water passing through the unit is exposed to the invisible radiation created by the UV lamp, and in order to disinfect microorganisms, the radiation must strike the cell. The UV energy penetrates the outer cell membrane, passes through the cell body, and disrupts its DNA, preventing reproduction. This is pretty straightforward, but keep in mind that UV does not alter the water chemically; nothing is being added except UV radiation. Also, keep in mind that these sterilized (not dead) microorganisms are not removed from the water, and UV disinfection does not remove organics, inorganics, or particles in the water.
The UV dose applied to the water determines the degree of deactivation. Common microorganisms have different dosage requirements, so it makes good sense to know what’s in your water, so that you know which unit to purchase. Keep in mind that UV does NOT effectively disinfect some organisms (most molds, protozoa, and cysts of Giardia and Cryptosporidium) since they require a higher dosage. There are alternative systems such as filtration and ozone that can remove most everything, so be sure to consider them before you make a purchase.
With proper maintenance, it is possible to achieve a 99.9% reduction in bacteria, but be careful with the “proper” part. Lamps need to be changed every year, the quartz lens needs to be kept clean. UV dosage needs to be monitored, and performance needs to be checked with a lab report. In fact, most manufacturers require that a water-softening device be installed before the UV unit if the hardness is above 7 grains (We have tested hardness as high as 30 grains in Los Cabos) to keep the lens clean of calcium. Check your Owner’s Manual!
There is always the concern of contaminants in your water which can reduce the transmission of UV light, which reduces the UV dose that reaches the bacteria. The one that we should be most concerned about is turbidity, which are suspended particles that shield bacteria from the UV light and allow them to pass through unaffected. This is why UV disinfection is most effective for treating high clarity water, like reverse osmosis or distilled water.
Be sure to size your UV unit properly by counting the total faucets in your home. The maximum flow rate of your UV system must be sufficient for your home. If you exceed the GPM of your unit, the water will flow through without enough UV exposure to do its job. This is a good time to contact H2O Baja.
One last word about UV; the disinfection takes place inside the quartz lens. Once your water leaves the chamber, there is no more disinfection taking place downstream. (Ozone, for example, disinfects all the way into your glass) If just one bacterium gets through, it can adhere inside a pipe on its way to your faucet and begin to multiply, forming biofilm. What do bacteria eat? Well, bacteria cells are not removed by a UV unit but are converted into pyrogens. Pyrogens are bacterial remains or decaying products of the bacterial cell walls, which produce a rise in body temperature. Bacteria thrive on pyrogens.
A UV disinfection unit is one tool that can be used to fight bacteria if it is maintained and operated properly, but it is not a magic bullet that can be installed, forgotten, and expected to keep your water bacteria-free. Unfortunately, maintenance is a lost art down here, and I see many units that are rusted out and no longer functioning. Be sure to consult with an expert before making your next purchase on a water system.
H2O Baja Water Products