In order to ensure that a UV system is effective as it can be, pre-treating the water is sometimes required.
What is UV pre-treatment and why is it important?
Ultraviolet disinfection is an extremely effective way to combat microbiological contamination in water. However, microbes have to be exposed to UV-C light in the proper amounts in order to effectively disinfect the water.
Water quality plays a major role in how much UV is passing through it. This is called UVT, or UV Transmission. In order for the appropriate amount of UV-C light to reach microbes to disinfect water, the UVT of the water has to be ideal. Low UVT occurs when there are organic molecules or minerals in the water that absorb or scatter the UV light, allowing microbes to pass through the UV system without ever being exposed to germicidal UV-C.
Because of these pre-treatment requirements, UV is not a stand-alone technology. Basic tap water generally comes out at 85-95% UVT.
Something as common as the chemicals used to treat public tap water can absorb or scatter UV light. Most UV systems can function at UVT values from 95%. In order to reach this UVT level in well water, water testing and pre-treatment is required to get the water to the proper quality for effective disinfection.
The ideal water quality for UV disinfection is:
Turbidity < 1NTU (Turbidity units)
Suspended Solids < 10mg/L
Colour – None
Total Iron < 0.3 mg/L
Manganese < 0.05 mg/L
Hardness <7 gpg (120 ppm)
What does all this mean?
Let’s start with turbidity. Turbidity is cloudiness or haziness in water that’s caused by particles that are generally invisible to the naked eye (such as organics, minerals, or chemicals). This will prevent the UV light from reaching microbes because these substances can absorb or scatter UV light. Turbidity is undesirable in drinking water because it can contribute to taste and smell issues, and viruses and bacteria can attach themselves to these molecules.
There are several ways to treat for turbidity, depending on the molecules that are causing it. The best way to determine turbidity is to do a water test, and to consult your water treatment professional to make recommendations based on your results.
Suspended solids are small solid particles that remain suspended in the water, which may or may not be visible to the naked eye. These particles are generally not soluble in water, scattering UV light and preventing effective disinfection. Depending on the type of suspended solids, different types of treatments will treat the water to remove these contaminants.
Colour is fairly obvious. If the water is coloured, it generally means there’s something in the water (turbidity, organic matter, suspended solids) that would prevent adequate UV transmission. Colour is generally undesirable in drinking water, and should be removed prior to water reaching the UV system to ensure effective disinfection.
Iron and Manganese are two unpleasant minerals that are often found in groundwater. These minerals are not just undesirable in drinking water and for creating adequate UVT, but they can also cause staining of appliances and fixtures, laundry staining, and the clogging of plumbing. Both of these minerals collect on the quartz sleeve and foul it, preventing UV light from penetrating the water and allowing microbes to “hitch a ride”.
There are many ways to remove these elements from your water, but the best way to deal with your specific water quality conditions is to test your water, and consult a water treatment professional to recommend treatment for your specific needs.
Hardness in water is an indicator there is a high mineral content in the water. This is very common in groundwater, because the water that percolates down from the surface through the rock dissolves these minerals as it passes through (sort of like water passing through coffee grounds), and carries them along with it. This hardness accumulates in the aquifer, and stays in the water until it’s removed. These minerals are removed through a process called water softening.
Hardness in water can reduce the amount of suds formed by soaps in water (making laundry soaps less effective), contribute to the formation of limescale on plumbing and appliances, and are a general nuisance. Although water hardness does not negatively impact human health, these other effects usually force homeowners to deal with the issue by softening the water. If you have water hardness (as indicated on a water test), talk to your water treatment professional for advice on the best way to remove it. Removing hardness is a definite necessity for UV pre-treatment, as hardness minerals will collect on the quartz sleeve of a UV system and reduce UVT.
With essentially all types of UV treatment, it’s recommended that the UV system be preceded by a 5 micron filter. UV pre-treatment will not only make your water taste and smell better, but it ensures that your UV system is working at maximum efficiency to protect you and your family 24/7.
If you have other water quality issues that need addressing, make sure to contact your local water treatment professional for recommendations on a complete water treatment solution for your specific needs.
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