Germicidal UV In Pools
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There are actually quite a few different ways you can chemically maintain swimming pool water using different chemical processes. One of the most effective of these potential options is combining the use of chlorine along with the installation of a germicidal UV light. These two work very well in combination with each other resulting in higher quality water than either could give you alone while also reducing on the total amount of chemical sanitizer that you need to use to maintain your pool water.
This particular pairing of chlorine and UV is uniquely useful for pools in that chlorine is the industry standard for keeping pool water safe, but the germicidal UV supplements the chlorine in all of the ways in which chlorine is arguably not that great at doing it's job. Germicidal UV is reliable, stable technology that does not cost too much when compared to other supplemental disinfectant options like AOP. It is easy to install and compatible with all types of swimming pools making it almost universally a good choice for pool owners. Let's look a little deeper into what germicidal UV will do for your pool water.
What does UV do in pools? - Germicidal ultraviolet light has emerged as a pivotal technology for improving pool water quality, particularly in the context of advanced disinfection strategies. Its effectiveness lies in its ability to disrupt the molecular bonds within the DNA of microorganisms, rendering them incapable of reproduction and thereby neutralizing their pathogenic potential. For a reader well-versed in this domain, it is important to delve into the mechanistic aspects of how germicidal UV impacts water quality, focusing on its interaction with spent chlorine, bacteria, and organic contaminants.
What does germicidal UV do? - Germicidal UV primarily operates in the UVC range (200-280 nm), with the peak germicidal effectiveness around 265 nm. UVC radiation penetrates the cell walls of microorganisms and is absorbed by the nucleic acids. This absorption leads to the formation of thymine or other pyrimidine dimers in DNA and uracil dimers in RNA, which are molecular linkages that distort the DNA helix and inhibit replication. This photochemical reaction is known as dimerization, which effectively 'inactivates' the microorganisms, including bacteria, viruses, and protozoa, making them harmless. In short, germicidal UV kills bacteria and organic debris, but technically speaking "kill" is not the right terminology and more accurately it is deactivating bacteria and parasites.
How UV allows for less chlorine use - One of the compelling aspects of UV treatment in pools is its ability to manage combined chlorine compounds, commonly known as chloramines. Chloramines, particularly trichloramine (NCl3), are formed when free chlorine reacts with nitrogenous organic matter such as sweat, urine, and body oils present in pool water. These compounds are responsible for the characteristic "chlorine smell" in pools and are associated with eye and skin irritation as well as respiratory issues. Germicidal UV systems are effective in breaking down these chloramines. The high-energy photons of UV light break the nitrogen-chlorine bonds in chloramines, leading to their decomposition. This process not only reduces the concentration of irritant compounds but also frees up chlorine to be available as a disinfectant, enhancing the overall sanitization efficiency. Every pool is unique but you might expect to see 30% to 60% less chlorine use with the addition of a germicidal UV system.
How does germicidal UV work? - The germicidal effectiveness of UV against bacteria and other pathogens is well-documented. UV radiation can inactivate a broad spectrum of microorganisms, including chlorine-resistant species such as Cryptosporidium and Giardia. The inactivation process, as previously discussed, involves the absorption of UV light by nucleic acids and the subsequent formation of pyrimidine dimers, which prevent replication. It's important to note that the effectiveness of UV disinfection depends on the dose of UV radiation delivered to the microorganism, which is a function of UV intensity and exposure time. This also means that water turbidity can impact how effective your UV system is.
Benefits of UV on other impurities - Germicidal UV also plays a role in the reduction of organic contaminants in pool water. These organic compounds, introduced into pools through various means such as body oils, sweat, cosmetics, and environmental debris, serve as substrates for microbial growth and can impact water clarity and quality. UV irradiation can lead to the breakdown of these complex organic molecules into simpler, more manageable forms. This process, known as photolysis, occurs when UV light energy breaks the chemical bonds in the organic molecules. While UV alone may not completely mineralize these organics, it can significantly reduce their concentration and, in turn, the load on the pool's filtration and disinfection systems.
Limitations of pool UV systems - In addition to reduced effectiveness due to water clarity mentioned above, a critical shortcoming of UV is that UV treatment does not provide a residual disinfectant effect in the pool, unlike chlorine. Hence, a combination of UV and chlorine treatment is often used to ensure continuous disinfection and maintain water quality and considered by many (myself included) to be one of the best water care methods for pools.
There may be better and stronger options like AOP systems (advanced oxidation process) however these are generally quite a bit more money than a germicidal UV system. A lesser costly option would be chlorine as a stand alone solution for water care and sanitizing. However, mixing the chlorine and germicidal UV together is superior to chlorine alone, and yet substantially less costly and technically complicated than AOP systems can be. Germicidal UV is a fantastic "bolt on" device that you can add to almost any pool and experience less chemical usage while having higher quality, safer pool water.
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Swimming Pool Steve is an award winning, second generation swimming pool specialist from Ontario Canada and one of the most trusted voices in the swimming pool industry. With over 20,000,000 views on the Swimming Pool Steve YouTube Channel, winner of the Pleatco Pool & Spa Industry Leadership award and author of hundreds of pool and spa articles both online and in print. Steve is committed to helping pool and spa owners as well as pool and spa industry workers learn more about the technical side of building, renovating, repairing and maintaining all types of swimming pools and spas. Follow Swimming Pool Steve on Facebook, Twitter and YouTube.
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