Ultraviolet Light (UV) is electromagnetic radiation with a shorter wavelength than visible light. UV light is part of the sun’s light spectrum or is artificially generated. It is divided into three wavelengths: UV-A (315-400 nanometers), UV-B (290- 315 nanometers), and UV-C (220-290 nanometers). UV light is used to generate ozone and as a supplemental disinfectant to inactivate microorganisms. However, exposure to UV light increases the chance of sunburn and skin cancer. Ultraviolet (UV) light is a high-energy, low-wavelength light used to disinfect water without chemicals. However, UV doesn’t create a disinfectant residual in the water, so it must be used in combination with a disinfectant that does. UV light can’t be stored or transported and must be generated on site for pool use. UV light disinfects by killing or inactivating bacteria, viruses, and parasites like Cryptosporidium and Giardia. Unlike chemical systems, UV inactivates pathogens with high energy. When the light intensity is high enough and the exposure is long enough, UV damages the DNA of the pathogens, stopping their reproduction. The effectiveness of UV as a disinfectant depends on the amount of energy that is applied within the treatment chamber, where the UV bulb is located. The energy level is expressed as: Dose = Lamp Intensity x Exposure Time.
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What is the Electromagnetic Radiation Spectrum?
The Electromagnetic Radiation Spectrum is a range of electromagnetic waves. It ranges from 10 nm (nanometers) to 400 nm. This spectrum includes UV rays, which are classified by radiation wavelength into UV-A from 400 to 315 nm, UV-B from 315 to 280 nm, and UV-C from 280 to 220 nm. X-rays begin at 10 nm and lower. Visible light starts at 400 nm with violet, then indigo, blue, green, yellow, orange, and red. Black light is from 300 to 400 nm. Most of the germicidal properties are found in the UV-C range.
What is UV Dose Terminology?
UV dose terminology refers to the amount of UV energy required to destroy different microorganisms. This amount varies because each type of microorganism has a unique cell structure that responds differently to UV energy. The UV dose, expressed in microwatt seconds per centimeter squared (mWsec/cm2) or milliJoules per square centimeter (mJ/cm2), is the product of intensity and time. The elimination of microorganisms is determined by the duration of the water’s exposure to UV light and the intensity of the UV radiation. UV lamps typically emit most of their energy at the 254 nm wavelength.
What is UV Disinfection?
UV disinfection is a process that exposes water and organisms to a special light that kills most living organisms. This UV light absorbs into the cell components, significantly affecting proteins and nucleotides in DNA and RNA. No chemical is added to the water, and there is no overdose risk. UV light at 254 nm wavelength is effective at disrupting RNA recombination in microorganisms, thereby suppressing them from causing illness.
What is the Role of Ultraviolet Radiation in Water Disinfection?
Ultraviolet (UV) systems use UV lamps to generate radiation that disinfects water. This process typically occurs after filtration. The pool or spa water continuously flows through the UV system, where it is exposed to UV radiation. This exposure inactivates bacteria and viruses, and also oxidizes chloramines. UV disinfection exposes water and organisms to a special light that kills most living organisms. UV light absorbs into the cell components, significantly affecting proteins and nucleotides in DNA and RNA. No chemical is added to the water, and there is no overdose risk. UV light at 254 nm wavelength is effective at disrupting RNA recombination in microorganisms, preventing them from causing illness. UV light disinfects by killing or inactivating bacteria, viruses, and parasites like Cryptosporidium and Giardia. When the light intensity is high enough and the exposure is long enough, UV damages the DNA of the pathogens, stopping their reproduction. The effectiveness of UV as a disinfectant is determined by the amount of energy it emits within the treatment chamber, where the UV bulb is located. The energy level is expressed as: Dose = Lamp Intensity x Exposure Time.
What is the history and technology of UV disinfection?
The bactericidal effect of sunlight was first reported in 1877. However, only 10 percent of sunlight that reaches the earth is in the UV range. Therefore, UV disinfection is a man-made technology process. The first use of large-scale UV light for drinking water was in Marseille, France in 1906. In the U.S., the first full-scale use was in Henderson, Kentucky in 1917. The use of UV for drinking water was abandoned by the late 1930s due to start-up costs, lamp replacement, and maintenance.
How does a UV Sterilizer work?
A UV sterilizer works by subjecting organisms and chloramines that enter the chamber to intense UV rays. The organisms must be in the chamber long enough and at the right intensity to be altered by the UV rays. Each organism requires a specific UV dose for inactivation.
How to Size a UV Sterilizer?
The process of sizing a UV sterilizer involves determining the desired UV dose and specifying the flow rate. Based on these parameters, the manufacturer recommends a unit that will deliver the specified UV dose at the given flow rate.
What are the Types of UV Lamps for Pool Treatment?
The types of UV lamps for pool treatment are Low Pressure (LP) and Medium Pressure (MP). Both types use a mercury vapor lamp. LP lamps are efficient in converting electrical energy to germicidal UV light, but their total UV output is less than that of MP lamps. MP lamps have a higher intensity UV output and a broader spectrum of UV output, which kills organisms and removes inorganic chloramines.
What are Lamp Sensors in UV Sterilizers?
Lamp sensors in UV sterilizers are built-in sensors that measure the UV light delivered to the water. These sensors monitor the lamp output intensity, which decreases over time. Using this data, they calculate the UV dose that is being delivered to the water. The lifespan of these lamps typically ranges from 6 to 16 months.
How Important is Keeping the UV Bulb Clean?
Keeping the UV bulb or sleeve clean is necessary. Oils, suntan lotion, soaps, and other personal-care chemicals coat the UV bulb or sleeve. Additionally, sulfates, carbonates, and phosphates of calcium, magnesium, and manganese coat the sleeves. Even trace amounts of iron and aluminum in the water coat the bulb or sleeve, reducing the UV transmission to a lower wavelength. This is not critical for chloramine destruction but is crucial for germicidal ability. Medium pressure bulbs will degrade faster than low pressure bulbs due to higher operating temperatures.
How Important is Proper UV Dose and Chlorine Concentration?
Maintaining a proper UV dose and sufficient free available chlorine or bromine concentration is crucial. When these levels are not properly managed, any remaining bacteria in the water has the potential to form a new chlorine-resistant colony. Many bacteria reproduce quickly in pool water, potentially increasing from one bacterium to one million in four hours.
What is the process of Free Chlorine Destruction by UV?
Free chlorine is destroyed by UV at 320 to 340 nm through the following reactions: UV + 2Cl2 + H2O ‚ 4HCl + O2 UV + 2OCl ‚ 2Cl + O2 UV + 2HOCl ‚ 2HCl + O2. The effective wavelength for significant destruction of free chlorine in water is 320 to 340 nm. The photolytic half-life of chlorine in water is about 12 minutes at pH 8.0 and about 37 minutes at pH 7.0. OCl‚ photolyzes more rapidly at sunlight wavelengths than HOCl.
How Does UV Light Affect Bromine?
UV light is used for disinfection and combined chlorine removal. However, UV light has the potential to also destroy free chlorine in water. UV kills most organisms with the right light intensity and exposure time. UV light does not oxidize swimmer waste and organic contaminants. Additionally, its effectiveness is limited to a short distance, that is within a few inches from the bulb.
What are the Uses of UV Systems in Pools?
UV systems are often installed in pools to reduce chloramines and combined chlorine, decrease the amount of chlorine use, and destroy or control organisms that are resistant to EPA-approved sanitizers. UV systems in pools serve multiple purposes. They are primarily used to reduce the presence of chloramines and combined chlorine in the water. Chloramines are formed when free chlorine reacts with ammonia. This combination causes an unpleasant smell and acts as body irritant. By reducing chloramines, UV systems improve the overall quality of the pool water. Additionally, UV systems decrease the amount of chlorine used in the pool, making the water safer and more comfortable for swimmers. Another significant use of UV systems is to neutralize or control organisms that are resistant to sanitizers approved by the Environmental Protection Agency (EPA). This includes bacteria, viruses, and parasites like Cryptosporidium and Giardia. UV systems disinfect the water by using high energy to inactivate these pathogens.
