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What is Ultraviolet Water Purification and How Does It Work?

Ultraviolet water purification is a technology that uses the UV light of wavelength 253.7 nanometers to destroy the DNA of microorganisms, thus leaving them unable to multiply and grow. UV water purification is the most effective method for removing microbiological contaminants as no bacteria, virus, algae, or mold can survive if exposed to the correct dose of UV light.
Ultraviolet water purification works by the UV rays penetrating the pathogens’ cell walls and destroying them by attacking their genetic core (DNA), thus inactivating them.
Considering the wide range of applications of UV technology, it is safe to assume that ultraviolet purification is a simple, efficient, and environmentally safe method of disinfecting water. UV systems kill harmful bacteria such as E. coli, giardia, or cryptosporidium without adding chemicals to the water.

The advantages of using an Ultraviolet water purification system are numerous, the most important being:

  • UV rays kill 99,99% of microorganisms
  • UV systems do not use harmful chemicals; therefore, overdosing is not an issue
  • The water’s chemical composition remains the same, so no changes in taste and odor are noticed
  • UV purification systems have low power consumption and represent a cost-effective method of water disinfection
  • Maintenance of UV water purification systems is simple and easy to carry out.

UV water purification systems represent a cost-effective solution for disinfecting water. The market is flooded with offers, the cheapest UV purification systems being available for $100. However, the quality of a UV water purification system highly depends on the price, so spending a few hundred dollars for such a system is better than settling for cheap versions.
Some of the best UV purification systems are Aquafine, American Ultraviolet, or Atlantic UV. The products offered by these companies represent sustainable water purification solutions that comply with the official international regulations.
The UV water purifying lamps have an average lifespan of 5,000 to 9,000 hours. During this time, the UV lamp operates at the optimum level for destroying microorganisms. It is recommended to change the UV lamp every year because the UV radiation decreases over time, although the lamp still emits light.
Another component of the UV water purifying system that requires periodic replacement is the quartz glass sleeve that encloses the lamp. Changing the sleeve every 24 – 36 months will ensure the UV water purifier functions properly.
The materials used in building the UV water purifiers should be high quality. For example, the best water chambers (the component that hosts the UV lamp and the sleeve (and controls the flow rate) are usually made from stainless steel. However, some manufacturers use different materials like aluminum or high-density polyethylene. Most experts recommend buying UV water purification systems that have a reactor chamber made of stainless steel.

How Does an Ultraviolet Water Purification System Work?

ultraviolet water purification systems

An Ultraviolet water purification system purifies water by eliminating harmful microorganisms with the help of a UV lamp.
The UV water disinfection technology uses UV light (wavelength of 240-280 nm) that penetrates the microorganisms and destroys their DNA. By absorbing the UV-C radiation, the internal chemical bonds are altered. This way, the bacteria, protozoa, fungi, and many other species are unable to reproduce.
A UV water purifier includes a chamber that encloses the whole system. This glass quartz sleeve holds the UV lamp, which runs on mercury vapors. These vapors are loaded into the lamp in the form of beads later vaporized to fuel the lamp. The glass quartz sleeve protects the lamp from water as it is well known that water and electricity mixture poses a life safety hazard.
Although the UV water purification systems are efficient against 99,99% of viruses, bacteria, or protozoa, some species are resistant to this UV light due to their thick cell walls. The UV water disinfection systems must be specifically designed to target these species (Cryptosporidium, Giardia).

Does Ultraviolet Light Purify Water?

Yes, Ultraviolet light purifies water by preventing the microorganisms from reproducing and multiplying. However, UV water purifiers only remove the microorganisms. The other water contaminants, such as heavy metals, iron, manganese, and many more, require a different filtration system.

Do UV Water Purifiers Kill Viruses and Bacteria?

Yes, UV light is very efficient in killing viruses and bacteria by preventing them from reproducing and multiplying. The UV-C radiation destroys the internal chemical bonds at the microorganisms’ DNA.
A portable low-pressure mercury arc lamp, known as a UV Waterworks purifier, was invented in 1993 by the Indian scientist Ashok Gadgil. His invention helped millions of people from developing countries and not only. However, the UV purification principles are much older.
The first mention of the UV light capability to sterilize bacteria is from 1878 and can be found in a paper published by Arthur Downes and Thomas P. Blunt. Using UV light for purifying water dates back to 1910 in the French town Marseille, where a prototype plant functioned for a short period.

How Long Does it Take UV Light to Kill Bacteria or Viruses in Water?

According to the UV water purification systems manufacturers, in specific conditions such as UV doses and exposure time, killing bacteria, viruses, algae, and mold in the water takes several seconds. Common bacteria will be killed within 10 seconds at a distance of 6 inches from the UV lamp. However, this time frame depends on a series of factors, including the microorganisms’ cell walls thickness and water quality.
The UV water purifying system effectiveness depends on a series of parameters, the most important being the exposure time and the lamp intensity. General water quality parameters are also important.
The minimum recommended exposure time for UV disinfection systems is 16,000 µwatt-sec/cm^2 to kill the microorganisms. Most UV lamps produced by different manufacturers offer an intensity of 30,000 – 50,000 µwatt-sec/cm^2. Some bacteria are destroyed at 7,000 µwatt-sec/cm^2 (coliform bacteria), so a lamp intensity of 30,000 µwatt-sec/cm^2 will do just fine.
It is important to keep in mind that UV lamp intensity decreases over time, so it is essential to replace the lamp after a while.
The estimated irradiation time to inactivate microorganisms at a dosage of 30,000 µwatt-sec/cm^2 of UV 254 nm differs from one species to another. For example, most bacteria are destroyed within 0.15 up to 1.23 seconds. Viruses will no longer reproduce within 0.08 to 16 seconds, while mold spores will require up to 8 seconds to become inactive.

Do UV Water Filtration Systems Kill All Microorganisms in Water?

The general scientific opinion is that the UV water filtration system kills all microorganisms in water. However, some voices state the UV light only puts the microorganisms in a dormant state and will reactivate as soon as the conditions get better for them to thrive.
Another factor that might affect the UV system’s effectiveness is the dissolved organic matter that will shield microorganisms from UV radiation. Some bacteria and microbes can repair the UV-induced damage and restore infectivity.
To avoid the issues mentioned above, the UV water purifying system must deliver a sufficient UV dose to induce a greater level of DNA damage. This way, the UV disinfection system will overcome the DNA repair mechanisms.

What are the Advantages of Using UV Water Purification?

benefits of uv water purificationUltraviolet water purifiers have many advantages hard to ignore when it comes to safety. The most important benefits of Ultraviolet water purification systems are:

  1. Efficient: According to scientific data, UV water purification destroys up to 99,99% of harmful microorganisms. This method is far more effective than chlorine against viruses, and it works great against some resistant bacteria such as Giardia or Cryptosporidium.
  2. Eco-friendly: UV water purification is a green alternative to traditional chemical disinfection methods. Sterilizing water by this method does not produce disinfection byproducts, and, also, there is no risk of overdosing.
  3. Water keeps its properties: Ultraviolet disinfection does not change the water’s taste and odor. For example, the chlorine chemical disinfection gives a specific taste and smell to the water that might be unpleasant for some. The UV light does not change the water’s chemical composition, so the sterilized product is tasteless and odor-free.
  4. Cost-effective: Purifying water with UV light is a very cost-effective method. Setting up such a disinfection system is far cheaper than chlorine or ozone methods. The operating costs are also low, so this is a budget-friendly method to purify hundreds of gallons of water.
  5. Fast: Water purification happens almost instantly.
  6. Easy to maintain: The UV water disinfection systems are very easy to install and maintain. All that is required is a periodic cleaning and an annual replacement of the UV lamp.

What are the Disadvantages of Using UV Water Purification?

The disadvantages of Ultraviolet water purification are as follows:

  1. Works only in clearwater: One of the limitations of UV light water disinfection is the fact that this method does not work well for murky waters. Dirt and debris prevent UV light from penetrating the water, thus reaching the microorganisms’ cell walls. The UV systems do their job only in clear waters.
  2. Heats the water: The water sitting beneath the UV lamp might get warm if not used for a while. If cool water is needed, the faucet must be run to pass down the drain of the warm water.
  3. Power outages: UV water disinfection systems require electricity to function. In case of power outages, the UV lamp is useless.

What are the Limitations in UV Water Purification Systems?

Despite the numerous advantages of using UV water purification systems, there are some limitations of UV disinfection, as well:

  1. Do not remove inorganic pollutants: The UV water purifying systems are effective against living microorganisms but do not remove other pollutants such as heavy metals, chemicals, salts, and many more. A traditional filtering system is required along with the UV light water treatment like granular activated carbon filters or kinetic degradation fluxion processes (efficient in removing lead, iron, mercury, or chlorine).
  2. No storage tank: UV water purification systems do not have the option to install a storage tank.
  3. No UV light shut off: Since UV light is invisible, it is almost impossible to see if the UV lamp stopped working. People might end up consuming impure water.

How Many Volts Does a UV Water Purifier Consume?

Typically, a UV water purifier uses around 158.4 kWh/million gallons of treated water if it works continuously. To put it simply, these systems consume as much as a 40-watt bulb.
The capacity or the flow rate of a UV water purifier is measured in gallons per minute (GPM), and it ranges from 0,5 GPM to several hundred GPM. This flow rate helps people choose the best UV purifying system for their homes.
The power consumption of a water purifier generally depends on the flow rate. For a standard apartment or house, a 10 GPM UV water purification system will do just fine. The power consumption for such a system is usually about 55-watt, 120 Volts.

Who Has Invented the Ultraviolet Water Purifier?

Discovered in 1801, UV light has been used for sterilization nearly a century later. The first scientist who used UV rays to treat infections was Niels Ryberg Finsen.
Born on the 15th of December 1860, Finsen studied Medicine at the University of Copenhagen in Denmark. After becoming a prosector of anatomy at the same university, Finsen dedicated his time to scientific work, focusing on the effects of sunlight on the organism. Soon he discovered and proved that most refractive rays from the sun or an electric arc have a stimulating impact on damaged tissues.
His research focused mainly on smallpox, lupus, and skin tuberculosis effects. He developed a method of treating lupus vulgaris, tuberculosis, and other skin diseases. The therapy benefits are due to the bactericidal and stimulating effect of sun rays on the affected tissues.
Due to his hard work and unique discoveries, Finsen was granted the Nobel prize in 1903. By that time, the Danish scientist was in a wheelchair due to the Pick disease he had suffered.
Niels Ryberg Finsen died on the 24th of September 1904, but his researches and discoveries made a significant difference.
The first UV water purifying system was used in Marseille, France, in 1910. Later on, the same principles were applied in Kentucky, the first UV water disinfection application in the United States.
UV lamps became commercially available in 1930, and they keep gaining more and more followers ever since.

What are the Parts of Ultraviolet Water Purifiers?

Each UV water purifier system has four main components:

  1. Reactor Chamber: this component encloses the UV lamp and the quartz sleeve. The reactor chamber is also the component that controls the water flow. Commonly, the reactor chambers are made from stainless steel, but other materials can be used (plastic, for example).
  2. UV Lamp: the UV lamp is the core of the purifying system because it produces UV-C radiation. Each UV lamp contains a bead of mercury and filaments. These filaments heat the mercury and cause it to evaporate into the space inside the lamp. The mercury vapors produce electrical arcs that create the UV light responsible for water disinfection.
  3. Quartz Sleeve: This long cylinder-shaped tube is made of quartz glass, and its role is to protect the UV lamp from touching the water. Water contaminants may cloud the quartz sleeve, so cleaning it every time the lamp is changed is mandatory for the system’s proper functioning.
  4. Controller Unit: controllers represent the brain of the water purifying system and may vary in complexity. Some might have low-UV alarms, motion sensors, malfunction indicator lights, etc.

The primary purpose of this unit is to control the electrical output of the lamp and the power produced by it.

Is UV Water Safe to Drink?

Yes. According to numerous departments of health and water research centers all over the world, UV water purifying systems are more than safe and eco-friendly. The UV water purification technology destroys 99,99% of microorganisms in water, thus making it fit for drinking.

How Much Does a UV Water Purification System Cost?

Typically, a UV water purification system price ranges between $200 and $1,000. The labor adds between $300 and $500 to the final bill to the system’s cost.
Top-notch UV water purification systems are made of 304 stainless steel, the same material used in the food industry and medical sector. Another aspect that adds to the final price tag of UV water purification systems is the inclusion of different features such as lamp age displays and alarms, increased safety measures, or error codes displays. The price is also affected by the system’s capacity and the lifespan of the UV lamp.
Even though UV water disinfection technology is used for more than 100 years, it is still considered a new method. However, considering the increased attention to environmental issues, increased demand for such systems is expected. Subsequently, the price of a UV water purification system might go down.

What is the Best UV Water Purification System?

When choosing the best UV water purifier for your home, some factors are very important to keep in mind. Apart from the house size, flow rate, pressure range, and brand name play an important role also.
The undisputed leader of the clean water industry is Pentair, a brand that produces sustainable water purifying solutions for both industrial and residential areas. Pentair’s best UV water purifier is Pelican PC-600, a long-lasting system that requires very low maintenance. This system comes in two versions, for 1-3 bathrooms and 4-6 bathrooms. Speaking of the price tag, the Pelican system is affordable ($1,530 / $1,992).
Another highly performant UV water disinfectant system is Aquasana Well Water Rhino, a product that includes a pre-sediment filter to remove larger particles. The price is around $1,250, which is more than affordable.
Similar to Pentair and Aquasana, HQUA is another reputed manufacturer that gained the trust of many satisfied customers. HQUA-OWS-124 UV water purifier is HQUA’s top product, a system known for its build quality and high performance. The system’s 55-watt UV lamp purifies 12 gallons of water per minute, and its price ranges somewhere near $100.
As seen above, UV water purifying systems are available at different price ranges, but it’s important to keep in mind that brand and quality are interlinked.

How to Choose the Right UV Unit Size?

Finding the perfect system for a residence might be a daunting task. UV water purifying systems come in a wide range of sizes. There are portable units but also large whole-home systems. Which one is the right one?
Before purchasing such a system, some factors need to be kept in mind.

  1. House’s size: Bigger homes require a higher GPM system so that the purified water is efficiently delivered. Small houses, apartments, or condos will require 10 GPM systems. For bigger homes with more than a bathroom, the ideal UV purifying system has at least a 15 GPM flow rate.
  2. Color of the water: A yellow tint color in the water signals the presence of the iron surface sediments. In such cases, the UV rays might face issues penetrating the water, so a bigger UV purifying system is needed.
  3. Plumbing size: Most UV purifying systems are designed to connect to the home plumbing. Before making the purchase, the homeowners should check the system’s fittings. An incompatible system will affect the water’s flow rate.

What is the Best Unit Size for an Ultraviolet Water Purification System?

The UV water purification system size depends on the flow rate. The bigger the flow rate, the bigger the system needs to be.

A whole-home UV water purification system can be chosen following the below guidelines:

  • 1 bathroom – 6 gallons per minute flow rate
  • 2 bathrooms – 9 gallons per minute flow rate
  • 3 bathrooms – 12 gallons per minute flow rate
  • 4 bathrooms – 15 gallons per minute flow rate
  • 5 bathrooms – 18 gallons per minute flow rate

In case of doubt, it is always better to size up the UV purifying system rather than undersize it. A system that cannot handle a specific water flow rate will not efficiently sterilize the water.

Where Can Ultraviolet Water Purification Be Used?

A UV purifier has a wide range of applications. It can be used anywhere and anytime. Some common areas where UV disinfection is used are:

  • At-home municipal water: Although the local area’s water is treated to remove harmful microorganisms, there is no guarantee that water is completely sterile. A whole-home UV system installed at the water’s entry point into the house will surely remove bacteria and any doubt.
  • While traveling: Portable UV water purification systems were specifically designed for those who travel or go camping so they could enjoy sterilized water during their trips. These units are battery powered so they can be used anywhere.
  • Purifying well water: Although the well water is cool and tasty, it still needs to be treated to remove bacteria and microorganisms. A whole-home UV water purification system is perfect for this job.

Can Ultraviolet Water Purification Be Used for Travel?

Yes, a portable handheld UV purification system is ideal for those who go camping and not only. These types of systems work with a wide range of recipients and provide clean water fast. They require only a set of batteries, and no elements to clean or replace are needed. However, they do not work well in murky waters.

Can Ultraviolet Water Purification be Used for Well Water?

Yes, UV water purification whole-home systems are perfect for disinfecting the water from wells. However, it is recommended to use a water filter before treating the water with UV light. Microorganisms might hide behind loose particles that exist in well water.

Why Do Ultraviolet Water Purification Systems Have Low Maintenance Cost?

The main reasons for which water purifier maintenance involves low costs are:

  • Designed for ease of use: The UV water purification systems are specifically designed to be easy to use and maintained. Their UV lamps require replacement after a year or 9,000 hours because it diminishes, thus reducing its effectiveness. A replacement UV lamp price ranges between $10 to $60, depending on the producing brand.
  • Easy to maintain: It is important to clean the quartz glass sleeve periodically (every couple of months or so). The iron hardness existing in the water might cloud the lamp, thus reducing its efficiency. All the maintenance work previously mentioned does not imply high costs. Cleaning the quartz glass sleeve does not cost a thing, and it takes only a couple of minutes.

Does a UV Water Purification System Need Periodic Maintenance?

Yes, UV water purification systems require periodic maintenance. The system’s UV lamp diminishes after a certain amount of time, usually 12 months or 9,000 hours. Also, the quartz glass sleeve might be clouded by water’s different particles, such as iron hardness. The average maintenance cost ranges around $100 per year, provided the sleeve is also replaced.

Do Ultraviolet Water Purification Systems Have Any Health Harm?
According to some scientists, UV water purification systems do not entirely disinfect water. For example, exposing some microorganisms to UV light might cause mutations. These mutations might initiate a further replication of the bacteria, and the new microorganisms might be even more resistant than their ancestors.
It is well-known that a UV water purifier modifies the microorganisms’ DNA structure but does not remove the inactivated bodies from the water. These remains might stay in a state of inactivity until proper life conditions activate them. They will start to replicate again; thus, the water becomes unfit for drinking.

What are the Other Similar Water Purification and Filtration Systems for Ultraviolet Water Purification Systems?

Choosing the best water purification system depends on many factors, the most important being the water quality in a specific area. Depending on the water source and the city’s water infrastructure, different filtration systems might be required.
These water purification systems are different. Some just remove a specific type of toxins, while others clear a wide range of impurities.

The most common types of water filtration systems are:

  1. Activated Carbon: Activated Carbon filtration media can be found in almost every whole-home water filtration system and not only. It is highly efficient in removing organic and inorganic contaminants and also mitigates the taste and odor left by the water’s chlorine treatments. An activated carbon filter contains treated char (created with high carbon content organic material such as coal, wood, or coconut shells). The char is turned into a porous material that holds toxins and impurities.
  2. Catalytic Carbon: Like the activated carbon filter, the catalytic carbon filter is used to remove chloramine from drinking water. The main difference is that if the activated carbon filter removes only a small percentage of chloramine, the catalytic carbon system removes most of the substance.
  3. Kinetic Degradation Fluxion (KDF): KDF water filter is a cheap alternative to the activated carbon filters. Although it does not remove the chloramine as efficiently as the other filter, it works better at higher temperatures and lasts longer. Made out of copper and zinc particles, the KDF reduces the levels of heavy metals and removes some bacteria and algae in the water. The best setup for a residence is to use the KDF upstream of a carbon filter because the KDF extends the carbon life while this one removes chloramine.
  4. Reverse Osmosis Membrane: Reverse osmosis water purifier works by pushing water through a semipermeable membrane that traps heavy metals, organics, and other impurities. Reverse osmosis membranes became quite popular during the last years.
  5. Activated Aluminium: The activated aluminum filters are part of the ion exchange units and work perfectly in removing magnesium and calcium, two metals responsible for water hardness. Depending on the type of activated aluminum, these filters can also remove fluoride, arsenic, radium, or barium.
  6. Manganese Dioxide: The manganese dioxide filters are ideal for reducing iron, manganese, and hydrogen sulfide in water.

Does Ultraviolet Water Purification Affect Hardness of Water?

No, Ultraviolet water purification does not affect the hardness of water; in fact, it is the other way around. UV water purification is used for removing harmful microorganisms from water. These systems cannot soften hard water. Moreover, the hardness of water might affect the UV water purifier efficiency.
Hard water usually stains the quartz glass sleeve, thus reducing the UV lamp efficiency. For better functioning of the UV purification system, the water hardness should not be higher than 7 GPG (grains per gallon). This can be achieved by placing other filters upstream and using water softeners.

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