How Does a UV System Purify Water?

Ultraviolet (UV) light has a wide variety of uses, but how can it help give your home cleaner water?

You’ve likely heard of UV rays from the sun. Those rays can be beneficial, helping your body create vitamin D, or they can be harmful, causing skin damage like sunburn.

Ultraviolet light is also present in lamps used in tanning beds, to sterilize medical equipment, and it’s inside black lights at nightclubs, roller rinks, and cosmic bowling.

However, one of the most beneficial uses of UV light is water purification.

Here’s how that works …

How UV Systems Disinfect Water

A UV water treatment system includes four main parts: the ultraviolet lamp, a high-quality quartz sleeve surrounding the lamp, a stainless steel chamber, and a system controller.

There’s a lot of complex science behind the process of UV water purification, but the idea is quite simple.

Water runs through the steel chamber where it is exposed to the UV light, which deactivates bacteria and waterborne pathogens. Then the water is safe to consume.

A specific dose UV light disables bacteria and viruses by attacking and disrupting their DNA.

Once a microorganism’s DNA is damaged, it can no longer function or reproduce, which means it can no longer cause an infection or harm.

Pathogens in water require different intensities of UV light in order to inactivate the DNA. Plus, the flow rate of water also has an effect as it determines the length of time microorganisms are exposed to the light.

There is an accepted standard for UV light application, and most manufacturers have various systems providing different doses depending on what is required.

The Benefits of a UV System for Water Purification

UV light treatment offers some impressive advantages for homeowners who choose to invest in this type of water treatment.

For one thing, UV purification is a physical process, not chemical, which means it doesn’t involve the use of chemical disinfectants such as chlorine. There are also some microorganisms that are chlorine-resistant, yet UV treatment is able to take them out.

Because these systems are chemical-free, they’re better for the environment. UV systems, such as those from Ultra Tec, are also energy efficient. A typical Viqua UV system uses the same amount of power as a 40 watt lightbulb.

Maintenance of your UV system is fairly easy, but some homeowners do choose to have a water treatment professional help them out when it’s time to replace the lamp or clean the quartz sleeve.

To ensure you’ll always have microbe-free water, UV system control units will alert you when the lamp needs to be changed.

How Water Softeners and UV Systems Work Together

Water-Right and Viqua make an excellent team as our products work together to give you the highest-quality water possible.

You see, sometimes pre-filtration is needed in order to get the most out of a UV system.

UV light does not remove hardness or other dissolved solids. In fact, suspended particles in water may actually protect some microorganisms from the ultraviolet light.

The turbidity or cloudiness of your water can also hamper UV effectiveness because light cannot travel through hazy water as easily. Instead, suspended particles absorb and diffuse the light.

The Viqua Home Plus series does offer some pre-filtration with a sediment and carbon filter. These filters will improve the water’s odor and taste, but can’t reduce hardness.

What is UV and How Does it Work?

Ultraviolet light is one energy region of the electromagnetic spectrum, which lies between the x-ray region and the visible region. Wavelenghts of visible light range between 400 and 700 nanometers (nm). UV itself lies in the ranges of 200 nm to 390 nm. Optimal UV germicidal action occurs at 254 nm.

Since natural germicidal UV light from the sun is screened out by the earth's atmosphere, we must look to alternative means of producing UV light. This is accomplished through the conversion of electrical energy in a low-pressure mercury vapor "hard glass" quartz lamp. Electrons flow through the ionized mercury vapor between the electrodes of the lamp, which then creates UV light.

Advantages of UV Sterilization

Here are some of the advantages of using UV and microfiltration over other water treatment technologies:

• Environmentally friendly, no dangerous or toxic chemicals to handle, no problem of overdosing (it's impossible), no need for specialized storage equipment, no WHMIS requirements.
• Low initial capital cost as well as reduced operating expenses when compared with similar technologies such as ozone, chlorine, etc.
• Immediate treatment process, no need for holding tanks, long retention times, etc.
• Extremely economical, hundreds of gallons may be treated for each penny of operating cost.
• No chemicals are added to the water supply - no chlorinated by-products are generated (i.e. chlorine + organics = trihalomethanes).
• No change in taste, odor, pH or conductivity or the general chemistry of the water, essential minerals and trace elements remain in the water.
• Automatic operation without special attention or measurement, operator friendly.
• Simplicity and ease of maintenance, periodic cleaning (if applicable) and annual lamp replacement, no moving parts to wear out.
• Easy installation, only two water connections and a power connection.
• Compatible with all other water processes (i.e. RO, ultrafiltration, ion exchange, etc.)

Installation and Maintenance Guidelines

Once the application has been determined, you should find a location that offers easy access for service. You will need to have access to the pre-filters, to the UV chamber for annual lamp changes and regular maintenance on the quartz sleeve. You will want to locate near an electrical outlet. Note: Using a UV system and a pump on the same electrical line may cause problems and shorten the life of the UV lamp and ballast. A surge protector with a rating of at least 3600 Joules should be installed to protect the electronic ballast from damage due to power spikes or lightning strikes. UV units are installed on the cold water line before any branch lines and should be the last point of treatment. Clearance for lamp change has to be considered during installation. All points of the distribution system after the sterilizer must be chemically "shocked" to ensure that the system is free from any downstream microbial contamination. Lamp changes should be done at least once every year. Filter changes are done according to the condition of the feed water. If there is residue left, you may need to use a non-abrasive cleaner that does not scratch the surface and is formulated to remove iron and scale buildup. Do not leave fingerprints on the glass! It is imperative to follow the manufacturers guidelines on feed water quality and operational procedures.

UV Applications

One of the most common uses of ultraviolet sterilization is the disinfection of domestic water supplies due to contaminated wells or surface water sources. Coupled with appropriate pre-treatment equipment, UV provides an economical, efficient and user-friendly means of producing safe potable water.