Method of operation

Ultraviolet light is an electromagnetic type of radiation with wavelengths shorter than visible light. UV can be separated into various ranges, with short range UV (UVC) considered “germicidal UV.”

At certain wavelengths UV is mutagenic to bacteria, viruses and other micro-organisms. At a wavelength of 2,537 Angstroms (254 nm) UV will break the molecular bonds within micro-organismal DNA, producing thymine dimers in their DNA thereby destroying them, rendering them harmless or prohibiting growth and reproduction.

It is a process similar to the UV effect of longer wavelengths (UVB) on humans, such as sunburn or sun glare.Micro-organisms have less protection from UV and cannot survive prolonged exposure to it.

Water sterilization

Ultraviolet disinfection of water consists of a purely physical, chemical-free process. UV-C radiation attacks the vital DNA of the bacteria directly. The bacteria lose their reproductive capability and are destroyed. Even parasites such as Cryptosporidia or Giardia, which are extremely resistant to chemical disinfectants, are efficiently reduced.

A UVGI system is designed to expose environments such as water tanks, sealed rooms and forced air systems to germicidal UV. Exposure comes from germicidal lamps that emit germicidal UV electromagnetic radiation at the correct wavelength, thus irradiating the environment. The forced flow of air or water through this environment ensures the exposure.

Advantages

• Environmentally friendly, no dangerous chemicals to handle or store, no problems of overdosing.
• Universally accepted disinfection system for potable and non-potable water systems.
• 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.
• Low power consumption.
• No chemicals added to the water supply – no by-products (i.e. chlorine + organics = trihalomethanes).
• Safe to use.
• No removal of beneficial minerals.
• No change in taste, odor, pH or conductivity nor the general chemistry of the water.
• Automatic operation without special attention or measurement, operator friendly.
• Simplicity and ease of maintenance, TWT Deposit Control System prevents scale formation of quartz sleeve, annual lamp replacement, no moving parts to wear out.
• No handling of toxic chemicals, no need for specialized storage requirements, no OHSA requirements.
• Easy installation, only two water connections and a power connection.
• More effective against viruses than chlorine.
• Compatible with all other water processes (i.e., RO, filtration, ion exchange, etc.)..

Drawbacks

• UV disinfection leaves no taint, chemicals or residues in the treated water.
• UV disinfection is most effective for treating a high clarity purified reverse osmosis distilled water. Suspended particles are a problem because microorganisms buried within particles are shielded from the UV light and pass through the unit unaffected.
• However, UV systems can be coupled with a pre-filter to remove those larger organisms that would otherwise pass through the UV system unaffected. The pre-filter also clarifies the water to improve light transmittance and therefore UV dose throughout the entire water column.

Key Factor

A key factor of UV water treatment too proper choose a model is the flow rate: if the flow is too high, water will pass through without enough UV exposure. If the flow is too low, heat may build up and damage the UV lamp.