UV technology is a non-chemical disinfection method used globally and extensively here in the Middle East. Many manufacturers would like you to think of it as something of a black art. We at Daly Middle East are here to help you better understand how to apply and use this very effective disinfection method.
In our experience, many systems are incorrectly specified for two reasons. First and foremost is a misunderstanding of the three different types of lamp technology available. Secondly, many units are undersized due to misleading marketing and incorrect sizing of systems that don’t take into consideration the required dose and the transmittance requirements of the application and medium respectively — often, in some cases rather conveniently, driven by commercial pressure during the writing of the original specification.
The process of UV disinfection is quite simple: water or air that passes through the chamber is exposed to germicidal UV light, which disrupts the DNA of microorganisms. This prevents microorganisms from replicating, rendering them inactive and unable to cause infection.
One of the primary benefits of UV for disinfection is that it does not contain or create any residuals or byproducts, which occur with chemical methods of purification. In fact, UV is sometimes used to remove residuals and by-products — such as chloramines, peroxide, ozone, and trihalomethanes — that result from other purification processes.
The Challenge in Specification
Different species of microorganisms require varying levels of UV exposure to be effectively eradicated. Breaking down different compounds, such as trichloramines, within the water also requires exposure to different levels of UV intensity and UV frequencies.
The principle of UV disinfection is often described as a principle of time and intensity — i.e. how long is the water exposed to the UV lamp, and what power of UV light is it exposed to. This is an oversimplification, and it often leads to low-pressure systems being specified where medium pressure is actually required.
Low Pressure or Medium Pressure?
A wavelength of 254 nanometres achieves maximum germicidal effectiveness and is lethal to viruses, bacteria, and mould spores. Low-pressure lamps target the 254nm wavelength specifically, allowing them to be highly efficient. Medium-pressure lamps, however, offer a broader spectrum output between 200–600nm that will break down materials a low-pressure system cannot — so it’s essential to know the makeup of the media to be disinfected and the application of the system prior to specification.
| Factor | Low Pressure | Medium Pressure |
|---|---|---|
| Wavelength output | Targets 254nm specifically | Broad spectrum, 200–600nm |
| Energy efficiency | Higher | Lower, but broader germicidal and chemical-breakdown effect |
| Best suited to | Straightforward microbial disinfection | Applications also requiring breakdown of chloramines or other compounds |
The applications for UV include, but are not limited to:
- Air extraction systems
- Swimming pools
- Drinking water
- Ponds & lakes
- Water features
- Dairy processing
- Sewage & wastewater
- SRB reduction
Why Sizing Matters as Much as Lamp Type
Two systems specified around the same lamp technology can still perform very differently if dose and transmittance weren’t properly accounted for at the design stage. Dose is a function of both intensity and exposure time — a system undersized for the actual flow rate it will see in service simply won’t hold water in the chamber long enough to deliver an effective dose, regardless of how powerful the lamp itself is. Transmittance — how much UV light actually penetrates the specific water or air being treated — varies with turbidity, organic content, and other water-quality factors, which is why a system sized correctly for clean, pre-filtered water can under-perform badly if the actual feed is less clear than assumed at the quoting stage.
This is exactly where the commercial pressure mentioned above causes real problems: a system quoted against an optimistic transmittance assumption will look cheaper on paper, but won’t deliver the dose it needs to in the actual application.
Getting UV Specification Right
If you would like advice on specifying a UV system correctly for your application — lamp type, sizing, dose, and transmittance — please get in touch at info@daly-me.com.
To see the range of UV systems we have available, please see our ultraviolet product section.