The Right Dose for UV Disinfection

UV is recognised* as a viable means of water, air and surface disinfection. UV systems that emit UV-C light are used around the world in industries like drinking water and wastewater treatment.
Posted: Tuesday, 15 March 2022

Bacteria and other pathogens are susceptible to UV-C light as it breaks down their DNA, rendering them unable to reproduce.

When using UV for water disinfection, you must first determine the correct dose. Proper efficacy relies on correct dosing, which is measured in energy per surface area delivered, typically as mJ/cm2.

How To Calculate The UV Dose

There is a commonly used formula to calculate the UV dose you will need for disinfection.

UV Dose = UV Intensity (µW/cm2) x Exposure Time (seconds)

Exposure time is how long the UV light is ON and delivering UV Light

Variables such as humidity and age of the UV lamp may influence the UV dose delivered

UV Dosing

UV at 254nm is usually a dose in the range of 40mJ/cm2. This is high enough to destroy the DNA of microbes such as E.coli, Salmonella, Hepatitis virus, Poliovirus and Rotavirus.

You will need to consider the distance of the water from the UV lamp and the process of the treatment cycle. Does the water pass over the lamp once or does it recirculate? This will usually depend on the purpose of your treated water. Drinking water, water for swimming pools or aquaculture requires a different UV system setup for each process.

Water Quality

The quality of the water is also significant as it can affect the Ultraviolet Transmittance (UVT). This is the measurement of UV that can pass through a water sample. Several factors can affect UVT including the water source, water turbidity and the level of organic compounds within the water.

WATCH: Five Ways UV Is Used Every Day



Alpha-Purify Can Help You

Call Alpha-Purify today to talk about UV lamps and find the correct lamp type for the dose you require. Our technical team are here to help with any questions you have.

Call us on +44 (0) 1327 368205 or email us at info@alpha-purify.com.