UV transmission: Understanding T10 in water quality analysis
UV transmission, or T10, measures how effectively ultraviolet (UV) light passes through a substance. This critical parameter primarily applies to liquids or air, with air remaining consistently transparent whilst liquids—even clear ones—exhibit remarkably varied transmission levels depending on their composition.
How T10 is measured?
The testing procedure is elegantly straightforward. We place a 10ml square vial filled with the liquid into our analysis device. The unit features a UV light emitter on one side of the vial and a UV receiver on the opposite side. The process involves projecting 254nm UV light through the sample, allowing the receiver to determine how effectively (or poorly) your liquid permits light transmission.
T10 in everyday water sources
Tap water from our office typically registers between 93-95% transmission. This range of 90-95% represents the standard benchmark for normal water quality. You might wonder why tap water doesn’t achieve 100% transmission. The answer lies in the minute quantities of chemicals added to make tap water potable. These substances either deflect or absorb some portion of the UV light, with daily fluctuations in chemical concentration causing variations in T10 readings.
Similar principles apply to other water sources, though the UV-blocking elements differ. In river water, for instance, the obstructions tend to be more organic in nature rather than chemical additives.
Borehole water: The untreated challenge
Water sourced from boreholes presents a different scenario altogether. Unlike mains water, borehole water receives no treatment and potentially contains various contaminants—both chemical and microbial. Our responsibility involves ensuring this water becomes safe for consumption from a germicidal perspective.
After passing through an appropriate UV treatment system, the water becomes free from harmful microorganisms, regardless of their initial concentration. The effectiveness of this treatment process depends significantly on the water’s composition, necessitating preliminary filtration to remove larger particles. Any microscopic particles that penetrate the filtration system are small enough to be effectively treated by UV radiation, essentially transforming them into “clean dirt”.
The problem with iron!
One element we frequently encounter that exhibits remarkable efficiency at blocking UV light is iron. Attempting to treat iron-rich water with UV is comparable to shooting arrows at a tank—largely ineffective. Research conducted by Ulman et al. (2017) demonstrated that iron concentrations above 0.3 mg/L can reduce UV transmission by up to 40%.
The only viable solution involves installing an iron filter upstream of the UV treatment unit. Several other elements produce similar effects to iron, but fortunately, they rarely appear in combination.
Engineering solutions for varying T10 levels
According to a comprehensive study by the Water Research Foundation (2023), UV penetrates significantly further into liquids with high T10 values, allowing for faster flow through the treatment chamber. Alternatively, this permits more compact units that consume less energy to operate.
For liquids with low T10 values, treatment remains possible but requires adaptation. This typically involves employing higher-powered lamps alongside chambers with reduced diameters. This configuration ensures that water furthest from the lamp remains relatively close, receiving an intensive dose of UV radiation during treatment.
The Journal of Water Treatment Technology (Thompson et al., 2022) confirms that properly designed UV systems can achieve 99.99% pathogen reduction even in waters with T10 values as low as 75%, provided the system incorporates appropriate intensity adjustments.
The importance of water quality when selecting a UV system
Understanding your water’s T10 value is absolutely essential when selecting an appropriate UV treatment system. As highlighted by the International Water Association’s guidelines (2024), properly matching your system specifications to your specific water quality can mean the difference between effective disinfection and potential treatment failure.
Prior to installation, comprehensive water testing should be conducted to determine not only T10 values but also iron content, turbidity, and other potential UV-inhibiting factors. This proactive approach ensures optimised performance, extends equipment lifespan, and ultimately guarantees the safety of your water supply.
Remember that water composition can change seasonally or after significant weather events, making regular monitoring a crucial component of any successful water treatment programme. The modest investment in thorough water quality assessment invariably pays dividends in system efficiency and reliable protection against waterborne pathogens.
If you have a question about, UV disinfection systems contact UVO3 today on 01480 355 446 or fill in our quick form below.
