UV light, especially in the wavelength range of 200-280 nm, is well documented to provide excellent water disinfection.
It is widely known that UV light, particularly at wavelengths between 200-280 nm, is highly effective in disinfecting water. So, with the technology seen to be so effective, why might it be important to have a UV system validated?
As you might expect, most of the studies on UV disinfection have focused on its antimicrobial effectiveness rather than the standardization of delivering UV energy to the process flow stream. UV intensity sensors positioned in a UV system can measure UV energy, as it is a form of electromagnetic radiation. But how does UV intensity, or the resulting UV fluence, translate into the actual antimicrobial function of each UV system design?
To further complicate this question, the antimicrobial function of the UV energy is associated with numerous primary variables, including changes in lamp lifecycle output, clarity of the quartz sleeve that the lamp’s energy passes through, location and type of UV sensor, flowrate through the system, and UV transmittance. Without a protocol that standardizes the relationship between UV antimicrobial activity, specific UV systems, and all of the highly dynamic UV intensity variables, it would be impossible for a designer or customer to know how a specific UV disinfection system would perform in their process water system.
Researchers have proposed many models for UV disinfection that aim to correlate the antimicrobial activity of a specific system with its corresponding UV intensity data. The success of these models has varied significantly. As might be expected, these models provide varying degrees of relevance to the different types of applications for UV systems. The best models for municipal and most industrial applications are UVDGM, DVGW, and NWRI. Correlation models use reproducibly measurable UV energy and laboratory-quantified antimicrobial activity, which are widely accepted.
All of these regulatory conventions include highly codified validation protocols, which have parallel UV-specific bioassays and standardized microbial reductions under a set of standardized changing conditions. Algorithms can generate a UV dose construct for each specific UV disinfection system. That UV dose construct allows the designer and customer to determine the expected antimicrobial activity of a UV system for their specific application and conditions.
Each UV system validation results from many hours of extremely standardized, multi-laboratory, and computational modeling, performed by highly qualified professionals in challenging biohazard environments. Validating a UV disinfection system is therefore an expensive task and not something that any system designer or customer should consider.
https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=600006T3.txt
https://www.dwi.gov.uk/stakeholders/guidance-and-codes-of-practice/uv-irradiation.pdf
https://nwri-usa.org/documents/UVGuidelines3rdEdition2012.pdf
It’s important to understand that a UV system providing a validated UV dose is very different from lesser UV systems, which are essentially just ‘a light in a pipe or a light in a channel’, until proven otherwise. Even in the pharmaceutical and life science industry, where all critical systems must go through Installation Qualification’, Operational Qualification’ and `Process Qualification’ (IQ/OQ and PQ) validation, they must demand Factory Acceptance testing and Master Validations from system component vendors. During the IQ/OQ/PQ process validation, it is important to test and document all system functions that may not be evaluated or systematically proven to ensure that they have been tested and documented beyond reproach.
This market entry-level requirement for UV disinfection systems must include providing UV validation with proven pathogen challenge disinfection documentation. Since it is extremely expensive, dangerous, and cost prohibitive for either the designer or customer to take on this primary UV disinfection system manufacturer responsibility, the market must demand non-bias, third-party UV validation. This would use one universally accepted standard validation protocol as the minimum entry into the disinfection system market.
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