UV DISINFECTION TECHNOLOGY
Which pathogens is the target for a recirculator? What is its efficiency against these pathogens?
Each microorganism requires a specific UV dose due to their individual sensitivity to UV radiation. For a different disinfection level (disinfection efficiency), different UV doses are required. To achieve the higher disinfection level you need to deliver a higher UV dose.
| Microorganism | Required UV dose (mJ/cm2) at disinfection efficiency level | |
| 90% | 99,9% | |
| Staphylococcus aureus | 4,9 | 6,6 |
| Escherichia coli | 3,0 | 6,6 |
| Pseudomonas aeruginosa | 5,5 | 10,5 |
| Salmonella sp. | 2 – 8 | 6 – 15 |
| Influenza virus | 3,6 | 6,6 |
| COVID-19 (SARS-CoV-2) | – | 10 – 20* |
| Poliovirus | 11 | 21 |
| Rotavirus | 13 | 24 |
| Klebsiella pneuomoniae | 12 | 17,5 |
| Acinetobacter baumannii | 3,3 | – |
| Penicillum fungi (Penicillium sp.) | 12 – 14 | 22 – 26 |
* according to the International Ultraviolet Association (IUVA) on 28-04-2020.
It follows from these data that the 99.9% effectiveness against Staphylococcus aureus (provided by a certain UV unit) may not be enough for other microorganisms:
| Microorganism | 99.9% efficiency |
| Staphylococcus aureus | + |
| Escherichia coli | + |
| Pseudomonas aeruginosa | - |
| Salmonella sp. | - |
| Influenza virus | + |
| COVID-19 (SARS-CoV-2) | - |
| Poliovirus | - |
| Rotavirus | - |
| Klebsiella pneuomoniae | - |
| Acinetobacter baumannii | - |
| Penicillum (Penicillum sp.) | - |
For this reason it is necessary to make sure that the given recirculator provides a high disinfection level against this specific pathogen.
Based on the above, the recirculator should provide a UV dose not less than 25-30 mJ/cm2 to be efficient against a wide range of pathogens.
Total bacterial count (TBC) – that indicates how many microorganisms are present in a certain volume – is easy to use for evaluation of recirculator performance.
It is the TBC indicator, along with other sanitary indicator microorganisms (Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella and Escherichia coli bacteria) that is used to analyze microbial contamination in medical facilities. And if your recirculator reduces TBC (by at least 99%), then it is effective. The only thing you need is to select the correct capacity
Ultraviolet technology for water, air and surface disinfection is based on germicidal effect of UV-C radiation.
UV radiation is electromagnetic radiation between x-rays and visible light. UV wavelengths range from 100 to 400 nanometer.| Ultraviolet in
electromagnetic spectrum |  |
Within the UV spectrum, UV-C range is considered the strongest UV radiation, which is easily absorbed by DNA, RNA and proteins. This range is often called germicidal due to its high disinfection efficiency against bacteria and viruses. The highest germicidal effect occurs at 205-280 nm and the maximum germicidal sensitivity of microorganisms at 265 nm.
| Mechanism of
UV disinfection | 
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The major advantages of this technology:
- high efficiency against a wide range of microorganisms including chlorine resistant ones (viruses and protozoa oocysts);
- no impact on physical, chemical and organoleptic properties of water and air; no by-products; no dangerous overdosing;
- low capital costs, power consumption and operational costs;
- UV systems are compact and easy to operate; no need for special operational safety precautions.
Main industrial available sources of UV radiation are low pressure amalgam lamps and mercury medium pressure lamps. Medium pressure lamp technology have higher power per lamp (several kW) but significant lower efficiency (9-12%) in comparison to low pressure lamp technology with efficiencies between of 35-40% and power per lamp up to 1000 watt.
The design of UV application depends on the required UV dose, flow rate and physical and chemical parameters of media to be disinfected. The facility design criteria, flexible, economical and sustainable operation are also the decisive design parameters.