UV Information

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What is UV Light?

UV is a natural component of the electro-magnetic radiation emitted by the sun. The majority of radiation produced during this process is absorbed by ozone in the Earth’s upper atmosphere. UV light, specifically UV-C light (240-280 nm), which does pass through the atmosphere, acts as a natural disinfectant by inactivating exposed microorganisms, such as those found in surface matter.

Pentair Aquatic Eco-Systems' Low-Pressure (Monochromatic) UV Lamps utilize the same principle as the sun. Much of their output energy (35-40%) is within the Germicidal Action Spectrum (240-280 nm), specifically 254 nm.

Coincidentally, living microorganisms absorb UV-C light, which, within seconds, triggers a photochemical reaction in the organism’s DNA thus preventing it from multiplying. The effectiveness of UV disinfection relies on the applied UV dose (i.e., the result of the time and UV

The Spectrum of Light

UV Light as UV Disinfection

UV Disinfection is the use of UV-C light to inactivate exposed microorganisms through a photochemical reaction in the organism’s DNA that prevents multiplication (disrupting the organism's life cycle).

The Approach to Successful UV Disinfection

Successful ultraviolet disinfection demands strict adherence to Established Engineering Guidelines (The Bolton Photosciences, Inc. "Ultraviolet Applications Handbook" and the EPA). Pentair Aquatic Eco-Systems understands the importance of openly sharing critical UV performance information with the public. Our approach is simple. Education instills confidence with the equipment which leads to successful operation. Ultraviolet sterilization is unmatched in its efficiency, simplicity, and dependability when applied as a microorganism disinfectant but does have its limitations. Realizing both the benefits and limitations of UV disinfection establishes a foundation for its successful application.

Ultraviolet Disinfection's Benefits and Limitations

UV Benefits:

UV treatment takes place only inside the UV vessel (exposure chamber) and leaves no residual downstream. Therefore, it is harmless to the animals in the pool. UV Disinfection is a proven solution to harmful waterborne pathogens commonly associated with aquatic recirculating systems. In contrast, chlorine/bromine leaves a residual in the water that can irritate the skin and eye tissue of mammals, reptiles, and birds. Ozone, if not measured and controlled properly, is capable of causing severe tissue damage, even death in fish and invertebrates.

UV Limitations:

Exposure time between the waterborne microorganism and the UV-C light is critical to achieving successful UV Disinfection. The condition of the application’s water (%UVT) will determine how well the UV-C light penetrates through it. UV-C is absorbed by the targeted microorganism or by other organic waterborne particles. It is for this reason that UV equipment should be positioned after the mechanical filter.

Harmful Pathogens

The threat of pathogens:

Sustainable seafood that includes, Salmon, Halibut, Sea Bream, Cobia, Rainbow Trout, and Oysters are all valuable commodities threatened by harmful pathogen infestation. But they’re not the only ones. Public exhibits of fish, invertebrates, mammals, reptiles, and birds—all living examples of our natural world—are also in constant danger of coming in contact with harmful pathogens.

It’s no secret that our world is faced with declining water purity and availability. This, combined with increased disease outbreaks, has resulted in continued pollution and the introduction of new waterborne pathogens to natural waters.

There is a solution... UV Disinfection.

The chart below lists the most common pathogens found in Aquaculture and identifies their required Fluence (UV dose) for inactivation.

Waterborne Pathogens

Harmful Waterborne Pathogens:

Aquaculture has used UV disinfection to control harmful waterborne pathogens for many years, but few design-consultants, purchasers, and operators truly understand UV’s limitations well enough to use it successfully and cost-effectively. To achieve successful UV disinfection one must apply it correctly! The first step in applying UV disinfection correctly is to familiarize yourself with the targeted pathogens. This helps to establish the application’s UV disinfection requirements. Keep in mind, no two pathogens are exactly alike and all require their own specific UV-C dose.

Microorganism Complex Life Cycle

Microorganism Complex Life Cycle

The diagram above demonstrates the complex life cycle of the warm water protozoa Cryptocaryon (marine white spot). The diagram illustrates the four life-cycle stages of this lethal protozoan. It reveals the microorganism’s physical size and actual life-span based of its life-cycle stage. The free-swimming Tomite excyst or infective stage, when the microorganism is smallest (25-60 µm), is the life-cycle stage where UV Disinfection is most effective.

Harmful Pathogens Associated With Aquaculture:



Chlorella vulgaris

22 mJ/cm2



Aeromonas salmonicida

3.6 mJ/cm2 (log-3)

Pseudomonas fluorescens (fin rot)

11 mJ/cm2 (log-3)

Listeria monocytogenes

16 mJ/cm2 (log-5)

Streptococcus sp. (seawater)

20 mJ/cm2

Bacillus subtilis (spores)

22 mJ/cm2 (log-3)

Vibrio anguillarum

30 mJ/cm2

Yersinia ruckeri

30 mJ/cm2

BKD (Bacterial Kidney Disease)

60 mJ/cm2 (estimate)

Flavobacterium psychrophilum
(Salmonid Bacterial Coldwater Disease)

126 mJ/cm2

Vibrio sp. (oyster)

155 mJ/cm2



Saprolegnia diclina (zoospores)

40 mJ/cm2 - 170 mJ/cm2



Sarcina lutea (Micrococcus luteus)

26 mJ/cm2 (log-3)

Ceratomyxa shasta

30 mJ/cm2 (log-3)

Perkinsus marinus (dermo disease)

30 mJ/cm2

Trichodina sp.

35 mJ/cm2 (log-3)

Myxobolus cerebralis (TAMs, Whirling Disease)

40 mJ/cm2

Ichthyophthirius multifiliis (freshwater white spot)

100 mJ/cm2

Amyloodinium ocellatum

105 mJ/cm2

Trichodina nigra

159 mJ/cm2

Cryptocaryon irritans (marine white spot)

280 mJ/cm2

Costia necatrix

318 mJ/cm2 (log-3)



KHV (koi herpesvirus)

4 mJ/cm2

ISA (Infectious Salmon Anemia)

8 mJ/cm2

CCV (Channel Catfish Virus)

20 mJ/cm2

IHNV (Infectious Hematopoietic Necrosis/CHAB)

20 mJ/cm2

OMV (Oncorhynchus masou Virus)

20 mJ/cm2

IHNV (Infectious Hematopoietic Necrosis/RTTO)

30 mJ/cm2

VHS (Viral Hemorrhagic septicemia)

32 mJ/cm2

CSV (Chum Salmon Virus)

100 mJ/cm2

AHNV (Atlantic Halibut Nodavirus)

105 mJ/cm2

IPNV (Infectious Pancreatic Necrosis Virus)

246 mJ/cm2

Log-1 = 90% • Log-2 = 99% • Log-3 = 99.9% • Log-4 = 99.99% • Log-5 = 99.999%

UV doses not accompanied by a specific log value, should be considered a minimal dosage. The listed data was collected from various sources and Pentair Aquatic Eco-Systems, does not accept any responsibility for the accuracy of this information. This information is meant to be a guideline and should be used as such.

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