UV Sterilization

UV sterilization controls pathogens and free-floating algae in an aquatic life support system by exposing the water to a specified ultraviolet dose; sizing depends on flow rate, target organism and the water's UV transmittance.

UV adds nothing to the water and leaves no residual. That makes it well suited to animal systems, and it also means it only treats what physically passes through the chamber.

What it controls

UV can be used to inactivate bacteria, viruses, parasites, and other microorganisms, but the required dose varies substantially by target organism. A meaningful UV specification should therefore identify the target performance, required dose, design flow, and relevant water-quality assumptions rather than simply calling for “a UV.”

Where it’s used

Aquarium and zoo exhibit systems. Quarantine and holding, where pathogen control is the entire point. Recirculating aquaculture. Hatcheries treating incoming water. Water features where public health drives the requirement.

Why specification matters

Dose is the specification. Measured in millijoules per square centimeter, dose is the product of intensity and exposure time. A unit is sized to deliver a stated dose at a stated flow. Change the flow and the dose changes with it. A UV that delivers its rated dose at design flow delivers materially less when someone opens a valve upstream.

UV transmittance (UVT) is a critical sizing input that is sometimes overlooked. UVT describes how effectively ultraviolet light passes through the water. Water with dissolved organics, color, turbidity, or other absorbing constituents can require different sizing than high-UVT water. Sizing a UV system without a realistic UVT assumption can result in a unit that operates but does not deliver the intended dose under actual conditions. If you don’t know what your UVT is, no problem, contact us at info@sivatwater.com and we can test a sample for you.

Filtration comes first. UV is a polishing step. Solids shadow organisms and pass them through untreated. UV downstream of inadequate filtration underperforms regardless of how it was sized.

Lamps age. Output declines across lamp life. Sizing should account for end-of-life output, not new-lamp output, or the system falls below specification months before anyone replaces a lamp.

Sleeves foul. Scale and film on the quartz reduce transmission. Systems requiring consistent performance may use wiper mechanisms, but the equipment room still needs adequate access and clearance for lamp, sleeve, and wiper maintenance.

Low pressure and medium pressure are different tools. Low-pressure amalgam lamps are more efficient per watt and run longer. Medium-pressure units deliver more output in a smaller footprint at higher energy and shorter lamp life. Which is right depends on space, flow, and what the facility can maintain.

How SIVAT helps

We check the specified UV against actual design flow, target dose, and the transmittance the water is likely to have. We verify the unit is positioned downstream of adequate filtration and that there is room to pull lamps and sleeves for service.

We price the unit, the lamps, the sleeves, and the spares the facility will need in year one.

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Common questions

What UV dose does an aquatic life support system need?

Dose is the product of intensity and contact time, and the required figure depends on the target organism rather than the volume of the system. General disinfection, protozoan control and virus inactivation all sit at different points on that scale, so the dose has to be set against what the system is being protected from before a unit is sized.

What is UV transmittance and why does it matter?

UV transmittance, or UVT, is the percentage of ultraviolet light that passes through the water rather than being absorbed by it. Low transmittance means the lamp output never reaches the far side of the chamber, so a unit sized on flow alone will under-deliver. Marine water, water carrying dissolved organics and water with color all reduce transmittance, and a unit selected without a UVT figure is selected on an assumption.

Where should UV sit in a treatment loop?

After mechanical filtration, so the water reaching the chamber is as clear as it will get, and after ozone residual destruction where ozone is present. UV placed ahead of filtration spends its output on particles rather than organisms.