Understanding UV systems in RAS
Ultraviolet (UV) disinfection has proven to be one of the safest, most effective treatment methods against pathogens in RAS water tanks. However, UV systems are also very sensitive to water conditions, require dedicated maintenance as control and real-time monitoring is difficult at best.
Aran Lavi, vice-president of product and head of sales for Europe and global aquaculture for Atlantium Technologies, presented at Aquaculture Europe 2020 to share a few guidelines to help RAS producers make more informed decisions about their UV water treatment systems.
Atlantium Technologies specializes in tailor-made disinfection solutions for aquaculture facilities.
“The main challenge, when it comes to sizing and deciding on UV systems suitable for your production needs, is how to predict its ability to deliver the required water biosecurity based on the technical specifications only,” said Lavi at his virtual presentation on April 14.
Because a UV dose cannot be measured in the same way that DO and CO2 levels can be monitored constantly, Lavi said there are four factors that producers can examine to understand the UV dose and effectiveness within their RAS. These are the flow rate, UV transmittance (UVT), power outputs of the lamps and overall system design.
“It’s important to know this equation because the basis for reliable and sustainable operation of a UV system depends entirely on the system’s ability to monitor, or at least, account for each of these factors,” he said.
Often times, the difference between third-party validated and non-validated systems can be two to three times less flow, or more energy consumption. Although non-validated systems tend to be cheaper, Lavi warns that “there are no magic wands” and companies should invest in reliability.
Norwegian Veterinary Institute (NVI) approval is not a substitute for third-party validation, like EPA or DVGW, he said. The sytem should also be designed according to minimum UV dose. However, without validations, this is impossible to verify, he added.
Having a lamp output sensor per lamp is a good way to monitor UV output. The majority of UV systems might have an indication of the kilowatts going into the lamp but not a sensor that measures the actual UV power emitted by each of the lamp in the system. Otherwise, the UV dose is strictly theoretical, he said.
UVT is one of the dominant factors to assessing UV dose in a system. Lavi recommends systems that have integrated UVT sensors that allow users to monitor how UVT changes considerably duringa production cycles.
“A UV system without a dedicated UVT system should be considered inferior and less inclined to deliver the required performance,” Lavi said.
Most UV systems work on fixed flow setups without real-time flow measurement feeds. This should also be considered inferior because it does not adjust according flow rate changes within the RAS.
The more lamps in a UV system, the more difficult it is to monitor and control performance and apply effective maintenance. Lavi recommends having one to four lamps within one system will provide producers more durable and dependable performance.