UV Technology

In most cases, ultraviolet disinfection is the last step of the water treatment process, destroying the tiniest particles that cannot be filtered out by existing filters. UV disinfection is the only solution that does not change any properties such as pH and temperature – which is essential for applications such as aqua life and ultra-pure water.

Ultraviolet disinfection is extremely effective in destroying microorganisms since no known bacteria or viruses are resilient to UV light. Furthermore, the technology today is optimized to a point where UV systems are usually the best OPEX and CAPEX wise due to energy use, footprint, and high level of automation. It also requires the shortest contact time without the need for additional supportive infrastructure.

Even though some of the alternative solutions possess sections of UV technology advantages, only UV disinfection delivers them all at once.

Besides standard disinfection, the other most common UV applications for water treatment are:

• De-chlorination: usually when the water in the inlet point has been pre-treated with chlorine and the further processes cannot tolerate it and its by-products. Commonly found in high-purity water applications like injection water for food and beverage, pharmaceuticals, and microelectronics industries. It is also extremely effective for swimming pool water.
• De-ozonation: ozone can sometimes be used to clean up the entire piping systems and places that cannot be accessed by maintenance teams. However, ozone is highly chemically reactive and needs to be eliminated, in order not to harm the end product in high-purity water environments or aquaculture species.
• TOC reduction: in the drinking water industry, TOC is directly associated with THMs and HAAs formation when chlorine is used. By destroying TOC, the formation of dangerous microorganisms is reduced significantly. It is also very common in pharmaceuticals and microelectronics industries.
• AOP: used in applications where the microorganisms are complex and cannot be destroyed by typical UV light, or where high purity water is required. The AOP process consists of UV and hydrogen peroxide, ozone, or both.

UV light has been proven to effectively eliminate the Covid-19 virus. However, based on the latest research, the covid-19 virus cannot survive the whole water treatment path. Because of this, there is no actual need to treat drinking water from covid-19.

The low pressure – high output ULTRATHERM™ UV lamps can be replaced every 16 000 hours (industry standard 12 000 hours), with medium-pressure ULTRATHERM™ UV lamps 9 000 hours (industry average 8 000 hours).

Some of the most important factors in determining the right UV system are knowing the location, application, flow rate, UV transmission, and targeted bacteria. ULTRAAQUA is able to assist in assessing all of the factors to ensure that the right UV system is chosen. By sending a sample to our headquarters in Denmark, we can help with assessing the bacteria to be targeted in our state-of-the-art laboratory.

By providing the desired log reduction and/or pre-filtration we can help find the perfect solution for your needs. The more information engineers have available, the better product fit and pricing can be offered to the requesting party.

Read more about finding the right UV system for intake water in Recirculating Aquaculture Systems here.

Operation costs are based on the power supply, which can vary greatly depending on the type of the UV system.

The UV maintenance costs are the lowest possible compared to its alternatives. It is also safe without involving dangerous chemicals. Depending on the application, the inspection should be done annually, with lamp re-placement up to two years (medium pressure more often), and quartz sleeves up to four years.

UV Transmittance is essential to know as it helps identify how clean the water is, resulting in better conditions to ensure proper water disinfection.

By knowing the UVT of the water to be disinfected, it becomes possible to properly size the UV system for optimal disinfection.

Read more about UV Transmittance here.

It is possible to install a UV system outside, however, the control cabinet should be covered from direct sunlight or rainfall.

TOC UV Systems uses UV lamps that emit light at 185nm wavelength. The light energy promotes the formation of OH-radicals from the photolysis of water. The OH-radicals react with the organic matter in the water leading to the oxidation into CO2 (carbon dioxide) and H2O (water), effectively resulting in the removal of TOC.

Read more here about TOC reduction here.

The time required for UV systems to kill bacteria in water varies significantly, based on factors such as the targeted bacteria, the intensity of the lamps, as well as the UV transmittance of the water. All relevant factors are naturally considered when sizing the optimal UV system for your requirements.

Even though UV disinfection provides extremely effective protection against pathogenic microorganisms, pre-filtration is often a neccesity before the UV treatment process.

Pre-filtration is used across numerous applications to filter out larger particles and solids that could create a shadowing effect. If a shadowing effect occurs, the potentially harmful microorganisms might not be able to receive the necessary amount of UVC light.

The amount of required pre-treatment varies a lot, but ultimately depends on the UV rays being capable of “reaching” all pathogens in the flow-through water. The better-pretreated water is, the less UV light is needed and therefore more energy savings. For low UVT environments, ULTRAAQUA offers multiple series that are optimized for energy-efficiency.

The best material depends on the source of water to be treated. If the environment is corrosive due to saline or air humidity, it can be a challenging setting for the commonly used UV system materials in stainless steel.

Based on 25 years of experience with seawater disinfection in warm and cold-water environments, ULTRAAQUA offers UV-stabilized polypropylene (PP) systems, which are resistant to warm seawater applications due to their non-corrosive construction.

For other environments such as cold seawater and freshwater applications, electropolished steel is a possibility, which provides up to 30% extra energy efficiency due to internal reflection.

For control cabinets, Glass Fiber Reinforced Plastic (GFRP) with passive or active cooling is a possibility, which causes the inside of the cabinets to be protected from any external factors.

Medium-Pressure lamps consume more electrical energy per unit of germicidal light output compared to Low-Pressure lamps. Additionally, MP lamps generally only convert up to 15% of their input watts into usable UV-C light watts, while LP lamps can be up to 40% more efficient.

However, UV systems based on MP lamp technology have the advantage when it comes to high-flow applications where a small footprint is essential and high-power densities are required.

The decision of what lamp technology to use should be based on operational and design advantages, taking the lamp characteristics and especially the site-specific conditions into consideration.

The UV intensity requirement varies a lot, based on industry and applications. The averages are as follows:

• Coliform bacteria, legionella, fecal bacteria, streptococci, nematodes (eelworms) and yeasts, etc. – 3 – 40 (mJ/cm²)
• Pathogenic fungi, such as fusarium, pithium, phytophtora, etc. – 30 – 120 (mJ/cm²)
• Viruses such as cucumber virus, olpidium, cholera, etc. – 60 – 250 (mJ/cm²)

Within the aquaculture industry, UV doses for common aquaculture diseases include:

Bacterial

• Aeromonas salmonicida – 5.0 mJ/cm2
• Aeromonas hydrophila – 5.0 mJ/cm2
• Flavobacterium psychrophilum – 126 mJ/cm2
• Vibrio salmonicida – 1.5 mJ/cm2
• Vibrio anguillarum – 4.0 mJ/cm2
• Pseudomonas Fluorescens – 11.0 mJ/cm2
• Renibacterium salmonicida – 20.0 mJ/cm2
• Bacterial Kidney Disease (BKD) – 60.0 mJ/cm2

Viral

• Infectious Salmon Anemia Virus (ISAV) – 10.0 mJ/cm2
• Infectious Pancreas Necrosis Virus (IPNV) – 250 mJ/cm2
• Nodavirus – 200 mJ/cm2
• Infectious hematopoietic necrosis Virus (IHNV) – 30.0 mJ/cm2
• Atlantic Salmon Paramyzo Virus – 240.0 mJ/cm2
• Heart Sceletal Muscle Inflammation (HSMI) – 250.0 mJ/cm2
• Nervous Necrosis Virus (NNV) – 70.0 mJ/cm2