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 destruction: 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).

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

• 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)

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, the better product fit and pricing can be offered to the requesting party.

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.

This varies a lot based on applications and industries. The most important factor for the UV disinfection system is that UV rays are capable of “reaching” all pathogens in the flow-through water, meaning the water has adequate UVT (see below). The better-pretreated water is, the less UV light is needed and therefore more energy savings. However, ULTRAAQUA UV has developed multiple series for low-UVT environments that also are energy-optimized.

UVT is short for UV transmittance. UV transmittance determines the UV light transmission factor in the water. Even though it is not visible to the human eye, all water is capable of having particles that absorbs or deflects UV light. The UVT is necessary to know in order to ensure proper water disinfection. UVT is a measurement of the amount of ultraviolet light at 254 nm that passes through a water sample. The measurement is expressed as a percentage – %UVT.

UVT can vary over time and from site to site as it relates to the quantity of organics, colloidal solids and other material in the water which absorbs the UV light as it passes through the water column. The effective UV dose is dependent primarily on the combined effects of the UV light intensity, the exposure time and the UVT. Different pathogens require different amounts of UV energy to inactivate them. Therefore, it must be clear which pathogens are to be inactivated for any UV system.

When dealing with pathogen inactivation, it is important to note that the relationship between the dose and the log removal is not linear. It takes a much higher dose to achieve log-4 removal compared to log-2 removal. Please consult one of our specialists if you are in doubt about specific UVT values.

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