Breaking from Common Practices

The benefits of ultraviolet (UV) light in destroying waterborne microorganisms are well established, but did you know that UV technology could be used on other hard-to-treat liquids?

These liquids include juices, liquid sugars, pharmaceuticals, process lubricants and other opaque materials. They are considered hard to treat due to their low transmission, color, viscosity and sometimes-higher temperatures.

In order to provide proper disinfection, the UV system must treat the liquids using a “thin film” design. A thin film design is when the UV lamps are spaced close together, which forces the liquid into close proximity to the light source. The use of internal baffles to introduce a bit of turbulence to the liquid also enhances the disinfection process.

The thin film design has proven to be extremely effective for these hard-to-disinfect liquids, but the designs vary based on the application. The following will show the different designs for a variety of real-world applications and products.

Juices & Fruit Drinks

Fruit juice can become a breeding ground for microorganisms. Units have been designed to treat a variety of beverages ranging from the exotic Tahitian Noni juice to the more common apple cider.

Apple cider poses significant health risks if not treated with pasteurization. E.coli, which is easily destroyed by UV light, is a major concern with apple cider processing. Biological testing has shown that a properly designed UV disinfection system can provide 99.99% reduction of E.coli in cider.

Many health agencies are now focusing efforts on regulating this industry. Because local farmers dominate the industry, UV disinfection can provide a cost-effective solution over the more expensive pasteurization process.

When designing a system for apple cider or other juice disinfection, the unit needs to be specially configured, sized and biologically tested. Traditional UV systems will not be effective due to lamp spacing issues.

It is extremely important to size these systems properly due to the critical nature of the applications and the known presence of microorganisms.

Liquid Sugars

Liquid sugars are used extensively in the food and beverage industries. Sugar syrups (sucrose and honey) with high osmotic pressure (brix 25-67) can be subject to microbial growth. This may result in health problems as well as spoilage (bad taste, shorter product life and color changes).

In addition to the challenges of the lower transmission, liquid sugars are often processed in higher heat environments. In order to maintain UV effectiveness, the lamps may need to be cooled to prolong life and output. UV lamps need to be maintained at a certain temperature to be effective. High heat or cold temperatures will cause the UV output to fall.

Typical systems are designed for flows up to 200 gpm and are manufactured using higher purity components.

As with all UV systems, the quartz sleeves can become fouled (quartz sleeves are the glass-like material that protect the UV lamps). The manufacturing plant should include the disinfection system in its chemical cleaning program. This will allow the quartz to be cleaned as part of a regular maintenance program.

In the event that the plant does not have a cleaning program, a supplemental chemical cleaning tank should be considered. This will allow for the periodic introduction and re-circulation of an FDA-approved citric acid to clean the quartz sleeves.

Systems have been effectively designed for manufacturing companies that produce soda, candy, honey and a variety of other food products.

Pharmaceutical & Health Care Products

Pharmaceutical companies are constantly looking for ways to improve and streamline their manufacturing processes. UV disinfection is a staple technology in all pharmaceutical plants for the treatment of clean process water as well as for wastewater.

For many of the same reasons that food and beverage manufacturers are using UV in their product lines (health, appearance, taste and product long-evity), the pharmaceutical industry has applied UV light to many of their hard-to-treat base liquid materials.

A large number of health care products incorporate sucrose, glucose and other components known as sugar alcohol. These liquids are all good candidates for thin film UV disinfection. While the osmotic pressure of these materials reduces the chance of microbial growth, spores can remain unharmed and can grow when introduced into the product line.

The use of UV allows these companies to prevent the problems before they occur.

Systems have been effectively designed for manufacturing companies that produce cough syrups, toothpaste, mouthwash and a variety of other consumer goods.

In addition to the treatment of these liquids, pharmaceutical companies have also employed UV light in various spectral ranges to create photochemical reactions. These systems are custom-designed based on the application.

Process Lubricants & Coolants

At the very heart of any manufacturing process is the use of coolants and lubricants to maintain equipment functionality. Coolants generally fall into the category of petroleum or synthetic based. Because these loops re-circulate, they become a breeding ground for microorganisms.

This growth can clog the lines and reduce system efficiency. UV disinfection systems have been successfully integrated to prolong coolant life.

The reasons why coolant maintenance is important are as follows:

  • It is expensive to purchase;
  • It is expensive to dispose of;
  • It impacts machinery life;
  • It impacts product appearance;
  • It can slow production lines; and
  • It can cause downtime.

Unlike thin film units for food and beverage, the units required for this type of application are of a commercial quality.

In order to maintain a UV system for the process loop, the lamps not only have to be closer together (creating a thin film), but they also have to come with a quartz cleaning mechanism. These mechanisms, manual or automatic, will allow the operators to clean off the build up on the quartz sleeves.

Once in place, the UV system will reduce the microorganisms and prolong the coolant life.

Systems have been effectively designed for manufacturing facilities and machine shops.


In addition to the primary water and wastewater systems, UV disinfection systems can be used in many process loops treating a variety of non-traditional liquids.

The introduction of these technologies will help manufacturers reduce chemicals and preservatives and provide the public with safer and better-tasting products.

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About the author

Adam Donnellan is the executive vice president of Sunlight Systems Ultraviolet, Allendale, N.J. He can be reached at [email protected].