UV – A Safe Way to Disinfect Bottled Water Without Producing Unwanted By-Products


Introduction

In an increasingly safety-conscious market the bottled water industry has to meet ever higher standards of quality. Contamination of incoming water supplies – be they from spring, well, surface or municipal sources – with Cryptosporidium, Giardia, E.coli or other pathogenic or spoilage microorganisms can have serious consequences for bottlers.

Bottled water

The threat of contamination is also higher now than ever before as producers respond to consumer demand for a reduction in chemical treatment. Effective microbial disinfection of the whole process – from source to final bottling – is therefore essential.

Until now ozone disinfection has been a popular method of disinfecting bottled water. While ozone has a number of advantages, it is coming under increasing criticism because of concerns about disinfection by-products – particularly bromate, a suspected carcinogen – formed as a result of the ozonation process. Bromide ions occur naturally in many spring waters and are completely harmless. If their levels are high, however, ozone can facilitate their conversion into bromate.

An alternative method of disinfection which is rapidly gaining acceptance across the whole spectrum of food and beverage industries is ultraviolet (UV) disinfection. UV kills all known spoilage microorganisms, including bacteria, viruses, yeasts and molds (and their spores) without producing any undesirable disinfection by-products. It is a low maintenance, environmentally friendly technology which eliminates the need for chemical treatment while ensuring very high levels of disinfection.

How UV disinfection works

UV is the part of the electromagnetic spectrum between visible light and X-rays. The specific portion of the UV spectrum between 185-400nm (also known as UV-C) has a strong germicidal effect, with peak effectiveness at 265nm. At these wavelengths UV kills microorganisms by penetrating their cell membranes and destroying the DNA, making them unable to reproduce and effectively killing them.

A typical UV disinfection system consists of a UV lamp housed in a protective quartz sleeve which is mounted within a cylindrical stainless steel chamber. The water to be treated enters at one end and passes along the entire length of the chamber before exiting at the other end. Virtually any liquid can be effectively treated with UV, including spring, surface or municipal water, filtered process water, viscous sugar syrups and effluent.

There are two main types of UV technology, based on the type of UV lamps used: low pressure and medium pressure. Low pressure lamps have a monochromatic UV output (limited to a single wavelength at 254nm), whereas medium pressure lamps have a polychromatic UV output (with an output between 185-400nm). Generally speaking, low pressure systems are best suited for small, intermittent flow applications, while medium pressure technology is better suited to higher flow rates.

Benefits of UV disinfection

UV disinfection has many advantages over alternative methods. Unlike chemical biocides, UV does not introduce toxins, residues or by-products into the process and does not alter the taste, odor or pH of the water.

UV treatment can be used for primary water disinfection or as a back-up for other water purification methods such as carbon filtration, reverse osmosis or pasteurization. As UV has no residual effect, the best position for a treatment system is immediately prior to the point of use. This ensures incoming microbiological contaminants are destroyed and there is a minimal chance of post-treatment contamination.

UV applications in the bottled water industry

Incoming water supplies
Although natural springs and municipal water supplies are normally free from harmful or pathogenic microorganisms, this should not be assumed. Surface water from wells, rivers or lakes – particularly in livestock farming areas – can be contaminated and should be disinfected.

CIP (Clean-in-Place) rinse water
It is essential that the CIP final rinse water used to flush out foreign matter and disinfecting solutions is microbiologically safe. Fully automated UV disinfection systems can be integrated with CIP rinse cycles to ensure final rinse water does not reintroduce microbiological contaminants. Medium pressure lamps are ideal for this application because of their mechanical strength, meaning they are not affected by any sudden changes in the temperature of the CIP water, such as when hot (80oC) liquid is instantly followed by cold (10oC).

Filter disinfection
Stored reverse osmosis (RO) and granular activated carbon (GAC) filtrate can be a breeding ground for bacteria. UV is an effective way of disinfecting both stored RO and GAC filtered water and has been used in the process industries for many years.

Dechlorination
GAC filters are also often used to dechlorinate process water, removing the ‘off’ flavors often associated with chlorine disinfection, meaning the flavor of the final product remains untainted and free from unwanted flavors or odors. Placing UV systems ahead of GAC filters used for dechlorination improves the performance of the filters and results in longer carbon runs, so decreasing operating costs.

Packaging & surface disinfection
Surface disinfection systems are used to reduce microbial counts on all kinds of packaging, including glass and plastic bottles, cans, lids and foils. By irradiating the surfaces with UV prior to filling, spoilage organisms are eliminated, extending the shelf life of the product and reducing the risk of contamination.

Sugar syrups
Sugar syrups used as flavorings can be a prime breeding ground for microorganisms. Although syrups with a very high sugar content do not support microbial growth, any dormant spores may become active after the syrup has been diluted. Treating the syrup and dilution water with UV prior to use will ensure any dormant microorganisms are deactivated.

Tank head space disinfection
UV systems can be used to disinfect displacement air for pressuring tanks or pipelines holding perishable fluids. Storage tanks are particularly susceptible to bacterial colonization and contamination by air-borne spores. To prevent this, immersible UV treatment systems have been designed to fit in the tank head air space and disinfect the air present.

Case Study

Angel Springs Limited, United Kingdom
Angel Springs Limited, situated in the picturesque Chiltern Hills outside London in the United Kingdom, bottles natural spring water for use in water coolers. The company replaced its ozone water disinfection unit with a UV system several years ago. It decided to make the switch because of concerns about bromate being formed as a result of ozone treatment.

“We were put off ozone by the potential for bromate formation as part of the ozonation process,” said Andrew Glaister of Angel Springs. “Even though bromide ion levels in our source water are not particularly high, we decided to go for the safer option and use UV instead,” Mr Glaister added. “UV has no disadvantages, only advantages, and since its installation we have been happy with its performance. The UV lamp only needs to be replaced after 8000 hours’ operation, so it is also very efficient.”

Angel Springs’ water originates from a natural spring on the site. After filtration to remove physical particles it passes through the UV chamber and is then bottled. There is no further water treatment and no chemical treatment.

Conclusion

Meeting the increasingly rigorous hygiene standards required in the production of bottled water is becoming more of a challenge, particularly with growing concerns about by-products such as bromate. Customers are also demanding a product that has not been treated with chemicals.

For those producers seeking to improve the quality of the end product, UV is an economic, realistic option. It is already a well established method of disinfecting drinking water throughout the world. It is also widely used for high purity applications such as pharmaceutical processing and semiconductor manufacturing, where water of the highest quality is required.

UV disinfection systems are easy to install, with minimum disruption to the plant. They need very little maintenance, the only requirement being replacement of the UV lamps every 8000 months, depending on use. This is a simple operation that takes only a few minutes and can be carried out by general maintenance staff.

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