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The decision by Nongfu Spring to opt for UV instead of ozone was driven by a number of reasons, not least of which were concerns about ozonation by-products such as bromate. In fact, Hanovia has noticed that more and more bottled water and soft drinks producers are now looking for ozone alternatives, and enquires about UV are on the increase.
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. The World Health Organization (WHO) lists bromate as a carcinogenic substance and recommends its maximum limit in mineral water be set at 0.01mg/l. In July 2008 the Chinese General Administration of Quality Supervision, Inspection and Quarantine (AQSIQ), recommended in a revised draft national standard for drinking water and mineral water that a maximum limit for bromate in bottled water be in line the WHO guidelines.
As an alternative to ozonation, UV has many advantages. It is already widely used across a wide spectrum of the food and beverage industries, and also in industries where water of the highest purity is required, such as pharmaceutical manufacturing. UV kills all known spoilage microorganisms, including bacteria, viruses, yeasts and moulds (and their spores) without producing any 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.
UV 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 bottling. 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 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’ flavours often associated with chlorine disinfection, meaning the flavour of the final product remains untainted and free from unwanted flavours or odours. 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.
Sugar syrups
Sugar syrups used as flavourings 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.
Effluent disinfection and/or re-use
UV allows effluent from processing facilities to be treated without the use of environmentally hazardous chemicals. This ensures all discharges meet with local environmental regulations. As already mentioned, because process water can be treated and re-used with UV, this also leads to a significant reduction in the amount of waste water produced.
Case Study
Angel Springs Limited, United Kingdom
Angel Springs Limited, situated in the Chiltern Hills in the United Kingdom, bottles natural spring water for use in water coolers. The company replaced its ozone water disinfection unit with a Hanovia 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 in the light of impending regulations in China on bromate levels. Customers are also demanding a product that has not been treated with chemicals. If improvements need to be made to plant and equipment, they need to bring quick returns on the investment and measurable improvements in product quality.
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 hours, depending on use. This is a simple operation that takes only a few minutes and can be carried out by general maintenance staff.
