Shining a light on water dechlorination

May 30, 2022 | Food Processing & Packaging, News

Medium pressure UV systems offer a sustainable solution in food and beverage

Due to its ability to neutralise microbial organisms in municipal and industrial water applications, free chlorine is used widely as a simple, inexpensive and scalable solution for water disinfection.

However, with sustainability becoming an ever-more important factor in company strategy and decision making, the food and beverage industry is waking up to the downsides of using free chlorine as a solution. Without the need for chemicals and as an effective two-in-one solution for both water disinfection and dechlorination, increasing numbers of businesses are opting for medium pressure UV systems instead. This allows them to maximise efficiency and safety with a solution that’s not only effective, but environmentally friendly too.

For mains water, residual chlorine is usually present to ensure disinfection at the point of use. For food and beverage applications however, the elimination of chlorine is crucial during the pre-treatment phase so as not to affect the taste and smell of the products, while also helping to maintain delicate RO membranes in functional condition and protect piping from chlorine’s corrosive effects.

Standard water dechlorination methods like granular activated carbon (GAC) beds and sodium metabisulphite are popular but also carry notable disadvantages. Medium pressure UV is a relatively unknown solution by comparison but offers a superior dechlorination solution, particularly from an environmental perspective.

Water dechlorination using medium pressure UV lamp technology

Modern brewery production line. Large vat for beer fermentation and maturation, pipelines and filtration system

Medium pressure UV systems, or high intensity broad-spectrum UV systems, have been proven in their effective reduction of free chlorine in water with concentrations up to 5mg/l. To produce photochemical reactions that dissociate free chlorine and combined chlorine compounds, these systems emit UV light with wavelengths of 180-400nm. The only by-product, hydrochloric acid, is then removed with ease.

UV systems help to reduce dependence on chemicals while minimising associated labour and costs incurred by the removal of their residuals after dechlorination. The technology limits by-product formations caused by chemical additions and does not introduce any poor taste or odour compounds to the liquid being treated.

Over time, due to incoming particulates and formation of fines, GAC beds used for dechlorination can experience excessive pressure drop and exhaust their capacity for chlorine absorption. When this happens, replacement and/or regular backwash cycles are required, adding time and costs to the dechlorination process. When combined with the absorption of organic matter, the porous structure of GAC beds can become a breeding ground for microbial growth*, which may require sanitisation.

As an alternative to GAC beds, UV offers water dechlorination with high levels of consistency and effectiveness, even with minimal head loss. UV systems are built in as a permanent, integrated element of water treatment apparatus, without the need for media replacement or regular microbial sanitisation, keeping equipment cleaner and operation costs lower.

Without the need for handling chemicals and replacement GAC media, high quality UV systems support businesses in becoming more sustainable. UV is energy-efficient, reduces chemical requirements and enables greater water re-use. It is effective against a wide range of micro-organisms including chlorine-tolerant pathogens, like cryptosporidium.

Evoqua Water Technologies range of UV dechlorination systems have been developed using scientific knowledge gathered over the past 20 years of operation. Outside of food and beverage, UV systems are also an ideal solution for water dechlorination applications within the microelectronics, pharmaceutical, and healthcare sectors.

*See, e.g., Wilcox, Chang, Dickson, and Johansson, Microbial growth associated with granular activated carbon in a pilot water treatment facility, Appl. Environ. Microbiol, Aug 1983; 46(2): 406-416.