As a simple, cost-effective, and scalable water disinfection solution, the use of free chlorine to tackle microbial growth in municipal and industrial water applications is here to stay.
But as sustainability continues to weigh in on company strategy and decision making, more businesses are adopting medium pressure UV systems as an effective, environmentally friendly solution; one that reduces the need for chemicals in both disinfection and dechlorination and helps to optimise processes for maximum efficiency and safety.
Mains water usually contains residual chlorine to ensure disinfection at the point of use. In food and beverage applications, the removal of chlorine is an essential step of water pre-treatment to resolve issues of taste and smell, protect delicate RO membranes and reduce its corrosive effect on piping.
Common dechlorination techniques include granular activated carbon (GAC) beds and sodium metabisulphite. These methods are popular despite their drawbacks, in part because medium pressure UV remains relatively unknown as a superior and environmentally friendly solution for water dechlorination.
Medium Pressure UV Lamp Technology for Dechlorination
Medium pressure UV systems, also known as high intensity broad-spectrum UV systems, are a proven method for the for the removal of free chlorine in water with concentrations up to 5mg/l. These systems use wavelengths between 180 to 400nm to generate photochemical reactions that dissociate free chlorine and combined chlorine compounds. The by-product, hydrochloric acid, can then be easily removed.
As a chemical-free solution, UV reduces the dependence on chemicals in food and beverage applications. This helps to minimise costs and labour required to remove residual chemicals after dechlorination, and the possibility of odour and taste implications that arise through the formation of sodium sulphate, which stimulates sulphate reducing bacteria.
By eliminating the need for extra chemicals in the dechlorination process, UV presents health and safety benefits to staff required to handle hazardous substances, as well as reducing costs associated with maintaining dosing equipment and the removal of scaling on RO membranes.
GAC beds used for dechlorination may require replacement and/or regular backwash cycles if the bed’s capacity for chlorine adsorption exhausts or develops excessive pressure drop in the presence of incoming particulates and formation of fines. The porous structure of GAC beds combined with adsorption of organic matter may also result in microbial growth* within the bed, potentially requiring sanitisation.
Alternatively, UV offers a highly consistent level of effectiveness that GAC cannot 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 far lower.
By removing chlorine and assuring water quality at the point of use, high quality UV systems help businesses to become more sustainable and reduce CO2 emissions by removing the need for the transportation and consumption of chemicals and GAC media. While removing chlorine, UV carries the added benefit of thorough water disinfection, including the ability to inactivate chlorine-resistant microorganisms.
Evoqua Water Technology’s range of UV dechlorination systems have been developed using scientific knowledge gathered over the past 20 years operation. Outside of food and beverage, UV systems are 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.
