Chlorine reduction in water using UV

Chlorine still remains the most commonly used method of providing water disinfection and protection against waterborne pathogens. But there are a number of documented disadvantages to using chlorine.

In some situations it is important to remove free chlorine, such as:

• during food and beverage manufacturing, as it can affect taste and odour;
• when manufacturing pharmaceutical products, to ensure specifications and safety parameters are achieved;
• in chlorinated swimming pools, as swimmers often have allergic reactions or asthma as a result of the combined chloramines that form;
• where reverse osmosis (RO) is used as part of the water treatment process, as the free chlorine can damage the membranes and other sensitive treatment processes.

Activated carbon is a popular method for reducing or removing free chlorine. Granulated carbon (charcoal) is activated by heat treatment resulting in the adsorption of chlorine, chloramines and other organic substances in the water. However, this method has limitations. For one thing, the media used is an ideal habitat for microorganisms, and it is expensive to regenerate or replace. Furthermore, in some situations activated carbon is unable to remove free chlorine to acceptable levels. Finally, removal of high levels of chlorine requires sizable carbon filters and there may be insufficient space to accommodate such a large footprint.

In recent times, UV treatment systems have become a popular option for free chlorine removal. A UV reactor has a smaller footprint compared to the large volumes of carbon required for the same application, and the amount of material requiring replacement and disposal is lower when using a UV system (compared with activated carbon). The method is also chemical-free, so it doesn’t require storage of dangerous chemicals and is environmentally friendly. Furthermore, it doesn’t affect the taste or odour of food and beverages and is safe to use when manufacturing pharmaceutical products. Finally, UV treatment can be used to supplement RO or activated carbon water treatment processes for extra protection. In fact, when used prior to an activated carbon chlorine removal system, UV treatment prolongs the life of the carbon media.

UV-Guard was invited to assist a company specialising in providing renal dialysis machines to hospitals. In this application, total chlorines need to be below 0.1 mg/L, as higher chlorine levels can negatively impact the health of patients. A rural renal dialysis unit was having an issue with fluctuating town water chlorine levels and was struggling to ensure the target of 0.1 mg/L was consistently being met.

UV-Guard proposed the use of a compact but powerful UV water treatment system that reduced total chlorine levels by 85–90%. Furthermore, the UV water treatment system was easy to retrofit into the existing treatment process.

This is a graphical representation of the total chlorine reductions achieved before and after UV treatment. For a larger image, click here.

In renal dialysis, water treatment systems use a combination of devices. As this simplified schematic shows, a UV water treatment system is easy to retrofit in an existing treatment process. For a larger image, click here.

Top image credit: ©stock.adobe.com/au/Sergey Ryzhov