Ultraviolet dechlorination (UV dechlorination) is not as well-known as UV water treatment. Due to the widespread use of chlorination of water, chlorine residue in water has become a problem in many industries. In our homes and many industrial processes, we need pure water that is free of chlorine. So, many dechlorination methods have been tried to get rid of the chlorine left in water. After practical use and selection, before the application of UV, the most popular methods are those that use granular activated carbon filters and neutralizing chemicals.
The use of granular activated carbon filters is a physical treatment method. When chemical treatment methods are mentioned, multiple neutralizing chemicals are the mostly used. As an oxidant used to control microbial levels, most water treatment plants use free chlorine in gaseous form. In addition to the direct use of free chlorine, they also introduce it into the water by using sodium hypochlorite, chlorine concentrations, or other chlorine compounds. Both the use of granular activated carbon filters and neutralizing chemicals can to some extent reduce the chlorine existed in the water to be treated.
However, with the use of the above two kinds of dechlorination methods, more and more problems emerged. That is why UV dechlorination has gained wider acceptance. Compared with the traditional methods, UV dechlorination show its superiority. Next, we will first look at why chlorine is not acceptable in the treatment of drinking water and for certain industrial use, followed by why UV dechlorination is better than the use of granular activated carbon filters and chemical dechlorination methods.
Chlorine in Drinking Water Treatment
When free chlorine is add to the water to be treated, trihalomethane (THM), a harmful by-product, will be formed if the water contains naturally occurring humic acids, fulvic acids or other substances. 90% of trihalomethane is chloroform. Other components include bromodichloromethane (CHCl 2 Br), dibromochloromethane (CHBr 2 CI), and bromoform (CHBr 3).
Since THM has been shown to cause cancer in animals in experiments even at a low concentration, the US Environmental Protection Agency has already set its maximum containment level in drinking water at 100 units per million as early as in 1979. To Learn more about chlorination of water, please go to our previous blog: UV Water Treatment and Chlorination Treatment.
Chlorine in Industries
The existence of chlorine is also unacceptable in certain industries, especially those with precise manufacturing processes. We have introduced why UV treatment is the only choice for sterilization without changing the taste in beverage production industry in our previous blog: Beverage UV Sterilization. The reason why UV is also great for dechlorination is that firstly, it is widely known that chlorine can affect both the taste and smell in drinking water and beverages. Secondly, chlorine in the water will also cause pollution, which will accelerate the erosion of vessels, valves and piping in certain equipment. In addition, the presence of chlorine can also cause damage to reverse osmosis (RO) membranes and deionization resin units in delicate processing equipment.
Therefore, chlorine should be completely removed once it has done its disinfection job. For industrial use, common dechlorination methods include the use of granular activated carbon filters and neutralizing chemicals like sodium bisulfite and metabisulfite. Both of the two types of methods can achieve the removal of chlorine to a certain extent. However, they all have their own drawbacks.
Granular Activated Carbon
Granular activated carbon is commonly used in the water treatment for households, beverage production, pharmaceutical manufacturing and point-of-use units in commercial applications. The problem lies mainly in its arrangement. Granular activated carbon filters are usually placed upstream of RO membranes. Because of the porous structure of the filters and the nutrient-rich environment, they often become incubators of bacteria.
Sodium Bisulfite and Sodium Metabisulfite
Both sodium bisulfite and sodium metabisulfite are commonly used dechlorination compounds in the industry. In the process, they are arranged in front of the RO membranes. The problems with both compounds are similar to those with granular activated carbon filters. Solutions that contain them can cause biological pollution to RO membranes just because they are themselves incubators of bacteria.
Not only that, the use of sodium bisulfite and sodium metabisulfite will also increase the maintenance work for equipment like dosing equipment. Sodium metabisulfite can scale on RO membranes. They also produce sodium sulfate, which will affect the odor and taste of the water.
UV Dechlorination
With the emergence of problems in the use of granular activated carbon filters and neutralizing chemicals, UV dechlorination has gradually become a competitive alternative. UV can provide a more efficient and thorough dechlorination solution.
UV can cause photochemical reactions in water, which will dissociate the free chlorine in the water and form hydrochloric acid. For the combined chlorine like mono-chloramine, di-chloramine, and tri-chloramine, all of them can be efficiently dissociated by the UV radiation. Through the exposure to high-intensity and broad-spectrum UV radiation, free chlorine and chloramines in the water can be converted into by-products that can be easily removed.
Thin-film composite membranes are widely used in many RO units of the water treatment systems. They are popular because they are highly efficient. However, they can’t withstand a high level of chlorine in the water. Therefore, placing UV dechlorination equipment upstream of the entire system can effectively dechlorinate the water. In addition, such arrangement can reduce the use of activated carbon and other chemical feeds.
When UV is used for water dechlorination, the selection of UV dose should be made based on the physical conditions of the water to be treated. They include the absorption of UV in the water, the total chlorine level in the water, the ratio of free chlorine and combined chlorine, background level of organics and the target reduction concentration. For removing free chlorine, the usual UV dosage should be 15-20 times higher than the normal 30,000 microwatt-seconds per square centimeter. For the high dose of UV applied, RO membranes can stay clean longer. Their lifespan can be significantly extended.
Other Advantages of UV Dechlorination
The advantages of UV in both water treatment field and dechlorination application stems from the fact that UV treatment is a non-chemical process. We have discussed the Advantages and Disadvantages of UV Water Treatment in our previous blog. Although UV treatment cannot be perfect, its comparative advantage over the chemical treatments is still clear.
In addition to what has been mentioned above, another advantage of UV dechlorination is that it can completely remove the total organic carbon (TOC) contained in the water. In addition, UV dechlorination eliminates the risks associated with the mixing of bisulfite and the risk of introducing harmful microorganisms into a RO system.
Applications of UV Dechlorination
Due to the problems existing in the traditional dechlorination methods, some industries are looking forward to the emergence of better dechlorination methods. UV dechlorination has been widely applied to meet this expectation. These industries include the food and beverage processing industry, pharmaceutical industry, power generation industry, electronics industry, etc.
Advantages of Buying Directly from a Manufacturer
In previous times, manufacturers encountered obstacles when it came to directly reaching consumers due to financial limitations. This led to the introduction of distributors, acting as intermediaries between manufacturers and consumers. These middlemen, commonly known
Select Your Right Sized UV Water Purifier
The significance of a UV water purifier for maintaining the cleanliness and health of your water environment, whether it's an aquarium, pond, or a commercial space, cannot be overstated. However, when it comes to choosing
Keep Your Water Safe and Clean with a UV Water Purifier
Water pollution remains a significant issue in the world today, affecting numerous people worldwide. This compromised water quality poses severe health hazards. UV water purifiers have emerged as an effective, chemical-free solution to combat these
