UV Water Treatment and Chlorination Treatment

Tap water must be pure. However, with the discovery of more and more sources of water pollution, our demand for water purity is higher than ever before. Insufficiently purified tap water can contain a variety of bacteria, viruses, and other harmful microorganisms. There are many water sterilization methods including precipitation, filtration, adsorption, distillation, boiling, chlorination and UV treatment. Among these methods, chlorination and UV water treatment are the most commonly applied solutions for the purification of tap water for family use.

Problems Associated with Chlorination

Chlorination treatment has a good effect on killing bacteria, viruses and other microorganisms in water. But with the use of chlorination treatment for many years, people have noticed the troubles caused by this kind of treatment. Even it is not obvious, but the effect of chlorination on the taste of the water was noticeable. However, this is not the only problem. Chlorine will react with other elements in the water during the sterilization process, resulting in the formation of a toxic ingredient called trihalomethane. EPA has confirmed the evidence of relation between long-term exposure to high levels of trihalomethane and bladder, colon and rectal cancers. There is also growing evidence of a relation between higher rates of birth defects in pregnant women and higher use of chlorinated tap water.

You might be thinking that since water chlorination is not so good, why not just give it up? This is because we have to. If the water is not chlorinated, the problems posed by harmful microorganisms in the water will far outweigh the effects of trihalomethane. Moreover, chlorination of water has long been the only viable sterilization method for municipal tap water. That’s why the problems in chlorination of tap water has been known for years, but we still use it. The good news is that we no longer need to rely solely on this approach. UV treatment can exceed chlorination in sterilization effectiveness while does not produce any by-products that are harmful to human health.

Principles of UV Water Treatment

Sunlight is the best disinfectant. But the truth is that ultraviolet light does not directly kill bacteria, viruses and other microorganisms. The function of UV sterilization is to control the further reproduction of microorganisms by penetrating the cells of the organism, destroying the DNA of the cells, thereby destroying their reproductive ability. If the cells of microorganisms are not capable of reproduction, then they are no longer harmful to the human body. In typical UV water treatment systems, UV lamps for sterilization are installed in quartz tubes or glass tubes. When the system works, the water to be treated will flow by these lamps. By receiving UV radiation, the water will be sterilized.

UV water treatment has a broad application range. Today, UV technology is not just available for municipal water treatment. UV treatment solutions are also widely adopted in aquariums, swimming pools and other commercial water-related environments. UV treatment also plays a big role in beverage production, liquid sugar processing and many other enterprises.

Advantages of UV Water Treatment over Chlorination

Compared with chlorination, UV water treatment offers a chemical-free but equally efficient method of sterilization. Compared with traditional sterilization methods, UV treatment has the following advantages:

1. Uv water treatment can better deal with chlorine-resistant microorganisms

Although chlorination of water can eliminate most harmful microorganisms, it has been discovered that chlorination is not able to kill all of them. For example, cryptosporidium and giardia are typical chlorine-resistant microorganisms. In recent years, many kinds of chlorine-resistant bacteria and microorganisms have been found by scientists. Some of them are extremely resistant to chlorination. For example, M. mucogenicum is one type of them. When M. mucogenicum was inactivated by chlorination, the CT value required needs to be 120 mg/L min. This is about 260 times that for commonly known Staphylococcus aureus. Therefore, it can be concluded that the killing effect of chlorination on such microorganisms is very limited. But UV treatment can effectively kill them.

2. UV water treatment is more economic

Let’s look at the cost of the two methods in terms of economic input. If municipal tap water needs to be chlorinated, large chlorine contact tanks or channels will need to be constructed unless they already exist. There are additional costs associated with excavation and concrete construction. Moreover, many chlorination processes use chlorine gas directly. Due to the danger of chlorine gas, emergency scrubber system and enclosed buildings need to be constructed in advance. Only in this way can a potential chlorine leak be avoided. In addition, if liquid chlorine (sodium hypochlorite) is used instead of chlorine gas, the safe storage of this highly corrosive chemical is bound to incur additional costs. Another requirement for the danger of chlorination is the training of operators. Only in this way can safe operation and proper response to emergency situations be ensured. And this also needs a certain amount of capital investment.

In a UV water treatment system, the maintenance cost of the system will be greatly reduced. UV treatment is free from the economic costs and safety concerns compared with the requirement of chemicals in water chlorination. UV bulbs are durable components which only need to be replaced once a year. This is a very low maintenance cost compared with the purchase of disinfectants that is often carried out in chlorination treatments. Also, the space occupied by UV treatment equipment will be less than that of the chlorination treatment equipment. When treatment time is concerned, UV sterilization only takes a few seconds, while chlorination takes minutes.

3. UV water treatment can effectively eliminate the residue of chlorination treatment

UV water treatment can even do the job that has been left over by chlorination. There are often harmful residues found in chlorinated water. According to sample studies, as high as 1-2 PPM of chlorine or chloramine residues are often present in chlorinated water. This is totally unavoidable in water chlorination since it is a chemical process. And that’s what causes the smell of water to change. Ultraviolet light can destroy chlorine and chloramines by providing energy to water in the form of radiation. UV can also significantly reduce the amount of TOC (total organic carbon) in water and contribute to the reduction of organic pollution. So, UV water treatment can easily achieve the thoroughness that is out of reach by traditional chlorination treatment.

In the above, we have introduced the advantages of UV water treatment compared with water chlorination. By comparison, we can see that UV treatment has obvious advantages in terms of thoroughness of sterilization, economic cost and elimination of chlorination residues. However, it should be noted that UV treatment itself also has certain limitations. This was also mentioned in our previous Blog: Advantages and Disadvantages of UV Water Treatment. But taken together, the advantages of UV water treatment far outweigh its disadvantages. Its shortcomings can be effectively dealt with by pretreatment measures. In addition, the water to be treated often needs to be evaluated and pretreated before UV treatment. For example, to a certain extent, the clarity and flow rate of the water will affect the final treatment effect. In our previous Blog, we have discussed the Influencing Factors in UV Water Treatment. If you want to learn more about UV water treatment, please check it out.