UP-TODAY

Overcoming the threat of typhoid

     Cholera and typhoid fever are acute infectious diseases caused by bacteria, most of which occur in areas with dense populations, poor sanitation, and unclean drinking water. In the 19th century, these infectious diseases claimed countless lives. At that time, people's understanding of bacteria was just beginning, and they did not know much about the transmission routes of infectious diseases, nor did they know that poor drinking water caused the disease to develop.

     It wasn't until people discovered that cattle on livestock farms began to gain weight after drinking water from other areas, that it was noticed that cleanliness in the water source could be the key.

     In 1908, An advisor to the water company, Dr. After John L. Leal began pioneering the use of chloride of lime (Calcium hypochlorite) in Jersey City's water sources, typhoid infection rates dropped dramatically. Chlorination and filtration of the water system reduced typhoid fever by 91% in 5 years, and the disease was nearly eradicated in 1936.

Worries of chlorine disinfection

    It is now known that the addition of chlorine to public water systems can reduce the immediate threat of bacteria, but with the gradual improvement of modern living standards, people's requirements for water quality are getting higher and higher.

     Chlorine dissolves in water to form hypochlorous acid, a strong oxidant with an unpleasant odor and high chemical activity, capable of oxidizing and destroying smaller microorganisms for disinfection. However, due to its strong chemical activity, it is not only damage bacteria but also oxidize with other organic molecules in water to form trihalomethanes (THMs), also known as disinfection by-products (DBPs). Long-term drinking of water containing THMs may increase the risk of cancer.

Use of chloramine

     Chloramines are used in public water systems as disinfectants to replace chlorine, which can reduce the level of disinfection by-products in water. Compared with chlorine, chloramines have lower reactivity and are less likely to generate THMs, so they can stably exist in water for a long time to ensure the safety of drinking water. However, the advantage of chloramine is also its disadvantage. The lower reactivity also means that the use of chloramine for bactericidal effect is insufficient in some high bacterial contamination conditions, and the bactericidal effect on specific bacteria is also limited. Also, due to its stable properties, it is relatively difficult to remove in water.

The impact of chlorine and chloramines on life

     The content of chlorine and chloramine added to drinking water is safe for drinking, but chlorine and chloramine have a pungent odor and poor taste, and there may be the risk of disinfection by-products in the drinking water after disinfection. Therefore, it is suggested that the water treated by drinking water purification plants can be boiled to remove chlorine and disinfection by-products before drinking. After boiling the water in the kettle, open the lid and continue to boil for three to five minutes to effectively remove chlorine and chloramines and reduce the content of THM.

     The high activity of chlorine can also cause damage to other water purification filters. For example, reactive functional groups on ion exchange resins tend to interact with chlorine to reduce capacity, thus leaving users unaware that they have been exposed to other contaminants.

     Additionally, excessive exposure to chlorine can dry out and irritate the skin, which can lead to allergic eczema.

Activated carbon technology for dechlorination

     Although boiling is effective for dechlorination and removal of disinfection by-products, it is rather inconvenient.

     The use of activated carbon and CTO activated carbon block can effectively dechlorinate and even remove other organic molecules (including THM, VOCs, etc.). Activated carbon has excellent physical (large surface area) and chemical properties (reactivity), which can quickly remove these annoying organic molecules from drinking water, making it more convenient and safer for humans or pets to drink and use.