Using Disinfectants other than Chlorine
Are there disinfectants other than chlorine for use in water treatment?
While chlorine is the most commonly used disinfectant in water treatment, it is not the only disinfectant available. Disinfection byproducts (DBPs) form when using chlorine. For this reason, water systems may choose to use alternate disinfectants. These alternate disinfectants for drinking water treatment include:
- Chlorine dioxide (ClO2)
- Ozone (O3)
- Ultraviolet Radiation (UV)
What are some of their advantages and disadvantages?
Each alternate disinfectant has its advantages and disadvantages. The following table shows these advantages and disadvantages. For comparison, chlorine is also shown.
Applied as gas or liquid (hypochlorite)
|Forms DBPs when organic substances are present
Not effective against Cryptosporidium protozoa
Can cause taste and odor problems
Formed by combining chlorine and ammonia
Produced by reacting sodium chlorite with chlorine or hydrochloric acid
Produced by electrical discharge through air or oxygen
Non-chemical disinfection by using ultraviolet radiation at certain wavelengths
* THM stands for trihalomethanes and HAA stands for haloacetic acids. Both are forms of DBPs.
Note: Most systems using any type of chemical disinfectant are required to monitor for total THM (TTHM) and five HAAs (HAA5) in addition to those indicated in the above table.
With all these alternatives, what should a small water system do if it needs to disinfect its water?
Most small water systems use only groundwater. Since most groundwaters have low levels of dissolved organic substances, DBP levels are usually not a major concern. If water systems use hypochlorite, they can use inexpensive equipment and widely available chemicals, and they will need no special technical skills to operate and maintain the equipment. Most small systems find that disinfection using chlorine, especially when added in hypochlorite form, to be the best method of disinfection of their water supply.
For more information
- Chlorination of Drinking Water (PDF, DOH 331-253)
- Stage 1 Rule: Disinfectants and Disinfection Byproducts (PDF, DOH 331-254)
- Disinfection Byproducts page
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