Further treatment of drinking water

1. Fluoridation

1.1. fluroride can help prevent tooth decay

1.2. in some water treatment plants around the world, fluoride is added to drinking water to help prevent tooth decay

1.3. the process is called fluoridation

2. Metonds to kill microorganisms in water

2.1. chlorination

2.1.1. we can kill the microorganisms in water by adding chlorine to it

2.1.2. the process of adding clorine is called chlorination

2.1.3. used in many water treatment plants and some swimming pools

2.1.4. but toxic and has an irritating smell

2.1.5. important to add the appropriate amount of chlorine to water

2.2. adding ozone

2.2.1. used to sterilize the water in swimming pools and some water treeatment works for killing microorganisms in water

2.2.2. ozone vs chlorine

2.2.2.1. more expersive

2.2.2.2. not have an irritating smell

2.2.2.3. more effective

2.2.3. inhaling ozone can cause headache and vomiting so it is important to control the amount of ozone added to water

2.3. using ultraviolet light

2.3.1. used in portable water purifiers, drinking fountains and aquariums