1. Filtration & The Water Cycle

2. Not Much To Go Around
There are 326 quintillion (million trillion) gallons of water on Earth. Most of it is found in the ocean.
326,000,000,000,000,000,000 gallons 
However, if Earth’s water could fit into a gallon container, only 3 tablespoons would be available to us. The rest would be frozen or salty.

3. Not Much To Go Around
Available for humans

4. Water Cycle
The water cycle, or “hydrologic cycle” describes the movement of water on Earth.

5. Evaporation Water  Gas
When liquid water becomes a gas and enters the atmosphere.
Water  Gas
Example:
When water boils, it EVAPORATES

6. Evaporation
Liquid water doesn’t need to boil to evaporate into the air.
If you leave a glass of water out, the water will eventually evaporate at room temperature.
Example:
Water from the ocean EVAPORATES, becomes water vapor and ascends into the atmosphere.

7. Transpiration
Evaporation of water from plant leaves; this vapor enters the atmosphere.

8. Condensation When water vapor (gas) cools and becomes a liquid.
Clouds are liquids! They are a made up of tiny droplets of water! As warm, moist air rises, it cools, becomes a liquid, and forms clouds.

9. Condensation is EVERYWHERE!
Water drops CONDENSE on the outside of a cold glass.
These water drops came from water vapor in the air, not your drink. The cold glass is cooling the air outside of it.

10. Precipitation
When water falls back to the earth.
RAIN
HAIL
SNOW

11. Runoff
Rainfall not absorbed by the soil will flow along the surface and into a river, lake, or ocean.

12. Seepage
When water absorbs into the ground

13. Other places water is stored

14. Water Treatment
So, how do cities convert precipitation into clean water for municipal use?

15. Water Treatment occurs in 7 steps:
1st Filtration
Coagulation
Settling
2nd Filtration
Chlorination
Aeration
Treatment

16. 1st Filtration
Screens used to remove large debris.

17. Coagulation
Also known as “flocculation”. Chemicals are added to clump dirt/soil for easy removal.

18. Settling & 2nd Filtration
For settling, the water is left undisturbed for several hours to allow particles to drop to the bottom for removal.
2nd filtration involves passing the water through a fine substance, such as sand or vermiculite, in order to remove tiny particles.

19. Chlorination
Liquid chlorine or chlorine gas is added to the water in order to kill microorganisms, including bacteria. This is essentially bleaching (bleach contains chlorine).
It doesn’t take much bleach to kill bacteria. The amount added does not affect health or taste.

20. Aeration & Treatment

21. Aeration & Treatment
Aeration is just another method of removing microorganisms. Oxygen and “friendly” bacteria are added to kill more threatening bacteria.
Fluoridation of water (adding the chemical Fluoride) began in the U.S. in the 1940s to serve public health. Over 75% of the U.S. population receives fluoridated water from its taps today.