5666065-salt water presentation with good information

salt water

1. Salt Water vs.
Fresh Water
A closer look

2. Salt Water vs. Fresh Water
Approximately 97% of the Earth’s water is
salt water in seas and oceans. Only 3% of
our global water supply is fresh water.
Most of this fresh water is not being used,
as it is locked up in glaciers and polar ice-
caps. The rest is located in rivers, lakes,
rain clouds, water vapour in the air and in
groundwater.

4. Salt Water vs. Fresh Water
When ocean water evaporates, the salt is
left behind. The water in clouds falls into
lakes and rivers as fresh water. As water
seeps through the soil, however, it can
pick up salts and minerals. This ‘salty’
water seeps into streams and rivers, which
then carry it back to the oceans.

6. Salinityis a measure of the quantity of
dissolved salt in water
Recall the density of fresh water and salt
water
Is there a way to change salt water into
fresh water?

7. Desalination
Desalination is the technology of
removing salt and other minerals from
water.
There are 2 processes by which this can
be done:
1.Distillation
2.Reverse Osmosis

8. Distillation
Distillation uses evaporation to separate
impurities, such as salt, from pure water. The
water must be heated until it evaporates, so the
pure water rises as steam and particulates stay
behind in brine water. The steam condenses in
another collection container while brine is
ejected.
Distillation has the advantage of using thermal
energy, such as sunlight, thus saving electricity
costs. However, it creates less fresh water as a
percentage of impure water (the recovery rate)
than reverse osmosis.

9. Reverse Osmosis
In reverse osmosis, the feedwater can be either
saltwater or recovered "gray" water from a city's
waste supply. The force of a fan presses
feedwater through membranes with pores that
let water molecules to permeate, but don't allow
salt and pollutants through. A series of filtering
membranes, with progressively sensitive
membranes, are more effective and don't clog
as easily.
Reverse osmosis requires a lot of electricity to
power the fans, as well as chemical treatment of
gray water, but has a recovery rate of close to
50%.

10. GE Desalination Process
http://www.gewater.com/what_we_do/wate
r_scarcity/desalination.jsp
http://www.youtube.com/watch?v=nCCimp
AaIzI&feature=related&safety_mode=true
&persist_safety_mode=1&safe=active
http://www.youtube.com/watch?v=nbPNw
3JaL7w&feature=related&safety_mode=tr
ue&persist_safety_mode=1&safe=active

11. Israeli Desalination Process
http://video.google.com/videoplay?docid=-
533393068543996960

12. Off-shore Desalination
http://www.dailymotion.com/video/x4y8x4_
water-desalination_shortfilms

13. Science Homework
Discuss how salt gets into Ocean water.