Transcript AIM: To explain the steps in the purification of water

AIM: To explain the steps
in the purification of
water
Do Now: List some things
that can cause water to
become unpotable.
Water Treatment
To remove
impurities from
water to make
it potable.
Impurities:
Salt,
microorganisms,
sediment
Desalination
Process to remove salts to obtain
freshwater
Methods of Desalination
1. Distillation
2. Reverse Osmosis
3. Freezing
Distillation
• Saltwater is boiled
and evaporated
• Leaves behind
residue (salt)
• Water vapor is
cooled, and the
freshwater is
collected.
Reverse Osmosis
• Saltwater is put
through a strainer
to trap salt.
• Water molecules
are small enough
to pass through the
strainer
• Salt molecules are
too big to pass
through the
strainer.
Freezing
• Saltwater is frozen
• It separates as it freezes forming ice
and brine slush- ice is free of
almost all salt.
Problem with desalination?
**** All of these methods of
desalination are very
expensive!!!!!
• https://www.youtube.com/watch?v=Jy0v6T
-vnJI
Water purification
To remove harmful chemicals
and microorganisms
1. Sedimentation
2. Filtration
3. Aeration
4. sterilization
1. Sedimentation
• Water is passed through screens to
remove debris (not bound to water
molecules).
• The water is then put into a settling
tank- heavy particles settle to the
bottom.
• Coagulants are added to help with the
settling process
– Coagulants clump sediments
together
2. Filtration
• After water leaves the settling
tank, it is filtered through sand
(1 meter thick)
THE WATER IS NOT STERILE
YET!!!
3. Aeration
• Taste and odor
• Exposure of water to air and
sunlight
• Water is sprayed into the air (mixes
with oxygen) and settles.
• *** Bacteria is still present at this
point
4. Sterilization
• Kills bacteria and microorganisms
• Extreme heat or chemicals
• Chlorine- purifies
– Easy to produce and store
• Ozone
– Sterilizes quicker than chlorine
– Expensive
– Difficult to use- refrigerated- cannot store
for a long time.
• Fluoride- prevents tooth decay
• **very little amount of chemicals are usedthey are dangerous at high concentrations.
1. What is desalination?
2. What are the three most common methods
of desalination? Briefly describe each one.
3. What is the main disadvantage of
desalination methods?
4. What methods are used to purify water?
5. What are some agents used to purify
water?
6. Why is water purification necessary?