Aeration for raw water for removing taste and odor which may either be due to organic waste for surface sours, or due to dissolved metals, salts and gases in ground water.

1. Aeration :-
1) Aeration is the process of exchange of
gases by creating good interface between
liquid phase and gas phase.
2) It is the process of bringing water in
intimate contact with air, while doing so the
water absorbs oxygen from the air.
3) CO2 can remove up to 60%.
4) Iron, Man
5) H2S & other gases are also removed up-to
certain extent from the water.

2. Objectives of Aeration :- 1) To add the oxygen, to
impart freshness to water.
2) To remove or decrease the CO2 content of water &
thereby reduces its corrosiveness & raise its pH value.
3) To remove H2S content of water & thereby removal
of odor.
4) To remove CH4 & taste caused due to organic
decomposition.
5) To convert iron & manganese from their soluble
states to their insoluble states, so that these can be
precipitated & removed and thereby we can remove
color, taste & odor.
6) To add oxygen, to oxidize organic matter & thereby
removal of volatile substances.

3. Factors Affecting Aeration Process :-
1) If the partial pressure is more, more will be the
solubility & rate of exchange of gas & thereby
more will be aeration.
2) 2) If the temperature of water is less, less will be
the solubility & less will be aeration.
3) If the concentration of impurities is more then
solubility will be less & thereby aeration will be
less.
4) If the surface area of interface is more, more will
be the rate of exchange of gases & thereby
aeration will be more.

4. 5) If the thickness of interface is more, less will be
the rate of exchange of gas & thereby aeration will
be less.
6) If time of contact is more then more will be
exchange of gas & thereby aeration will be more.
7) If degree of under saturation is more then fast
will be rate of exchange & thereby aeration will be
more.

5. Limitation of Aerations :-
1) It is not an efficient process for removal of tastes
& odors caused by relatively nonvolatile
substances such as oils, algae & industrial
wastewater.
2) Odor removal is 50% when symura bacteria is
present.
3) Aeration may add more oxygen in water &
making it more corrosive.
4) Fe & Mn can not be precipitated by aeration
when organic matter is present.

6. 5) Possibility of air borne contamination is there.
6) Additional lime may be required to neutralize the
CO2 that would be removed by aeration.
7) Aeration is not economical in colder months or
state or area.

7. Types of Aerators :-
1) Spray Aerators.
2) Air Diffuser basins or Diffused Aerators.
3) Gravity Aerators:
a) Cascade Aerator
b) Multiple Tray Aerator
c) Inclined Apron Aerator
d) Slopping Tray Aerator

8. Cascade Aerators :-
1) Simplest free fall
aerator.
2) Waterfalls & weirs of
any kind are cascade
aerator.
3) Water allowed to fall
through a certain height
of 1 to 3 m due to this
water comes into close
contact with air.
4) It consist of 3 to 9 steps
of concrete or metal.
5) Rise of steps should be
20 to 50 cm.

10. Inclined Apron
Aerators :-
1) Water allowed to
fall along an
inclined apron
which is usually
studded with riffle
plates.
2) Due to the riffle
plates water jumps
into the atmosphere
causing more
aeration.

11. Spray Aerators :-
1) Spray aerator divide the water flow into fine
streams & small droplets which come into
intimates contact with the air in their trajectory.
2) Water is sprinkled into atmosphere in the form of
fine spray or jets or droplets through nozzles.
3) It requires considerable head (0.75 to 1.5 Kg/cm2)
4) It reduces CO2 by 70 % or more.

12. SPRAY AERATOR

13. Air Diffuser basins :-
1) Perforated pipe network is installed at the
bottom of the aeration tank & compressed air is
blown through these pipes.
2) The air bubbles travel upward through water,
thus causing aeration.
3) Air diffuser basins have a retention period of
about 15 minutes and a depth of 3 to 5 m.