Environmental Engineering -I

L-9
AERATION
UNIT-II
- BY PROF S S JAHAGIRDAR
INTRODUCTION

Aeration is used to remove tastes
and odours, and
to remove minerals such as iron
and manganese from water,...
OBJECTIVES OF AERATION

1. Removes taste and odours caused
due to organic gases.
2. Increases dissolved oxygen content
3. ...
4. Decreases CO2 content and raises
pH.
5. Removes Iron and Manganese.
6. Due to agitation bacteria may get
killed.
7. Can...
HOW DOES AERATION WORK?
Aeration

is the intimate exposure of
water and air.
It is a way of thoroughly mixing the
air an...
Scrubbing action
Oxidation
 Aeration

removes or modifies the
constituents of water using two
methods - scrubbing action and
oxidation. Scrubbing ac...
Scrubbing

action will remove tastes
and odors from water if the problem
is caused by relatively volatile
gases and organ...
When air is mixed with water, some
impurities in the water, such as iron
and manganese, become oxidized.
 Once oxidized, ...
EFFICIENCY
 The

efficiency of the aeration process
depends almost entirely on the amount of
surface contact between the ...
IRON AND MANGANESE REMOVAL
Iron and manganese in well waters occur as soluble ferrous
and manganous bicarbonates. In the a...
The

oxidation products, ferric
hydroxide and manganese dioxide,
are insoluble.
 After aeration, they are removed by
cla...
TYPES OF AERATOR

1. Free fall or gravity aerator
i. Cascade aerator
ii. Inclined apron aerator
iii. Slat tray aerator
iv....
1. CASCADE AERATOR
Simplest

of free fall aerator
Can be constructed of concrete or
metal
Height is 1 to 3 m.
50 to 60...
2. INCLINED APRON AERATOR WITH RIFFLE
PLATES
Water

falls along inclined
plane/apron.
Breaking up of water due to aprons...
3. SLAT TRAY AERATOR
 Consists

of closely stacked super
imposed wood slat-trays
 Water is sprayed evenly on top tray.
...
4. GRAVEL BED AERATOR
Water

is sprayed at the top and it
trickles down the bed of coke or
anthracite.
Thickness of bed ...
TRICKLING BEDS
3-4

trays are kept filled with coke or
stone
Thickness of bed is – 0.5 to 0.6 m
Distance between trays ...
OBJECTIVE QUESTIONS
1. Air diffusion is type of _______ system.
(chlorination/aeration/flocculation/sedimentation).

2. Ir...
THEORY QUESTIONS

Q1. Write note on objectives of
aeration. Also enlist types of
aerators. (Dec 2011, 5 marks)
Q2. Enlist ...
L 9 aeration
L 9 aeration
L 9 aeration
L 9 aeration
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L 9 aeration
L 9 aeration
L 9 aeration
L 9 aeration
L 9 aeration
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L 9 aeration
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Environmental Engineering-I (Water Supply Engg.) - TE (CIVIL)
Course material by PROF S S JAHAGIRDAR, NKOCET, SOLAPUR.

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L 9 aeration

  1. 1. Environmental Engineering -I L-9 AERATION UNIT-II - BY PROF S S JAHAGIRDAR
  2. 2. INTRODUCTION Aeration is used to remove tastes and odours, and to remove minerals such as iron and manganese from water, and to remove carbon dioxide from the water. 
  3. 3. OBJECTIVES OF AERATION 1. Removes taste and odours caused due to organic gases. 2. Increases dissolved oxygen content 3. Removes Hydrogen Sulphide and odour due to it.
  4. 4. 4. Decreases CO2 content and raises pH. 5. Removes Iron and Manganese. 6. Due to agitation bacteria may get killed. 7. Can be used for mixing chemicals
  5. 5. HOW DOES AERATION WORK? Aeration is the intimate exposure of water and air. It is a way of thoroughly mixing the air and water so that various reactions can occur between the components of the air and the components of the water.
  6. 6. Scrubbing action Oxidation
  7. 7.  Aeration removes or modifies the constituents of water using two methods - scrubbing action and oxidation. Scrubbing action is caused by turbulence which results when the water and air mix together. The scrubbing action physically removes gases from solution in the water, allowing them to escape into the surrounding air. 
  8. 8. Scrubbing action will remove tastes and odors from water if the problem is caused by relatively volatile gases and organic compounds. Oxidation is the other process through which aeration purifies water.
  9. 9. When air is mixed with water, some impurities in the water, such as iron and manganese, become oxidized.  Once oxidized, these chemicals fall out of solution and become suspended in the water. The suspended material can then be removed later in the treatment process through filtration. 
  10. 10. EFFICIENCY  The efficiency of the aeration process depends almost entirely on the amount of surface contact between the air and water.  This contact is controlled primarily by the size of the water droplet or air bubble.  The goal of an aerator is to increase the surface area of water coming in contact with air so that more air can react with the water.
  11. 11. IRON AND MANGANESE REMOVAL Iron and manganese in well waters occur as soluble ferrous and manganous bicarbonates. In the aeration process, the water is saturated with oxygen to promote the following reactions: 4Fe(HCO3)2 + ferrous bicarb onate O2 oxygen 2H2O = 4Fe(OH)3 - + 8CO2 water + ferric hydroxide carbon dioxide 2Mn(HCO3)2 + O2 = 2MnO2 manganese bicarbonate oxyg en manganese dioxide + 4CO2 carbon dioxide + 2H2O water
  12. 12. The oxidation products, ferric hydroxide and manganese dioxide, are insoluble.  After aeration, they are removed by clarification or filtration.
  13. 13. TYPES OF AERATOR 1. Free fall or gravity aerator i. Cascade aerator ii. Inclined apron aerator iii. Slat tray aerator iv. Gravel bed aerator 2. Spray aerators 3. Air diffusers 4. Mechanical aerators
  14. 14. 1. CASCADE AERATOR Simplest of free fall aerator Can be constructed of concrete or metal Height is 1 to 3 m. 50 to 60% CO2 reduction
  15. 15. 2. INCLINED APRON AERATOR WITH RIFFLE PLATES Water falls along inclined plane/apron. Breaking up of water due to aprons cause agitation Agitation increases contact of air and water
  16. 16. 3. SLAT TRAY AERATOR  Consists of closely stacked super imposed wood slat-trays  Water is sprayed evenly on top tray.  Water trickles from one tray to the other.  Air is supplied at the bottom with the help of blower (Air flow is in upward direction).  Ventilator discharges air and gases
  17. 17. 4. GRAVEL BED AERATOR Water is sprayed at the top and it trickles down the bed of coke or anthracite. Thickness of bed is 1 to 1.5 m
  18. 18. TRICKLING BEDS 3-4 trays are kept filled with coke or stone Thickness of bed is – 0.5 to 0.6 m Distance between trays is 0.5m Water is sprayed from distribution pipe at the top.
  19. 19. OBJECTIVE QUESTIONS 1. Air diffusion is type of _______ system. (chlorination/aeration/flocculation/sedimentation). 2. Iron and Manganese are removed by ____________ action in aeration. 3. ___________ aerator is commonly used in water treatment plants. 4. Diffused and mechanical aerator are mostly used in _____________ treatment.
  20. 20. THEORY QUESTIONS Q1. Write note on objectives of aeration. Also enlist types of aerators. (Dec 2011, 5 marks) Q2. Enlist different types of aerators and discuss with neat sketch any one in detail.
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