Unit 2

SUBJECT- ENVIRONMENTAL ENGINEERING
CSMSS CSCOE,AURANGABAD
1
Prof.C.P.Thosar@ CSMSS
CSCOE,AURANGABAD

MODULE - 2
TREATMENT OF WATER
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CONTENT
 CONVEYANCE OF RAW WATER PIPELINES AND CANALS
 DESIGNING OF RISING MAINS
 TYPE OF VALVES
 TYPE OF PUMPS
 INTAKE STRUCTURE
 TREATMENT OF WATER
 AERATION
 SEDIMENTATION
 COAGULATION
 RAPIT MIXING
 CLARIFLOCCCULATOR
 DESIGN CRITRRIA FOR FLOCCULATION BASIN USING
ROTATION PADDLES
 PLATE SETTLER
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CONTENT
 TUBE SETTLER
 FILTRATION
 TYPESOF FILTERS
 DISINFACTION
 REQUIREMENT OF AN IDEAL DISINFACTANT
 MECHANISM OF DISINFACTION
 WATER SOFTENING METHODS
 DEMINERALISATION/DEIONIZATION
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2.1CONVEYANCE OF RAW WATER
PIPELINES AND CANALS
 2.1.1.Pipelines
 2.2.2.Aqueducts
(Open channels)
 2.1.3.Advantages of Pipelines and Aqueduct
Systems
 2.1.4 Disadvantages of Pipelines and Aqueduct
Systems
 2.1.5 Hydraulics of Conduits
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2.1.5 Hydraulics of Conduits
 Fluid Flows
1.Classification Based on Variation with time
2. Classification Based on Variation with space
 Flow Type & Examples
A steady flow can be uniform or non-uniform and
similarly an unsteady flow can also be uniform or
non-uniform.
For steady flow discharge is constant with time and
for a uniform flow the area of cross section of the
fluid flow flow is constant through the flow path.
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2.1.6 Laying of Pipes
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2.1.7 Joints in Pipes
1.Joints in Cast Iron Pipes
(a)Bell and Spigot Joint
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(b)Expansion Joint (c)Flanged
Joint
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2.Joints in Concrete Pipes
(a)Cement Collar Joint (b)Simplex
Joint
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2.1.8.Testing of Pipelines
 A Pipeline section about 300 m length is tested
for leakage, strength etc.
1.Pressure Test
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 2.Leakage Test
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2.2DESIGNING OF RISING MAINS
2.2.1 RISING MAINS
The water, after pumped, is taken to the high levelled
gravity pipe through the rising main.
 The rising main may be of cast iron or asbestos cement
pressure pipes.
 The velocity of flow in the rising main should not be less
then 0.75 m/sec. at any time of flow.
2.2.2 DESIGN STEPS
Following are the step for design of the rising main.
STEP 1:Assume the velocity of flow in the rising main.
STEP 2:Determine required cross-sectional area of the
rising main.
STEP 3: 2:Determine required diameter of rising main.13
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2.3 TYPE OF VALVES
 The fixtures which are fixed along the distribution
system are know as valves.
 PURPOSES SERVED
1.Control the rate of flow of water.
2.Releases or admits air into the pipeline.
3. Prevents or detects leakage.
4.Meets the demand during emergencies.
5.Make the distribution system more efficient.
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2.3.1 SLUICE VALVE.
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2.3.2 AIR RELIEF VALVE
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2.3.3.PRESSURE RELIEF
VALVE
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2.4 TYPE OF PUMPS
 2.4.1Gear Pumps
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 2.4.2 Rotary Vane Pumps
 2.4.3Screw Pumps
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 2.4.4 Bent Axis Pumps
 2.4.5 Inline Axis Pumps
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 2.4.6 Radial Piston Pumps
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2.5 INTAKE STRUCTURE
 The raw water required for any water supply
scheme is withdrawn from a surface source like
river, reservoir, lake or canal, or from underground
source like well or spring.
 When the withdrawal of water is from surface
source, a constriction called intake structure is
provided to collect fluctuating levels, and discharge
it into pipe.
 Intake structure mainly consist of:
1) Conduit with protective works,
2) Screens at open ends
3) Gates and valves to regulate the flow, and
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2.5.1 FACTORS GOVERNING THE
LOCATION OF INTAKE
 It should be near the treatment plant to cut down the cost
of conveyance.
 It should be located in the comparatively pure zone of
water source to reduce the load on treatment work.
 It should not be located on the downstream side of the
sewage disposal.
 It should not be located on curves.
 It should be located at such a site from where it can draw
water even during driest period of year.
 It should be away from navigation channels as it may
admit raw water polluted by discharge of wastes by
ships.23
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2.5.2 TYPES OF INTAKES
 1.SUBMERGED OR LAKE INTAKE
 2.EXPOSED INTAKES
A) Canal Intake.
B) Reservoir Intake.
 3.RIVER INTAKE.
 4. MOVEBLE INTAKE
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1.SUBMERGED OR LAKE INTAKE
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2.EXPOSED INTAKES
A) Canal Intake.
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B) Reservoir Intake.
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3.RIVER INTAKE.
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4. MOVEBLE INTAKE
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2.6 TREATMENT OF WATER
2.6.1 Necessity of Treatment of Water
 The following are the objectives of treatment of water.
 To make water odour free and tasty.
 To make the water safe and sparkling for drinking and
domestic purposes.
 To make it colourless.
 To remove dissolved gases and turbidity of water.
 To make it free from all objectionable impurities
present in suspension, colloidal or dissolved from.
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 To remove harmful bacteria.
 To remove hardness of water.
 To make the water suitable for a wide variety of
industrial purposes like dyeing, brewing, soft
drinks, steam generation etc.
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2.6.2.LAYOUT AND
COMPONENTS OF WATER
TREATMENT PLANT
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2.7 AERATION
 The process of exposing large surface of water to
the atmospheric air is called aeration.
 Its main purpose is to absorb more oxygen and
let out unpleasant odours and gases and oxidise
Fe and Mn in water.
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2.7.1 Objectives of Aeration
 To increase oxygen contents in water for
imparting freshness.
 To expel volatile substances and gases like
H2S,CO2,causing bad taste and odour.
 To oxidize iron and manganese so that these can
be precipitated and removed.
 To destroy bacteria to some extent, by agitation of
water during aeration.
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2.7.2 METHODS OF
AERATIONS
1.By Using Fountains, Spray Nozzles.
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2.Gravity or Free Fall Aerators.
(a)Cascade Aerators:
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(b)Inclined Apron Aerator:
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3.Trickling Beds or Multiple Trays.
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4.BY AIR DIFFUSION
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EXAMPLES
 The maximum daily demand of water is 114 MLD.
Design aeration fountain(cascade aerator).
Solution:
Q=114MLD
(i) Diameter of bottommost cascades:
Design flow, Q= 114MLD
= 114 X 106 Lit/day
= 4750 m3/hr.
Loading rate= 0.03m2/m3/hr.
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2.8 SEDIMENTATION
 Principle of sedimentation is applied for the
removal of
(i) Grit in grit chamber
(ii) Destabilized floc in clariflocculators,
(iii) Particulate matter in primary and secondary
settling basins.
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2.8.1 TYPE OF
SEDIMENTATION
1.PLAIN SEDIMNETATION
(Settling velocity of a discrete particle depends upon
specific gravity and diameter of the particle,
gravitational acceleration and kinematic viscosity)
2. SEDIMENTATION WITH COAGULATION OR
CHEMICALLY ASSISTED SEDIMENTATION
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2.8.2 Type of Sedimentation
Tanks
 1.Fill and Draw Type.
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2.Continuous Flow Tank
(a) Horizontal Flow Type:
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(b)Vertical Flow Type:
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2.9 COAGULATION
 The process of mixing certain chemicals to water to neutralize the
electrical charges and to form an insoluble, gelatinous flocculent
precipitate for absorbing and entraining suspended and colloidal particles
of impurities is called coagulation.
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Factor affecting Coagulation
 Type of coagulant
 Dose of coagulant
 Time and method of mixing the coagulant.
 Character of water
1. Ph of water
2. Temperature of water
3. Nature and quantity of suspended matter.
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2.9.2. Coagulation process
 Following processes
1. Feeding
2. Mixing
3. Flocculation
4. Clarification or sedimentation.
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By toothed wheel By helical screw
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1. Feeding- a)Dry feeding

B) Wet feeding
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 Mixing
In order to cause the complete dispersion of the
added coagulant into the entire mass of water,
mixing devices are required.
The violent agitation of water can be achieved by
using mixing devices like compressed air,
centrifugal pumps and mixing basins.
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 Compressed air device.
(By passing compressed air from bottom surface of
mixing basin)
 Centrifugal pump.
(There will be efficient dispersion of coagulant in water
while passing through the impeller of pump.)
 Mixing channel with flume.

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 Mixing basin with baffle walls.

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 Mixing basin with mechanical devices

 Flocculation
In colloid chemistry, flocculation refers to the process
by which fine particulates are caused to clump together
into a floc. The floc may then float to the top of the liquid
(creaming), settle to the bottom of the liquid
(sedimentation), or be readily filtered from the liquid.
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 Clarification or sedimentation.
After flocculation water is admitted into basins called
clarifiers or settling basins.
Water is detained in a such tank for a detention
generated under flocculation, settles down in the
form of sludge
The clear water taken out through outlet
arrangements and generally admitted to filtration
tanks for further purification.
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2.9.4 Common Coagulants
Following common coagulants are used:
1. Alum or aluminum sulphate.
2. Chlorinated copperas
3. Magnesium carbonate and lime
4. Ferrous sulphate and lime
5. Sodium aluminate
6. Polyelectrolytes.
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2.11 CLARIFLOCCULATOR
 Clariflocculator is a combination of flocculation and
clarification in a single tank. It has two concentric
tanks where inner tank serves as a flocculation basin
and the outer tank serves as a clarifier.
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2.15 FILTRATION
 Filtration is the process of separating suspended solid
matter from a liquid, by causing the latter to pass
through the pores of some substance, called a filter.
The liquid which has passed through the filter is called
the filtrate.
 Filtration is a process of removing particulate and
bacterial impurities which could not be removed in
earlier processes, from water by passing it through a
porous medium.
 It is an important stage in the purification of water.
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2.15.2 FILTER MATERIALS
 Sand
 Anthracite
Anthracite, often referred to as hard coal, is a hard,
compact variety of coal that has a sub-metallic luster. It
has the highest carbon content, the fewest impurities, and
the highest energy density of all types of coal and is the
highest ranking of coals.
[ Carbon content (%): 92 – 98]
 Garnet sand or limonite
 Locally available materials
 Gravel
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2.16 TYPE OF FILTERS
2.16.1 SLOW SAND FILTER
The filter media is supported by this base material
LAYER SIZE OF GRAVEL
First layer(Bottom) 40 TO 65 mm
Second layer 20 TO 40 mm
Third layer 6 TO 20 mm
Fourth layer(Topmost) 3 TO 6 mm
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2.16.2 RAPID SAND FILTER OR
MECHANICAL SAND FILTER.
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2.17 DISINFECTION
 Disinfection is a process of killing all pathogens.
 Sterilization is a process in which the total and
complete destruction of all types of bacteria takes
place.
 Theory of Disinfection
Safe water means
1.Water free from bacteria.
2.Water aesthetically acceptable.
3.Water free from excessive minerals and
poisonous matter.
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Factors affecting the efficiency of
disinfection.
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 Nature and concentration of organisms.
 Nature and concentration of disinfectant.
 Temperature of water.
 Time of contact
 Nature of physical agent.
 Nature of water to be disinfected.
 pH of water.

Disinfecting agents.
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1.Physical agents.
 Heat
 Light (natural sun radiation, artificial)
2.Chemical agents.
 Potassium permanganate (used in hospitals)
 Ozone
 Chlorine and its compounds
 Bromine (use in swimming pools)
 Iodine (used in tablet form)
 Phenol and phenolic compounds
 Acids and alkalies
 Heavy metals and related compounds
 Dyes
 Soaps and synthetic detergents
 Hydrogen peroxide
 Quaternary ammonium compounds.

CHLORINATION
 Chlorination is the process of adding chlorine to
drinking water to disinfect it and kill germs.
Different processes can be used to achieve safe
levels of chlorine in drinking water
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CHLORINATION PRACTICS
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Plain or Simple Chlorination:
The application of chlorine to raw water before
releasing for drinking is called as plain chlorination.
 This is use when, turbidity and colour of water is low.
 Row water is less polluted.
 Iron and manganese concentration is less then 0.3
mg/lit

Breakpoint chlorination
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 Breakpoint chlorination is the application of sufficient chlorine to
maintain a free available chlorine residual.
 The addition of chlorine to a water that contains ammonia or nitrogen-
containing organic matter produces an increased
combined chlorine residual.

Water softening methods
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 Ion-exchange resin method.
 Lime softening.
 Washing soda method.
 Distillation and rain water.
 Reverse osmosis.

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