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UPFLOW SLUDGE BLANKETCLARIFIER
BY
N.MANIKANTH
(13MT03ENV008)
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INTRODUCTION
It incorporates the processes ofmixing, coagulation, flocculation and
filtration in a single unified vessel
It is a hopper bottom tank
Suitable for rural areas and small
towns
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SOLID CONTACT
CLARIFIER
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SLUDGE BLANKET CLARIFIER
PRINCIPLE
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PRINCIPLE
In a sludge blanket clarifier, the floc particlesare suspended in a condition of equilibrium
The larger particles will accumulate and form
a sludge blanket
When the water passes through this blanket,the flocs are entrapped
This entrapment gives this unit an edge overthe normal horizontal flow tanks
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IVES THEORY
ASSUMPTIONS:-
The velocity distribution of up- flow over any
horizontal plane is uniform.
The diameter and the density of the individual
floc particle in the blanket is uniform at all
levels.
The free fall velocity of an individual floc
particle can be obtained by using Stokeslaw.VS=g ( S- )d2/ (18* )
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Blanket layers can be considered toremain in a state of equilibrium
momentarily when up flow velocity is
equal to settling velocity of flocs.
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BLANKET STABILITY
The sludge blanket is more or less a floc-filter which entraps turbidity from rawwater and allows only clear water to passthrough.
Efficiency of clarifier depends upon thestability of the blanket.
Under unstable blanket condition, theeffluent may have even higher turbiditythan the influent.
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FACTORS EFFECTING
BLANKET STABILITY
Blowing up of blanket by sudden
increase in up-flow velocity
Rupture/cracking of blanket
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ADVANTAGES
In a single unit, processes such ascoagulation, floculation and clarification orfiltration are carried out
Detention time of 1-2 hours may be sufficient
The unit can be so designed such that itmakes use of hydraulic energy only
It provides higher over floe rates thanconventional horizontal flow tanks
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As the previously formed sludge helpsin clarification, lesser chemical dosage
is required
Microbial removal is better than in
conventional horizontal flow tanks
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DISADVANTAGES
Requirement of skilled personnel
Low waste sludge solids content
Sludge blanket control
Surfacing of light flocs during low
turbidity flow
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APPLICATIONS
Potable WaterTreatment
Softening
Turbidity Removal
Iron and ManganeseRemoval
Color Removal
Wastewater Treatment Phosphorus Removal
Filter BackwashReclamation
Industrial Process &Waste Treatment
Suspended Solids
Removal
Metals Precipitation
Landfill Leachate
Boiler Blowdown
Cooling Tower
Makeup
Coal Pile Runoff Many Others
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DESIGN CONSIDERATIONS Kawamura
1 Flocculation Time = approximate = 20 min
2 Settling Time = 1 - 2 hr
3 Surface Loading = 2 - 3 m/hr
4 Weir Loading = 7.3 - 15 m3/hr
5 Upflow Velocity = < 10 mm/min
6 Slurry Circulation rate = up to 3 - 5 time the raw water inflow rate
7 G = 30 - 50 s-1
8 MAXIMUM MIXER TIP SPEE 0.9 m/s (Baffled Channel)
= 0.9 m/s (Horizontal Shaft with Paddles)
= 1.8 - 2.7 m/s (Vertical Shaft with Paddles)
Equation mixer tip speed = DN
9 Free Board is approxim = 0.6 m
10 Water Depth = 4 - 5 m.
11 Length and Width ratio = 6 : 1 (minimum 4 : 1) (Rectangular Basin)
12 Width and Water Depth = 3 : 1 (maximum 6 : 1) (Rectangular Basin)
13 Blade area/Rapid Mixing Tank area = 0.1 - 0.2 % (page 121)
14 Blade : Diameter Blade/Diameter Mixing Tank = 0.2 - 0.4 (page 121) 15 Shaft rpm = 8 - 12
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Cont..,
Q,Sim
1 Detention Time = 2 Hr
2 Surface Loading = 2 - 4 m/hr
3 Weir Loading = 7.1 m3/m.hr
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Cont.,
Sheet Master Degree of Environmental Engineering 1 Weir Loading = 7.1 m3/m.hr
2 Surface Koading
- Q < 0.35 m3/min = 0.5 - 1.0 m/hr
mixer tip speed = DN
8:16 AM/2/28/2007 1/2 Design Clarifier Tank(Skert)/DesignCriteria
- Q > 0.35 m3/min = 1.25 - 1.85 m/hr
3 Water Depth = 3 - 5 m.
4 Paddle radius = 65 - 75% of radius for Flocculator
5 Detention Time = 1 - 3 Hr 6 Diameter Tank < 45 m
7 Paddle at bottom tank high bottom =15 - 30 cm
8 Paddle Velocity = 2 - 3 rpm
9 Effective Paddle Area = 10 % Sweep area of the fllocculator
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Cont,
Water Work Engineering Book 1 Flocculation
1.1 Detention Time = 20 - 60 min
1.2 Velocity Gradie = 15 - 60 S-1
1.3 GT = 1x104 - 15x104
1.4 Periperal Velocity of Paddle =0.3 - 0.6 m/s
1.5 Shaft rotation speed = 1.5 - 5 rpm
2 Sedimetation (Coagulation)
2.1 Detention Time = 2 - 8 hr
2.2 Surface Loading = 20 - 40 m3/m2.day
2.3 Weir Loading = 200 - 300 m3/m.day
3 Sedimentation (Softening) 3.1 Detention Time = 1 - 6 Hr
3.2 Surface Loading = 40 - 60 m3/m2.day
3.3 Weir Loading = 250 - 350 m3/m.day
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CASE STUDIES
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CASE STUDY 1
LOCATION : Beaux Bridge, LA (1998)
AIM : Removal of hardness
RAW WATER CHARECTERISTICS :
o Source: well
o Total hardness: 380-400 mg/l as CaCO3
o Flow Rate: Design flows of 104 GPM min-1,042 GPM
maxCHEMICALS : Alum and Lime
RESULT: The effluent total hardness is about 100 mg/l
as CaCO3
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CASE STUDY 2
LOCATION: Trinity River Authority of Texas -Huntsville Water Treatment Plant (1999)
AIM: Turbidity removal
RAW WATER CHARECTERUSTICS:
o Source: Trinity River
o pH: 7 - 8
o Turbidity: 30 - 40 NTU
o
Total Alkalinity: 100 - 120 (as CaCO3)o Flow Rate: 390 GPM min - 3,680 GPM
max
The above analysis are normal values, but
during rainy season the turbidity is over 100NTU
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CHEMICALS:
Oxidant: Chlorine dioxide
Alkalinity Adjustment: Lime
Coagulant: Alum
Coagulant aid: Cationic Polymer
RESULT: Effluent is consistently less
than 1 NTU
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REFERENCES
C. Schlicht The MC CLARIFLOW The
Ultimate upflow solids contact
clarifier (1999)
Dr. S.M.Dhabadgaonkar, Study of
some aspect of sludge blanketclarification in WTP (1977)