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TABLE OF CONTENTS
EXECUTIVE SUMMARY 2
SLUDGE TREATMENT IN WASTEWATER TREATMENT 3
SLUDGE TREATMENT IN PAAKY 7
RETURN SLUDGE PUMPING STATIONS .............................................................................................................7
EXCESS SLUDGE PUMPING STATIONS ..............................................................................................................7
DISSOLVED AIR FLOATATION UNIT ...................................................................................................................7
SLUDGE STORING TANK ........................................................................................................................................8
SLUDGE DEWATERING BUILDING ......................................................................................................................8
FILTRATE PUMPING STATION ..............................................................................................................................9
AS IS DESIGN 10
PROCESS CALCULATION ......................................................................................................................................10
HYDRAULIC CALCULATIONS .............................................................................................................................15
COST ANALYSIS ........................................................................................................................................................26
MODIFIED DESIGN 27
CALCULATIONS ........................................................................................................................................................27
COST ANALYSIS ........................................................................................................................................................27
NEW DESIGN 28
ANAEROBIC DIGESTION 32
DESIGN CRITERIA FOR ANAEROBIC DIGESTION ......................................................................................33
DESIGN OF ANAEROBIC DIGESTER 34
PROCESS CALCULATION ......................................................................................................................................34
COST ANALYSIS ........................................................................................................................................................49
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EXECUTIVE SUMMARY
his report is prepared to present the design of sludge treatment in Paaky
Wastewater Treatment Plant and Anaerobic digestion. The flowrate is taken
as 100,000 m3 / day and the peak flowrate is 125,000 m3 / day. It includes an
as is, a modified and a new design of the sludge lines and a new design
for anaerobic digestion.TIn as is design of sludge treatment units of Paaky Wastewater Treatment Plant all
process and hydraulic calculations are done for the DAF, sludge storage tank and centrifuge
units. The approximate cost of this project is 4,300,000 $.
In modification of Paaky Wastewater Treatment Plant, sludge storage detention time
is minimized and tank is reconstructed according to chosen storage day. The approximate cost
of this project is 10,000 $.
In new design of Paaky Wastewater Treatment Plant is average flowrate is taken as
100,000 m3 / day. This new design is performed to adapt the range of design criteria. The
approximate cost of this project is 4,700,000 $.
Anaerobic digestion has been designed according to Paaky influent wastewater
parameters. All calculations were done including dimensioning, amount of gas production, heat
requirements. The approximate cost of this project is 10,000,000 $.
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SLUDGE TREATMENT IN WASTEWATER TREATMENTSLUDGE TREATMENT IN WASTEWATER TREATMENT
Wastewater treatment objectives are accomplished by concentrating impurities into solid form
and then separating these solids from the bulk liquid. These concentration of solids, referred to
as sludge, contains many objectionable materials and must be disposed ofproperly. The sludgeresulting from wastewater treatment operations and process is usually in the form of a liquid or
semisolid liquid that typically contains from 0.25 to 12 % solids by weight, depending on the
operations and processes used. Of the constituents removed by treatment, sludge is by far the
largest in volume, and its processing and disposal is perhaps the most complex problem facing
the engineer in the field of wastewater treatment. Sludge disposal facilities usually represent 40
to 60 % of the construction cost of wastewater treatment plants, account for as much as 50 %
of the operating cost, and are the cause of a disproportionate share of operating difficulties. [1]
[2]
Gravity Thickening
Gravity thickening is accomplished in a tank similar in design to a conventional sedimentation
tank. Normally, a circular tank is used. Dilute sludge is fed to a center - feed well. The feed
sludge is allowed to settle and compact, and the thickened sludge is withdrawn from the bottom
of the tank. Conventional sludge - collecting mechanisms with deep trusses or vertical pickets
are used to stir the sludge gently, thereby opening up channels for water to escape and
promoting densification. The supernatant flow that results is returned to the primary settling
tank or to the headworks of the treatment plant. The thickened sludge that collects on the
bottom of the tank is pumped to the digesters or dewatering equipment as required; thus, storage
space must be provided for the sludge. Gravity thickening is most effective on primary sludge.
A photo of gravity thickener is shown below.
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Gravity thickeners used dewatering the treatment sludge are designed on the basis of solids
loading. To maintain aerobic conditions in gravity thickeners, provisions should be made for
adding 24 to 30 m3/m2.day of final effluent to the thickening tank. Typical concentrations of
unthickened and thickened sludges and solids loadings for gravity thickener are shown below.
[3]
[4]
An operating variable, sludge volume ratio normally range between 0.5 and 20 day; the lower
values are required during warm weather. For operation, alternatively, sludge - blanket depth
should be measured. Blanket depths may range from 0.6 to 2.4 m; shallower depths are
maintained in the warmer months.
Flotation Thickening
There are three basic variations of the flotation thickening operation ; dissolved - air flotation
(DAF), vacuum flotation, and dispersed - air flotation. Dissolved - air flotation is being
widely preferred for especially waste activated sludge. Air is introduced into a solution that is
being held at an elevated pressure. When the solution is depressurized, the dissolved air is
released as finely divided bubbles carrying the sludge to the top, where it is removed. Photos of
DAF are shown below. [5]
[6]
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[7]
Activated sludge solids from the secondary clarifiers which are not returned to the aerators are
wasted. The DAF (Dissolved Air Flotation) thickener tanks receive the wasted solids. Solids
enter the DAF tank where they are mixed with water and compressed air. As the air and water
mix, solid particles are lifted to the surface by rising air bubbles in the tank.
The floating solids are then collected by a series of tank skimmers while the water is recycled
back to the raw sewer to be processed through the plant. The solids from the DAF are pumped
to the anaerobic digesters. [8]
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[9]
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SLUDGE TREATMENT IN PAAKYSLUDGE TREATMENT IN PAAKY
RETURN SLUDGE PUMPING STATIONSRETURN SLUDGE PUMPING STATIONS
Return sludge from the clarifiers is pumped back to the distribution chamber before the Bio-P
Tanks.
For each two clarifiers a Return Sludge Pumping
Station is constructed. Each pumping station is
equipped with 5 return sludge pumps, 2 for each
clarifier plus a common stand by. The pumps are
submersible pumps. The pumps are automatically
operated, controlled by the inlet flow meter in order to
achieve a constant return sludge rate.
EXCESS SLUDGE PUMPING STATIONSEXCESS SLUDGE PUMPING STATIONS
Excess sludge is taken from channel 4 and 2 in each of the Process Tank. A total number of 3
eccenter screw pumps are used. Each has a capacity of 167 m/h, 3rd is stand-by. The pumps are
controlled by a timer to remove a preset amount of excess sludge every day. The starting order
of the pumps is alternated once a day to distribute the running time of pumps as equally as
possible.
DISSOLVED AIR FLOATATION UNITDISSOLVED AIR FLOATATION UNIT
The excess sludge is concentrated in dissolved air flotation unit (DAF Unit). The sludge is
mixed with recycled reject water, which is over saturated with atmospheric air under pressure.
When this mixture enter the DAF Unit, fine air
bubbles will from and carry the sludge to thesurface of the DAF Unit, where it is scraped off.
In the unit two pumps are in operation and one
is stand-by. The pumps are operated at the same
time and with the same capacity as the excess
sludge pumps. The starting order of the pumps
alternated once a day to distribute the running
time of pumps as equally as possible.
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Each pressure tank is equipped with a pressure transmitter for the pressure tank in the tank a
pressure switch to activate the compressor.
SLUDGE STORING TANKSLUDGE STORING TANK
The concentrated sludge from the DAF Unit gratitates to a Sludge Storage Tank. The tank is
equipped with slow moving mixers to keep the sludge homogenized and bottom air diffusors to
keep it aerobic. The blowers for the diffusors are controlled by the oxygen transmitter in the
tank. One blower is on duty one is stand-by. The starting order of the blowers is alternated
weekly to distribute the running time of blowers as equally as possible.
Sludge Storage tank before dewatering (centrifuge)
SLUDGE DEWATERING BUILDINGSLUDGE DEWATERING BUILDING
The sludge is dewatered in 2 centrifuges. The sludge is fed into each centrifuges with a 2 step
eccenter screw pump. Each pump has a capacity of 10 m/h. Polymer is added by 2 step
eccenter screw pumps working in parallel with the feeding pumps. The polymer is added on the
suction side of the feeding pumps and mixed with the sludge in the pipe using in line static
mixer.
The sludge pumps and dosing pumps are automatically operated controlled by the pressure in
the centrifuges. The dewatered sludge is transported by a system of eccenter screw pump to an
outside container area situated at the backside of the Sludge Dewatering Building.
The centrifuges and the Sludge Storage Tank are interconnected so that centrifuge cannot be
started unless sufficient amount of sludge is available in the storage tank.
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FILTRATE PUMPING STATIONFILTRATE PUMPING STATION
Filtrated water from the centrifuge is sent to the collection distribution chamber. There are 2
submersible pumps one is stand-by.
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AS IS DESIGNAS IS DESIGN
PROCESS CALCULATIONPROCESS CALCULATION
DISOOLVED AIR FLOATATION
( )( )1.3 1a
a
s f P RA
S S Q
=
A/S = Air to solids ratio, ml(air)/mg (solids)
0.005 0.06 [13]
sa = air solubility, ml/l
f = fraction of air dissolved at pressure P, usually 0.5 [13]
P = pressure ,atm
p = gage pressure, kPa ( 275-350 kPa) [15]
Sa = influent suspended solids, g/m3 (mg/L)
R = pressurized recylce, m3/d
Q = mixed-liquor flow, m3/d
Temp., oC 0 10 20 30
sa, mL/L 29.2 22.8 18.7 15.7
[13]
sa = 18.7 mL/L
P =101.35
101.35
p +=
275 101.35
101.35
+= 3.71 atm
( )( )1.3 18.7 0.5 3.71 10.05
300 1600
R =
R = 1385.6 m3/d
Velocity of the solids = 8 160 L/m2.min
Surface Area =3 3 3
2
1385.6 / 10 /
8 / .min 1440min/
m d L m
L m d
= 120.3 m2
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A =2
4
D= 120.3 => D = 12.5 m => A = 122.7 m2
Solids Loading = 1.2 3 kg/m2hr [13]
Solids Loading = ( ) ( ) 21600 1385.6 4 4 / .122.7
RQ Q x kg m hr A
+ + = = (NOT N THE RANGE)
DAF detention time =3
3
6000.37 9
1600 /
md hr
m d= =
SLUDGE STORAGE TANK
Diameter = 27 m
Depth = 4.3 m
Volume =2 2
327 4.3 24604 4
Ddepth m
= =
Sludge storage tank detention time =3
3
246015.4
160 /
md
m d= (NOT IN THE RANGE) [13]
SLUDGE MASS BALANCE
Input Parameters;
BODinfluent = 320 g/m3
SSinfluent = 300 g/m3
Organic N = 10 g/m3
NH4 = 17 g/m3
TN = 27 g/m3
TP = 5 g/m3
Waste Activated Sludge
Biomass Production;
,
1000000,4(240 135) 0,15 0,081 100000 0,4(240 135)9,23 100000 0,12 20
1 (0,081 9,23) 1 (0,081 9,23) 1 (0,081 9,23)
6235.23 /
x bio
x x x x xP
x x x
kgVSS d
= + +
+ + +=
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31 16235.23 / 1558.8 /1000 0,004
kg d m day =
% Total Solids is assumed 0,4
WASN =
3 3 1 12.21558.8 / (1 8) / 6235.23 0.8 622.56 /1000 100
m day g m kgN d + + =
BOD in WAS = [ ]6235.23 0.65 1.42 0.68 3913.3 /kg d =
NDN =
3 3
3
1 1100,000 27 / 100,000 9 / 622,56
1000 1000
1177.44 /
kg kg g m g m
g g
kgNO N day
=
NDN = (QIR+ QR)NO3.N effluent
1177.44 = (QIR+ 100,000) x 8
QIR= 47,180 m3/day
IR = 0,47
WASP =( )3 3 3100,000 / 5 / 2 / 300 /m d g m g m kg day =
% TP in SS =
300 /4.8%
6235.23 /
kg day
kg day=
% TP in in VSS =
300 /6%
6235.23 / 0.8
kg day
kg day=
P release = ( )6% 2.3% (6235.23 0.8) 184.55 /kg day =
WAS : C60 H81 O23 N12 P mw = 1374 g
TN = (12 x 14) / 1374 = 12.2 %
TP = 31g / 1374g = 2.26 %
Dissolved Air Floatation
Biomass Production;
,
1000000,4(240 135) 0,15 0,081 100000 0,4(240 135)9,23 100000 0,12 20
1 (0,081 9,23) 1 (0,081 9,23) 1 (0,081 9,23)
6235.23 /
x bio
x x x x xP
x x x
kgVSS d
= + +
+ + +=
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31 16235.23 / 155.88 /1000 0, 04
kg d m day =
% Total Solids is assumed 4%
DAFN =
3 3 1 12.2155.88 / (1 8) / 6235.23 0.8 609.93 /1000 100
m day g m kgN d + + =
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Sludgeamount(kg/d) 6235,23
% solid 0,4solid
sludge(m3/d) 1558,81
EFFLUENT
Sludgeamount(kg/d) 6235,23
Sludgeamount(kg/d) 6235,2
Sludgeamount(kg/d) 6235,23
% solid 4 % solid 4 % solid 25
solidsludge(m3/d) 154,337
solidsludge(m3/d) 151,34
solidsludge(m3/d) 24,21
AERATION
CENTRIFUGEDAF SLUDGESTORAGE
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HYDRAULIC CALCULATIONSHYDRAULIC CALCULATIONS
Headloss through Pipe from Secondary Clarifiers to RAS Pumping Station
Q = 100,000 m3/d / 4 = 25,000 m3/d
D = 500 mm
L = 27.53 m
Assume % 1 sludge
Kentrance = 0.5
Kexit = 1
e (roughness coefficient) = 0.045mm = 0.000045m for steel
= 1.14x10-3N.sec/m2 for 15 C
= 1000 kg/m3
00009.05,0
000045.0
104.6sec/.1014.1
)/47.1()5.0()/1000(Re
/47.14/)5.0(
/28.0/
5
23
3
2
3
==
=
==
===
D
e
mN
smmmkgDV
smsm
AQV
f = 0.020 (from Moody Diagram)
H = Hmajor + Hminor
mg
smg
smm
mH
g
VKKK
g
V
D
LfH exitentrance
23.02
)/47.1()15.0(2
)/47.1(5.053.27020.0
2)2(
222
2
90
2
=++=
+++=
RAS Pumping Station
There are 4 + 1 pump:
Type: Submercible
Flowrate: 3.6 m3/h
Head: 10m
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Power: 2.4 kW
Rotation: 2830 d/d
Brand: Flyt/CD 3085 HT 250
Cost: 2.4 kW x 4 x 0.07$ x 365 x 24 = 5,887 $ / year
Headloss through Pipe from RAS Pumping Station (Clarifiers 1 & 2) to CDC 2
Q = 100,000 m3/d / 2 = 50,000 m3/d
D = 700 mm
L = 391 m
Assume % 1 sludgeFind yield stress from Figure 14-6, (a) (Ref: M&E, 2003)
sy = 0.05 N/m2
Find coefficient of rigidity from Figure 14-6, (b) (Ref: M&E, 2003)
= 0.001 kg/m/s
smsm
V
A
QV
/50.1
4
)7.0(
/58.02
3
==
=
Reynolds Number:
VDNR =
where:
NR: Reynolds number, dimensionless
: density of sludge, kg/m3 = 1000 kg/m3
V: average velocity, m/s
: coefficient of rigidity, kg/m/s
63
101//001.0
)7.0)(/5.1)(/1000(xsmkg
msmmkg
NR ==
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Hedstrom Number:
2
2
ysDHe=
9
2
332
1047.1)//001.0(
)/1000)(/03.0()7.0(x
smkg
mkgmNmHe ==
where:
He: Hedstrom number, dimensionless
sy: yield stress, N/m2
Find friction factor from Figure 14-6, (c) [13]
f = 0.0025
D
LVfP
22 =
223
/4189)7.0(
)/5.1)(391)(/1000)(0025.0(2mN
m
smmmkgP ==
msmmkg
mN
P 42.0)/81.9)(/1000(
/418923
2
==
Hminor =g
VKKKK exitent
2)2(
2
9045 +++
Hminor = mg
x 41.02
)5.1()275.06.015.0(
2
=+++
HT = 0.42m + 0.41m = 0.83m
Headloss through Pipe from RAS Pumping Station (Clarifiers 3 & 4) to CDC 2
Q = 100,000 m3/d / 2 = 50,000 m3/d
D = 700 mm
L = 468 m
Assume % 1 sludgeFind yield stress from Figure 14-6, (a) [13]
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sy = 0.05 N/m2
Find coefficient of rigidity from Figure 14-6, (b) [13]
= 0.001 kg/m/s
smsm
V
A
QV
/50.1
4
)7.0(
/58.02
3
==
=
Reynolds Number:
VDN
R
=
where:
NR: Reynolds number, dimensionless
: density of sludge, kg/m3 = 1000 kg/m3
V: average velocity, m/s
: coefficient of rigidity, kg/m/s
1050000//001.0
)7.0)(/5.1)(/1000( 3==
smkg
msmmkgNR
Hedstrom Number:
2
2
ysDHe=
24500)//001.0(
)/1000)(/05.0()7.0( 2
332
==smkg
mkgmNmHe
where:
He: Hedstrom number, dimensionless
sy: yield stress, N/m2
Find friction factor from Figure 14-6, (c) [13]
f = 0.002
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D
LVfP
22 =
223
/6017
)7.0(
)/5.1)(468)(/1000)(002.0(2mN
m
smmmkgP ==
msmmkg
mNP 45.0
)/81.9)(/1000(
/601723
2
==
Hminor =g
VKKKK exitent
2)3(
2
9045 +++
Hminor = mg
x 5.02
)5.1()375.06.015.0(
2
=+++
HT = 0.45m + 0.50m = 0.95m
Headloss through Pipe from 4th Aeration Tank to Excess Sludge Pumping Station
Q = 1558.8 m3/d
D = 400 mm
L = 99 m
Assume % 0.4 sludge
Kentrance = 0.5
Kexit = 1
e (roughness coefficient) = 0.045mm = 0.000045m for steel
= 1.14x10-3N.sec/m2 for 15 C
= 1000 kg/m3
0001125.04,0
000045.0
1026.5sec/.1014.1
)/15.0()4.0()/1000(Re
/15.04/)4.0(
/018.0/
4
23
3
2
3
==
=
==
===
D
e
mN
smmmkgDV
smsm
AQV
f = 0.021 (from Moody Diagram)
H = Hmajor + Hminor
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mg
sm
g
sm
m
mH
g
VKKK
g
V
D
LfH exitentrance
094.02
)/15.0()5.115.0(
2
)/15.0(
4.0
99021.0
2)2(
222
2
90
2
=+++=
+++=
Excess Sludge Pumping Station
Type: monopump
Flowrate: 167 m3/h
Pressure: 3 bar
Head: 20m
Power: 30 kW
Rotation: 270 d/d
Brand: CB 12 K AC IRS/monopumps Dresser
Cost = 30kW x 2 x 365 x 24 x 0.07$ = 36792$/year
Headloss through Pipe from Excess Sludge Pumping Station to DAF Unit
Q = 1558.8 m3/d
D = 400 mm
L = 62.15 m
Assume % 0.4 sludge
Kentrance = 0.5
Kexit = 1
e (roughness coefficient) = 0.045mm = 0.000045m for steel
= 1.14x10-3N.sec/m2 for 15 C
= 1000 kg/m3
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0001125.04,0
000045.0
1025.5sec/.1014.1
)/15.0()4.0()/1000(Re
/15.04/)4.0(
/018.0/
4
23
3
2
3
==
=
==
===
D
e
mN
smmmkgDV
smsm
AQV
f = 0.021 (from Moody Diagram)
H = Hmajor + Hminor
mg
sm
g
sm
m
mH
g
VKKK
g
V
D
LfH exitentrance
064.02
)/15.0()75.015.0(2
)/15.0(
4.0
15.62021.0
2)(
222
2
90
2
=+++=
+++=
Headloss through Pipe from DAF Unit to Sludge Storage Tank
Q = 155.88 m3/d
D = 200 mm
L = 120.65 m
Assume % 4 sludge
Find yield stress from Figure 14-6, (a) [13]
sy = 5.5 N/m2
Find coefficient of rigidity from Figure 14-6, (b) [13]
= 0.012 kg/m/s
smsm
V
A
QV
/057.0
4
)2.0(
/018.02
3
==
=
Reynolds Number:
VDNR =
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where:
NR: Reynolds number, dimensionless
: density of sludge, kg/m3 = 1010 kg/m3
V: average velocity, m/s
: coefficient of rigidity, kg/m/s
10.2//5.5
)2.0)(/057.0)(/1010( 3==
smkg
msmmkgNR
Hedstrom Number:
2
2
ysDHe=
1543055)//012.0(
)/1010)(5.5()2.0(2
32
==smkg
mkgmHe
where:
He: Hedstrom number, dimensionless
sy: yield stress, N/m2
Find friction factor from Figure 14-6, (c) [13]
f = 1
D
LVfP
22 =
223
/122
)2.0(
)/01.0)(65.120)(/1010)(1(2mN
m
smmmkgP ==
msmmkg
mNP 012.0
)/81.9)(/1000(
/12223
2
==
Hminor = negligible
HT = 0.012m
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Headloss through Pipe from Sludge Storage Tank to Centrifuge
Q = 155.8 m3/d
D = 200 mm
L = 22.5 m
Assume % 4 sludge
Kentrance = 0.5
Kexit = 1
e (roughness coefficient) = 0.045mm = 0.000045m for steel
= 1.14x10-3
N.sec/m2
for 15 C = 1000 kg/m3
000225.04,0
000045.0
101sec/.1014.1
)/057.0()2.0()/1000(Re
/057.04/)2.0(
/018.0/
5
23
3
2
3
==
=
==
===
D
e
mN
smmmkgDV
smsm
AQV
f = 0.021 (from Moody Diagram)
H = Hmajor + Hminor
mg
sm
g
sm
m
mH
g
VKKK
g
V
D
LfH exitentrance
006.02
)/057.0()15.0(
2
)/057.0(
2.0
5.22021.0
2)2(
222
2
90
2
=++=
+++=
Headloss through Pipe from Centrifuge to CDC 2 for Supernatant
Q = 130.93 m3/d
D = 300 mm
L = 129.3 m
Kentrance = 0.5
Kexit = 1
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e (roughness coefficient) = 0.045mm = 0.000045m for steel
= 1.14x10-3N.sec/m2 for 15 C
= 999 kg/m3 for 10 C
00015.03,0
000045.0
1052.5sec/.1014.1
)/021.0()3.0()/999(Re
/021.04/)4.0(
/0015.0/
3
23
3
2
3
==
=
==
===
D
e
xmN
smmmkgDV
smsm
AQV
f = 0.036 (from Moody Diagram)
H = Hmajor + Hminor
mg
sm
g
sm
m
mH
g
VKKK
g
V
D
LfH exitentrance
004.02
)/021.0()5.115.0(
2
)/021.0(
3.0
3.129036.0
2)2(
222
2
90
2
=+++=
+++=
Supernatant Pumps
# of pumps: 2:
Type: submercible
Flowrate: 360 m3/h
Head: 6m
Power: 8.8 kW
Brand: Flyt/CP 3140 LT 610
Headloss through Pipe from DAF Unit to CDC 2 for Supernatant
Q = 1402.2 m3/d
D = 300 mm
L = 24.34 m
Kentrance = 0.5
Kexit = 1
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e (roughness coefficient) = 0.045mm = 0.000045m for steel
= 1.14x10-3N.sec/m2 for 15 C
= 999 kg/m3 for 10 C
000015.03,0
000045.0
1095.5sec/.1014.1
)/22.0()3.0()/999(Re
/22.04/)4.0(
/016.0/
4
23
3
2
3
==
=
==
===
D
e
mN
smmmkgDV
smsm
AQV
f = 0.020 (from Moody Diagram)
H = Hmajor + Hminor
mg
sm
g
sm
m
mH
g
VKKKK
g
V
D
LfH exitentrance
011.02
)/22.0()75.06.015.0(
2
)/22.0(
3.0
34.24020.0
2)(
222
2
9045
2
=++++=
++++=
Centrifuges
There are 2 centrifuges.
Capacity: 255 kg solid/h
Nominal velocity (Va): 3500d/d
Nominal Power: 30kW
Boul diameter: 340mm
Brand: Guinard/D3LLC 30C HP
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COST ANALYSISCOST ANALYSIS
UNIT UNIT COST COST
Construction 1,000,000 $
Excess Sludge Pumps 3 20,000$ 60,000$
Compressors (250 l / day) 2 50,000$ 100,000$
Mixers 4 50,000$ 200,000$
Diffusers (9) 340 200$ 68,000$
Sludge Blender 2 10,000$ 20,000$
Sludge feeding pumps 2 5,000$ 10,000$
Polyelectrolyte feeding
pumps2 3,500$ 7,000$
PE ring pump 1 5,000$ 5,000$
Exit sludge pump 2 5,000$ 10,000$
Centrifuges 2 1,000,000$ 2,000,000$
Liquid PE feeding pump 1 10,000$ 10,000$
TOTAL COST
4,300,000$
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MODIFIED DESIGNMODIFIED DESIGN
Storage should be provided to smooth out the fluctuations in the rate of solids and biosolids
production and to allow solids to accumulate during periods when subsequent processing
facilities. Storage is particularly important in providing a uniform feed rate ahead of the
following processes; mechanical dewatering, lime stabilization, heat drying and thermal
reduction.
Sludge tanks may be sized to retain the sludge for a period of hours to a few days. If sludge is
stored longer than 2 to 3 days, it will deteriorate, become odorous, and be more difficult to
dewater.
In as is design sludge retention time is too long (15 days). Therefore diameter of the tank isreduced by constructing inner sidewall.
CALCULATIONSCALCULATIONS
Sludge Retention Time is assumed 4 days
Required Volume of storage tank = (4days) x (154,337 m3/day)
[ (D2) / 4] x 4,3 m = 617 m3
D= 13.5 m
Diameter is taken 13.5 m.
Sludge Retention Time = 4 days
COST ANALYSISCOST ANALYSIS
COST
Construction 10,000$
TOTAL COST
10,000$
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NEW DESIGNNEW DESIGN
MECHANICAL SLUDGE THICKENER
In wastewater treatment plants, the sludge cannot be or is not desired to be directly taken into
the dewatering equipment as the sludge content is too low. The solids content of sludge has to
be brought to a higher level, in other words, the sludge has to be thickened prior to dewatering
to obtain maximum efficiency form the dewatering equipments.
Various mechanical thickening devices have started to be frequently utilized in treatment plants
in the last years, including pre-dewatering belts. The pre-dewatering belts can either be used as
a compact unit together with the beltpress, or be used separately as an independent unit.
Advantages;
No separate building
construction is required.
When utilized as a compact
unit with the beltfilterpress,
it does not take up any extra
land, it only causes an
increase in height.
Even in cases where it is
used as a separate unit, it
requires less land than a
DAF thickener or a gravity
thickener of the same capacity.
The initial investment costs are low.
It requires lower polymer and energy consumption compared to other mechanical
thickeners.
The selection of the most suitable pre-dewatering belts is based on the properties of the sludge
to be thickened and the capacity.
The pillow blocks used in the pre-dewatering belt allow effective contact between the sludge
and the belt surface, and thus maximize the efficiency of the equipment. The number of and thespace between the pillow blocks are determined based on the process.
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Comparison of Capacity of Mechanical Thickeners
models Hydraulic capacity (for sludge with a solid content of %0.4-0.8)m3
/h
PDWB-
L
10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105
10 X X X X
15 X X X X X
20 X X X X X X X
25 X X X X X X X
Belt width m 2
width m 2.32
Length m 4.5
Height m 1.3
Filtration length m 3.6
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Motor power kW 0.75
Belt speed m/min 3.7-10.9
Washing water requirement m3/h 7
Air requirement lt/min 50
Belt tension Mechanical
Belt aligment Pneumatic
Sludge scraping Mechanical
Belt protection With proximity limit sensor
Washing nozzles Manually cleaned
COST ANALYSES
UNIT UNIT COST COST
Construction 800,000 $
Excess Sludge Pumps 3 20,000$ 60,000$
Compressors (250 l / day) 2 50,000$ 100,000$
Mixers 4 50,000$ 200,000$
Diffusers (9) 200 200$ 40,000$
Sludge Blender 2 10,000$ 20,000$
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Sludge feeding pumps 2 5,000$ 10,000$
Polyelectrolyte feeding
pumps2 3,500$ 7,000$
PE ring pump 1 5,000$ 5,000$
Exit sludge pump 2 5,000$ 10,000$
Centrifuges 2 1,000,000$ 2,000,000$
Liquid PE feeding pump 1 10,000$ 10,000$
Mechanical Sludge
Thickener1 1,000,000$ 1,000,000$
TOTAL COST
4,700,000$
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ANAEROBIC DIGESTIONANAEROBIC DIGESTION
Anaerobic digestion is among the oldest process used for the stabilization of solids and
biosoldis.In the anaerobic digesters another group of bacteria begin to digest and dissolve the
solids to their basic components. This process uses bacteria which do not need atmospheric
oxygen to survive, so therefore, no air is bubbled into the tanks. In fact, air mixed with the
gasses may be explosive, so we strive to keep all air out. The anaerobic digesters produce a
stable sludge which is readily dewatered. The process is also a source of methane gas, which is
used as a fuel source for heating the digesters, heating several buildings, and fueling the engine
generator to produce electricity. The digester is kept at an optimum temperature of between 90-
95 degrees F. About 40,000 cubic feet of methane gas is produced per day. [10]
[11]
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Flow Diagram of a Basic Anaerobic Digester
DESIGN CRITERIA FOR ANAEROBIC DIGESTIONDESIGN CRITERIA FOR ANAEROBIC DIGESTION
PARAMETER UNITS VALUE
Solids Loading Rate kgVSS/m3.d 1,6 4,8
Solids Retention Time days 15 20
VS destroyed m3/kg 0.75-1.12
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DESIGN OF ANAEROBIC DIGESTERDESIGN OF ANAEROBIC DIGESTER
The purpose of this project was to design and build an anaerobic digester to meet the following
criteria.
The design should
Attempt to maximize the amount of biogas produced per unit time,
Be simple and easy to understand so that the average person is able to grasp the function
and theory behind each component of the design with only a small amount of guidance.
The idea here is to encourage people looking at the design to think and understand the
requirements for controlled anaerobic digestion and the continuous flow model.
Be a durable, compact, versatile design which is capable of being shifted around if
necessary to be displayed.
Be operated with a minimum of monitoring, regulating, and adjusting (in other words,
be easy to operate).
Attempt to reduce time and money costs associated with maintenance
Attempt to minimize the cost of setting up and running the digester without
compromising the performance of operation or the other specifications of the brief
PROCESS CALCULATIONPROCESS CALCULATION
Observed Yield for BOD Removal
51
5
,
/24.0)25)(06.0(1
/60.0
1kgBODkgTVSS
dd
kgBODkgTVSS
k
YY
CBODd
BOD
obs =+=
+=
Observed Yield for Nitrogen Removal
NkgNHkgTVSSdd
kgBODkgTVSS
k
YY
CNd
Nnobs =+
=+
= + 4/088.0)25)(05.0(1/20.0
1 15
,
,
Soluble BOD in the Effluent
Total Soluble
BOD in the =Total BOD in the effluent BOD exerted by TSS in the effluent
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effluent(S)
BOD exerted
by TSS in = 30 mg/l x (0.65 biodeg.solids/kg TSS) x 1.42 BODL/solid
the effluent x 0.68 kg BOD5/kg BODL
= 18.83 mg/l
S = 20 18.85
= 1.17 mg/l
Biological Solids increase due to BOD5 Removal
TSS increase = dkgSSQY effOobs /7172)17,1300(000,10024.0)( ==
Biological Solids increase due to Nitrogen Removal
TSS increase = dkgSSQY effOobs /140)117(000,100088.0)( ==
Total TSS increase
Ratio of TVSS/TSS is assumed as 0.8
Total TVSS increase = dkgdkgdkg /7312/140/7172 =+
Total TSS increase = dkgkgTSSkgTVSS
dkg/9140
/8.0
/7312=
TSS loss in the effluent = 30 mg/l x 110,000 m3/day = 3000 kg/d
TSS in the WAS = 9140-3000 = 6140 kg/d
Volume of WAS
TSS increase = 3/5/8.0
/4000 mkgkgTSSkgTVSS
LmgTVSS =
Volume of WAS = daymmkgdkg /1228/5//6140 33 =
Total BOD in the WAS
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BOD exerted by TSS=
dkgkgBODkgBOD
solidskgbiokgBODkgTSSsolidkgbiodkg
L /7.3853/68.0
.deg/42.1/.deg65.0/6140
5
5
=
Soluble BOD5 = 1.17g/m3x 1228 m3/day /1000 = 1.44 kg/day
Total BOD5 = 3853.7 kg/day + 1.44 kg/day = 3855.14 kg/day
Return Sludge
10,000 g/m3 x (QR m3/day) = 5000 g/m3 x [(Q+QR) m
3/day]
10,000 g/m3 x (QR m3/day) = 5000 g/m3 x [(99,676+QR) m
3/day]
QR = 99,676 m
3
/day
WASN (Total Nitrogen in WAS)
Org.N = 0.122 kg Org.N/kg TSS x 6140 kg TSS/day x 0.8 kg TVSS/TSS = 599.3 kg/d
NH4+-N = 1 g NH4+-N/m3 x 1228 m3/d x (kg/1000 g) = 1.23 kg/d
NO3N = 8 g NO3
N/m3 x 1228 m3/d x (kg/1000g) = 9.8 kg/d
Total N = 610 kg/day
NDN = TN in the influent to the biological system TN lost in the effluent
TN in WAS
= 24.57 x 99,676/1000 897kg/day -610 kg/day
= 942 kg/day
WASP (Total Phosphorus in WAS)
WASP = 99,676 x (5-2)/1000 = 299.028 kg/day
% TP in SS = 299.028 / 6140 = 4.87 %
% TP in VSS = 299.028 / (6140 x 0.8) = 6.08 %
PO4P Release = ( 6.08-2.3) x (6140 x 0.8) = 185,7 kg/d P
ALUM ADDITION
TSS caused by Al3+ precipitation as AlPO4
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TSS increase = (molar wt. of Al / molar wt. of P ) x (amount of PO43P precipitated or
released )
=27
185.7 / 209 /
31
x kg d kg d=
TSS caused by precipitation as Al(OH)3
TSS increase = (molar wt. of Al(OH)3 / molar wt. of P ) x (amount of PO43P precipitated or
released ) in primary sludge
=78
185.7 / (2.5 1) 701 /31
x kg d kg d =
TSS increase = 910 kg/d
Total TSS increase = 6140 kg/d + 910 kg/d = 7050 kg/d
Total amount of Al3+ applied = (amount of PO43P precipitated / molar wt. of P ) x applied
AL3+/P molar ratio x molar wt. of Al
=185.7
2.5 27 404.3 /31
x x kg d= kgAL3+/day
Volumeof liquid alum solution =
Total amount of Al3+ applied x molar wt. of Al2(SO4)
2 x molar wt. of Al x 0.25 x 1300 kg/m3
=3
3
404.3kg/d x 3427.88 /
2 x 27 x 0.25 x 1300 kg/mm d=
Total volume of WAS = 1220.12 + 7.88 = 1228 m3/day
Characteristics of combined and blended sludge
Total TSS increase = 7050 kg/d + 15,000 kg/day = 22,050 kg/day
Total Volume of combined sludge = 324 m3/day + 1228 m3/day = 1552 m3/day
BOD5 in combined sludge = BOD5 in WAS + BOD5 in primary sludge
= 9600 kg/day + 3855,14 kg/day = 13,553 kg/day
Thickener Area =2
2
22050 kg/d470
46,9 kg/d/mm=
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Volume of dilution water =3
3
29.8 470 1552 3054 /
.
mm d
d m =
At 30 mg/L
TSS with dilution water = 3054 30 91.62 /1000
kg d =
LIME ADDITION
TSS caused by Ca2+ precipitation as Ca3(PO4)2
TSS increase = (molar wt. of Ca / molar wt. of P ) x (amount of PO43P precipitated or
released )
= 3/88.717.1853112 mkgx =
TSS caused by precipitation as Ca(OH)2
TSS increase = (molar wt. of Ca(OH)2 / molar wt. of P ) x (amount of PO43P precipitated or
released ) in primary sludge
= 3/3.413)15.2(7.18531
46mkgxx =
TSS increase = 485.2 kg/d
Total TSS increase = 6140 kg/d + 485.2 kg/d = 6,625 kg/d
Total amount of Cal2+ applied = (amount of PO43P precipitated / molar wt. of P ) x applied
Ca2+/P molar ratio x molar wt. of Ca
= 7.179125.231
7.185=xx kgCa2+/day
Specific gravity of Ca(OH)2=481 kg/m3
Volumeof hydrated lime = 3243
2
kg/m2509x0.25xCaofmolar wt.x2
)(POCaofmolar wt.xappliedCaofamounttotal +
= daym /86.2kg/m481x0.25x12x2
46kg/d179.7 33
=
Total volume of WAS = 1225.14 + 2.86 = 1228 m3/day
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THICKENER
*1 truck capacity = 10 m3
Thickener effluent = ( )22050 91.62 0.85 18820.4 /kg d+ =
Volume = 318820.4 /
304.5 /0.06 1030
kg dm d=
BOD5 = 11478 kg/d
VSS = 18820.4 / 0.72 13551 /kg d kg d =
VSS / SS = 0.72 [15]
13551 0.52 7046.5 /stabilized
VSS kg d = =
VSSdestruction = 52 % [15]
13551 7046.5 6504.5 /remaining
VSS kg d = =
18820.4 7046.5 11774 /remaining
SS kg d = =
Kg/d 18820.4
% TS 6
m3/d 304.5
Number of truck* 30
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ANAEROBIC DIGESTIONANAEROBIC DIGESTION
SUPERNATANTSUPERNATANT
304.5 m3/d
EFFLUENTEFFLUENT
11774 kg/d = Wsludge + Wsupernatant
sup tan3304.5 /0.05 1030 0.004 1000
sludge erna tW W
m d= +
Wsludge = 11774 kg/d - Wsupernatant
sup sup311774
304.5 /
0.05 1030 0.004 1000
W Wm d
= +
62727 = 47096 4 Wsup + 51.5 Wsup
Wsupernatant = 329 kg / d
3
sup tan
32982.25 /
0.004 1000erna t m d = =
Wsludge = 11774 kg/d - 329 kg/d
Wsludge = 11445 kg/d
m3/d 82.25
% TS 0.4
m3/d 329
(kg/m3) 1000
BOD5 3000
Org N 0.34
NH4N 0.05
m3/d 11445
% TS 5
m3/d 222.2
(kg/m3) 1030
BOD5 4344.45
Org N 848.3
NH4N 127.25
Truck 22
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311445 222.2 /0.05 1030sludge
m d = =
Total Mass of Other Components in Digested Sludge:Total Mass of Other Components in Digested Sludge:
BOD5 = ( )3
3
311478 / 1 0.6 3000 82.25 10 4344.45 /
g mkg d kg d
m d
=
BOD5 stabilized = 60 % [15]
Org N in the effluent of thickener = 18820.4 / 0.122 0.8 1837 /kg d kg d =
Org N = ( )11445 222.2
(1837) 1 0.1 0.15 (1837) 0.1 848.3 /
11774 304.5
kg d + =
Conversion of Org N into NH4-N = 15 % [15]
NH4-N =848.3 / 0.15 127.25 /kg d kg d =
Conversion of Org N into soluble org N = 10 % [15]
Conversion of non-precipitated phosphorus (NPP) into soluble P = 30 %
PP capture = 100 %
BOD5 in supernatant = 3000 mg/L
Org N sup = ( )329 82.25
(8.94) 1 0.1 0.15 (8.94) 0.1 0.34 /11774 304.5
kg d + =
NPP in the effluent of thickener = 91.62 / 0.122 0.8 185.7 /kg d kg d =
NPP = 185.7 kg /d
CentrifugeWsludge = 11445 kg/d
Centrifuge = % 30
3
3
sup
11445 /37 /
0.3 1030
up tan 222.2 37 185.2 /
11445 0.15 1716.7 /
11445 1716.7 9728.3 /sludge
kg dDewateredsludge m d
S erna t m d
W kg d
W kg d
= =
= == =
= =
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Kg/d (sludge) 9728.3
% TS 30
m3/d 3
Number of truck 4
Anaerobic Digestion Capacity & Dimensions:Anaerobic Digestion Capacity & Dimensions:
There are 4 methods to calculate digester capacity. According to below results suitable volume
will be chosen at worst conditions.
1) Qavg = 304.5 m3/d
Digestion period = 15 days
3
3304.5 15 4567.5m
Digester days md
= =
2) High rate digerter = 2.5 kg / m3.day
TVSS = 18820.4 / 0.72 13551 /kg d kg d =
3
3
13551 /5345
2.5 / .
kg dDigester m
kg m day = =
3) Volume per capita
Assume =
30.03m
capita [15]
Population served = 250000
3
30.03 250000 7500m
Digester mcapita
= =
4) Volume reduction method
( )2
3in in out t Q Q Q D =
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DT= Digestion period (d)
Qin = Sludge amount (m3/d) = 304.5 m3/d
Qout = Effluent sludge amount (m3/d) = 222.2 m3/d
( )32304 304 222.2 15 3744.5
3Digester m
= =
Chosen volume = 7500 m3
Provide a 1 m depth for grit accumulation in the bottom cone.
Provide 0.6 m depth for scum blanket.
Provide 0.6 m between the floating cover and max. digester level.
Total inactive cone depth = 1 m
Total inactive upper depth = 1.2 m
Active side water depth = 20 m
Number of digester = 2
37500 37502
EachDigester m = =
23750 187.520
EachDigesterArea m= =
Diameter of each digester =2
187.5 15.44
DD m
= =
15.4 0.4 = 15 m3
2
375021.2
154
mVerticalsidedepth m
= =
1.2 m
20 m
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2.5 m1 m
3.16 m1 m
3 m
1.5m
7.5 m
( )2
22 320 15 1 115 2.5 3 2 1 3672.24 3 4 3 4
ActiveDigester m = + =
33672.2 2 7344.4TotalActive m = =
( )2
2 31.2 15 1 3 2 1 221.44 3 4
TotalInactive m = + =
37344.4 221.4 7565.8Total m = + =
7344.40.97
7565.8Active ratio = = > 0.8 IT IS IN THE RANGE! [15]
7344.424
304.5DigestionPeriodatAverageFlow d= =
7344.4 15.1487.2
DigestionPeriodatExtremeHighFlow d= =
7344.438.6
190.3DigestionPeriodatLowFlow d= =
3
3
18820.4 /2.56 / .
7344.4
kg dSolidsLoading kg m d
m= = [it is in the range] [13]
Gas ProductionGas Production
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There are 4 different methods to calculate the amount of gas production. The less value of gas
production will be chosen.
1) BOD5 in thickened sludge = 11478 kg/d
11478 /16879 /
0.680.05 0.8 16879
392.5 /1 1 0.03 24
L
Ox
c
kg dBOD insludge kg d
Y E SP kg d
kd
= =
= = =
+ +
Y = 0.04 0.1 mg VSS /mgBOD utilized
( )3
30.35 0.8 16879 1.42 392.5 4531 /m
ofmethane m d kg
= =
If methane volume is % 66 of digester gas:
31
4531 6865 /0.66
Digestergasproduction m d= =
2) Gas production based on total volatile solids
30.50m
GasproductionratekgTVSS
=
30.5 18820.4 0.71 6681.2 /Gasproduction m d = =
3) Gas production based on TVS reduction
30.9m
GasproductionkgTVSreduced
= [13]
3
30.9 7046.5 6341.8 /m
Gasproduction m d kgTVSreduced
= =
4) Gas production based on TVS reduction
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30.032m
Gasproductionratepopulationbasedcapita
=
30.032 250000 8000 /Gasproduction m d = =
Gas production volume = 6341.8 m3/d
Digester Heating Requirements
( )2 1R pH flow C T T=
Cp = Specific heat of sludge = 4200 J / kgoC
T2 = Digestion Temp = 35 oC
T1 = Sludge Temp = 12 oC
( ) 1018820.4
4200 35 12 5.19 10 /0.035R
H J day= =
Heat Losses from digesters
( )2 1LH U A T T=
U = Heat transfer coefficent
A = Area in which heat losses occurs
T2 = Digestion Operating Temp = 35 oC
T1 = Outside Temp
Roof Area:
2
SlantlengthRoofArea D=
2 2
2
7.5 0.6 7.52
15 7.52177.2
2
Slantlength m
RoofArea m
=
= =
U = 0.90 J/sm2 oC
Heat losses from the cover & roofing
( ) 80.90 177.2 35 0 86400 4.8 10 /LH J d= =
Area of Side Walls:
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Assume 50 % below ground
exp
2
osedheightSidewallareaaboveground D=
215 21.2 4992
Area m = =
U = 0.68 J/sm2 oC
Heat losses from the side wall above the ground
( ) 90.68 499 35 0 86400 1.03 10 /LH J d= =
Heat losses from the side wall below the ground
U = 0.80 J/sm2 oC
( ) 90.80 499 35 0 86400 1.2 10 /LH J d= =
Roof Area:
2 2 2115 7.5 2.5 186.32
BottomArea m= + =
U = 0.62 J/sm2 oC
Heat losses from the bottom cone
( ) 80.62 186.3 35 5 86400 2.89 10 /LH J d= =
( ) 8 82.89 4.8 10.3 12 10 30 10 /LTotalH J d = + + + =
% 20 minor losses
% 25 emergency conditions
8 10 630 10 2 1.45 6.06 10 / 2.56 10 /L
H J d kJ hr= = =
Selection of Heating UnitsSelection of Heating Units
External heat exchanger
Provide 2 units each rated 2.3 x 106 kJ/hr with natural gas
Digester gas for heating purposes, %65 of heating value of natural gas
Each unit will be derated = 6 62.3 10 0.65 1.49 10 /kJ hr =
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Total heat provided by 2 uints = 6 61.49 10 / 2 3 10 /kJ hr kJ hr =
Extra available % =6 6
6
3 10 / 2.5 10 /%17
3 10 /
kJ hr kJ hr
kJ hr
= =
Digester gas requirement
% 75 efficiency of heating units
63 3
2
3 10 /164.6 / 3950.4 /
0.75 24300 /
kJ hr Digestergasneeded m hr m d
kJ m
= = =
Produced gas = 6341.8 m3/d
6341.8 m3/d > 3950.4 m3/d
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COST ANALYSISCOST ANALYSIS
UNIT UNIT COST COST
Construction 800,000 $
Excess Sludge Pumps 3 20,000$ 60,000$
Compressors (250 l / day) 2 50,000$ 100,000$
Mixers 4 50,000$ 200,000$
Diffusers (9) 340 200$ 68,000$
Sludge Blender 2 10,000$ 20,000$
Sludge feeding pumps 2 5,000$ 10,000$
Polyelectrolyte feeding
pumps2 3,500$ 7,000$
PE ring pump 1 5,000$ 5,000$
Exit sludge pump 2 5,000$ 10,000$
Centrifuges 2 1,000,000$ 2,000,000$
Liquid PE feeding pump 1 10,000$ 10,000$
Mechanical Sludge
Thickener1 1,000,000$ 1,000,000$
Primary Sedimentation 1 50,000$ 50,000$
Digester Tank 1 5,000,000$ 5,000,000$
Heat Exchanger 1 10,000$ 10,000$Circulation Pump 1 10,000$ 10,000$
Compressor 1 50,000$ 50,000$
TOTAL COST
10,000,000$
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7/31/2019 Son Olarak Bitiyooo
50/50