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International Journal of Recent Engineering Research and Development (IJRERD)
ISSN: 2455-8761
www.ijrerd.com || Volume 03 – Issue 05 || May 2018 || PP. 35-61
35 | Page www.ijrerd.com
Design of sewage treatment plant at Jubilee Mission hospital,
Thrissur
Geethu. E.S, Anitha . K
Malabar College of Engineering and Technology, Kerala Technological University,
Desamangalam, Kerala
Abstract: Hospital waste water is a type of waste water, generated from all the medical and non medical
activities The need for waste water treatment is to collect and treat i.e., to limit the pollution and health risks,
before being returned to the environment at large. The sewage treatment plant is to be designed and constructed
to treat the sewage, generated from various sources of the hospital. To design the sewage treatment plant,
parameters like pH, total dissolved solids, Bio chemical oxygen demand, oil and grease being determined using
IS code specification. The sewage treatment plant is designed by extended aeration activated sludge process.
The treated water is discharged in to land for irrigation purposes and balance to public drain. The steady
incremental of new construction blocks in the hospital results, increase of the sewage generation. But still now
there is a lower capacity treatment plant. When considering the population inflation and future developments in
the hospital, the capacity of the current STP would be insufficient. So, there is a need for design the STP which
would be sufficed to handle the future sewage requirements of the hospital. My project deals with the design of
sewage treatment plant at Jubilee mission hospital, Thrissur and also prepare the estimation and rate analysis for
the sewage treatment plant, to develop a small scale model for the STPs as per designed values so as to check
the method is preferable or not, and environmental impact assessment (EIA) of existing sewage treatment plant
at Jubilee mission hospital to understand if any type of environmental impact is generated due to the current
STP, if yes, suggest recommendations to avoid the problems.
Keywords: Extended aeration activated sludge process, Environmental impact assessment
1. INTRODUCTION Hospital waste water is a type of waste water, generated from all the medical and non medical activities
from the operating rooms, emergency and first aid, laboratory, diagnosis, radiology, kitchen and laundry etc.
The waste water from hospital may contain various potential hazardous materials including, microbiological
pathogens, radioactive isotopes, disinfectants, drugs, chemical compounds such as antibiotics ,cytostatic agents,
anesthetics, disinfectants (due to their major use in hospital practice), platinum, mercury (in preservatives in
diagnostic agents and as active ingredients of disinfectants), and pharmaceuticals. My project is deals with the
design of STP to treat the sewage water from Jubilee mission hospital. It includes the major components such as
inlet chamber, screen chamber, grit chamber, collection tank, aeration tank, secondary clarifier, and tube filter.
When considering the population inflation and future developments, to hospital, the capacity of current STP is
insufficient. (800 cum/day). So, STP which can be handles the future sewage requirement of hospital to be
design for 30 years. The existing STP having lower capacity, i.e. 800 cum/day can be replaced by the STP
having 1700 cum/day. Proper treatment of hospital waste water is essential. Why because, if the effluent from
hospital is discharged directly into the land without any proper treatment, it will negatively impact the
environment as well as human beings. Hence, the selection of suitable treatment technology is essential. The
design of sewage treatment plant followed by extended aeration type of activated sludge process. Especially for
smaller plants up to 4 MLD capacities, it was decided to use extended aeration type of activated sludge plant,
which eliminates primary settling tank as well as sludge digestion tank. The other reason for selecting extended
aeration activated sludge process is the limited land area. It was decided to design the S.T.P using activated
sludge process for the secondary treatment instead of using the trickling filter. The various treatment
technologies used for treat the of hospital wastewater are, activated sludge process (ASP), extended aeration
(E.A.), fluidized bed reactor (FBR), submerged aeration fixed film (SAFF) Rector and movable bed bio-reactor
(MBBR). ASP is very old and user’s friendly technology. E.A. is exactly similar kind of treatment technology
like ASP, except more hydraulic retention time to give extended aeration for the complete digestion of organic
matter. SBR is also similar to E.A system. But biodegradation as well as settling of solids and removal of sludge
is done from same tank. It is also known as a draw-and-fill activated sludge treatment system. FBR is the latest
advance in attached as well as suspended growth aerobic biological treatment technology. Influent is treated
through a bed of small ring pack media at a sufficient velocity to cause fluidization in a reactor. SAFF is also a
latest advance in attached growth process and has been implemented in recent years as fixed film media into
activated sludge reactors to improve the performance of sewage treatment plants. MBBR is also used to treat
International Journal of Recent Engineering Research and Development (IJRERD)
ISSN: 2455-8761
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wastewater which works on the principle based on the filtration of activated sludge through the concept of using
flat sheet type or hollow fiber type submerged membrane modules in bioreactors. My project also deals with the
estimation and rate analysis of the designed STP, environmental impact assessment of the existing plant, to
develop small scale model for STP as per the designed value , to check whether it’s working is satisfactory or
not.
1.2 Environmental impact assessment (EIA)
Based on the project details and the environmental status, potential impacts as a result of the
construction and operation of the existing STP at Jubilee Mission Hospital, Thrissur have been identified. The
impacts on various factors of environment have been quantified to the extent possible. This study deals with the
anticipated positive as well as negative impacts. As the part of the project, visited site of the existing STP. In
order to make the work a comprehensive one, collected data from various departments related to the STP. A
survey was conducted near the STP site to know about the majority opinion about the existing plant. All the
local peoples are cooperated. From the survey conducted, negative and positive feedback from the peoples were
obtained. Majority of feedback were positive. Collected water samples from school and houses near the of
existing STP site to test the parameters such as BOD, COD, SS, pH and oil & grease. From the data’s and
opinion, conducted environmental impact assessment by check list method.
Table: 1 Environmental impact assessment (EIA)
Houses and school were located nearer to the current STP. So any improper working of STP would
affect students as well as persons directly. For analyzing this, the current status of water in wells near the STPS
is checked. The result shows that the water sample is pure and potable.
Sl
no Name and address
Distance
from the
plant in
meter
Impact
Odour Smoke Noise Taste
1 School 2 X X
2
Luise joseph
Eastfort
Thrissur 10 X
3
John joseph chiramal house
Eastfort,Thrissur 20 X
4
Shony francis
Manjla house
Near thoppil stadium
Eastford,Thrissur 25
5
Ronald henly
Molangery parambil house
Eastfort,thrissur 30
6
M.c anto
Marotical house
Saminary Road
Eastfort Thrissur 35
7
Jestin M.J
Holiday home
Eastfort Thrissur 65
8
A.K.John
Ainikkal Garden 68
9
Jerom M.A
Mmanjila House
Eastfort Thrissur 70
10
K.K Unnimone
Naduvilpurakkal house
Eastfort Thrissur 72
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1.3 Existing features: Quantity and characteristics of effluent
Total No of Beds: 1700 Any.
Designed period: Life time
The quantity of waste water to be generated in the hospital is from (bathroom, operation theatre,
laboratory, wash basins, washing area / laundry section, and septic tank overflow etc.)
Qty. of Waste water partially treated in the old treatment plant : 800Cu.m./day.
The current capacity of the beds in hospital is 1700, and the old plant was designed for handling only 2000
beds. But actually 1500 beds were present at that time. The new STP designed for 3065 beds. For 3065 Beds,
the average flow is 1700 m3/day. When considering the population inflation and future developments in the
hospital, the capacity of the current STP would be insufficient. So, there is a need for design the STP which
would be sufficed to handle the future sewage requirements of the hospital.
1.4 Design procedure
Given Data
Average flow = 1700 m3/day
Peak flow = 2.5×1700 = 4250 m3/day = 0.049m
3/sec
Table: 1 Characteristics of influent and effluent water
PARAMETERS INFLUENT
(mg/L)
EFFLUENT
(mg/L)
pH 5.9 6.8
TDS 400 200
BOD 310 12
COD 565 64
OIL & GREASE 8 NIL
1.5 Choosing the type of secondary treatment:
Since the desired quality of the treated effluent was of a high standard, and the available land area for
construction of plant was limited, it was decided to design the S.T.P using activated sludge process for the
secondary treatment instead of using the trickling filters.
Moreover, considering the various advantages offered by the extended aeration process, especially for
smaller plants up to 4 MLD capacities, it was decided to use extended aeration type of activated sludge plant,
which eliminates primary settling tank as well as sludge digestion tank.
Inlet chamber
Average flow = 1700 m3/day
Peak flow = 2.5×1700 = 4250 m3/day
= 0.049m3/sec
Plan dimension of inlet chamber = 1.3m × 1m
Provide free board = 1m
Provide minimum size 1.3x1m of inlet chamber.
The outflow from the inlet chamber shall be taken to the screen chamber.
Screen chamber One Screen chamber/channel shall be provided as per sound engineering practice.
The flow from the inlet chamber to the screen channels shall be controlled by C.I. penstock gates.
Q max =
0.049 cubic meter/sec
Assumptions:
Shape of Bar =
Size =
Clear spacing between bars =
M.S. Flats
10 mm × 50 mm (10mm facing flow)
20 mm
Inclination of bars with horizontal =
Assuming velocity normal to screen =
At peak flow, net inclined area required =
45 degree (Cleaning - manually)
0.8 m/sec
Q max / Assumed velocity normal to screen
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=0.049/0.8
= 0.061 m2
Gross inclined area =
Net inclined area required x Average annual rate of
flow
= 0.061 ×1.7
= 0.1037 m2
Gross vertical area required
= 0.1037× sin 80°
= 0.1021 m2
Provide submergence depth = 0.3 m
∴ Width of channel =
Check velocity in duct =
0.1021 / 0.3 ≈ 0.35 m
Q max / (Width of channel × 0.3)
= 0.049
(0.35×0.3)
= 0.466 m/s
(Velocity u/s of screen) > 0.4 m/sec
Provide 20 bars of 10×50mm at 20mm clear spacing as per the results
Provide screen chamber shall be170cm width
U/s of screen, a C.I. penstock gate shall be provided for the channel
Min. drop of 150mm shall be provided in the bed of screen channel
Size of penstock shall be provide as 350×450mm
∴ Provide minimum size of the chamber = 2.5m×0.9m×0.9m
Grit chamber
Flow from screen chamber shall be taken into grit chamber, provided in duplicate.2 nos. C.I. gates, one each at
inlet and outlet, are provided for each Grit chamber.
Design flow =
=
=
2.5×Avg flow
2.5×1700
4250 m3/day
Surface loading = 1100 m3/m
2/day (assumed)
To account for turbulence and short circuiting reduce the surface loading to about 800 m3/m
2/day
Area required =
design flow
surface loading
=4250/800
= 5.31≈ 5.4m2
Detention time =
Volume =
60 sec design flow ×detention time
24×3600
= 4250 ×60
24×60×60
=2.951 m3
Liquid depth =
=
Original depth =
volume/area
2.951/5.4
0.546 m
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Size of the Grit chamber = 0.546 + 0.6 FB=1.14≈1.2 m
2.7m×2.7m×1.2m size provide for grit chamber.
Check for horizontal velocity
C/S area of grit chamber =
=
breadth x Original Liquid depth
2.7×0.546
= 1.474m2
Velocity =
=
design flow
C.S area ×24×3600
4250
2.7×0.546×24×60×60
= 0.0333m/s
= 3.33 cm/s < 18 cm/sec, Hence ok.
Grit generation = 0.05 m3per 1000 m
3 of sewage flow (assume)
Even though the grit is continuously raked, still 8 hrs. Grit storage is provided for average flow
Storage volume required =
1700 ×8
24 x
0.05
1000
= 0.028 m3
Grit storage area =
𝜋
4 × 2.7
2
= 5.725 m2
Grit storage depth =
storage volume
grit storage area
= 0.028/5.725
= 0.0048 m
Total liquid depth =
=
liquid depth + grit storage depth
0.546 + 0.0048
≈ 0.6 m
Provide grit chamber size =
2.7×2.7× (0.6+0.6 FB)
2.7m×2.7m×1.2m
Out flow from grit chamber shall be carried out to the aeration tank through a 600mm wide R.C.C. channel
provided with fine bar screen (manually operated). The clear spacing between the bars shall be 10mm.
Collection tank
Average flow =
1700 m3/day
Provide hydraulic detention time = = 12
12 Hours
The volume of tank =
1700× 12
24 = 850 m3
Liquid depth = 6m
Area =
850
6 =
800
6
= 141.66 m2
Assume surface loading rate average flow = 15 m3/m2/ day
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Surface area to be provided =
1700
15
= 106.6 m2
The area, A = 113.33 m 2
Diameter of the circular tank, d =
141.66×4
𝜋
= 13.42 m ≈ 13.5 m
Actual area provided = 𝜋
4×13.52
= 143.14 m2
Check for wear loading
Average flow = 1700 m3/ day
Wear loading = 1700
𝜋×13.5
= 40.083 m3/ day/ m <185 m3/ day/ m .
Hence ok.
Provide 13.5 m diameter and overall depth = 6 + free board
= 6 + 0.3
= 6.3m
Aeration tank
No. of tanks =
2
Average flow to each tank =
=
1700/2
850 m3/day
The total BOD entering S.T.P = 310 mg/L
Assuming that negligible BOD is removed in screening and grit chamber (since it mainly removes inorganic
solids), the BOD of sewage coming to aeration tank.
Y0 =
310 mg/L
BOD left in the effluent YE = 12 mg/L
Therefore,
BOD removed in activated plant =
Y0 −YE
=
298 mg/L
Therefore,
Minimum Efficiency required in the activated plant
=
298
310 × 100
=
96 %
Hence ok. Since the adopted extended aeration process can remove BOD up to 95-98%
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Volume of aeration tank can be designed by assuming a suitable value of MLSS and 𝜃c (F/M) ratio
Let us assume MLLS (X) = 3000 mg/L (b/w 3000-5000)
F/M ratio =
0.12 (b/w 0.10-0.18)
Now using eqn, we have, =
F
M=
Q
V×
Yo
X
= 0.12 =850
V ×
310
3000
V = 732 m3
Where,
Q =
Average flow (m3/day)
V = ?
Y0 = BOD of raw water in mg/L
X =
Assumed MLLS concentration
F/M = Assumed (0.10-0.18)
Let us adopt aeration tank dimension such as liquid depth 3.5m and width 7m. Then,
The length of the tank = V
BD
= 732
3.5×7
29.87m ≈ 30 m
Therefore, volume (V) provided = 30×7×3.5
= 735 m3
Check for aeration period or H.R.T (t)
t = V
Q× 24
=
735
850 × 24
=
Since it lies between 10 – 25 hr., hence ok 20.75 ≈ 21 hrs.
a) Check for volumetric loading
=
Q×Yo
Vgm /m
3
=
850×310
735
=
363.488 gm /m3 ≈ 364 gm /m
3
=
0.36 kg/m3
Since it should lie between 0.2and 0.4, hence ok.
c) Check for return sludge ratio (for SVI ranging from 50 – 150 ml/g)
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Using eqn. we have, =
QR
Q=
𝑋
166
SVI−X
= 3000
106
112−3000
=
0.506
Since it should be within 0.5 – 1.0, Hence ok.
d) Check for S.R.T (θc)
V. X =
α .Q. Yo−YE .θc
1+Ke .θc
Where,
αy =
1.0 (constant for municipal sewage w.r.t MLLS)
Ke =
Y0 =
YE =
0.06-1
(constant for municipal sewage)
BOD of raw water in mg/L
BOD of treated water in mg/L
V( volume) = 735 m3
X =
3000 mg/L
Q =
850 m3/day
735×3000 =
1×850×(310−12)θc
1+0.06θc
θc =
20.78 ≈ 21 days
Since it lies from 10 to 25 days, hence ok.
Adopt an overall size of the aeration tank = 30m×7m×(3.5+0.6 FB)
=
30m×7m×4.1m
The effluent will be taken to the secondary clarifier. The inflow to the secondary clarifier shall be by means
of 250mm ϕ C.I. pipes, which will be a velocity of 0.78 m/sec at peak flow.
Aerators sizing
B.O.D5 applied to each tank =
310 mg/L
Avg. flow in each tank =
850 m3/day
B.O.D5 to be removed in each tank = 850×0.310
=
=
=
263.5 kg/day
263.5/24 =10.97 ≈ 11 kg/hr
11 kg/hr.
Oxygen requirement =
1.2 kg/kg B.O.D applied
Peak oxygen demand = 125 %
Oxygen transfer capacity of the aerator in standard conditions
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= 1.9 kg/HP/kwh
=
1.41 kg/HP/hr.
Oxygen transfer capacity of the aerator at field conditions
=
0.7×1.41
= 0.98 kg/HP/hr
Oxygen to be applied in each tank =
1.2×11×1.25
= 16.5 kg/hr.
HP of aerator required =
16.5 /0.98
= 16.83 HP say 18 HP
Provide 2 aerator each of 9 HP in each tank
Check for mixing consideration
As per practice power required for mixing = 0.02 kw/m3
Vol. of each aeration tank =
735 m3
SHP required = 735×0.02
=
14.7 kW
Provide 2 aerators and considering gear efficiency as 97 %
HP of each aerator required =
14.7
2×0.97
= 7.58 HP
Considering a power margin 25 % on motor rating
Motor HP required = 7.58×1.25
=
9.47 HP Say 9 HP
Provide 2 Nos of 9 HP aerators in each tank.
The dimension of the tank selected on the basis of suitable aerator motor is the zone of influence.
The zone of influence for each aerator will be about 11m2 with 3.5 m depth. The suitable aerator be selected,
and accordingly, the depth and size of aeration tank adjusted. The submergence of the aerator will be
between 75mm to 115 mm.
Secondary clarifier
No. of secondary clarifier = 1
Average flow =
1700 m3/day
Re circulated flow, say 50% =
850 m3/day
Total inflow =
2550 m3/day
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Provide hydraulic detention time = 2 hr
Volume of tank (exclusive of hopper portion)
=
Total inflow ×hydraulic detention time
24
= 2550 × (2/24)
= 212.5 m3
Assume liquid depth =
3.5 m
Area (superficial) = 212.5/ 3.5
= 60.714 m ² ≈ 60 m2
Surface loading rate of average flow = 15m3/m
2/day (assumed)
Surface area to be provided =
Average flow / Surface loading rate (m2)
=
1700/15
= 113.33 m2 ≈ 113 m
2
(Provide area greater of two) Area, A = 113 m2
Diameter of Circular tank (d)
d = 113×4
π ≈ 12 m
Actual area provided =
𝜋
4 ×12
2
= 113 m2
Check for Weir Loading
Average flow =
1700 m3/day
Weir loading = Average flow / (π × d)
=
1700
𝜋×12
=
< 185 m3/day Hence ok
45.09 m3/day/m
Check for Solids loading
Recalculated flow =
850 m3/day
Average flow =
1700 m3 /day
MLSS in the tank =
=
3000 mg/L
3 kg/day
∴Total solids in flow = (1700 + 850) ×3
=
7650 kg/day
Solids loading =
Total solids in flow / Surface area to be provided
=
=
7650/113
68 kg/day/m2
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Provide a clarifier diameter 12 m having liquid depth 2.5 m, Hopper slope shall be 1 in 12 and free board
will be 0.3 m. Sludge will be withdrawn from the clarifier through C.I. pipe. The sludge will be taken to the
return sludge pump house. The treated effluent from the secondary clarifier can be disposed of in the nearby
valley.
Tube settler
Average flow = 1700 m3/day
Provide hydraulic detention time = 2 Hour
Volume of the tank exclusive of hopper bottom = 1700×2
24= 141.66 m3
Assume liquid depth = 2.5 m
Area = 141.66
2.5
= 56.664 m2
Surface area to be provided = 1700
15
= 113.33 m2
Take higher value area A = 141.66 m²
Assume the depth of tube settler = 16 m
Length of the tube settler = 141.66
16 = 8.853m
Check for weir loading
Average flow = 1700 m3/ day
Weir loading = 1700
2×16×8.853
6.01 m3/day /m < < 185 m3/day /m hence, ok
Check for solid loading
Total inflow = 1700 m3/day
MLSS in the tank = 3000 mg / L
= 3 kg/ L
Total solid inflow = 1700×3
= 5100 kg/ day
Solids loading = 5100
141.66
=36 kg/day/m2
Provide clarifier of 6.67m×16m×3 m (2.5+F.B). Hopper slope shall be 1 in12.
1.6 Mechanical equipments
Mechanical instruments which are used in STPs are effluent transfer pump, fixed type aerators, sludge
recirculation pump, flash mixer, flash mixer feed pump, tube deck, chemical storage tank, lime preparation tank
with stirrer, hypochlorite storage tank ,pressure sand filter feed pump, Pressure sand filter, blower for collection
tank ,filter press feed pumps and Filter Press.
Effluent transfer pump No : 1 + 1
Capacity : 40Cub.m/Hr.
Type : Horizontal, centrifugal, non-clog Self priming pump
Head : 10MLC
Manufactures : KIRLOSKAR/JOHNSON
Fixed type aerators
No : 8
Type : Surface aerators
Motor HP : 2 nos of 7.5HP
Accessories : Gearbox, Motor, Base plate etc.
Make of Gearbox : Greaves/Santhi
Sludge recirculation pump
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No : 1 + 1 stand by
Capacity : 20 Cub.m./hr.
Head : 20MLC
Type : Semi-open impeller, self-Priming, non-clogging, Centrifugal
Manufactures : KIRLOSKAR/JOHNSON
Flash mixer
No : 1
Size : 1.25m x 1.25m x 1.25m
Construction : M.S. with epoxy coating
Flash mixer feed pump No : 1+ 1 common stand by
Capacity : 40Cub.m/hr.
Type : Horizontal, centrifugal, non- Clog Self priming pump
Head : 20MLC
Manufactures : KIRLOSKAR/JOHNSON
Tube deck
Quantity : 25Cu.m.
Material of construction : PVC
Manufactures : MM Aqua
Accessories : Necessary supports
Accessories for tube settler: Lime Tank with stirrer, reagent tank etc.
Chemical storage tank No : 1
Capacity : 10KL
Material of construction : HDPE
Lime preparation tank with stirrer
No : 1
Capacity : 2KL
Material of construction : M.S. with epoxy coating
Accessories : Paddle type stirrer
Motor HP : 0.5HP
Manufactures : KIRLOSKAR
Hypochlorite storage tank
No : 1
Capacity : 500Litres
Material of construction : HDPE
Accessories : Dosing Pump
Manufactures : ASIA –LMI
Pressure sand filter feed pump
No : 1 + 1 stand by
Capacity : 40 Cub.m/hr.
Type : Horizontal, centrifugal, non-clog Self priming pump
Head : 40MLC
Manufactures : JOHNSON
Pressure sand filter
No : 1
Size : 2.5m Dia. x 2.4m SWD
Construction : M.S. with epoxy coating
Accessories : Graded Sand and pebbles
BLOWER FOR COLLECTION TANK
NO : 1+1
HP of motor : 12.5HP
Type : Twin lobe roots blower
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Make : KAY
ACCESSORIES : PIPE DISTRIBUTION SYSTEM
Filter press feed pumps
Quantity : 2 Nos
Capacity : 5 cum/hr. @ 40 MLC Head
Filter Press
Size : 36" x 36"
No. of Plates : 41
Type : Recessed type
2. ESTIMATION OF DESIGNED STP Estimation is a technique for computing or calculating the various quantities and the expected
expenditure to be incurred on a particular project. The estimation of the designed STPs done by long wall short
wall method. In this method, the wall along the length of the room is considered to be long wall while the wall
perpendicular to the long wall is said to be short wall.
Table: 2 Estimation of STP (Designed)
SL.N0 PARAMETERS
No L
(m)
B
(m)
D
(m)
QUANTITY
(m3) REMARKS
I) INLET CHAMBER
1
2.1
1.8
1.2
4.536 m3
L=1.3+0.3+0.3
= 1.9m
1.9+0.10+0.10 =
2.1m
B = 1.0+0.3+
0.3+0.10+0.10
=1.8 m
D = 1.00+0.20
=1.2. m
2.
Cement concrete 1:3:6 for
floor & foundation
1
2.1
1.8
0.2
0.756 m3
First class brick 1:4cm in
inlet chamber
1) Long wall
2) Short wall
2
2
1.9
1.0
0.3
0.3
1.0
1.0
1.14 m3
0.600 m3
L=1.3+0.3+0.3
= 1.9m
Total 1.740 m3
4. G.I sheet for roofing 1
12 mm cement plaster 1:3
mortar mixed with std.
Earth work in
excavation
1
.
1
3
5
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water proofing compound
in Inlet chamber
1) Long wall
2) Short wall
2
2
1.30
1.00
1.0
1.0
2.60 m2
2.00 m2
Total 4.60 m2
20 cm cement plastering
1:3 with std. water proofing
compound in floor of inlet
chamber
1
1.3
1.0
1.30 m2
100mm SW pipe laying
&joining with 1:3cm Inlet
from hospital to Inlet
chamber
1
100
m
100 m
ii) SCREEN CHAMBER 1
3.3 1.8 1.2 7.128 m3
L=2.5+0.3+0.3=
3.1m
0.10+0.10 = 3.3 m
B=1.0+0.3+0.3+0.
10+0.10 = 1.8 m
D = 1.00+0.20 =
1.2m
Cement concrete 1:3:6 for
floor & foundation 1 3.3 1.8 0.2 1.188 m3
First class brick 1:4cm in
screen chamber
1) Long wall
2) Short wall
2
2
3.1
1.00
0.3
0.3
1.00
1.00
1.86 m3
0.600 m3
L=2.5+0.3+0.3=
3.1m
Total 2.460 m3
4. G.I sheet for roofing 1 1 nos
5.
12 mm cement plaster 1:3
mortar mixed with std.
water proofing compound
in screen chamber
1) Long wall
2) Short wall
2
2
2.5
1.00
1.00
1.00
5.00 m2
2.00 m2
Total 7.00 m2
6.
20 cm cement plastering
1:3 with std. water proofing
compound in floor of
screen chamber
1
2.5
1.00
2.50m2
7.
100mm SW pipe laying &
joining with 1:3cm
Inlet from Inlet chamber to
6
1
Earth work in
excavation
1
2
3
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screen chamber
1
2
2 m
iii) GRIT CHAMBER 1
1.
Earth work in excavation
1
3.5
3.5
1.4
17.150 m3
L=2.7+0.3+0.3+0.
10+0.10 = 3.5 m
B=2.7+0.3+0.3+0.
10+0.10 = 3.5 m
D = 1.2+0.2 = 1.4
m
2
Cement concrete 1:3:6 for
floor & foundation
10
20
1) Rectangular
2) Triangular
1
1
3.5
2.7
3.5
2.7
0.2
.05
2.45 m3
0.36 m3
Total 2.814 m3
First class brick 1:4cm in
grit chamber
1) Long wall
2) Short wall
2
2
3.3
2.7
0.3
0.3
1.2
1.2
2.376m3
1.994 m3
Total 4.32 m3
4. G.I sheet for roofing 1 1 Nos
5.
12 mm cement plaster 1:3
mortar mixed with std.
water proofing compound
in grit chamber
3) Long wall
4) Short wall
2
2
2.7
2.7
1.2
1.2
6.48m2
6.48 m2
Total 12.960 m²
6.
20 cm cement plastering
1:3 with std. water proofing
compound in floor of grit
chamber
1
2.7
2.7
7.290 m2
7.
100mm SW pipe laying &
joining with 1:3cm
Inlet from screen chamber
to grit chamber
1
2
2 m
iv) COLLECTION TANK 1
1.
Earth work in excavation for
collection tank
1
𝜋/4 ×d2 ×h
𝜋/4 ×14.42 ×7.2
1172.590m3
D=13.5+0.3+0.
3+0.15+0.15
=14.4m
h=6.30+0.20+0.
6+0.10 = 7.2m
2. Cement concrete for P.C.C 1 𝜋/4 ×14.42 ×0.1
16.290 m3
3 3
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3.
Cement concrete for
foundation 1 𝜋/4 ×14.42 ×0.6
97.120 m3
4. Cement concrete for walls 1
(𝜋/4 ×14.12 ×6.3)-
( 𝜋/4 ×13.52 ×6.3)
81.940 m3
D=13.5+0.3+0.
3 = 14.1 m
5.
R.C.C roof 20 cm thick
precast slab including steel
reinforcement complete laid
in position
1
𝜋/4 ×14.12 ×0.2
31.230 m3
.
1) Inlet from grit chamber to
collection tank 600mm ϕ
2) Outlet pipe from
collection tank to aeration
tank
1
1
4m
8m
4m
8m
v) AERATION TANK 2
Cement concrete 1:3:6 for
floor
2
30
7
0.30
2
First class brick 1:4 cm in
aeration tank
1.) L.W
2.) S.W
2
2
30.6
7.60
0.3
0.3
4.1
4.1
75.280 m3
18.696 m3
Total
93.976 m3 =
93.976×2
= 187.950 m3
L.W
S.W
2
2
30
7.0
4.1
246.00 m²
57.4 m²
303.4 m² =
303.4x2
=606.8m²
20 cm cement plastering 1:3
with std. water proofing
compound in floor of
aeration tank
1
1
126 m3 1
12 mm cement plaster
1:3 mortar mixed with
std. water proofing
compound in aeration
tank
Total
4
5
4.1
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vii TUBE SETTLER 1
Cement concrete 1:3:6
floor & foundation
0.46
4.300m
1) Rectangle
2) Triangle
2
2
4.300
4.300
8.0
8.0
0.30
0.08
20.640 m3
5.504 m3
L=8.9/2 =4.4m
4.40-0.45/2=4.3m
Total
26.144 m
3
2.
Cement concrete for 1:3:6
wall
1) L.W
2
16.4
0.2
8.9
58.384 m3
L= 16+0.2+0.2 =16.4
m
2 30.0 7.0 420.000 m2
100mm SW pipe laying &
joining with 1:3cm
Outlet from aeration tank to
secondary clarifier
3.00 m
vi) SECONDARY
CLARIFIER
1
1.
Cement concrete 1:3:6 floor
& foundation
0.46
5.8 m
1) Rectangle
2) Triangle
2
2
5.8
5.8
12
12
0.30
0.08
41.760 m3
11.136 m3
L= 12/2 = 6m
6-0.45/2 =5.8m
Total
52.896 m3
2. Cement concrete 1:3:6 wall
1
(𝜋/4 ×12.8×3.26) -
( 𝜋/4×122 ×3.26)
50.790 m3
d=12=0.4=0.4=1
2.8 m
h=2.8+0.46=3.26
m
3
.
Sludge withdrawn C.I pipe
to filter press 450mm ϕ
1
1 nos
4. Cement concrete for
overflow channel 450 mm
ϕ and 450 mm depth
π/4×13.82×0.10×0.45 1.950 m
3
3 1
1
1
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2) S.W 2 8.9 0.2 8.9 31.684m3
Total 90.068 m3
3.
Sludge withdrawn C.I pipe
to filter press 450mm ϕ
1 1 nos
4.
Cement concrete for
overflow channel 450 mm
ϕ and 450 mm depth
1
(17.5×10.4×0.45)-
(17.3×10.2 ×0.45)
2.493 m3
3. RATE ANALYSIS DESIGNED STP (AS PER P.W.D RATES 2017) The rate analysis for the designed STP is followed as per P.W.D rates 2017.At various stages in project
management, need to know how much is cost of executing unit amount of work, and how many equipments are
required to execute unit amount of an item of work. For getting the all data’s rate analysis should be done as per
current rate available in PWD.
Table: 3 Rate analysis (As per P.W.D rates 2017)
SL.NO: DESCRIPTION UNIT QUANTIY RATE AMOUNT
i) INLET CHAMBER
1. Earth work in excavation Cum
4.536 m3 1339.45 6075.745
2. Cement concrete 1:4:8 for floor & foundation
Cum
0.756 m3 6180.00 4672.080
3. First class brick 1:4cm in inlet chamber
Cum
1.740 m3 7227.35 12575.589
4. G.I sheet for roofing Nos 1 1012.5
5.
12 mm cement plaster 1:3 mortar mixed with
std. water proofing compound in Inlet chamber
Sqm
4.600 m2
318.15 1463.490
6.
20 cm cement plastering 1:3 with std.water
proofing compound in floor of inlet chamber
Sqm
1.30 m2
450.8 586.04
7.
100mm SW pipe laying & joining with 1:3cm
Inlet from hospital to Inlet chamber
Meter
100 m 1707.90 170790
ii) SCREEN CHAMBER
1. Earth work in excavation Cum 7.128 m3 1339.45 9547.599
2.
Cement concrete 1:4:8 for floor & foundation
Cum
1.188 m3
6180.00
7341.84
3. First class brick 1:4cm in screen chamber
Cum
2.460 m3
7227.35 15582.17
4. G.I sheet for roofing Nos 1 nos 1012.50
5.
12 mm cement plaster 1:3 mortar mixed with
std. water proofing compound in screen chamber
Sqm
7.00m2
318.15 2227.05
6.
20 cm cement plastering 1:3 with std.water
proofing compound in floor of screen chamber
Sqm
2.50 m2
450.80
1127.00
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7.
100mm SW pipe laying & joining with 1:3cm
Inlet from Inlet chamber to screen chamber
Meter
2 m 1707.90 3415.80s
iii) GRIT CHAMBER
1. Earth work in excavation Cum 17.150m3 1339.45 22771.567
2. Cement concrete 1:4:8 for floor & foundation
Cum
2.814 m3 6180.00 17390.52
3. First class brick 1:4cm in grit chamber
Cum
4.32 m3
7227.25 31221.72
4. G.I sheet for roofing Nos 1 nos 1012.50 1012.50
5.
12 mm cement plaster 1:3 mortar mixed with
std. water proofing compound in grit chamber
Sqm
12.960 m2
318.15 4123.224
6.
20 cm cement plastering 1:3 with std. water
proofing compound in floor of grit chamber
Sqm
7.290 m2
450.80
3286.332
7.
100mm SW pipe laying & joining with 1:3cm
Inlet from screen chamber to grit chamber
Meter
2 m 1707.9 3415.80
iv) COLLECTION TANK
1. Earth work in excavation for collection tank
Cum
1172.590
m3 1535.09 1800031.2
2. Cement concrete for P.C.C Cum 16.290 m3 5857.75 95422.74
3.
Cement concrete for foundation
Cum
97.120 m3
6180.00
600201.60
4. Cement concrete for walls Cum 81.940 m3
6180.00 506389.20
5.
R.C.C roof 20 cm thick precast slab including
steel reinforcement complete laid in position
Cum
31.230 m3
2180.45 68095.4535
6.
1) Inlet from grit chamber to collection tank
600mm ϕ
2) Outlet pipe from collection tank to aeration
tank
Meter
Meter
4 m
8 m
1060
1060
4240
8480
v) AERATION TANK
1. Cement concrete 1:4:8 for floor
Cum
126.000 m3
6180.00 778680
2. First class brick 1:4 cm in aeration tank
Cum
187.950 m3 7227.25 1358361.63
3.
12 mm cement plaster 1:3 mortar mixed with
std. water proofing compound in aeration tank
Sqm
606.800 m3
318.15
193053.42
4.
20 cm cement plastering 1:3 with std.water
proofing compound in floor of aeration tank
Sqm
420.0m3
450.80 189336
5.
100mm SW pipe laying & joining with 1:3cm
Outlet from aeration tank to secondary clarifier
1707.9 5123.7
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Meter
3 m
vi) SECONDARY CLARIFIER
1. Cement concrete 1:4:8 floor & foundation
Cum
52.896 m3
6180.00 326897.28
2. Cement concrete 1:4:8 wall Cum 50.790 m3
6180.00 313882.2
3.
Sludge withdrawn pvc pipe to filter press
500mm ϕ
Meter
1 nos 4150 4150
4.
Cement concrete for overflow channel 450 mm
ϕ and 450 mm depth
Cum
1.950 m3
6180.00 12051
vii) TUBE SETTLER
1.
Cement concrete 1:4:8 floor & foundation
Cum
26.144 m3
6180.00 161569.92
2. Cement concrete for 1:4:68wall
Cum
90.068 m3
6180.00 556620.24
3.
Sludge withdrawn C.I pipe to filter press
500mm ϕ
Meter
1 nos 4150 4150
4.
Cement concrete for overflow channel 450 mm
ϕ and 450 mm depth
Cum
2.493 m3
6180.00
15406.74
TOTAL 7322795
4. Methodology 4.1 Materials for STP model
Small scale model for STP s were developed using glass and plastic containers as per obtained
designed value. Materials used for the small scale STPs were sand, activated carbon, and coarse aggregate for
filtration process. Other materials were, mini motors, small aerators, Lime, and nutrient agent etc.Aeration tanks
and tube settler were made by glass material having size 37 x18x10 cm and 23x18x40 cm. To avoid purification
of effluent mini motors were used. Oxygen is supplied by means of small aerators.
4.1.1Sand
Sand is a loose granular substance typically pale yellowish brown, resulting from the erosion of
siliceous and other rocks and forming a major constituent of beaches, river bed, etc. The sand is collected from
the market, located at Ollur. Sand passes through IS 2.36 mm is used . The filter medium should be of uniform
grain size to make sure that the pores between grains are the same size, so that the filters efficiency should be
equal over the bed. The sand used in the filtration process must have low silt content and hence the river sand is
preferred due to have less soluble salts in it. Sand must be washed thoroughly before it should be used as filter
media.
Fig :1 Sand passes through IS 2.36 mm sieve
As the water passing through the fine grained medium, pathogens are strained out as they encounter
small pore spaces. Pathogens are controlled by a bio film of beneficial microorganisms which are forms on the
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surface of sand grains and removes pathogens through interactions and competitions. The most removal occurs
within the top few centimeters of sand bed where the biological activities are greatest.
4.1.2 Activated carbon
Activated carbon can be considered as a material of phenomenal surface area made up of millions of
pores - rather like “molecular sponge. The activated carbon was collected from house itself. Activated charcoal
or activated carbon is a typical form of carbon which is prepared by burning of coal or organic matter like
animal bones or coconut shells in controlled conditions.
Fig: 2 Activated carbon
4.1.3 Coarse aggregates
Coarse aggregate is provided to support the sand bed and to permit uniform drainage of the overlaying
sand. This layer allows water to drain freely from the sand bed while preventing sand from escaping to the outlet
tank. To accomplish the above purposes, aggregates must be graded. The aggregate which passes through 10
mm IS sieve and retain on 20 mm IS sieve is used.
Fig : 3 Coarse Aggregate passes through 10 mm
IS sieve and retain on 20 mm IS sieve
4.1.4 Lime
Lime is a calcium containing inorganic mineral in which carbonates, oxides, and hydroxide are
predominate. Otherwise it is defined as it is a colorless crystal or white powder and is obtained when calcium
oxide is mixed, or slaked with water.
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Fig : 4 Lime
4.1.5 Nutrient agent
Nutrient agents added to the raw sewage water for perfect biosynthesis. Cow dung was added as a
nutrient medium. Cow dung is the undigested residue of plant matter which has passed through the animals gut.
An MLSS concentration of 4000mg/L is to be maintained in the aeration tank for enough bacterial growth.
Fig: 5 Nutrient agent
4.2 Experimental set up for small scale STP
Small scale model for STP s were developed using glass and plastic containers as per obtained
designed value. About 2.5 L sewage waste water was collected from Jubilee mission hospital, Thrissur. Sewage
water diluted and to made as 5L. Checked the parameters of diluted sewage water. A plastic container of 22 L
capacity is used as an inlet chamber. From inlet chamber, the sewage was passed through the screens having an
opening of 4mm and 2 mm respectively. Plastic container of size 35cmx25cmx15 cm used as screen chamber.
The screens were placed at 45 degree to the chamber. After screening, the effluent was collected in a collection
tank where air is bubbled by means of mini motors to avoid purification of effluent. Plastic container with
diameter 24 cm, depth 17 cm and slope height is 9 cm was used as collection tank. Two aeration chambers were
made up of glass material having size 35 cmx18 cmx10cm to receive the sewage water from collection chamber.
Two numbers of small aerators were used for providing oxygen to the bacteria’s for their speedy survival. A
plastic container of 24 cm diameter and 10 cm depth was used as secondary clarifier. Its slope height is 9 cm.
Used a plastic container of diameter 24 cm and depth 17 cm as a sump. Tube settler received the effluent from
sump made up of glass material had size 23 cmx18cmx30 cm, with sloping height of 9 cm. For further
purification of the effluent, the effluent should be passed through the filter made by glass of size
18cmx18cmx30 cm. The components of STPs were described below.
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Fig: 6 Experimental set up for small scale model for STPs
4.2.1Collection tank
Collection tank serves the purpose of maintaining desired flow rate as well as for making mixture
homogeneous. The effluent from screen chamber will lead to the collection tank. Plastic container with diameter
of 24 cm, depth 17 cm and slope height is 9 cm was used as collection tank. After screening process, the effluent
is collected in a collection tank where thoroughly mixing is made by means of mini motors for 6 hours to avoid
purification of effluent.
Fig: 7 Collection tank
4.2.2 Aeration chambers
Two aeration chambers were made up of glass material having size 35 cmx18 cmx10cm to receive the
sewage water from collection chamber and subjected to activated sludge process. Oxygen is supplied by means
of small aerators for 6 hours. An MLSS concentration of 4000mg/L is to be maintained in the aeration tank for
enough bacterial growth. Nutrients in the form of cow dung added for perfect biosynthesis.
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Fig: 8 Aeration tank
4.2.3 Secondary clarifier with sump
A plastic container of 24 cm diameter and 10 cm depth was used as secondary clarifier. Its slope height
is 9 cm. The overflow from the aeration tank is sent to the hopper bottom settling tank where the sludge settles
and clear liquid overflows. The overflow from the hopper bottom settling tank is collected in an intermediate
sump for lime mixing. Mini motors are used for mixing purpose. Mixing time provided for 6 hours. A plastic
container of diameter 24 cm and depth 17 cm was used as an intermediate sump.
Fig: 9 Secondary clarifier with sump
4.2.4Tube settler
Tube settler received the effluent from sump made up of glass material had size 23 cmx18cmx30 cm,
with sloping height of 9 cm in size .Tube settler is used for sludge settlement.
Fig: 10Tube settler
4.2.5 Filter
Glass chamber of size 18cmx18cmx30 cm, used as filter. Layers of materials were filled inside. The
bottom most layer 90 mm was filled with coarse aggregates passed through 10 mm IS sieve and retained on 20
mm IS sieve. The layer above coarse aggregate , activated carbon, placed about 40 mm depth. A layer of cotton
cloth was placed in between each medias. Sand passing through 2.36 mm IS sieve at a height of 90mm is filled
above the activated carbon layer. In the top most layer, the aggregate which is passes through 10 mm IS sieve
and retain on 20 mm IS sieve was filled ,at a depth about 90 mm.
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Fig: 11 Filter
4.3 Methodology for STP model
Small scale model for STP s were developed using glass and plastic containers as per obtained
designed value. The method behind the small scale STP model is based on the extended aeration activated
sludge process. About 2.5 L sewage waste water was collected from Jubilee Mission hospital, Thrissur. Sewage
water diluted and to made as 5L. Checked the parameters of diluted sewage water. A plastic container of 22 L
capacity is used as an inlet chamber. The main process carried out in the sewage treatment plant is the
wastewater generated from various sections is first passed through screen chamber for removing large particles.
After screening, the effluent is collected in a collection tank where air is bubbled by means of mini motor
instead of blower through pipe grid to avoid purification of effluent. From the collection tank, the wastewater is
pumped at a suitable rate to the aeration tank and subjected to activated sludge process. Oxygen is supplied by
means of small aerators. An MLSS concentration of 4000mg/L is to be maintained in the aeration tank for
enough bacterial growth. Nutrients in the form of cow dung added for perfect biosynthesis. The overflow from
the aeration tank is sent to the hopper bottom settling tank where the sludge settles and clear liquid overflows.
Excess sludge is taken to the filter press in hospitals. In the intermediate sump, the combined effluent is mixed
thoroughly by mini motors instead of flash mixer where adequate dosage of lime and reagent are added.
Coagulation of residual suspended solids and dissolved organics takes place. The precipitated slurry is then
send to the tube settler where the sludge is settled and clear liquid is allowed to overflow. A mild dosage of
hypochlorite is added to the tube settler for disinfection. From tube settler, the raw sewage water sent to sand
filter for final polishing. Checked the current status of effluent which is obtained after the treatment from small
scale STP model. The treated water is discharged in to land for irrigation purposes and balance to public drain.
5. Results and Discussions 5.1 Environmental impact assessment
As the part of the project, conducted an impact survey. The survey was carried out school and houses
which are located near to STP. From impact survey, understood the impact of the present STP. Majority of
peoples problem was the smell generated from the STP at the time of cleaning. Which will badly affect the
school. The suggestion to the school authority was the cleaning should do after the school time. Night time is the
best time for the cleaning of the STP. This will also help to reduce the smell . From this impact survey can
concluded that smell is the only impact due to STP , so the current STP would be safe while changing the
cleaning time.
Table: 4Water characteristics near the current STP
Bore well
water Well water School water
Drinking
water
desirable
limit IS
:10500,1991
Distance from
plant in (meter) 10 30 2
BOD(mg/L) Nil Nil Nil Nil
COD(mg/L) Nil Nil Nil Nil
pH 7.2 6.5 7.3 6.5 -9
TDS(mg/L) 500 500 500 500
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Same result is been observed when testing the water samples from a nearby bore well, well for house, well for
school which are 10 m, 30 m and 2 m away respectively. The test results are within the standards of IS :
10500,1991. So the current STP is safe.
5.2 Size of designed STP
The sewage treatment plants for Jubilee mission hospital was designed as per extended aeration
activated sludge process. The size of the screen chamber obtained as 2.5m×1m×1m. Screen chamber is used to
prevent the entry of solid particles/ articles above a certain size; such as plastic cups, paper dishes, polythene
bags, condoms and sanitary napkins into the STP. Size of the grit chamber, diameter and depth of collection
tank, size of aeration tank, clarifier and tube settler were tabulated in table 6.3.1. Grit chambers are nothing but
like sedimentation tanks, designed to separate the intended heavier organic materials. The main function of the
aeration tank is to maintain a high population level of microbes.
The main function of secondary clarifier is, allow settling of biomass solids in the mixed liquor (biomass slurry)
coming out of the aeration tank, to thicken the settled biomass, and to produce clear supernatant water.
Table: 5 Items and its size as per designed STPs
Item Size
Inlet chamber 1.3mx1mx1m
Screen chamber 2.5mx1mx1m
Grit chamber 2.7x2.7x1.2m
Collection tank 13.5m diameter, D= 6m
Aeration tank 3omx7mx4.1m
Secondary clarifier 12 m diameter, D= 3.5 m
Tube settler 16mx8.9m
5.3 Estimation and cost of designed stps
Estimation of the designed sewage treatment plant is done by long wall short wall method. The rate
analysis for the designed STP is followed as per P.W.D rates 2017. The total cost for work is approximate 73
lakhs.
Table: 6.Cost for construction
SL.NO: DESCRIPTION AMOUNT
i) Inlet chamber 197175.44
1. Screen chamber 40253.95
2. Grit chamber 83221.66
3. Collection tank 3082860.19
4. Aeration tank 2524554.75
4. Secondary clarifier 656980.48
5. Tube settler 7322793.39
TOTAL 7322795
5.4 Small scale model for STPS
Small scale model for STP was developed as per designed values to check whether the method is
preferable or not. The influent from hospital diluted to ( 50% of influent ) Effluent from the model meets the
standards of CPCB for irrigation purposes. So, the working is satisfactory.
Table : 7 Effluent characteristics
Parameters Influent effluent Limit for land irrigation
given by CPCB
pH 5.11 6.7 5.5 -9
TDS 350 (mg/L) 200
(mg/L)
200 (mg/L)
BOD 200(mg/L) 27(mg/L) < 30 (mg/L)
COD 420 (mg/L) 240 (mg/L) < 250 (mg/L)
OIL & GREASE 7 (mg/L) 6 (mg/L) <10 (mg/L)
International Journal of Recent Engineering Research and Development (IJRERD)
ISSN: 2455-8761
www.ijrerd.com || Volume 03 – Issue 05 || May 2018 || PP. 35-61
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6. Conclusions The project is intended to design a of STP to treat the sewage water from Jubilee mission hospital
Thrissur. It is based on extended aeration activated sludge process. When considering the population inflation
and future developments, to hospital, the capacity of current STP is insufficient. (800 cum/day). So, STP which
can be handles the future sewage requirement of hospital to be design for 30 years. The existing STP having
lower capacity, i.e. 800 cum/day can be replaced by the STP having 1700 cum/day. The available space for the
construction is limited, hence it is designed as two storied structure. The designed STP was estimated using long
wall short wall method. The total construction cost is approximately 73 lakhs. A small model for STP was also
developed as per the designed values to check its working and it was satisfactory. The sewage effluent was
treated by this model and treated water is tested and found that the water quality parameters within the limit of
CPCB for irrigation purpose.
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