Feasibility Report
Feasibility Report on Water Pollution Control System for Proposed Residential Building called
“STERLING GRANDE TOWERS” coming up on Part of Sy No. 112, 113 & 14 of Seegehalli Village,
Bidarahalli Hobli, Bangalore East Taluk.
With a view to conserve fresh water resources and adopt re-cycle and re-use measures, they propose to
set up a water pollution control and re-use system for the wastewater generated from entire complex The
source of wastewater is from toilets in the proposed building and therefore domestic in nature.
This report details the following of Collection, Treatment & disposal of domestic Effluents from the
proposed facility.
9.1 WATER CALCULATIONS
Recycled
No. of
Sl.No
Description
Units
Per capita
Fresh Water
Population requirement Requirement
Water
Total Water
Requirement
Requirement
Residential
1
Development
2
3
280
1400
135
126000
63000
189000
Visitors
70
135
6300
3150
9450
Retail
200
45
4000
5000
9000
TOTAL
1400
136300
71150
207450
137
71
208
GRAND TOTAL IN KLD
TOTAL WATER REQUIREMENT
:
208 KLD
WASTEWATER GENERATED (95%)
:
198 KLD
STP CAPACITY
:
200 KLD
WATER BALANCE CHART
Fresh Water – 137
Recycled Water 71 KLD for
flushing
Panchayat
Total Water Consumption
– 208 KLD
95% after Diversity
Wastewater Generated – 198 KLD
Sewage Treatment Plant of capacity –
200 KLD (SBR)
97% of treated water available = 192 KLD
Landscaping – 23
KLD
For Avenue Plantation / Nearby
Construction Activities- 98 KLD
Flushing – 71
KLD
Hydraulic loading computation for utilization of treated sewage effluent on land for gardening:
1.0 classification of soil
: Sandy loam
2.0 Hydraulic loading rate applicable to sand loam soil as per KSPCB
: 175-225 m3/2.441 acres/day
Now the total area available for landscaping is
: 3906.852Sqmtrs
According to hydraulic loading the apartment complex can use maximum of 23 KLD of treated sewage
for on land gardening.
9.2 Method adopted for the design
The design is made keeping in mind the total quantity of generation of wastewater is 200 KLD. The
modular technology is adopted in the design, i.e., when the flow increases drastically, the present units
itself can be used with Additional units attaching to it in modules, which would be economical and saves
on the area required too.
9.3 Characterization:
The general characteristic of sewage is considered as shown in the table below.
General characteristics:
pH
:
6 – 8.5
BOD5
:
250-300mg/lt.
COD
:
600mg/ltr
SS
:
150mg/ltr
The anticipated final water quality:
PH
:
6 – 8.5
BOD5 :
< 10 mg/lts
COD
< 150 mg/lts
:
SS
: < 10 mg /lt.
Turbidity :
E.Coli
:
< 2 NTU
None
Mode of Treatment:
TREATMENT METHODOLOGY ADOPTED
The methodology adopted for treatment of sewage is based on Sequencing Batch Reactor (SBR) followed
by disinfection. The sludge from the process is aerobically treated in aerobic digester.
The Sequencing Batch Reactor (SBR) process is a sequential suspended growth (activated sludge) process
in which all major steps occur in the same tank in sequential order. There are two major classifications of
SBRs: the intermittent flow (IF) or “true batch reactor”, which employees all the steps and the continuous
flow (CF) system, which does not follow these steps. Both have been used successfully worldwide
installations. SBRs can be designed and operated to enhance removal of nitrogen, phosphorus, and
ammonia, in addition to removing TSS and BOD. The intermittent flow SBR accepts influent only at
specified intervals and, in general, follows the five-step sequence. There are usually two IF units in
parallel. Because this system is closed to influent flow during the treatment cycle, two units may be
operated in parallel, with one unit open for intake while the other runs through the remainder of the
cycles. In the continuous inflow SBR, influent flows continuously during all phases of the treatment
cycle. To reduce short circuiting, a partition is normally added to the tank to separate the turbulent
aeration zone from the quiescent area.
DESIGN DETAILS OF SEWAGE TREATMENT PLANT
Design of the individual units:
Bar Screen Chamber:
Provide a chamber of size 1.0 m x 0.65 m to suit sewer gradient to accommodate an inclined bar screen
with opening less than 10 mm. Provide a bar screen of 20 X 6 mm flats with 10mm spacing in between.
Design Criteria:
Velocity through screen
: 0.8 m/Sec.
Discharge
: Discharge / day /8
=2, 00,000/8
=6.94x10-3 Cum. /sec
Peak Load
: 3 times the discharge
=6.94x10-3 x3.0
=0.020 m3 /sec
Adopting screens with bars of 10 mm width and 20 mm clear opening considering 1.2 times the net area
of opening,
Net Area
= 0.020 /0.80 =0.025 m2
Gross area
= 1.2 times of the net area of opening
= 1.2 X 0.025 =0.03 m2
Assuming the inclination of screen of 60° to horizontal. Gross area of screen needed would be 1.0X0.45
Mt. for ease of maintenance.
Equalization Tank:
The flow from the bar screen chamber is let into the equalization tank of minimum 8 hours capacity. This
tank is provided to even out the flow variation, and to provide a continuous feed into the secondary
biological treatment units.
Design flow
=
2, 00, 000Lt/day
Provide min 8 hours holding capacity.
Hence required volume of the tank
= 66.66m3
Provide a tank of 66,000 Lt. Capacity.
The tank size would be 6.0X4.5X2.5 m SWD (effective volume)
Sequential Batch Reactor (SBR) tank
Biological stabilization of the wastewater is accomplished in the SBR tank in the presence of
microorganisms, for the respiration of which oxygen is supplied by means of diffused aeration comprising
of membrane diffusers and air blowers. As micronutrients such as nitrogen and phosphorus will be
already present in sufficient quantities, no external supplementation will be necessary.
The aeration tank is provided with diffused aeration system to supply the air for the microorganism’s
growth. The nutrients required for the microorganism’s growth are organic matter, which is present in the
domestic effluent.
The MLSS level is maintained in this process to enhance the aeration process. Optimum concentration of
MLSS to be maintained is in the range of 3500 – 4500 mg / lit. During the aeration, the sludge starts to
settle in this tank. At that time, the blower will be off.
Here the settling of the solids takes place and the clear water from the top is pumped to the clear water
tank.
Design flow
= 2, 00,000 Lt/day
Considering the 3 batches
Volume of the tank
= 200/ (3 batches x 3 reactors x 0.5 decanting ratio)
= 200 / ( 3 x 2 x0.5 )
Hence required volume of the tank
= 66.66 cum/ reactor
Provide a tank of 67 cum/ reactor capacity
The sizes of the tank will be
Air Blowers
= 6.8X4.0X2.5 m
Flow Quantity
200 cum/day
BOD In
300mg/l
BOD Out desired
<10mg/l
Tank Volume
2 x 67cum
Diffusers
Fine Pore Diffusers
Food X Microbe
0.12
MLSS
4000mg/l
No. of tanks
3 Nos.
Sewage inflow/batch
= 200/6 = 33.33 cum.
Total BOD5 load
= 250 mg/l.
BOD load in tank in Kg
= ( 250x33.33 ) / 1000 = 8.33 kg/batch
For 1 kg of BOD removed 1.2kg of oxygen is required
Density of air
= 1.17
% of oxygen in air = 21%
= 0.21
Alpha factor = 0.65
Beta factor = 0.90
Oxygen transfer efficiency
= 0.12
There for Air required
= 8.33 x 1.2 / ( 1.17 x 0.21 x 0.65 x 0.9 x 0.12)
= 9.99 / 0.017
= 587.64 cum/ batch
Aeration time = 4hr
There for air required in cum/ hr = 146.91 cum/ hr = 86.46cfm.
Consider 35% excess considering the air required in the equalization tank
Total air required = 116.72cfm
Hence provide 3 blowers of 60cfm
One as standby with an operating pressure of 0.5KSC.
Transfer rate of oxygen in 1m.
Long membrane diffusers = 10 cum/ hr
There for total number of membranes required = 116.72/10 = 12 nos.
Clarified Water Tank – 1 NO:
The settled water from the settling tank is expected to meet the standards with respect to BOD and TSS
for discharge to island surface waters. However, it is our intention to improve the quality of effluent
further in order to make it fit for reuse. For this reason, further secondary treatment in the form of
coagulation, filtration and disinfection is proposed. The clear water from the settling tank shall be fed to
the clarified water tank, from where it will be pumped to the filters.
Design flow
= 2, 00,000Lt/day
Provide min of 16 hours holding capacity.
Hence required volume of the tank
= 133.33 m3
Provide a tank of 1,35,000 Lt. Capacity
The sizes of the tank will be 8.5X6.3X2.5 m
Pressure Sand Filter:
Flow
=
2,00,000Lt/day
Loading rate
=
15 cum/ Sqmt/hr
Considering the operation of 20 hours of filter
Provide a Pressure Sand filter of 1221mm dia with sand as media over layer, under drain pipe, laterals
face piping etc.,
Activated Carbon Filter:
Flow
=
2,00,000liter/day
Loading rate
=
15 Cumec/Sqm/hr.
Considering the operation of 20 hours of filter
Provide a pressure sand filter of 1221-mm diameter with activated carbon filter media with under
drainpipe, lateral face piping.
Chlorination:
The filtered water is further chlorinated through an online automatic chlorination system with
electronic dosing pump for disaffection. Provide one no. 100 Lts capacity automatic Chlorinator with
electronic metering pump to ensure the residual chlorine level to be less than 2 PPM for disinfect ion so
that it will not effect the plantations. The Chlorinator shall be coupled with the filter outlet.
Pumps:
Provide 3 Nos. sewage transfer pumps (one working and one standby)
Quantity
3Nos. ( 2 working + 1 Stand by)
Type
Open impeller non-clog centrifugal Pumps
Avg Rate of Flow
25 cum/hr @ 10m head
Temp
Ambient
Solids
35mm Maximum
pH
6.0-8.0
Provide 2 Nos Filter feed pumps (one working and one standby)
Quantity
2Nos. ( 1 working + 1 Stand by)
Type
Open impeller non-clog centrifugal Pumps
Avg Rate of Flow
15 cum/hr @ 10m head
Temp
Ambient
Solids
10mm Maximum
pH
6.0-8.0
Duty: To pump the Treated effluent from the Pre-filtration tank through the Pressure Sand Filter and
Activated Carbon Filter.
Sludge Disposal:
The biomass in the aeration tank stabilizes BOD in wastewater by consuming the organic matter in the
wastewater. The metabolic activity results in growth of the biomass population in the aeration tank.
Consequently, in order to contain the level of MLSS in the aeration tank to the design level of 4000mg/l,
it will be necessary to bleed off or waste the excess activated sludge. For this purpose, a sludge-holding
tank of 20 cum with air supply and one no. filter press is proposed.
Capacity
20.0 cum/day
Sludge Volume Index
100-150mg/l
Filter Press:
The present invention relates to a method and apparatus for treating the sludge is generally known as
"reburning", lime sludge in order to regenerate the sludge, which in a flash dryer making method has been
separated in connection with a causticizing process, to form active lime.
The units and its sizes as designed are:
Civil works
Name of the Unit
Size in mt.
1.
Bar Screen Chamber
1.00m X 0.45 m
2.
Equalization Tank
6.0X4.5X2.5 m
3.
SBR Tank
6.8X4.0X2.5m - 2 nos.
4.
Final effluent tank
8.5X6.3X2.5 m
5.
Clear water tank
8.5X6.3X2.5 m
6.
Pressure Sand Filter
1221 mm dia and 1219 mm
Sl. No
height.
7.
Activated Carbon Filter
1221mm dia and 1219 mm
height
8.
Chlorinator
200 lts capacity
9.
Mechanical Filter Press
50m3/day plant
Mechanical Equipment Proposed
SL NO
ITEM
Qty
1
Bar Screen
1No.
2
Pumps
6 No
3
Diffuser membranes
12 lot
4
Coarse Bubble grid
1 lot
5
Blowers
3 Nos.
6
Pressure Sand filter
1 No
7
Activated carbon filter
1 No
8
Chlorinator
1 No
9
Mech. Ventilation
STP Hydraulic Flow Diagram:
1
Lot
Pump
EQT
Equaliz
SBR
Seqenti
CWT
Clarified
MV
Multipor
PSF
Pressur
ACF
Activate
Control
Non Re
Pump
EQT
Equalization tank
SBR
Seqential Batch Reactor
CWT
Clarified water tank
MV
Multiport valve
PSF
Pressure sand filter
ACF
Activated carbon filter
Control / Isolation valve
Non Return valve
SCHEMATIC FLOW CHART
Flow 198 m3/day
Bar screen
chamber
Receiving Tank
Raw sewage pump
Sludge pump
SBR cum settling tank
SBR cum settling tank
Sludge
holding tank
Decant Tank
Mechanical
filter press
Filter feed pump
Pressure
Sand filter
Activated
carbon filter
UV Sterilizer
Common Treated water
sump
Treated water transfer pump
Reused for landscape development/toilet flushing
Purpose/Surplus to Avenue Plantation & Nearby
Construction Activities
Sludge used as
manure