Treatment unit description,
·
General
The proposed Sewage Treatment Plant (STP) of Capacity 20 MLD comprises
of the following units,
a.
Primary Treatment System
i.
Inlet Chamber
ii.
Fine Screens
iii.
Grit Removal Unit
iv.
Parshall Flume
b.
Sequential Batch Reactor
(SBR) - C-Tech
c.
Chlorination System
d.
Sludge Handling
i.
Sludge Thickener
ii.
Thickened Sludge Sump and Sludge
Transfer Pumps
iii.
Mechanical Dewatering Unit
iv.
Polymer Dosing System
e.
Utilities
i. Plant water sump & pumps
·
Sewage Treatment Plant (STP)
·
Primary Treatment
·
Inlet Chamber
The Inlet chamber is provided at higher
ground level to receive raw sewage from Raw Sewage Pumps through discharge Pipelines. The purpose of providing
inlet chamber is to reduce the velocity of sewage (pressure
flow) coming via pumping to achieve better efficiency in screening.
Inlet Chamber
Design Flow : 46.84 MLD
Number of Units : 1
No.
Material of Construction : RCC
·
Fine Screen Channels
Raw sewage from the inlet Chamber flows
by gravity into the Fine Screen Channels. There are two parallel fine screen channels provided, one for mechanical
screen and another for manual screen.
The Mechanical Fine Screen is step type screen with automatic mechanism to
remove the floating and oversized
material more than 6 mm size such as plastic, debris, paper and cloth rags that could foul the downstream
units. These screenings mechanically collected over a conveyor Belt and conveyed through Chute to wheelbarrow /
trolley positioned at Ground Level.
Mechanical screen operation will be controlled depends upon the head loss
across screen which will be monitored by differential level transmitter provided
in the screen channel.
Manual fine screen is provided as standby arrangement and will be taken in
working during maintenance of mechanical screen. Sluice gates are provided
on the upstream & downstream of screen channels
to regulate the flow and to isolate
them for maintenance.
Mechanical Fine Screen
Channel
Design Flow : 46.84 MLD
Number of Units : 1
No. (1W)
Material of Construction : RCC
Mechanical Fine Screen
Design Flow : 46.84 MLD
Number of Units : 1
No. (1W)
Material of Construction : SS304 wetted Parts
Mechanical Screen
Type : Step type screen
Manual Fine Screen
Channel
Design Flow : 46.84 MLD
Number of Units : 1
No. (Standby)
Material of Construction : RCC
Manual Fine Screen
Design Flow : 46.84 MLD
Number of Units : 1
No. (Standby)
Material of Construction : SS304 wetted Parts
·
Grit Removal
Unit
The Screened Sewage from screen flows in
to Vortex Grit Removal Unit for removal of grit and small inorganic particulates. The Vortex grit chamber is
provided with Vortex Agitator, Grit Pump
and Grit Classifier. The Chamber consist of an upper separation tank, where
grit is removed from the flow and lower tank which stores settled
grit. Within the Vortex grit separation
tank a slow speed mechanical drive agitator regulates internal vortex action to ensure that while grit settles
to bottom of the grit chamber, organics
are maintain in suspension
and carried out with the degritted flow. The vortex agitator driven by the
geared motor located on the vortex
grit chamber bridge. Settled Grit automatically removed from the vortex grit chamber on the time basis
using grit pump located on the vortex grit chamber bridge. The grit slurry from the vortex grit chamber storage
tank is fed through grit pump to external
grit classifier for removal of grit. After de-gritting the sewage overflows
into the outlet channel. Sluice
gates are provided at the inlet and outlet of Vortex Grit Chambers to isolate them for maintenance.
Vortex Grit Chamber
Design Flow : 46.84 MLD
Number of Units : 2
Nos. (1W + 1SB)
Material of Construction : RCC
: Wetted Parts – SS316
·
Parshall Flume
Screened and de-gritted sewage from
vortex grit chamber flows through Parshall Flume. The Parshall Flume channel is equipped
with ultrasonic flow meter for measuring the flow.
Parshall Flume
Design Flow : 46.84 MLD
Quantity : 1
No.
Design : As
per CPHEEO standards
Material of Construction : RCC
·
Sequential Batch Reactors (C-Tech)
Refer complete design and description of
biological treatment process based on SBR (C-Tech) for 20 MLD capacity
provided in section
4.
·
Chlorination System
Treated sewage from SBR flows by gravity into Chlorine
Contact Tank (CCT) through RCC Channel
where chlorine is added for disinfection at suitable dosing rate to achieve the
desired Fecal Coli-Form Standards.
Baffle Walls are provided in the CCT to facilitate mixing of treated sewage. Adequate contact time is provided
in the CCT to ensure proper disinfection of treated sewage. Weir is provided at outlet of the CCT. A Chlorination
House is provided to house the Chlorination
System comprising Vacuum Chlorinators, Water Booster Pumps, Interconnecting Piping & valves, Chlorine Tonners,
Trunions / Roller Supports, Lifting Device, Safety Equipment and other Accessories.
Chlorination System
Design Flow : Decant Flow
Number of Chlorinators : 2
Nos. (1W + 1SB)
Chlorine Contact Tank
Design Flow : Decant Flow
No. of Units : 1 No.
MOC : RCC
·
Treated Water Sump and Pumping station
Treated sewage from Chlorine Contact Tank
(CCT) flows by gravity into Treated Water Sump. Treated Sewage pumps are provided in Treated Water Sump to
transfer treated sewage from STP to starting
of Nala.
Treated Water Sump
Design Flow : Decant Flow
No. of Units : 1 No.
MOC : RCC
Treated Water Pumps:
Type : Submersible Pump
Material of Construction : Casing – CI IS: 210 Gr. FG 260 with
: Impeller – 2.5% Ni-cast
Iron IS:210, FG 260
: Shaft – SS 410
Quantity : 3
Nos. (2W + 1SB)
·
Sludge Handling
·
Sludge Thickener
Sludge Thickener will receive the sludge from SBR basin through SAS pumps.
The Sludge Thickener is designed to thicken the sludge from SBR. The sludge
enters in feed well zone it underflows
& spreads in the main tank for effective settling. The sludge settles and
thickens on the sloping
floor of the tank from where it is mechanically scrapped towards the central pocket
for sludge collection & discharge. The thickened sludge from the
Gravity Sludge Thickener is collected
in sludge sump and then pumped to centrifuge using centrifuge feed Pumps. The supernatant overflows into effluent
launder and sent to Filtrate/Centrate sump by gravity.
Gravity Sludge Thickener:
Design Flow : Sludge from SBR
No. of Units : 1 No.
Solid Loading Rate : 25 - 30 kg/day/m2 Solid concentration in thickened sludge : 3.0% (minimum)
Hydraulic loading : 12000 liters/day/m2
Thickener Recirculation Sump and Pump:
Thickener Recirculation sump is provided to maintain
the hydraulic loading of Gravity Sludge Thickener along with individual
recirculation pumps.
Thickener Recirculation Sump:
Number of Units : 1
No.
Detention period : 0.5 hr.
Material of Construction : RCC
Thickener Recirculation Pump:
Type : Submersible Pump
Material of Construction : Casing – CI IS: 210 Gr. FG 260 with
: Impeller – 2.5% Ni-cast
Iron IS:210, FG 260
: Shaft – SS 410
Quantity : 2
Nos. (1W + 1SB)
·
Thickened Sludge
Sump & Pumping House
Thickened Sludge generated from thickener will be collected into the thickened sludge sump by gravity. From sludge sump, sludge will be fed to the solid bowl type centrifuge by screw type pumps. Sludge sump is complete
with submersible mixer for sludge mixing.
Thickened Sludge Sump:
Design Flow : Sludge generation from Thickener.
Number of Units : 1
No.
Detention period : 12 hr.
Material of Construction : RCC
Sludge Sump Mixer:
Type : Submersible
Material of Construction : SS304
Quantity : As
per Requirement
Centrifuge Feed Pump:
Type : Progressive Cavity Pump
Material of Construction : Casing – Cast Iron IS 210 Gr. FG 260
: Rotor – SS316 Hard chromed plated
: Shaft – SS316
Quantity : 2
Nos. (1W + 1SB)
·
Mechanical Dewatering Device
Sludge dewatering is carried out by Solid Bowl Centrifuge. Two numbers (1W + 1SB) of Mechanical Dewatering Devices are provided
to dewater the sludge. Thickened Sludge from
Thickened Sludge Sump is fed to Solid Bowl Centrifuges for dewatering to the required
consistency so that it can be easily disposed off. The centrate from
sludge dewatering machine shall be
sent to filtrate/centrate sump by gravity. Polyelectrolyte is dosed online at
the inlet of Centrifuge to enhance
sludge dewatering efficiency. The dewatering system is located at first floor so that the de-watered sludge can
directly collect into trolleys / drums / bins without use of any material handling unit.
Polyelectrolyte is dosed online at Centrifuge inlet with minimum dosage of is 3 Kg / Ton of dry solids in
sludge at 0.2% solution strength. Two numbers (1W + 1SB) of Polyelectrolyte Dosing Tanks are provided. Each Tank is
equipped with Slow Speed Mixer to
prepare Polyelectrolyte solution. The solution is fed to Centrifuge using
Positive Displacement type Dosing
Pumps. There are dedicated Dosing Pumps provided to each Sludge Dewatering machines. The Pumps are interlocked with Mechanical Dewatering Device.
Sludge dewatering unit
Design Flow : Thickened Sludge from Thickener
Type : Solid Bowl Centrifuge
Quantity : 2
Nos. (1W + 1SB)
Polymer Dosing Tank:
No. Polymer
Dosing Tanks : 2
Nos. (1W + 1 SB)
Material of Construction : RCC
Polymer Dosing Tank Agitator:
No. of Agitator : 1
no. / tank
MOC of Agitator : SS316
Polymer Dosing Pump:
No. Polymer
Dosing Pumps : 2
Nos. (1W + 1 SB)
MOC : Body: CI,
Wetted Parts:
PP
·
Filtrate / Centrate Sump and Pumps
Filtrate
/ Centrate sump is provided
to collect thickener
supernatant from thickener
and centrate from
centrifuge. Filtrate / Centrate pumps are provided to transfer Filtrate /
Centrate to inlet chamber.
Filtrate / Centrate
Sump:
Design Flow : Filtrate / Centrate from Thickener. &
Centrifuge
Number of Units : 1
No.
Detention period : 20 min.
Material of Construction : RCC
Filtrate / Centrate
Pumps
Type : Submersible Pump
Material of Construction : Casing – CI IS: 210 Gr. FG 260 with
: Impeller – 2.5% Ni-cast
Iron IS:210, FG 260
: Shaft – SS 410
Number of Units : 2 Nos. (1W + 1SB)
·
Plant Water
Pumps
Plant water Pump is provided
in Treated water
sump for gardening, cleaning of equipment, flushing of
pipelines and general purpose.
Plant water Pumps
Type : Submersible Pump
Material of Construction : Body: CI, Wetted Parts: SS
: Casing – CI IS: 210 Gr. FG 260 with
: Impeller – 2.5% Ni-cast
Iron IS:210, FG 260
: Shaft – SS 410
Number of Units : 2
Nos. (1W + 1SB)
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