1 Introduction 2 Design Basis 2.1 Raw water Quality 2.2 Flow Rate Calculations 2.3 Pretreatment System 2.4 Demineralisation System 2.5 Potable Water System 3 Process Description System configuration 3.1 Pretreatment System 3.1.1 Clarifier System 3.1.2 Filtration System 3.2 Demineralization System 3.2.1 Reverse Osmosis System 3.2.2 Degassification System 3.2.3 Mixed Bed Ion Exchange System 3.2.4 Demineralised Water Storage transfer system 3.3 Potable Water System 3.3.1 Nano Filtration System 3.3.2 Potable Water Storage transfer system 4 Detailed operation concept 4.1 Pretreatment System 4.1.1 Clarifier System 4.1.1.1 Startup procedure 4.1.1.2 Normal operation procedure 4.1.1.3 Shutdown procedure 4.1.1.4 Chemical preparation procedure 4.1.2 ConventionalFiltration System 4.1.2.1 Startup procedure 4.1.2.2 Normal operation procedure 4.1.2.3 Shutdown procedure 4.1.3 Membrane Based Filtration System 4.1.3.1 Startup procedure 4.1.3.2 Normal operation procedure 4.1.3.3 Shutdown procedure 4.1.3.4 Chemical Preparation Procedure 4.2 Demineralisation System CM1L3M01GC52100001001 Process Description for the Water Treatment system Revision B 26 July 2006 Page 2of 36 4.2.1 Reverse Osmosis System 4.2.1.1 Startup procedure 4.2.1.2 Normal operation procedure 4.2.1.3 Shutdown procedure 4.2.1.4 Chemical Cleaning Procedure 4.2.1.5 Chemical Preparation Procedure 4.2.2 Degassification System 4.2.2.1 Startup procedure 4.2.2.2 Normal operation procedure 4.2.2.3 Shutdown procedure 4.2.3 Mixed Bed Ion Exchange System 4.2.3.1 Startup procedure 4.2.3.2 Normal operation procedure 4.2.3.3 Shutdown procedure 4.2.4 Demineralised Water Storage transfer system 4.2.4.1 Startup procedure 4.2.4.2 Normal operation procedure 4.2.4.3 Shutdown procedure 4.3 Potable Water System 4.3.1 Nano Filtration System 4.3.1.1 Startup procedure 4.3.1.2 Normal operation procedure 4.3.1.3 Shutdown procedure 4.3.1.4 Chemical cleaning Procedure 4.3.2 Potable Water Storage transfer system 4.3.2.1 Startup procedure 4.3.2.2 Normal operation procedure 4.3.2.3 Shutdown procedure ANNEXURE A FLOW RATE CALCULATION
Trang 1Process Description for Water Treatment System
Contents
1 Introduction
2.1 Raw water Quality
2.2 Flow Rate Calculations
2.3 Pretreatment System
2.4 Demineralisation System
2.5 Potable Water System
3 Process Description & System configuration
3.1 Pretreatment System
3.1.1 Clarifier System 3.1.2 Filtration System 3.2 Demineralization System
3.2.1 Reverse Osmosis System 3.2.2 Degassification System 3.2.3 Mixed Bed Ion Exchange System 3.2.4 Demineralised Water Storage & transfer system 3.3 Potable Water System
3.3.1 Nano Filtration System 3.3.2 Potable Water Storage & transfer system
4 Detailed operation concept
4.1 Pretreatment System
4.1.1 Clarifier System
4.1.1.1 Startup procedure 4.1.1.2 Normal operation procedure 4.1.1.3 Shutdown procedure 4.1.1.4 Chemical preparation procedure 4.1.2 Conventional-Filtration System
4.1.2.1 Startup procedure 4.1.2.2 Normal operation procedure 4.1.2.3 Shutdown procedure 4.1.3 Membrane Based Filtration System
4.1.3.1 Startup procedure 4.1.3.2 Normal operation procedure 4.1.3.3 Shutdown procedure 4.1.3.4 Chemical Preparation Procedure
4.2 Demineralisation System
Trang 24.2.1 Reverse Osmosis System
4.2.1.1 Startup procedure 4.2.1.2 Normal operation procedure 4.2.1.3 Shutdown procedure 4.2.1.4 Chemical Cleaning Procedure 4.2.1.5 Chemical Preparation Procedure 4.2.2 Degassification System
4.2.2.1 Startup procedure 4.2.2.2 Normal operation procedure 4.2.2.3 Shutdown procedure 4.2.3 Mixed Bed Ion Exchange System
4.2.3.1 Startup procedure 4.2.3.2 Normal operation procedure 4.2.3.3 Shutdown procedure
4.2.4 Demineralised Water Storage & transfer system
4.2.4.1 Startup procedure 4.2.4.2 Normal operation procedure 4.2.4.3 Shutdown procedure 4.3 Potable Water System
4.3.1 Nano Filtration System
4.3.1.1 Startup procedure 4.3.1.2 Normal operation procedure 4.3.1.3 Shutdown procedure 4.3.1.4 Chemical cleaning Procedure
4.3.2 Potable Water Storage & transfer system
4.3.2.1 Startup procedure 4.3.2.2 Normal operation procedure 4.3.2.3 Shutdown procedure
Trang 3
1 INTRODUCTION
Water Treatment shall cater to the needs of both Camau 1 & Camau II for Boiler feed and
potable water needs Water from Municipal water supply (Filtered water) is treated in the
Pre-treatment system before it is divided into two streams, one for Boiler feed Pre-treatment and the
Potable water treatment The plant essentially consists of the following three systems:
1 Pretreatment System
2 Demineralisation System
3 Potable water System
The following P&ID may be referred to for Process description:
1 CM1-L3-M1-01GC-52-100001-001-Raw water transfer system
2 CM1-L3-M1-01GC-52-100001-002-Pretreatment dosing system
3 CM1-L3-M1-01GC-52-100001-003- Pretreatment reactivator clarifier
4 CM1-L3-M1-01GC-52-100001-004- Prefiltration multigrade filter (MGF)
5 CM1-L3- M1-01GC-52-100001-005- Prefiltration activated carbon filter (ACF)
6 CM1-L3- M1-01GC-52-100001-006- Micro filtration system
7 CM1-L3- M1-01GC-52-100001-007- Micro filtration permeate storage and distribution
8 CM1-L3- M1-01GC-52-100001-008- Reverse Osmosis (RO) dosing and filtration
9 CM1-L3- M1-01GC-52-100001-009- RO and degasser system
10 CM1-L3- M1-01GC-52-100001-0010- Demineralised water (DM) polishing
11 CM1-L3- M1-01GC-52-100001-0011- DM water storage and distribution
12 CM1-L3- M1-01GC-52-100001-0012- Potable water treatment
13 CM1-L3- M1-01GC-52-100001-0013- Potable water storage and distribution
14 CM1-L3- M1-01GC-52-100001-0014- Chemical cleaning
Trang 42 DESIGN BASIS
2.1 Raw water quality
The plant is designed for the analysis mentioned in the original tender However the design of
water treatment plant can handle the below analysis also
Trang 5All other parameters are considered as nil
The raw water analysis shows nil silica Hence we have assumed reactive silica of
<20ppm and nil colloidal silica
2.2 Flow Rate Calculations:
Detailed calculation for flow rate at different system outlet is enclosed as Annexure A
2.3 Pretreatment system:
The pretreatment system is designed to provide water suitable for feeding into the
subsequent Reverse Osmosis and Nano filtration System with the following feed limiting
The pretreatment plant is designed for a feed capacity of 94 m3 / hr into the Reactivator
clarifier, which after treating the water through Multi grade filter, Activated carbon filter and
Microfiltration (MF) system will produce 77.4 m3/hr of pretreated water
The Reactivator clarifier is designed for continuous operation on 24 hours a day basis The
Multi Grade filter & Activated Carbon filters will be in duplicate for continuous filtration even
during back wash of spent filters Three Numbers Micro filtration skids are provided where in
two skids will be in service and the third one will come into service when any one skid is taken
up for chemical cleaning
2.4 Demineralisation System:
The Demineralisation process will be done is two stages with Reverse osmosis technology
adopted for substantial removal of dissolved solids and Resin based Mixed Bed Ion
Exchanger provided for final polishing of the remaining dissolved solids to achieve the
following treated water quality
Trang 6PH 7 + 0.2
The entire demineralization plant is designed to produce treated water of 50 M3/Hr on a
continuous basis to meet the requirement of make up water to boiler and for secondary
cooling water systems for Ca Mau 1 &2 Both the Reverse Osmosis and Mixed Bed
exchangers shall be provided for a net output capacity of 3 x 25 m3/hr so that under normal
operation two streams will be under operation and the third one will be on standby The
Reverse osmosis plant will operate continuously at a recovery of 75% and the stand by plant
will come in to service when one of the streams goes in for chemical cleaning The Mixed bed
exchanger will be regenerated once every 24 hours and the stand by skid will come in to
service when one of the exchanger goes in for regeneration It shall be so operated that the 3
mixed bed exchangers will go in for regeneration one after the other in Round robin
The Demineralisation plant shall be capable of producing a maximum flow capacity of 75
M3/Hr when all the streams are in operation - for intermittent emergency requirements
However, for continuous output the guaranteed flow shall be 2 x 25 M3/Hr During
regeneration the plant shall achieve 2x25m3/hr only
2.5 Potable Water system
The potable water treatment plant shall be using Nano Filtration Technology and shall be
designed for a capacity of 6 m3/hr operating at a recovery of 70% Two streams shall be
provided one each as operating & standby The standby skid will come into operation when
the other stream goes for chemical cleaning The treated water will meet the WHO standards
Trang 73 PROCESS DESCRIPTION & SYSTEM CONFIGURATION
3.1 Pretreatment system
As the feed water contains Zinc of around 3.0 ppm, aluminium and copper around 0.2 ppm
each, and small quantities of iron, arsenic, cadmium, Lead, Manganese and selenium etc and
as heavy metals is one of the feed limiting condition for RO and NF, the following pre-treatment
is provided prior to water treatment system
3.1.1 Clarifier system (Drawing Nos CM-L3-M1-01GC-52-100001-001 to 003)
Zinc and other heavy metals shall be removed by precipitating them in a Reactivator clarifier
(01GCK15 BB001) Lime will be added (dosed) in the inlet line of clarifier to raise the pH of
the influent water followed by addition of suitable coagulant (FeCl3) Coagulant may be added
to increase the size of the particles for effective settling The raw water indicates the presence
of aluminium which will precipitate as aluminium hydroxide Flocculant (Polymer) is added to
form bigger flocs and to precipitate the Zinc and other heavy metals
Treatment chemicals are added to the inlet flow before it enters the fast mix tank The
chemicals and water are thoroughly mixed in the fast mix chamber to begin the coagulation
process Coagulated particles flow upward into the slow mix chamber where polymer is added
to facilitate flocculation A portion of the agglomerated floc is internally recirculated back into
the fast mix chamber from the bottom of the slow mix chamber to seed the coagulation
process Agglomerated floc flows downward from the slow mix chamber into the sedimentation
chamber In the sedimentation chamber, the flow reverses to upward and agglomerated floc
settles The treated water flows upward to the outlet collection launders from where the clear
water flows by gravity to the clarified water storage tank
Jar tests are used to establish chemical dosage requirements and predict clarifier effluent
turbidity levels They simulate the chemistry and physical operation of a clarifier Jar tests are
used to determine coagulant, polymer dosages and the operating pH for the clarifier
The precipitates formed in the clarification zone will settle at the bottom of the clarifier The
raker arm provided in the clarification system which will continuously be in slow rotation
scrapes and moves the sludge towards the centre of the clarifier The sludge so collected will
be transferred to the sludge thickener using sludge transfer pumps The operation of the
sludge transfer pumps will be controlled by the torque signals received from the torque switch
of the raker arm through the PLC which will be set for start / stop
Hypochlorite is dosed in the Clarified water storage tank to take care of any organics present in
the water and oxidation of any heavy metal that would have slipped from the clarifier
3.1.2 Filtration System (Drawing Nos CM-L3-M1-01GC-52-100001-004 to 007)
Clarified water from the clarifier will flow by gravity into a Clarified water storage tank The
clarified water from the tank will be pumped through filtration plants for further processing
Particle Filtration
Multi grade filter (01GCB 11/12 AT001) is provided to remove suspended solids and turbidity
present in the clarified water The unit is charged with quartz sand of different grades supported
by underbed media Suspended matters and turbidity gets removed when raw water is passed
in downward direction through this filter bed under pressure The unit should be backwashed
whenever the pressure drop exceeds the preset value (0.8 Kg/cm2) During backwash cycle,
the filter bed is lifted by water to remove accumulated particles After the backwash cycle, the
filter bed is allowed to settle While it settles, the filterbed media will classify with the heaviest
media particles settling first, and the lightest particles settling on the top
Trang 8An air scour system has been provided to loosen the media before backwash for effective
removal of settled solids This comes in handy if the impurities on the media bed are particularly
difficult to breakup with a normal backwash
Activated carbon filter (01GCB 14/15 AT001) is provided to remove organics, color and chlorine
from the filtered water Chlorine is added to water for various reasons such as disinfection or
oxidation of heavy metals, control of taste and color This chlorine must be removed in water
treatment systems, as it causes oxidative damage to downstream RO & NF membranes The
unit consists of quartz sand media and activated carbon for the purpose If the bed is clogged
with particulate matter escaping out of the upstream multi grade filter, which will be indicated by
high pressure drop across the filter, the unit should be backwashed Activated carbon filter will
be backwashed once in a week or lesser frequency based on the field experience
Micro filtration system
Water after passing through the conventional pre treatment is passed through membrane
filtration system for achieving SDI (Silt Density Index) < 3 which when ensured enhances the life
of the RO membrane and considerably reduces the down time of RO Basket filter is provided
upstream of Micro Filtration membranes (01GCB30/31/32 AT001) to prevent any large particles
(larger than 200 microns) from entering the MF membranes thus allowing it to do its job of
removing fine particles
Microfiltration system helps to bring down the Turbidity level and ensures near complete
removal of colloidal particles if any present in the feed They are also used for the reduction of
suspended solids and to maintain consistent SDI Chances of slippage of Organics, Bacteria,
Colloidal Particulate Matters, Suspended Impurities, and Turbidity are high in conventional pre
treatment, which will lead to frequent break down of RO system However with MF pre
treatment the above factors are completely removed and hence there is considerable reduction
of RO membrane fouling
Membrane filtration system is a dead end filtration wherein the inlet water fed to the system will
pass through the membrane and permeate will be collected from the permeate port The
membranes are operated inside-out which means that the substances that are retained by the
membranes are in a clearly defined space, where they are easily removed by either
backwashing or chemical cleaning The solids that are retained on a membrane surface are
washed away periodically by means of a permeate backwash, that does not involve any
chemicals Solids are removed every time a backwash is executed, thereby avoiding excessive
accumulation of solids on the membrane Any substances that may have adsorbed to the
membrane surface and are difficult to remove by back wash are removed by in situ chemically
enhanced backwash (CEB).The inlet pressure should be less than 1.5 Bar which is ensured
with the help of Pressure switch The permeate from the MF will be taken to the MF Permeate
water tank
The modules will be backwashed with the permeate from the MF Permeate storage tank over a
preset interval of time (controlled from PLC) for a preset duration or when the transmembrane
pressure reaches preset value (typically 0.4 Bar), which needs to be set at site based on the
experience over a few cycles Typically, this will be for 30 - 40 seconds every 25minutes at a
flow rate of 160 M3/Hr per stream In spite of the frequent back wash cycles, it is normal for
particles to settle on the surface of the membranes which is difficult to dislodge in the form of
fouling and scaling for which a Chemically Enhanced back wash is provided once in a day
During the CEB small amount of chemicals are introduced during the backwash After a short
soaking period (typically 10 minutes), the chemicals are rinsed out of the plant, thereby
restoring the membranes to its original, clean state This is done by dosing a certain quantity of
HCl and NaOCl into the back wash water flow of 80 M3/Hr per stream
The following equipment form part of the pretreatment
S.No Description of
equipment
Trang 91.1 Raw water transfer
pumps
3 Nos (3x50%)
1.3 Lime dosing tank-Dosing
1.5 Lime dosing
pumps-Dosing system CLF
1.6 Coagulant dosing
tank-Dosing system CLF
Preparation tank 600Ltr – 1 No 1.7 Coagulant dosing
pumps-Dosing system
CLF
1.8 Flocculant dosing
tank-Dosing system CLF
tank 500Ltr – 1 No 1.9 Flocculant dosing
pumps-Dosing system
CLF
1.10 Reactivator clarifier 1 No Civil tank by Lot 4
and internals by Lot
3
10000diax3800SWD
mm
1.14 Clarified water storage
tank
1.15 Clarified water transfer
pumps
each 1.22 Chemical cleaning tank
Trang 10The feed water to RO should be dechlorinated as free chlorine can increase the oxidation
potential of the membranes and irreversibly open the membrane pores rendering it useless To
protect the membranes from residual chlorine which would have slipped from activated carbon
filtration, if any, SMBS (Sodium Meta bi sulphite) will be dosed to dechlorinate the influent water
An auto dump valve connected to the ORP (oxidation/reduction potential) analyzer is provided
before the feed water enters the RO skid When ORP analyzer senses presence of free
oxidants in the feed, it would send a signal to PLC, which will then open the auto dump valve
and trip the system Thus the water containing free chlorine is drained thereby protecting the
RO membranes The condition needs to be attended and rectified before the plant is restarted
The dosage rate of SMBS will be set at site based on the residual chlorine level of water
actually measured at site
Antiscalant dosing system
During the process of Reverse osmosis, the feed water as it passes across each membrane
increases the concentration of dissolved salts, due to pure water exiting the system in the form
of permeate As this condition may cause scaling on membrane surface scale inhibitors are
dosed to prevent precipitation of salts on the membrane surface In the event of scaling the
membrane pores will be blocked rendering less area available for process thus bringing down
the output from the system
Antiscalants will be dosed online and continuously and these will keep the ions in dissolved
form and hence avoid the scaling of the membranes The dosage rate of antiscalant will be set
at site based on the chemical software run with the actual water analysis measured at site
Acid Dosing system
As per the Design of RO system and based on the water analysis considered for design, the
feed water to RO shall be with a pH of 7.5 to 8 Since we have increased the PH of raw water in
the clarifier (for the purpose of precipitating heavy metals), we have to reduce the PH before the
water enters the membranes (to protect the RO membranes from scaling) Acid is dosed to
contain the calcium carbonate scaling and also to avoid scaling of the sparingly soluble salts
Reverse Osmosis system
The chemically treated water is passed through 5 Micron Cartridge type filtration elements
located inside a housing This is essential to ensure that no particles larger than 5 microns
enter the RO membranes due to accidental intrusion in the MF storage tank or from the dosing
system
The dissolved salts from the water are substantially removed using the membrane technology
process of reverse Osmosis Reverse osmosis, as the name indicates, is the reverse process
of the natural Osmosis process In reverse Osmosis certain pressure is applied to the
Concentrated Water so as to over come the Osmotic Pressure which forces water molecules to
flow against a through the semi permeable membrane This is a cross flow system where in
there is a continuous flow of water across the surface of the membrane and a pre determined
proportion of the water is allowed to pass through the membrane and the remaining
concentrated brine is washed out of the system This ratio of purified water coming out of the
system and the feed water is called the Recovery (in this case 75%) The recovery is
controlled by a brine control valve (01GCF12/22/32 AA101) which is used to adjust the
transmembrane pressure to control the water forced through the membrane
The high pressure required for RO System operation is developed using Multistage Centrifugal
Pumps The RO system comprises of R.O membranes housed in Pressure tubes
(01GCF10/20/30 AT001) These pressure tubes are mounted on the RO Skid The RO
Membranes are provided with necessary accessories like Brine Seals, Interconnectors and
Vitaulics.Influent enters the housing under pressure and must pass through the filter elements
in order to exit the housing There must be a sufficient number of filter elements in the housing
Trang 11to be able to handle the flow rate The skid-mounted system will be complete with
interconnecting piping, Cartridge filters, HP Pump, and dosing systems mounted
Over a period of time the membranes will accumulate scale deposits on its surface requiring a
process of cleaning of the R.O membranes This is characterized by increase in
transmembrane pressure for getting the same output or a reduction in the output flow The
cleaning process involves circulation of Cleaning chemical through the membrane surface
until the scales are removed and trans membrane pressure is brought down to design levels
RO membranes are not back washable and hence the flow has to be in the same direction of
service flow The frequency and duration of chemical cleaning entirely depends on the actual
operating conditions, but for design purposes is considered as once in 3 months for duration
of about 6 hours
The nature and type of chemicals depends on the type, nature and extent of scaling The
scales can primarily be classified as Inorganic and Silica apart from biological fouling
experienced in certain systems Chemical cleaning system comprises of Chemical
preparation tank, chemical solution transfer pump and a cartridge filter unit One chemical
cleaning system shall be provided common to three streams
3.2.2 Degassification system (Drawing Nos CM-L3-M1-01GC-52-100001-009)
Free Carbon Dioxide in the raw water that is generated as a result of addition of acid will pass
through the RO membranes and remains as a constituent contributing to the conductivity of the
product water This is removed up to a level of 6 mg/l by scrubbing action in the Degasification
tower (01GCF40 BB001) thereby reducing the load on the downstream Mixed Bed ion
Exchange unit The Degasification tower will be atmospheric tower, with top distributor Water
will flow from the top to bottom through the packing media of PP pall rings From the bottom of
tower, High flow low-pressure air is blown using an air blower The free CO2 will be removed by
scrubbing action between water and air and the CO2 will escape from the top vent The
degasified water is then stored in the DG water tank From this tank the water is further
pumped to downstream units
3.2.3 Mixed Bed Ion Exchange System (Drawing Nos
CM-L3-M1-01GC-52-100001-010)
Mixed bed is provided for the final polishing of RO permeate water to meet the boiler water
quality The unit is charged with mixture of MB grade of Strong Acid Cation Resin (Gel / Macro
porous) and Strong Base Anion Resin Type-I (Gel / Macro porous) The water will pass in down
ward direction in the Mixed Bed unit (01GCF60/70/80 BB001) where it comes into contact with
cation & anion resins one after the other multiple times and the cationic & anionic impurities are
absorbed in the resins thereby removing all remaining ions from the DM water achieving
required end water quality The Demineralised water is then stored in a DM Water Storage tank
from where it is fed into the boiler system of Camau1 The water is also transferred to another
DM water storage tank of Camau2 for catering to the needs of Boiler system of Camau2
After a predetermined period of time (designed at 24 hours in this case) the resins will be
exhausted and will require to be regenerated before putting back into service The process of
regeneration of the MB unit will start with backwash of the resin bed During the back wash
process the resin bed is lifted and as the Anion resins are lighter, the same will accumulate in
the upper layer with the cation pushed into the lower layer thus separating the Cation-Anion
resins Regenerant distributors are provided in such a way that the Acid (HCl) is distributed to
the cation layer and Alkali (NaOH) is distributed to the Anion layer properly The injection of acid
and alkali is done is such a way that a pre determined (designed) quantity of acid & alkali at a
particular concentration is injected at designed flow rates in to the resin column This is done by
the aid of a ejector mechanism which when provided with power water will draw measured
quantity of Acid / Alkali prepared in a regeneration tank Regenerant injection is followed by
rinsing of respective resin beds where in any excess Acid / Alkali is washed out of the resin bed
The resins are once again mixed by blowing low pressure (0.35kg/cm2) air across the resin bed
and the unit is ready for service
Trang 12The regeneration time for each MB will be 3-3.5Hrs
The following equipment form part of Demineralisation Water System
S.No Description of
equipment
tank-1 No 1.03 Antiscalent dosing
pumps
1.11 Chemical cleaning tank
tank
3.2.4 Demineralised Water Storage & Transfer System (Drawing Nos
CM-L3-M1-01GC-52-100001-011)
The demineralized water from the mixed bed flows under pressure to the two DM Water
storage tanks DM water distribution pumps are offered for feeding the boiler One set of
pump will take care of the nominal load of boiler and the other set will take care of the
maximal load of boiler DM water is also transferred to the DM water storage tank present in
Ca Mau II
3.3 Potable water system
A membrane based Nano filtration treatment system is provided for potable water system
3.3.1 Nano-Filtration System (Drawing Nos CM-L3-M1-01GC-52-100001-012)
Nanofiltration
Trang 13Nanofiltration is a similar process like Reverse Osmosis with the difference being the pore size
of membrane being larger than RO membranes As a result of this the pressure required is not
high as that of Reverse Osmosis system The Microfiltration permeate water is pumped through
nanofiltration system and the system produces water as per drinking water standards
mentioned The system consists of High-pressure pump for creating necessary driving force for
membrane filtration followed by Nano filtration membrane unit (01GKA22/32 AT001) As in the
case of Reverse Osmosis, cartridge filtration, Acid dosing, SMBS and antiscalent dosing system
is provided prior to Nano filtration to protect the membranes from oxidation and scaling
The NF permeate water is dosed with hypochlorite solution for the final disinfection This is
done to maintain residual chlorine of 0.1ppm in the drinking water
3.3.2 Potable Water Storage and Pumping System (Drawing Nos
CM-L3-M1-01GC-52-100001-013)
The potable water from the NF system is stored in two potable water tanks of capacity 150m3
The water is pumped to the overhead tank which will serve as the final distribution tank The
water is finally taken for distribution from the overhead tank by gravity
The following equipment form part of potable water treatment
S.No Description of
equipment
1.07 Antiscalent dosing
pumps
1.09 High pressure pump for
NF
skids 1.11 Chemical cleaning tank
Trang 144 DETAILED OPERATION CONCEPT
4.1 Pretreatment System
This section will elaborate in detail the operation philosophy of the equipments belonging to
the pretreatment system The Pretreatment system can be operated in either Manual or Auto
The operator will check and ensure manually that all the suction & discharge valves
(01GCK11 AA001, AA003, etc.) of all the three Raw Water pumps are in the open condition
The operator will pre select two out of the three Raw Water Pumps (01GCK11 AP001,
01GCK12 AP001 & 01GCK13 AP001) for feeding Filtered water from the Filtered Water
tanks
The operator will check and ensure manually that the Lime dosing tank (OIGCN21 BB001)
contains enough Lime solution until the next refilling time The procedure for preparation of
lime is detailed separately elsewhere in this document
The operator will pre select one out of the two Lime dosing Pumps (01GCN 22 / 23 AP001)
The operator will check and ensure manually that all the suction & discharge valves
(01GCN22 AA001 / AA002) of the two Lime dosing pumps are in the open condition
The operator will check and ensure manually that the Coagulant dosing tank (OIGCN31
BB001) contains enough Coagulant solution until the next refilling time The procedure for
preparation of Coagulant is detailed separately elsewhere in this document
The operator will pre select one out of the two Coagulant dosing Pumps (01GCN 32 / 33
AP001) The dosing rate will be manually set on both the pumps as per the results of jar test
to be conducted in the laboratory periodically
The operator will check and ensure manually that the discharge valves (01GCN 32 AA002) of
the two Coagulant dosing pumps are in the open condition
The operator will check and ensure manually that the Flocculant dosing tank (OIGCN41
BB001) contains enough Flocculant solution until the next refilling time The procedure for
preparation of Flocculant is detailed separately elsewhere in this document
The operator will pre select one out of the two Flocculant dosing Pumps (01GCN 42 / 43
AP001) The dosing rate will be manually set on both the pumps as per the results of jar test
to be conducted in the laboratory periodically
The operator will check and ensure manually that the discharge valves (01GCN 42 / 43
AA002) of the two Flocculant dosing pumps are in the open condition
The operator will check and ensure manually that the Hypo dosing tank (O1GCN45 BB001)
contains enough Sodium Hypo Chlorite solution until the next refilling time The procedure for
preparation of Sodium Hypo Chlorite is detailed separately elsewhere in this document
The operator will pre select one out of the two Hypo dosing Pumps (01GCN 46 / 47 AP001)
The dosing rate will be manually set on both the pumps as per the site results to achieve
residual chlorine level of 1 ppm at the feed of filters
Trang 15The operator will check and ensure manually that the discharge valves (01GCN 6 / 7 AA002)
of the two Hypo dosing pumps are in the open condition
The operator will check and ensure manually that the suction & discharge valves (01GCS 05 /
10 / 20 / 30 AA002 etc.) of the two Sludge transfer pumps are in the open condition
The operator will pre select one out of the two Sludge Transfer Pumps (01GCS10 / 20
AP001) for transferring sludge from the clarifier to Sludge thickener
The operator will ensure that the drain valve (01GCK16 AA401) of clarified water storage tank
(01GCK16 BB001) is in the closed condition
Under Automatic Start up sequence, the operator will initiate Sequential start up of the pre
treatment system from the operating console as a result of which the following actions will
occur sequentially
- The lime dosing tank agitator (O1GCN21 AM001) is started
- After a period of 2 minutes, the selected Raw Water pumps will be started
- The selected lime dosing pump will be started
- The selected Coagulant dosing pump will be started
- The selected Flocculant dosing pump will be started
- The Flocculator drive of clarifier will be started
- The Rake arm drive of the clarifier will be started
- The selected hypo dosing pump will be started
Under the manual operation each of the drives will be started manually in the same sequence
mentioned above
4.1.1.2 Normal operation procedure
The PLC system will monitor the level of the Filtered Water storage tank through the Level
transmitter When the level goes below the set level (Normally 5%) the raw water pumps are
turned off The pumps are automatically restarted once the levels cross the pre set level
(Normally 30%) The condition will be visible in the operating interface where there will be
alarms before tripping off condition is reached
Under any condition of tripping of any of the raw water pumps (except due to low level in
Filtered water tank or high level in Clarified water storage tank), the PLC system will
automatically start the stand by pump and initiate an Alarm This is also monitored by flow
condition sensed by FIT (01GCK14 DF01) or pressure condition sensed by Pressure switch
(01GCK14 DP01) which will initiate an alarm for Manual intervention of switching the
operating pump to standby and vice versa All these conditions will be visible in the operating
interface
Under any condition of tripping (except low level of dosing tanks) of any of the Dosing pumps
(Lime, Coagulant, Flocculant and Hypo), the PLC system will automatically start the stand by
pump and initiate an Alarm The tripping of agitator will also raise an alarm in the operating
interface which has to be attended to by the operator The low level switches (01GCN21 / 31 /
41 DL01 & 01GCN10 DL01) will trip the respective dosing pump and initiate an alarm in the
operating interface The Operator will have to inititate immediate action to refill the dosing
tank or to initiate shut down procedure
The pH Transmitter (01GCN10 DA01) will continuously monitor the pH of the water and will
vary the frequency of power supply to the Lime dosing pump motor through the PLC and
Variable frequency Drive The value of pH can be set, monitored and altered from the
operating interface based on the Jar test results
Trang 16The clarifier drive will be continuously monitored and any tripping will initiate an alarm in the
operating interface The operator will have the choice of taking the entire plant for shut down
or manually bypass the clarifier by closing the clarifier inlet valve and opening the by pass
valve Under this condition, the lime dosing pump may need to be shut down (from the
operating interface) and the dosing rates of coagulant, Flocculant and Hypo chloride may
need to be altered (Manually)
Sludge discharge will be automatically controlled by monitoring the torque level of the scraper
arm drive of the clarifier Torque switch will be set to act at a pre set level when the PLC will
start the pre selected Sludge transfer pump and will continue to run for a pre set period of
time (typically 30 minutes – to be set during commissioning based on actual sludge
accumulation experienced) after which the pump will be shut down It will restart when the
sludge level increases thereby increasing the torque and the torque switch will initiate
restarting the sludge pump Sludge can also be transferred by setting time in the PLC The
time at which sludge should be extracted is set in the PLC during commissioning Normally
sludge will be discharged once in 4 or 5 hours Before starting the sludge pump it is flushed
by service water at the suction and discharge side using automatic valves (01GCS20/30
AA001)
The water level in the clarified water storage tank is continuously monitored with the help of
Level Transmitter (01GCK16 DL01) and when the tank level reaches set level (Normally
95%), the entire pretreatment system will be shut down The High level switch (01GCK16
DS02) (normally set at 100% level) will be an overriding back up arrangement for shut down
in the event of failure of level transmitter The system will be automatically restarted once the
tank level reaches the preset level (normally 70%)
Under Manual operating conditions all the above operations shall be manually conducted with
monitoring of condition and alarms at the control desk
4.1.1.3 Shut down procedure
The pretreatment system shall be automatically shut down under the following conditions:
- When the Filtered water level is below the preset value
- When the clarified water storage tank is above the preset value
- When none of the Raw water pumps are in operation
The pretreatment system shall be shut down by manual initiation under the following
conditions:
- Low level in dosing tanks (Lime, coagulant, flocculant & Hypo) persists beyond a pre
set time period (typically 30 minutes)
- Clarifier drives trip
- Lime dosing tank agitator trips
- When the sludge pumps are not operating
- pH level is not maintained for over a preset period time period (typically 30 minutes)
The shut down procedure shall be as under:
- Raw Water Transfer pumps will be turned off
- All the dosing pumps will be turned off
- The lime dosing tank agitator will be turned off
- The clarifier flocculator drive will be turned off
- The clarifier Raker arm will continue to rotate for 12 hours before it is turned off
- The sludge transfer pump, if in operation, will be turned off after it completes its
preset time cycle
- The sludge pump shall be flushed with service water by opening the automatic valve
4.1.1.4 Chemical Preparation procedure
Chemical preparation is a manual process and is to be done once every day
Trang 17Lime solution:
Based on the amount of Lime solution to be prepared for one days operation and the quantity
of lime powder and water to be mixed to achieve the desired concentration, water is first filled
in by manually operating the valve (01GHD10 AA001) in the Lime preparation tank (01GCN10
BB001) The water level is observed on the level indicator (01GCN10 CL01) and the valve is
closed once the desired level is reached The motorized agitator is started from local Push
button station and Lime is manually carried and fed into the Lime preparation tank through the
feed hopper The solution is allowed to be fully prepared by agitating it for a pre fixed period
of time
The lime solution is ready to be transferred to the dosing tank which is done by manually
operating the valve (01GCN10 AA001) During the preparation of lime there would be some
amount of sludge generated which shall be drained off periodically (typically once a week) by
manually operating the valve (01GCN10 AA401)
Coagulant solution:
Based on the amount of Coagulant (FeCl3) solution to be prepared for one days operation
and the quantity of Coagulant and water to be mixed to achieve the desired concentration,
water is first filled in by manually operating the valve (01GHD10 AA002) in the Coagulant
preparation tank (01GCN20 BB001) The water level is observed on the level indicator
(01GCN20 CL01) and the valve is closed once the desired level is reached The operator
from the control room starts the FeCl3 transfer pump in the Chemical storage area in order to
make it available for preparation of coagulant solution The motorized agitator is started from
local Push button station and Coagulant is fed into the Coagulant preparation tank by
manually operating the valve The solution is allowed to be fully prepared by agitating it for a
pre fixed period of time
The Coagulant solution is ready to be transferred to the dosing tank which is done by
manually operating the valve (01GCN20 AA002)
Flocculant solution:
Based on the amount of Flocculant (PAC) solution to be prepared for one days operation and
the quantity of Flocculant and water to be mixed to achieve the desired concentration, water
is first filled in by manually operating the valve (01GHD10 AA003) in the Flocculant
preparation tank (01GCN30 BB001) The water level is observed on the level indicator
(01GCN30 CL01) and the valve is closed once the desired level is reached The motorized
agitator is started from local Push button station and Flocculant is manually carried and fed
into the Lime preparation tank through the feed hopper The solution is allowed to be fully
prepared by agitating it for a pre fixed period of time
The Flocculant solution is ready to be transferred to the dosing tank which is done by
manually operating the valve (01GCN30 AA002)
Hypo solution:
Since Hypo (NaOCl) solution is dosed at the commercially available concentration no
preparation is required and the commercially available solution is directly fed in manually into
the dosing tank of quantity required for one days operation
4.1.2 Conventional Filtration System
Trang 18The filtration plant is automatically operated plant with manual override option Both the Multi
grade filters (01GCB11 / 12 AT001) and the Activated Carbon filters (01GCB14 / 15 AT001)
are provided with the following pneumatically actuated valves for the automatic operation of
the plant
1 Service inlet valve (01GCB11 / 12 / 14 / 15 AA01 / AA101)
2 Service outlet valve (01GCB11 / 12 / 14 / 15 AA01 / AA101)
3 Backwash inlet valve (01GCR14 / 15 /16 / 17 AA01 / AA101)
4 Backwash outlet valve (01GCB11 / 12 / 14 / 15 AA301)
5 Air inlet valve (01GCP 63 / 64 AA01) – Only for Multi Grade Filter
6 Rinse outlet valve (01GCB14 / 16 / 15 / 16 AA301 / 302)
7 Air release valves (01GCB15 / 16 AA501, 01GCB 14 / 15 AA501)
4.1.2.1 Start up procedure
The operator will check and ensure manually that all the suction & discharge valves
(01GCK17 / 18 / 19 AA001, AA003) of all the three Clarified Water Transfer pumps are in the
open condition
The operator will check and ensure manually that all the suction & discharge valves
(01GCR11 / 12 AA001, AA003) of the two Back wash pumps are in the open condition
The operator will check and ensure manually that all the discharge valves (01GCP60 / 61
AA002) of the two MGF Air blowers are in the open condition
The operator will pre select one out of the two MGF Air blower (01GS60/61 AN001) to be
used for air scouring before back wash of filters
The operator will pre select two out of the three Clarified Water Transfer Pumps (01GCK17 /
18 / 19 AP001) for feeding Clarified Water into the filter units
The operator will pre select one out of the two Back wash pumps (01GCR11 / 12 AP001) for
back wash of the filter units
The operator will pre select one out of the two Multi grade filters (01GC811/12 AT001) and
one out of the two Activated Carbon filters (01GC814/15 AT001) for operation
Once the water level in the clarified water tank is above the preset value (normally 30%),
measured by the Level Transmitter (01GCK16 DL01) and monitored by the PLC, the following
valves of the selected Multi grade filter and Activated Carbon Filter are opened automatically
by the PLC system
- Air release valves
- Service inlet valves
- Service outlet valves
The selected clarified water transfer pumps (01GCK17 / 18 / 19 AP001) will be started
After a pre fixed period of time (normally 5 minutes), the air release valve will be closed
4.1.2.2 Normal Operation procedure
The following are the various modes of operation in the filtration plant during normal
operation
• Normal service
• Draindown (part of air scour)