1

SUBJECT : PT. MENAMAS

NUMBER.

BELAWAN UF, RO Pass-1, RO Pass-2 AND MB DATE : 21.07.2009

WATER TREATMENT PACKAGE.

REV. A / 25.12.2010

SUBJECT : PT. MENAMAS

NUMBER.

BELAWAN UF, RO1, RO2 AND MB

DATE : 21.07.2009

WATER TREATMENT PACKAGE.

REV:1 DT 25.12.2010

OPERATION AND MAINTENANCE MANUAL

FOR

WATER TREATMENT PACKAGE

PROJECT

PT. MENAMASBELAWANSUPPLIED BY

ION EXCHANGE ASIA PACIFIC PTE. LTD.,SINGAPORE.

INDEX

1. INTRODUCTION2. DESCRIPTION

3. OPERATING PHILOSOPHY4. OPERATING INSTRUCTION5. CHEMICAL CONTROL

6. TROUBLE SHOOTING

7. MAINTENANCE

8. SAFETY

SECTION 1

INTRODUCTION

1.0 INTRODUCTION1.10 GENERAL

This document is produced as a Training Manual of Water Treatment Package which is a part of the MENAMAS, BELAWAN Power Station. This manual has to be considered as a basis for operation in conjunction with the operating philosophy.

This manual is basically divided in various sections mainly as:

Introduction: This gives a general introduction and basic water treatment fundamentals.

Description: This gives the description of the total package and also the details of individual equipment used write from the water intake upto production of De-mineralised water which will be used in the power plant.

Operating Philosophy: The operating parameters, the sequential operation of the units and interlocks.

Erection Instructions: this section describes about the general erection procedures.

Chemical Control: This section basically gives the laboratory analytical procedures for various parameters involved in water treatment.

Trouble Shooting: This section gives the trouble shooting of the plant. Maintenance: This gives the general maintenance of the water treatment plant.

Safety: This gives the safety procedures for the chemical handled in water treatment plant.

1.20 FUNDAMENTALS OF WATER TREATMENT:

1.20.1 WATERWater, which is required for Industrial or process use, is available from two sources. Surface supplies - such as from rivers, lakes and surface wells - and underground supplies such as tube - wells.

Natural water contains dissolved salts. The water dissolves these salts in flowing over limestone, gypsum, dolomite and other mineral deposits containing them. Natural water is likely to contain different concentrations of:-

Alkaline salts such as Bicarbonates and (rarely) Carbonates of Calcium, Magnesium and sodium.

Neutral Salts such as Sulphates, Chlorides and Nitrates of Calcium, Magnesium and Sodium.

Other dissolved impurities such as Silica, dissolved Carbon Dioxide and metals - Iron, Manganese - and Organic Matter may also be present to a lesser extent. The range of minerals contained in most natural waters is quite limited. The CATIONS present are normally Calcium, Magnesium and Sodium while the ANIONS are mainly Chlorides, Sulphates and Bicarbonates with lower concentrations of Nitrate and Silica.

Thus for most waters, analysis of the ions mentioned above will give the TOTAL DISSOLVED SOLIDS.

The range of uses of water in Industry is very wide. Where water is to be heated within a process such as in boilers, heating and cooling systems, laundries, bottle washing, scale formation is the most immediate hazard but for high pressure boilers, for laboratory purposes, electronic and metal finishing industries any dissolved impurities in the water may contaminate the product and the complete removal of all dissolved ions - DEMINERALISING OR DEIONISING becomes necessary.

1.20.2 ULTRAFILTRATION PROCESS

Ultra filtration is a tangential flow, pressure driven filtration process that separates particles on the basis of their molecular size. Pore diameters of Ultra filtration membranes are in the range of 1,000 to 1,000,000 Molecular Weight Cut Off (0.001 to 0.02 micron). Solvents and species having a diameter smaller than the pore size of the membrane will pass through the membrane and emerge as UF Product, known as Permeate. Rejected species are progressively concentrated in the reject stream. Ultra filtration membranes are reusable and cleanable with standard chemicals.

Ultra filtration of process water provides:Specific Removal of virtually all-particulate matter, suspended solids, bacteria, viruses, and pyrogenic species purely based on their Molecular Weight Cut Off from pharmaceutical and industrial process water.

Removal of colloidal material (non-reactive silica, iron, aluminium, Turbidity, Silt etc.)

Removal of high molecular weight organic.

The Ultra filtration membrane is a thin polymeric material, either polysulfone or polyacrylonitrile, with an anisotropic pore structure. This means the membrane does not have the same pore structure throughout its matrix.

The combination of the very smooth surface with small pores and the support structure with much larger pores results in filtration of small particles with a low resistance to flow.

Ultra filtration is a cross flow or tangential flow process. The stream to be purified (the feed stream) flows along the surface of the membrane. These results in a fluid shear condition at the wall on the inside of the fiber, which will tend to keep the surface of the membrane free of fouling matter. The suspended material of the feed stream will be concentrated and exit the process as the reject stream. This tangential flow process technique serves to prevent particles from building up on the surface of the membrane and enhances long term productivity of the filter between cleaning cycles.

The difference in pressure between the feed and reject streams will determine the flow of water across the surface of the membrane. In addition, a portion of the feed stream will pass through the membrane. This product stream is the Ultra filtrate, otherwise known as Permeate. The pressure difference between the feed stream and the product side of the membrane is directly related to the product flow. When pressure is applied to the feed stream, it flows tangential to the membrane surface. Ultra filtration is a dimensional separation process. Generally Ultra filtration membranes are rated on their Molecular Weight Cut-off, abbreviated MWCO. This is an indicator of the relative size of the globular molecules, which a membrane will remove. Koch Membrane Systems has Ultra filtration membranes with MWCO ranges between 1,000 and 1,000,000. The aqueous phase and material smaller than the membranes nominal MWCO will pass through the membrane. Therefore, the product stream will contain water, ionic species, and low molecular weight material, whereas colloidal matter, particles, bacteria, viruses and pyrogenic species will be rejected by the membrane.

1.20.3 REVERSE OSMOSIS PROCESS

This section describes the process of demineralisation by reverse osmosis (RO) and the main equipment used.

Osmosis and Reverse Osmosis

Osmosis is a natural process involving fluid flow across a semi permeable membrane barrier. It is selective in the sense that the solvent passes through the membrane at a faster rate than the dissolved solids. The difference of passage rate results in solvent solids separation. The direction of solvent flow is determined by its chemical potential, which is a function of pressure, temperature and concentration of dissolved solids.

Pure water in contact with both sides of an ideal semi permeable membrane at equal pressure and temperature has no net flow across the membrane because the chemical potential is equal on both sides. If a soluble salt is added on one side, the chemical potential of this salt solution is reduced. Osmotic flow from the pure water side across the membrane to the salt solution side will occur until the equilibrium of chemical potential is restored. Equilibrium occurs when the hydrostatic pressure differential resulting from the volume changes on both sides is equal to the osmotic pressure. This is a solution property independent of the membrane.

Application of an external pressure to the salt solution equal to the osmotic pressure will also cause equilibrium. Additional pressure will raise the chemical potential of the water in the salt solution and cause a solvent flow to the pure water side, because it now has a lower chemical potential. This phenomenon is called reverse osmosis.

In the reverse osmosis process, the water that passes through the membrane is commonly referred to as permeate or product water, the water that remains behind the membrane along with dissolved and suspended solids is referred to as the concentrate, brine or reject water. We have used these terms interchangeably in this manual.

Pressurised feed water is introduced into one end of the pressure tube. Some of the water, driven by the feed pressure through the RO pressure tube feed port permeates through the membrane, passes into the product tube and exits the pressure tube from the pressure tube product port as product water, less most of the dissolved solids and all of the suspended solids. The remainder of the water passes along the surface of the membrane with the concentrated dissolved and suspended solids and passes out of the pressure tube concentrate port as concentrate, brine or reject.

The pressure tubes are generally arranged in stages when more product water is desired than one module can produce. The staging of the modules is designed to optimise the water flow patterns across the surface of the membrane. This uniform water flow promotes good flushing velocity across the membrane surface to prevent the accumulation of suspended solids on the surface which would foul the membrane and reduce the productivity. Multiple stages are referred to as arrays.

Different ions also pass through the membrane to different extents depending on various factors such as valency, ionic size, concentration, etc. Therefore, the product water does have some salts, usually approximately 10% of the salts in feed water. Salt passage is defined as the ratio of total dissolved solids (TDS) in permeate to TDS in feed water.

A certain minimum reject water flow is always maintained to flush the membrane surface and also keep certain sparingly soluble salts below their solubility limits. As a result, the ratio of the product water or permeate flow to feed water flow, called the recovery, is always less than 1.0.

1.20.4 MIXED BED ION EXCHANGE PROCESS

The mixed bed demineralization process consists of SAC and SBA resins intimately mixed in the same unit to bring about the demineralization of water. In effect it is multiple and random two bed demineralising pairs resulting in very high quality of demineralised water.

The strong acid cation (SAC) resin exchanges all cations in water. The cations associated with alkalinity or those combined as neutral salts are all removed by the SAC resin. Hence this resin is used universally in a demineralization process.

Likewise the strong base anion (SBA) resin exchanges all anions in water. Alkalinity, anions of neutral salts and weakly ionised species such as carbon dioxide and silica are all removed by the SBA resin. Hence this is used also universally for complete removal of all anions present in water

The SAC resin is in the hydrogen form and the SBA resin is in the hydroxide form.

But the leakage of ions, caused by the regenerative effect of free mineral acidity (FMA) or of sodium hydroxide (NaOH) formed in the exchange process, is absent in the mixed bed demineralization process. This is so because FMA generated by the SAC resin is exchanged by neighbouring SBA resin; likewise NaOH generated by the SBA resin is exchanged by the adjacent SAC resin. In this manner the products of reaction of the resins are immediately removed driving the reactions to completion and the equilibrium reactions do not exist. This results in good quality of treated water and the multiple contacts provides a polishing action yielding extremely pure demineralised water.

Conductivity is an importation indicator of water quality. The final treated water from the mixed bed unit with conductivity less than 1 S/cm and mostly in the range 0.2 - 0.5 S/cm

Silica residual obtained from mixed bed demineralization are generally in the range 0.02 - 0.05 mg/l commonly achieved in mixed bed demineralization.

When the treated water quality from the mixed bed is out of specification or the designed throughput is attainted, the unit requires regeneration.

1.20.5 INLET WATER QUALITY

Because the Ultra Filtration Membrane must be kept clean to function efficiently, the inlet water or RAW WATER must be cold, clean and colourless.

The water should be free of suspended matter, organic matter, oil, algae, slime and heavy metals such as iron, aluminium. These impurities would collect on or within the resin particles and reduce their capacity for removal of the ions. Hence some waters may require coagulation and filtration prior to being fed into the UF system.

1.20.5.1ULTRA FILTRATION SYSTEM DESCRIPTION

The system consists of UF MODULES / MEMBRANES of 10 dia x 72 long hollow fiber module. The treated water will have SDI less than 1 and Turbidity less than 1 NTU. The feed shall be Bore Well.

The system consists of the following:-

a) Koch Membrane system 10 dia x 72 long cartridge / module of 1, 00,000 Molecular Weight Cut-off.

b) Stainless Steel Centrifugal pumps which is used for Recirculation and Back flush operation of the Ultra filtration System.

c) SS316 basket strainer (100 microns).

d) Feed / CIP Tank, Permeate water tank.

e) Pressure gauges.

i) Differential pressure across the feed and reject of membrane.

ii) Trans membrane pressure across the UF module.

f) Set of pipes/fittings (SS316 / PVC)

1.20.5.2 REVERSE OSMOSIS PASS-1 SYSTEM DESCRIPTION

The entire system is mounted on a Skid (excluding tanks)The following gives brief description regarding the major components

2.1 Pretreatment cartridge filter (CF)

The Cartridge Filter which is installed upstream of the high pressure pump removes particulate matter up to 5 microns from the feed water and minimises the fouling of the RO membrane elements.

2.2 High pressure pump

A high pressure pump of stainless steel construction is provided to boost the feed pressure for the reverse osmosis membrane. A low pressure switch is provided at the pump suction to safeguard the pump.

A stainless steel globe/ball/butterfly valve is provided on the pump discharge for regulating the pressure and flow to the reverse osmosis membrane.

A pressure gauge is provided upstream of this valve to monitor the pump performance.

2.3 Reverse Osmosis system

Basically the system consists of Reverse Osmosis membranes, pressure vessels (called pressure tubes) in which the membranes are mounted and piping for feed, reject and product with necessary instruments.

A cut-away view of the Reverse Osmosis membranes shows the details of the spirally wound configuration. The feed water is applied at one end of the membrane at high pressure. Because of the high pressure, reverse osmosis process takes place and permeate flows through the membrane and is collected through the core tube and normally flows out of the end opposite the feed. The reject is also collected from the opposite side.

In order to maximize the recovery, a number of membranes are put end-to-end in a pressure tube made of FRP. The pressure tube is designed to withstand the pressure at which the RO system has been designed.

To further improve the recovery, a number of pressure tubes are arranged in different combinations in such a way that the reject from the first "stage" becomes the feed for the next, and so on. Permeate is normally collected in a parallel manner from all the pressure tubes. The exact arrangement of staging would depend on the raw water characteristics and the desired treated water quality.

High pressure piping with necessary fittings is provided for the above purpose.

1.20.5.3 REVERSE OSMOSIS PASS-2 SYSTEM DESCRIPTION

3.1 Wet panel

A "Wet" panel is provided for mounting of pressure instruments.

A high pressure gauge & a low pressure gauge are provided on the wet panel with a 5-way & a 3-way valve. By operating the valve, the operator can note the feed pressure to various stages and the concentrate pressure. From these, stage wise pressure drop can be calculated.

Stainless steel sample valves are also provided to collect samples from the various stages and final concentrate.

3.2 Electrical control panel

The electrical control panel has a sheet steel enclosure and houses the controls and instruments for operation of the RO unit.

Relay/timer based controls are provided for starting and stopping of the RO unit and for the safety of the high pressure pump.

Please see the Technical Data Sheet for details of instruments provided.

1.20.5.4 MIXED BED UNIT:

In the Mixed Bed Polishing, the Cation and Anion exchange resins are mixed in certain proportion to achieve the finest quality to meet the Boiler water requirements.

The unit essentially consists of carbon steel rubber lined pressure vessel. It is externally fitted with rubber lined pipe work, necessary valves, pressure gauges and sampling valves at the inlet and outlet.Internally the unit is provided with an inlet distributor, caustic distributor, middle collector for acid / caustic effluent during regeneration. A bottom collecting system is provided for collecting the treated water and distributing the acid during regeneration and distributing air during air mix operation. Bottom collector will also used for giving the water during the backwash operation.

The middle collector is of header lateral type. Polypropylene strainers are fitted to the laterals which are connected to the header.

The vessel is provided with inspection windows, one at interface of cation and anion resins to watch resin separation during backwash and mixing operation during air mix and other one at the top of the unit to observe the inside water level during DRAIN DOWN operation and one below the center to observe mixing of resin during the air mix operation.

Water from a strong base anion unit enters mixed bed unit for removing the traces of impurities remaining in the demineralised water. The mixed bed exchanger contains a mixture of cation and anion resins, thus presenting a large number of demineralising stages (cation and anion resin combination) inside the unit. This results in production of extremely pure water.

When treated water quality goes beyond the conductivity of 0.5( S/cm or reactive silica content of 0.02 ppm as SiO2 or the pH (@25 deg. C) beyond the range of 6.5 to 7.5 or the unit has delivered its specified output of 1000 m3 between two regenerations whichever appears first, the unit is said to be exhausted at this stage the unit needs to be regenerated. y.

4.1 REGENERATION:

The regeneration of the mixed bed consists of the following basic steps

Backwash

Regenerant injection

Regenerant rinse

Air mix

Final rinse4.2 Backwash

The backwash is a very important and critical step in the regeneration of the mixed bed. It brings about the separation of the SAC and SBA resins to enable their individual regeneration.

During backwash, water is admitted into the bottom of the unit and flows upwards to expand and fluidise the resin bed. The wash water is led to drain.

The wash flow rate is so adjusted as to bring the lighter anion resin to the top and permit the denser cation resin to settle down. In this manner the cation and anion resins are separated distinctly into two layers with the anion layer on top of the cation layer.

The backwash also performs the other functions of decompacting the resin bed, cleaning it and reclassifying the beads each so important for satisfactory resin functioning.

Care must be taken during backwash to prevent loss of costly ion exchange resins by carryover through excessive flow rate.

Insufficient backwash flow rate will not separate the resins completely and lead to improper regeneration affecting the quality of water and the throughput.

Backwash is done for a minimum specified time and until clean effluent is obtained.

4.3 Regenerant Injection

Once the resins are separated thoroughly, they can be regenerated properly to bring them into the operating forms.

To regenerate the SBA resin, the solution of sodium hydroxide is introduced above the resin bed, flows through the anion resin layer and is withdrawn at the interface of the anion and cation resins.

The SAC resin is regenerated by injecting the solution of hydrochloric acid or sulphuric acid at the anion-cation interface down through the cation layer and out from the bottom of the unit.

A small upward (buffer) flow of water is maintained through the cation resin during the injection of regenerant into the anion resin to minimise the diffusion of sodium hydroxide into the cation layer and avoid its exhaustion.

Likewise during the injection of regenerant into the cation resin, a downward (buffer) flow of water is maintained through the anion layer to reduce the diffusion of acid into the anion resin and minimise its contamination.

The above buffer flows are necessary when the regenerants are injected successively.

The regenerants may be injected simultaneously in which case the sodium hydroxide flows as before downwards through the anion resin but the acid flows upwards from the bottom of the unit through the cation resin. The combined waste effluents are withdrawn from the anion - cation interface.In this method of simultaneous regenerant injection there are the following advantages

saving of overall time of regeneration

saving of waste water as the buffer flows are not required during the injection and subsequent rinse stages

Instantaneous neutralization of the acidic and alkaline waste effluents from the SAC and SBA resins respectively.

The injection concentrations are indicated below

Sodium hydroxide 5 % w/v

Hydrochloric acid 5 % w/v

The regenerant must be injected within a particular range of flow rates to maintain adequate contact time for the regeneration reactions to take place.

4.4 Regenerant Rinse

This rinse operation is done subsequent to regenerant injection and follows the same direction of flow as the injection and at nearly the same flow rate.

The rinse enables a better utilization of the regenerant lately injected to contact the rest of the resin bed. It also washes the excess regenerant off the resin to minimise the cross exhaustion of resins in the subsequent stages.

A few bed volumes of water are required for this purpose.

4.5 Air Mix

The air mix is the next critical step after backwash in ensuring good treated water quality. The better the mix of the two resins, the better is the quality of treated water.

In this step air is used to agitate, stir and mix the cation and anion resins thoroughly to provide the infinite stages of two bed demineralization. When the mixing is not adequate, there are layers rather than pairs of resin and the effect of multiple stages is not realised.

As the agitation with air is done with water present in the unit, some settlement does take place. This is minimised through a partial drain down prior to air mix.

The air mix operation is done for a specified time with low pressure air at a particular flow rate.

2.3.10 Final Rinse

This is the last step of the regeneration stage and aims at settling the resin in the mixed state after air mixing and washing away the trace regenerants from the resin bed.

The final rinse must follow the air mix quickly to prevent reclassification of resins under gravity resulting in some centimeters of anion resin at the top and cation resin at the bottom of the bed.

The final rinse is normally at service flow rate or a specified minimum flow rate with influent water.

The end of rinse is determined by water quality usually its conductivity or silica content. When these parameters are normal, the rinse is stopped and the regeneration of the mixed bed is complete. The mixed bed may be isolated or taken to service for production of demineralised water.

The mixed bed demineraliser is a down flow service unit. The SBA resin in it is always regenerated co flow while the SAC resin is amenable to both co flow and counter flow regeneration.

The mixed bed is normally employed as a polisher downstream of a two bed demineraliser.

TECHNICAL DATA SHEET1.3.1FEED WATER SPECIFICATIONS

Water Inlet:Well Water

Temperature:< 45( C

PH:6 - 8

1.3.2UF MEMBRANE SPECIFICATIONS

Molecular weight cut off:100,000 MWC

Nominal operating pressure:10-70 PSI

Maximum Operating temperature:65( C.

A. QUANTITY:10 NUMBERS

Diameter/Length of cartridge:10 diameter x 72 long.

B. Fast flush Pump

Capacity (Maximum)

:114 m3/hr @ 2.0 kg/cm2.

C. Back flush pump

Capacity(Maximum)

D. Material of Construction

:

124 m3/hr @ 2.5 kg/cm2

All wetted parts other than UF:SS 316 / PVC

Ultra filtration Membrane:Polysulphone

Pre filter :Stainless Steel

Gasket material:Silicone/EPDM

E. Service utilities

Electrical:380V/50Hz/3 Phase

Feed water: 50 m3/hr

RO MEMBRANE SPECIFICATIONS

1.3.3.1 RO FEED PUMPQuantity

2 Nos.Model

CR 45 - 2Capacity m3/h

45Head meter

35Make

Grundfos

MOC

SS316 / CI HOUSINGMotor rating kw

7.5

Motor speed RPM

2900

Make

Grundfos

1.3.3.2 Micron Cartridge Filter

Quantity

1 No.

Size

Jumbo 20 Long

MOC

PP

Filter Element /Type

5-micron

1.3.3.3 RO PASS-1 HIGH PRESSURE PUMP

Quantity

2 Nos.

Model

CR 64-5-1

Capacity m3/h

45Head meter

120Make

Grundfos

MOC

SS316 / CI HOUSINGMotor rating kw

30

Motor speed RPM

2900

Make

Grundfos

1.3.3.4 Reverse Osmosis Pass-1

Model No.

RO PASS -1 Number of stages

2Array

4 X 6 : 3 X 6

Pass 1Number of pressure tubes

7

Pressure tube rating psi

250

Make of pressure tube

Advanced Composites Size of pressure tubes

8

Elements/pressure tube

6

Element model

TM 720-370

Number of elements

42 nos.

Maximum feed flow

45 m3/h

Maximum permeate flow

35 m3/h

Maximum reject flow

5 m3/h

Reject recycle flow

5 m3/h

Recovery

70%

1.3.3.4 RO PASS-2 HIGH PRESSURE PUMP

Quantity

2 Nos.

Model

CRN 45-4Capacity m3/h

32Head meter

80Make

Grundfos

MOC

SS316

Motor rating kw

15

Motor speed RPM

2900

Make

Grundfos

1.3.3.5 Reverse Osmosis Pass-2

Model No.

PASS-2Number of stages

3Array

3 X 6 : 2 X 6 : 1 X 6

Pass 2

Number of pressure tubes

6

Pressure tube rating psi

250

Make of pressure tube

Advanced Composites - Goa

Size of pressure tubes

8

Elements/pressure tube

6

Element model

TM 720-370

Number of elements

36 nos.

Maximum feed flow

32.4 m3/h

Maximum permeate flow

27.5 m3/h

Maximum reject flow

4.9 m3/h (TO RO-1 FEED)

Recovery

85%

1.3.3.6 DEGASSER TOWER, TANK WITH BLOWER:

Degasser tower Diameter

600mm

Degasser tower Height On Straight

3200mm

Blower Capacity

6m3/minute

Head meter

50mmWCMake

IEI

MOC

CSMotor rating kW

0.37

Motor speed RPM

2900

Degasser tank diameter

2000mm

Length On Straight

4000mm

1.3.3.7 Cleaning system:

CIP tank capacity

2000Litres

Tank MOC

HDPE

CIP Pump

1 No.

Model

CRN 32-2

Capacity m3/h

27

Head meter

35Make

Grundfos

MOC

SS316

Motor rating kW

4

Motor speed RPM

2900

Make

Grundfos

1.3.3.9 Mixed Bed Feed Pump:

Model

GSHF 40-100

Capacity m3/h

25Head meter

35Make

Goulds

MOC

SS316

Motor rating kW

5.5

Motor speed RPM

2900

1.3.3.10 Mixed Bed Unit:

Diameter

1400mm

Height On Straight

2800mm

Material of Construction

Carbon Steel

Internal Protection

Rubber Lining

Cation Resin 225 H

800 Litres

Anion Resin FFIP

1250 Litres

Cation Bed Depth

500mm

Anion Bed Depth

800mm

Hydrochloric Acid (100%)

80 Kgs

Caustic Soda (100%)

125 Kgs1.3.3.11 Mixed Bed Regeneration Pump:

Model

GSHF32-200

Type

Horizontal Centrifugal

Capacity m3/h

15

Head meter

35Make

Goulds

MOC

SS316

Motor rating kW

3

Motor speed RPM

2900

1.3.3.12 MIXED BED BLOWER:

Blower Capacity

4.5m3/minute

Head meter

5Make

IEI

MOC

CS

Motor rating kW

0.18

Motor speed RPM

2900

1.3.3.13 Neutralization Pit Waste Transfer Pump:

Model

NH 405 PW N CVType

Self Priming Magnetic Driven Seal less

Capacity m3/h

20Head meter

25Make

Pan World Pumps (Japan)MOC

FRPPMotor rating kW

3.7

Motor speed RPM

2900

1.3.3.14 BULK CHEMICAL TANKS:

Diameter

1800mm

Height On Straight

2500mm

Capacity

5M3

Material of Construction

FRP Vinyl Ester

Type

Horizontal Dished End

Pressure

Atmospheric Pressure

Temperature

Ambient 25 D Celsius

Application

Chemical Storage

Breather Pot

Provided

Level Transmitter

Top Mounted

1.3.3.15 CHEMICAL DOSING TANKS:

Diameter

1800mm

Height On Straight

2500mm

Capacity

5M3

Material of Construction

FRP Vinyl Ester

Type

Horizontal Dished End

Pressure

Atmospheric Pressure

Temperature

Ambient 25 D Celsius

Application

Chemical Storage

Breather Pot

Provided

Level Transmitter

Top Mounted

2.DESCRIPTION

2.1 DESCRIPTION OF RAW WATER

The Raw water source is from the borewell in the backwater is a manual system consisting of two pumps, each stream capable of pumping the full flow rate of 55 m3/hr. Can be automatically Start and Stop. The pumps are designed to be operated at a constant flow rate (Clients Scope).

2.1.1 DESCRIPTION OF ULTRA-FILTRATION PLANT

2.1.2 DESIGN BASIS OF ULTRA-FILTRATION

2.1.3 Operating Data

NUMBER OF STREAM

:ONE

NORMAL FLOW

:45 M3/HR.

2.1.4 Design raw water quality

Raw WaterUF Product

pH

7.3-7.5

7.3-7.5

TOTAL DISSOLVED SALTS

1796

1796

TOTAL SUSPENDED SOLIDS ppm

5

1/2 M Nil 2 (M-P) 2P-M

P = M Nil Nil P

The above results are expressed in parts/million (ppm) as CaCO3.

Note :

Screened Methyl Orange Indicator solution.

Preparation of Indicator Solution :

Dissolve 0.2 g of Crystalline Methyl Orange in a mixture of 25 ml. Methylated Spirits and 25 ml. Deionised Water. Dissolve 0.28 g. Xylene Cyanol FF in a mixture of 25 ml. Methylated Spirits and 25 ml. deionised water. Mix the two solutions together.

For most RAW WATER samples, as also LIME SOFTENED water a 100 ml. sample can be used. For BOILER WATER samples use 10 ml. or 20 ml. sample.

Use Sodium Thiosulphite solution before addition of Methyl Orange only if water has been chlorinated e.g. from Bottling Precipitators.

5.9 DISSOLVED AND TOTAL IRON

Spectrophotometer Method :

Principle :

Iron is brought into solution, reduced to the ferrous state by boiling with acid and hydroxylamine hydrochloride and treated with 1- 10 phenanthroline at pH 3.2 to 3.3. Three molecules of phenanthroline chelate each atom of ferrous iron to form an orange - red complex. The coloured solution obeys Beer"s law; its intensity is independent of pH from 3 to 9. A pH between 2.9 and 3.5 insures rapid colour development in the presence of an excess of phenanthroline.

Apparatus :

Spectrophotometer, for use at 510 nm providing a lightpath of 1 cm or longer.

Acid wash glassware. Wash all glassware with conc. hydrochloric acid and rinse with distilled water or iron free DM water.

Reagents for Dissolved Iron :

10% W/v hydroxylamine hydrochloride in 100 ml distilled water or iron free DM water.

Ammonium Acetate buffer solution (NH4C2H3O2).

Dissolve 250 g Ammonium acetate in 150 ml distilled water or iron free DM water. Add 70 ml conc. (glacial)Acetic acid. Because even a good grade of acetic acid contains a significant amount of iron, prepare a new reference standard with each buffer preparation.

1 - 10, Phenanthroline solution.

Dissolve 100 mg 1, 10. Phenanthroline monohydrate (C12H7N2H20) in 100 ml distilled water or iron free DM water by stirring and heating to 80 Deg C. Discard the solution if it darkens. Heating is unnecessary if 2 drops conc. HCl are added to the distilled water.

Stock Iron solution :

Dissolve 1.404 g ferrous ammonium sulphate Fe (SO4)2 (NH4)2 in 250 ml distilled water or iron free DM Water.

Add separately 20 ml Conc. H2SO4 in 50 ml distilled water or iron free DM water.

Add both the solution together in a 1000 ml volumetric flask and add 0.1 N Potassium permaganate(KMnO4) drop wise until a faint pink colour persist. Dilute to the mark with distilled water or iron free DM water.

Working Iron Solution :

Pipette 50 ml stock solution and dilute to 1000 ml.

1 ml = 10.0 ug Fe (Microgram Fe.)

Preparation of Calibration Curves :

Pipette out 1.0, 2.0, 3.0, 4.0, 5.0 ml of working iron solution in 50 ml volumetric flask, corresponding to 0.20, 0.40, 0.60, 0.80, and 1.00 ppm.

Add 5 ml hydroxylamine hydrochloride followed by 10 ml Ammonium acetate buffer and shake it thoroughly. Now add 2 ml 1-10 phenanthroline and make up to the mark. Wait for 10 minutes and take the reading in spectrophotometer at 510 nm against a reagent blank prepared by distilled water or iron free DM water and plot the graph.

Procedure for Dissolved Iron :

Take 25 ml sample in a 50 ml volumetric flask.Add 5 ml hydroxylamine hydrochloride followed by 10 ml Ammonium Acetate Buffer. Shake it thoroughly and add 2 ml 1-10. Phenanthroline and dilute upto the mark with distilled water or iron free DM water. Wait for 10 minutes and measure the reading at the 510 nm, and find out the concentration from the standard graph (Use Reagent Blank).

Procedure for Total Iron :

Take 25 ml sample in a volumetric flask and add 2 ml HCl followedby 1 ml 10% hydroxylamine hydrochloride. Add a few glass beads and heat to boiling. To ensure dissolution of all the iron continue boiling until volume is reduced to 15 to 20 ml. Cool to room temperature and transfer to 50 ml Volumetric Flask. (Next follow the Dissolve Iron Procedure).

Calculation :

mg/l Iron = ppm iron (from graph) x Dilution factor.

Interference :

Among the interfering substances are strong oxidising agents, Cyanide, Nitrite, and Phosphate. Cobalt and copper in excess of 5 mg/lt and Nickel in excess of 2 mg/lt. Bismuth, Cadmium, Mercury, Molybdate and Silver precipitate phenanthroline.

5.11 FREE CHLORINE OR CHLORAMINE :

Reagent and Apparatus :

Lovibond Comparator

Disc for Free Chlorine 0-1.0 ppm

Two 10 ml. test tubes for Lovibond Comparator

0.1 ml. pipette

Ortho-Toluidine Indicator

Method :

Fill the two test tubes to the mark with the sample to be tested.

Fit the disc into the comparator and with the hinged lid facing D. Place one of the tubes in the left hand compartment.

To the other tube add 0.1 ml. of Ortho-Toluidine solution, mix well and place in the right-hand compartment of the comparator. Allow to stand for 5 minutes when estimating Chlorine, 20 mins. when estimating Chloramine.

Holding the comparator upto a good source of northern day light, rotate the disc until a colour match is obtained.

Result :

The residual Chlorine or Chloramine content can then be read off from the window at the bottom right hand corner of the case.

Note :

If the presence of Nitrites is suspected, add a small crystal of Sodium Thiosulphite to the sample containing the Ortho-Toluidine. The yellow colour due to the presence of Chlorine or Chloramine will be discharged, but if there are any nitrites present, the solution will remain yellow.

5.12 FREE CARBON DIOXIDE :

Reagents and Apparatus :

Burette for Sodium Carbonate solution

Sodium Carbonate solution 0.04N (N/25)

Phenolphthalein indicator (solution or tablets)

100 ml. Nessler cylinder

Glass stirring rod

Procedure :

Fill the Nessler cylinder to the 100 ml. mark with the water to be tested avoiding splashing and add 2 tablets or 20 drops of Phenolphthalein indicator.

Run in 0.04N Sodium Carbonate, a few drops at a time with gentle stirring until a pale pink colour is produced which persists for one minute. Take the buretter reading :

Interpretation of result :

Free CARBON DIOXIDE, as ppm CaCO3 = Burette reading(ml) x 10

5.13 EQUIVALENT MINERAL ACIDITY (E.M.A.) :

Reagents :

AMBERLITE IR-120 strongly acidic cation exchange resin

Approximately 2N hydrochloric acid

Screened methyl orange indicator

0.02N sodium hydroxide solution

Method :

Measure under water, 50 ml. settled volume of AMBERLITE IR- 120 into a chromatographic tube. The tube should be fitted with an outlet tap or screwclip at the bottom. If an ordinary glass tube is used, above this outlet a plug of glass wool to support the bed of ion exchange resin is required. Backwash the ion exchange resin in an upward direction with distilled or deionised water to loosen the bed, allow the bed to settle, drain water down to the resin surface and pass 250 ml. of 2N hydrochloric acid in a downward direction through the column at a rate of 3-5 ml/min. Rinse the column with distilled or deionised water until the effluent is alkaline to screened methyl orange. Pass 50 ml. of sample and discard the effluent. Pass two 100 ml. aliquots through the column at the same rate collecting the respective effluents separately. Titrate each of the effluents in turn with 0.02N sodium hydroxide using screened methyl orange as indicator.

Calculation :

EMA, as ppm CaCO3 = ml of titration x 1000

ml of sample

Note :

The column prepared in the above manner may be used for several determinations before it is exhausted. It is capable of exchanging the equivalent of 5000 mg. of calcium carbonate. When exhausted it need simply be washed, regenerated and rinsed again.

When the figure for E.M.A. (or FMA) is used to calculate the total Anion load (TA) for an anion exchange resin unit, the following method of calculation is to be used. This applies when Screened Methyl Orange is used as the Indicator.

a = volume of sample (ml)

b = volume of titration (ml)

E.M.A., as ppm CaCO3 = [b + {0.008 (a+b)}] x 1000 a

This test actually determines the acidity equivalent to the dissolved neutral salts in the water (Sulphate + Chloride + Nitrate)

5.14 SILICA 1-20 PPM :

Reagents and Apparatus :

BDH Lovibond Nessleriser.

Disc with colour standards 0.05 mg. to 1.0 mg. SiO2.

10 % w/v Aqueous solution of Ammonium Molybdate.

2N Sulphuric Acid Solution.

Method :

Fill one of the Nessler glasses to the 50 ml. mark with the sample and place in the left hand compartment of the Nessleriser.

Fill the other Nessler glass with the sample, at 25-30 Deg C.

Add 4 ml. of 2N Sulphuric Acid and 2 ml. of the Ammonium Molybdate solution. Mix thoroughly, place in the right hand compartment and allow to stand for 10 minutes.

Fit the standard disc of silica in the hinged lid.

Stand the Nessleriser facing a uniform source of light, looking north if possible, and compare the colour of the sample with the colours in the disc. Rotate the disc until the colours are matched.

Interpretation of result :

SILICA as ppm SiO2 = disc reading x 20.

If the colour in the test solution is deeper than the deepest standard, a fresh test should be carried out using a smaller quantity of sample and diluting to 50 ml. with distilled water before adding the reagents. Necessary correction to be made for dilution of sample in calculating the silica content.

Note :

Most colourless salts, even when present in relatively large quantities, are without influence upon the colour produced in the test provided the concentration of free acid is not unduly disturbed. Phosphates, however, must be absent, since they respond to the test and yield a yellow colour similar to that produced by silica. Phosphates may be removed by treating 100 cc of the solution under test with 50 ml. of Sorensen's borate buffer solution (pH 10.0) and 2 ml. of 2N calcium chloride solution; after mixing and allowing to stand for 2 hours the mixture is filtered. The test is made on 50 ml. of the filtrate by the method described above. As Sorensen's borate buffer invariably contains silica derived from the glass bottle, a blank test should be carried out and the necessary correction made. The result be multiplied by 1.5.

5.15 SILICA 0-1 PPM-MOLYBDENUM BLUE METHOD :

Reagents :

Acid Molybdate Solution :

75 gms of Ammonium Molybdate analar grade are dissolved in 500 ml. of distilled water. 322 ml. of 10/N Sulphuric Acid are added gradually with constant shaking. The solution is then made up to one litre with silica free water.

10 % w/v Oxalic Acid solution.

Reducing Agent :

90 gms. Sodium Metabisulphite are dissoved in 800 ml. of silica-free water.

7 gms anhydrous Sodium Sulphite are dissolved in 100 ml. silica free water, together with 1.5 gm. of 1 - amino, 2 - naphthol, 4 -Sulphonic acid. The two Solution are mixed and the total volume made up to one litre with silica-free

water.

Apparatus :

Lovibond Nessleriser

Disc for Silica 0.2-1.0 ppm

Two 50 ml. graduated tubes of Nessleriser.

Pipettes

Alternatively a spectrophotometer may be used at the wave length corresponding to a maximum absorption (but the exact wave length will have to be checked on each individual instrument).

Method :

50 ml. of the water under test is treated with 2.0 ml.Acid Molybdate solution and allowed to stand for 5 mins. at a temperature of 20-30 Deg C. If a tinge of yellow appears in the sample there is more than 1 ppm Silica present, and the test described for 1-20 ppm Silica should be carried out on a fresh aliquot. If no tinge of yellow appears, 4 ml. of 10% Oxalic acid is added to the sample followed by 1.0 ml. of reducing agent and the sample allowed to stand for 20 mins. The blue colour of the sample is compared with that of a blank solution prepared by adding reagents to Silica free water, using either a B.D.H. Lovibond Nessleriser or a previously calibrated absorption meter.

Note :

Silica free Water :

Prepare and store in a polythene bottle a large batch of water containing not more than 0.005 ppm silica. Determine the Silica content of the water by treating it as a sample as under `Method'. This water is used to prepare reagents and standards, and to dilute samples when necessary. Distilled water from an all metal `Still' or water which has been passed successively through a mixed bed dionisation unit and strongly basic anion exchanger unit regenerated with NaOH at a level of 320 gms/litre has been found to meet this specification.

5.16 OXYGEN ABSORBED IN 4 HOURS :

Outline of the Method :

This is determined by estimating the amount of standard potassium permanganate solution consumed by the sample in 4 hours under specified conditions.

Test Temperature :

This determination is carried out at a temperature of 37 Deg C.

Reagents :

Stock Potassium Permanganate Solution :

Dissolve 3.951 g of potassium permanganate (dried at 105 Deg C) in distilled water and make up to 1000 ml. This solution must be kept in the dark and its strength must be checked periodically.

Standard Potassium Permanganate Solution N/80 :

This solution should be prepared immediately before use by suitable dilution of stock potassium permanganate solution. One millilitre of this solution is equivalent to 0.1 mg of oxygen.

Dilute Sulphuric Acid :

Add slowly 50 ml of concentrated sulphuric acid to 130 ml of distilled water, cool and make up to 200 ml with distilled water. Add standard permanganate solution until a very faint pink colour persists after 4 hours.

Potassium Iodide :

Stock Sodium Thiosulphate Solution :

Dissolve 31.2 g of sodium thiosulphate and 6 g of sodium bicarbonate in water and make up to 1000 ml.

Standard Sodium Thiosulphate Solution N/80 :

This should be prepared by suitable dilution of stock sodium thiosulphate solution. Before using the solution the strength must be checked by titration with standard potassium permanganate solution.

Starch Indicator Solution :

Dissolve 1 g of starch in 100 ml of warm (80 Deg C - 90 Deg C) distilled water and add a few drops of formaldelyde solution.

Procedure :

Place 250 ml of the well-mixed sample into a clean, glass- stoppered bottle of 400 ml capacity. Add 10 ml dilute sulphuric acid, followed by an accurately measured volume (see note) of standard potassium permanganate solution. Mix by gentle rotation and place in a water-bath or incubator at 37 Deg C for 4 hours. If the sample contains much suspended matter, it should be mixed by gentle rotation several times during the period of incubation. At the end of 4 hours, cool to about 15 Deg C, add a few crystals of potassium iodide and titrate in the bottle with standard sodium thiosulphate solution, using a few drops of starch indicator soltuion. A blank for oxygen absorbed in 3 minutes shall be carried out. Express the result to the nearest 0.05 mg/l.

Note :

The measured volume of standard potassium permanganate solution taken must not be less than 10 ml, but should be such that at the end of 4 hours, the amount remaining unchanged is between 5 and 15 ml. If it is found that the volume required was anticipated incorrectly, the determination must be repeated.

Calculation :

Oxygen absorbed in 4 hours, mg/l = 0.4V

Where,

V = Volume in ml of standard potassium permanganate solution

consumed in reaction with the sample.

SECTION 6

TROUBLE SHOOTING

6.1 UF TROUBLE SHOOTING

6.1.2LOW PERMEATE FLOW RATE

Check unit for proper operation and make sure operating pressures are at the appropriate values. Clean the system using appropriate cleaning chemicals.

6.1.3HIGH BACTERIAL LEVELS

Sanitize the system after appropriate cleaning.

6.1.4HIGH PERMEATE FLOW RATE

a) System specifications are for a minimum flow rate using clean membranes and prefiltered water at 50 psid and 25 deg. C. Flux (permeate) rates may exceed the operating flux rate printed herein. Some UF cartridges may exceed minimum specifications and hence produce slightly higher permeation rates. This is not to be confused with membrane by-pass.

b) Check with IEI for permeate flow vs temperature correction factor to determine appropriate flow for the operating temperature. Also check system feed pressure.

6.2 TROUBLE SHOOTING FOR RO PASS-1 AND PASS-2:

This section gives the symptoms, likely causes and corrective actions required for the RO unit. For smooth operation of the plant, continuous attention must be given to feed water quality, operating parameters and routine maintenance.

Sr.NoSymptom

Likely cause

Consequences if

not correctedCorrective action

1.Increase in SDI at CF outletChange in quality of raw water

Coagulant / Flocculant dosing malfunction

Channeling in the sand filter.

Inferior quality of chemical.

Inadequate backwash of filterFouling of membranes leading to reduction in product flowCheck raw water quality

Check coagulant / Flocculant dosing system.

Carry out fresh jar test if required.

Check sand filter

Use right quality of chemicals.

Give sufficient backwash to the filters.

2.High/Low pH

Acid level low /

Blockage in acid line

Feed water quality / flow changeFouling of membranes

Damage to the membranesRefill acid / Check acid pump suction and discharge.

Check feed water flow, adjust dosage as needed.

3.Residual chlorine at Cartridge

filter outletChange in quality of raw water.

Maloperation of sodium hypochlorite dosing pump.

Change in raw water flowDamage to RO membranes (decrease in salt rejection)Check raw water quality. Adjust dosing rate.

Repair the pump.

Adjust raw water flow.

4.Low pressure at H.P. pump suctionRaw water pump malfunction. Excessive pressure drop at MGF/CF

Malfunction of auto feed water valve/solenoid valve.H.P. pump may get damaged due to cavitation.Check raw water pump.

Give backwash to MGF, change cartridges. Recalibrate pressure gauge / pressure switch. Check solenoid valve/auto feed water valve.

5.Auto feed water valve does not open.Solenoid valve malfunction.

Wrong installation of this valve.RO unit will not function.Check solenoid valve.

Check installation of auto feed water valve.

6.Increase in RO feed pressureIncrease in RO feed conductivity

Fouling / Scaling of membranes

Reject valve maloperation

Pressure gauge malfunctionLower product flow

Lower membrane lifeCheck raw water quality / SDI

Membrane cleaning.

Adjust recovery

Check pressure gauge.

7.Low reject flow.RO flow and pressure imbalance.

H.P. pump malfunction.

Incorrect reject flow indicator.Scaling / fouling of membrane.Adjust reject control valve.

Check pump.

Calibrate reject flow indicator.

8.Increase in pressure drop.Pressure gauge malfunction. Membrane scaling / fouling.

Entry of particulate materials.Decrease in product flow. Lower membrane life.Check pressure gauge.

Clean the membranes.

Check SDI and particulate content.

9.Decrease in normalised permeate flowScaling /fouling of membranes.

Malfunction of permeate flow indicator

Change in temperature of waterLower product flow. Increase in RO feed pressureCheck raw water quality / SDI. Clean the membranes

Check permeate flow indicator

Use suitable temperature correction factor.

10.Decrease in normalised salt rejection.O ring leakage. Membrane damage.

Membrane scaling /fouling.

Product cond. indicator malfunction.Inferior product quality (high product conductivity)Probing / profiling to find O ring leakage / membrane damage. Replace damaged membranes / O rings. Eliminate the cause of damage.

Clean the membranes.

Recalibrate product cond. indicator.

11.High pressure at HP Pump discharge Reject / Recycle valve closed

Membrane fully choked / fouled

Membrane may damage

HP pump may get damaged

Leakage of joints / connectorsCheck the valves

Check fouling on membranes

Any blocks / foreign particles water passage through pressure tubes / pipes

12.ORP dump valve does not open Solenoid valve malfunction.

Wrong installation of this valve.RO unit will not function.Check solenoid valve.

Check installation of auto feed water valve.

6.3 MIXED BED TROUBLE SHOOTING

Sr. No.DEFECTSCAUSESREMEDIES

1.Decrease in capacity between regenerations.1. Flow instrument defective.

2. Plant being used intermittently.

3. Insufficient chemicals used.

4. Increase in ionic load.

5. Resin quantity insufficient.

6. Channeling in bed

7. Resin dirty.

8. Resin fouled.Check the instrument.

Avoid this situation.

Check. For the consumption.

Check analysis.

Check & top up.

Check the distribution.

Give the prolonged backwash

If Cation giveHCL wash or if Anion give alkali brine treatment

2.Treated water quality not upto the standard.1. Softener resin exhausted.

Check the conditions.

Treated water quality not upto the standard.2. Unit idle.

3. Unit insufficiently rinsed.

4. Excessive flow rate.

5. Resin deteriorated.Check.

Rinse the unit till the satisfactory quality is achieved.

Adjust between min.& max. flow rate.

Check resin quality & replace if necessary.

3.Unit rinse takes long time.1. Flow rate too low.

2. Unit exhausted.

3. Backwash valve passing

Increase the flow rate.

Regenerate the unit.

Check & rectify.

4.Flow rate too low.1. Choked valve & suction of the pump.

2. Cavitation in the pump

3. Distribution & collecting system choked.

Check.

Check the pump design & operating conditions.

Check.

Sr. No.DEFECTSCAUSESREMEDIES.

5.Pressure drop across the bed increasing.1. Defective pressure gauge.

2. Defective valves.

3. Packed resin bed & resin fines.

4. Collecting system choked.Check & calibrate the pressure gauge.

Check.

Give extended backwash with open manhole and scrap off the finesand top it up with fresh resin.

Check & give the backwash.

6.Resin being lost from the unit.1.Excessive backwash pressure.

2. Faulty collecting system.

Check the inlet pressure and reduce if necessary.

Check the collecting system by opening the resin trap outlet valve.

7.Ejector not working.1.Low power water pressure.

2. Air lock in the unit.

3. Choked or defective valves.

4. Ejector nozzle choked.

5. Too much back pressure from the unit.

Check the pressure.

Open the air release and backwash outlet valves.

Examine & rectify.

Open & check the ejector nozzle.

Check for the collecting system.

Check & rectify

8.Incorrect reading from rotameter..1.Choked orifice or sub orifice or impulse line.

2.Dirty glass & float.Check & rectify.

Clean the glass

DEFINITIONS OF TERMS

CONCENTRATE

The portion of the feed stream which does not pass through the membrane. It contains retained dissolved or suspended materials at a concentration higher than that of the feed stream. Also known as RETENTATE.

CONCENTRATION POLARISATION

The condition which results when the retained dissolved materials become concentrated in the thin boundary layer adjacent to the membrane surface. The gel layer thus formed presents a barrier to fluid migration to the membrane and reduces overall flux. Proper design of cross flow filtration and cleaning techniques minimizes the effect.

DIAFILTRATION

The continuous exchange of process solution with fresh solvent, thereby removing membrane permeating species from the batch.

ENDOTOXINS

Generally refers to the lipopolysaccharides coming from the cell walls of dead bacteria. Frequently used interchangeably with pyrogen.

FEED

The influent stream to the ultrafiltration system, which is then split into a permeate stream and concentrate stream.

FLOW DEPENDENT

UF feed streams where fouling mechanisms must be controlled to allow predictable permeation rates through the membrane.

FLUX

Rates at which fluid permeates or flow through the membrane, usually expressed in gallons per square foot of membrane per day (GSFD).

GEL LAYER

A layer of highly concentrated or precipitated solids, usually of high molecular weight species, adjacent to the active surface of an operating ultrafiltration membrane. The gel layer permeability rather than membrane permeability often controls ultrafiltration flux.

HUMIC ACID

Any of various organic acids that are insoluble in alcohol and organic solvents and are obtained from humus.

HUMUS

A brown or black complex and varying material formed by the partial decomposition of vegetable or animal matter the organic portion of soil.

LAL

Limulus Amebocyte Lysate is a chemical, which is sensitive to the presence of pyrogenic material (endotoxin). The LAL test measures the concentration of pyrogens which is reported as endotoxin units (EUs) in a specified volume.

MEMBRANE ANISOTROPIC

A synthetic polymeric membrane composed of a very tight thin skin on one side supported by a sponge like layer. The skin or active membrane, functions as the semi-permeable barrier to solute flow causing rejection of macromolecules in solution and any colloidal or suspended material.

MOLECULAR WEIGHT CUTOFF

The membrane specification describing the normal rejection of a known molecular species dissolved or suspended in the feed stream.

PERCENT RECOVERY

Ration of permeate flow to feed flow

PERMEATE

Portion of the feed stream, which passes through the membrane, essentially free of colloidal, particulate and microbiological species.

POINT-OF-USE SYSTEM

A filtration system which is installed very near to the location where the water is consumed. this is in contrast to a central water system or loop, which is generally, located a considerable distance from the point where the water is used.

POLYETHERSULFONE

An engineering thermoplastic polymer from which ultrafiltration membranes having desirable properties of toughness, chemical resistance and thermal stability can be formed.

PPB

Parts Per Billion, refers to the concentrations by weight of a material relative to fluid in which it is placed.

PRESSURE DEPENDENT

UF feed streams where fouling or concentration polarization is relatively unimportant.

PYROGEN

Any substance, which causes a temperature rise when, injected. A common source is bacteria fragments. See endotoxin.

RECOVERY RATE

The amount of fluid (permeate) collected which has passed through the membrane expressed as a percent of the feed stream.

REJECTION RATE

One (1) minus the ratio of a specific solute concentration in the permeate to the concentration of the solute in the feed expressed as a percentage.

RETENTATE

See CONCENTRATE, Reject from Ultrafiltration System,

REVERSE OSMOSIS

By application of pressure (above osmotic pressure) on a salt solution against a semi-permeable membrane, pure water is forced through the membrane leaving behind salts.

SOLUTE REJECTION

A measure of the ability of the ultrafilter to block the passage of material dissolved or suspended in the feed stream.

SOLUTE

The constituents of a solution which are dissolved in the solvent.

TIC

Total Inorganic Carbon is similar to TOC but measures inorganic carbon.

TOC

Total Organic Carbon or Total Oxidizable Carbon measures the total organic material by high temperature oxidation or carbon dioxide. Detects presence of organic material down to parts per billion.

ULTRAFILTRATION

A membrane separation process similar to reverse osmosis in which relatively higher molecular weight materials are separated from a feed stream.

18 MEG-OHM WATER

Water which has been treated to remove conductive materials. For pure water, the theoretical value for resistivity is 18 meg-ohm at 25 deg. C.

SECTION 7

MAINTENANCE

7.1 PRETREATMENT

The recommended pretreatment is a prefilter (100 micron strainer). The life of the filter is a function of the degree of cleanliness of the feed water. The life times given below must be considered as a maximum, this could be much shorter if the feed water is highly contaminated with particles and colloids.

Strainer Prefilter cleaning differential pressure exceeds 20 psi (whichever is sooner)

7.2SANITIZATION

In order to preserve the performance of the UF cartridge as well as to maintain a low bacteriological count in permeate water, it is necessary to sanitize the system on a regular basis (once a week minimum). The most efficient sanitization is achieved through injection of diluted chlorine bleach into the feed water line with an accessory injection pump. The average chlorine concentration measured on permeate line is 200 to 250 ppm.

During sanitization cycle the permeate flow is diverted to the drain.

7.3WEEKLY CHECKING

We recommend to sanitize the UF system once a week minimum. The weekly checking required is pump performance and permeate flow rate.

Permeate flow rate should be in accordance with figure 3.2 section.

7.4PROLONGED SHUTDOWN

If the system is used once or twice a week, we recommend to sanitize it before using the water. If the system is shut down for more than one week, it is necessary to remove the UF cartridge and to store it immersed in a 3% formaldehyde or caustic chlorine solution or follow long term membrane storage procedure (6.4)

7.5PUMP INSPECTIONOnce in a week, pump should be checked for any mechanical damage, current drawn. Necessary steps, as given in attached manual, should be carried out in case of any performance deterioration.

7.6CARTRIDGE REPLACEMENT AND CLEANING

Basket / Conical filter (prefilter) should be cleaned or replaced as

suggested.

7.7LOG BOOK

Logbook of UF system should be maintained and recorded properly.

7.8 Integrity Testing :

Integrity testing of Hollow Fiber membrane modules is recommended prior to water processing to ensure an integral membrane. The three procedures listed below give a gross indication of membrane integrity. They are not intended as an absolute check of membrane integrity.

A. Permeate Side Pressurization Test

1. Install the module on a system.

2. Fill the feed side of the module with clean water.

3. Close off the inlet valve (bottom side) to the system and open the outlet side.

4. Connect a clean air or nitrogen line to the permeate port. Air or nitrogen pressure just be regulated to 2-3 psi. Inject air or nitrogen into the cartridge.

5. Watch for bubbles in the clear elbow on the top side of the cartridge, or bubbles exiting the outlet line. The presence of large bubbles indicates a broken fiber. Some diffusion of air may occur during this process, and should not be confused with a membrane failure.

B. Feed Side Pressurization

1. Cap or close the valve on the top side of a hollow fiber cartridge. Cap the low permeate port.

2. Attach a clean air or nitrogen line to the other feed side of the cartridge.

3. Fill the permeate side with as much water as possible until it pours out the top port permeate.

4. Inject 2-3 psi of air or nitrogen into the feed side of the cartridge and watch for bubbles on the permeate side. If a fiber is damaged, large bubbles can be seen through the clear plastic housing. Some diffusion of air may occur during this process, and should not be confused with a membrane failure.

5. Invest the cartridge and repeat the procedure to check the portion of the cartridge that was on filled on the permeate side.C. Pressure Hold Test

1. Install cartridges on system and fill with water.

2. Pressurize the feed side of the system with 15psi clean air or nitrogen. Higher pressures may be applicable for some membrane types.

3. Monitor the pressure decay with a diffusion monitoring instrument over time (usually 5 minutes or less).

7.9DOS AND DONTS

DOSDONTS

1.Do check the water level in Feed tank, so that the pump suction is fully flooded1.Dont run the system dry or without sufficient water in the buffer

2.Check water temperature regularly and shut off the system immediately if feed water temperature is greater than 50 deg. C.2.Dont run the system with feed water temperature more than 50 deg. C continuous. Exception during hot water sanitization when temperature is at 90 deg. C max. for 20 min. at a time.

3.Clean the prefilter when pressure drop across it exceed 15 psi3.Dont run the system when pressure drop across prefilter exceeds 15 ~20 psi

4.Do flush the system sufficiently for about 30 min. at rated capacity before taking samples4.Dont take sample without proper flushing of dead zones in the system.

7.10 Precautions

Read and understand the following precautions. Personal injury and/or premature failure could result if these precautions are not followed.

1. DANGERPRESSURIZED DEVICE The membrane modules and piping provided with this system may cause loss of life, severe bodily injury and/or property damage if not properly installed, operated and maintained. Read and understand all equipment guidelines given before attempting to open, operate or service the system. Failure to follow these instructions and observe every precaution may result in malfunction and could result in catastrophic failure; Misuse, incorrect assembly or use of damaged or corroded components can result in high velocity release of hardware.

2. Do not perform any system or Module maintenance unless the system control power is OFF, the pump starters are OFF and LOCKED-OUT and INTERNAL PRESSURE HAS BEEN RELIEVED from the system. Failure to do so may result in serious injury.

3. The UF membranes must not be allowed to dry out. The membranes must remain wet any time the system is shutdown for any reason, including maintenance. Membrane dry out is irreversible, and will damage membrane permanently.

4. The UF membranes must not be allowed to freeze. Freezing will permanently damage the membranes.

5. Do not expose the UF membranes to acidic pH chlorine. Always adjust water to >pH 8 prior to chlorine addition. It is recommended that the chlorine concentration not exceed 250 ppm.

6. If the system is to be shutdown for a period exceeding one week, arrangements must be made to clean the membranes to eliminate possible biological fouling. See Membrane Protection section.

7. No anti-foam agents of any kind are to be introduced into the Koch Ultrafiltration Membranes system without prior review.

8. No silicone based materials, including any waterproofing sprays, lubricating or cutting fluids or greases, etc. are to be used in or around the Ultrafiltration System. Using these materials in the Ultrafiltration Systems may cause complete and irreversible membrane fouling.

7.2 RO PASS 1&2 MAINTENANCE

7.2.1 INDUSTRIAL REVERSE OSMOSIS UNIT & CLEANING SYSTEM

This section describes in detail mechanical maintenance aspects. There is an extensive discussion regarding the various foulants affecting the RO membranes and regarding membrane cleaning.

7.2.2 Mechanical Maintenance

Regular maintenance of Reverse Osmosis unit is required for a long troublefree performance. It will also enable the operator to pinpoint the causes of defective performance quickly.

In general, since the Reverse Osmosis unit involves high pressure, it is necessary to ensure that there are no leaks and to attend to them immediately should they occur. It is also necessary to keep an inventory of essential spare parts so that problems can be attended to as soon as they occur.

7.2.3Change of filter cartridges

(Normally done when the pressure drop across the filter exceeds 1 kg/cm2)

1. Turn the RO unit main switch to OFF position.

2. After ensuring that the pressure in the cartridge filter pressure gauge is zero, open the cartridge filter cover and unscrew the nuts holding the cartridge filter elements. Remove the existing cartridge filter elements and discard them.

3. Observe the particulates to see if there is any abnormal carryover of sand, or activated carbon or any other material.

4. Drain the cartridge filter body and wash it with water.

5. Install new cartridges/filter elements and refix the covers tightening the bolts evenly.

6. Turn the main switch to AUTO and restart operations.

7.2.4Lubrication of high pressure pump

1. Turn the main switch to OFF position.

2. Insert two strokes of lubricant from the hand operated becoming lubricant pump into the grease filling near the motor end of the pump.

3. Turn the main switch to AUTO position.

7.2.5Maintenance schedule

Sr.

No.ActivityFrequency

1Inspect and attend leaksDaily

2Change filter cartridgesOnce in 3 months or when the pressure drop > 1.0 kg/cm2 whichever is earlier

3Lubrication of high pressure pumpOnce in 6 months

4RO membrane cleaningSee Note 1 below.

5RO membrane replacementSee Note 2 below.

6Instrument calibrationRefer instrument manuals.

Note 1

When the "normalised" productivity rate is more than 15% below that for clean membrane, or

When the RO feed pressure is 2.00 kg/cm2 higher than that with clean membrane.

Note 2

When after repeated cleaning performance is not restored to the desired extent.

7.2.6 Membrane Cleaning

This section provides general information about the usual foulants affecting the performance of Composite Polyamide Reverse Osmosis (RO) membrane elements and the removal of these foulants. The information in this section applies to 4 inch and 8 inch diameter RO membrane elements.

Note

The Composite Polyamide type of RO membrane elements may not be exposed to chlorinated water under any circumstances. Any such exposures will cause irreparable damage to the membranes. Absolute care must be taken following any disinfection of piping or equipment or the preparation of cleaning or storage solutions to ensure that NO trace of chlorine is present in feed water to the RO membrane elements. If there is any doubt about the presence of chlorine, perform chemical testing to make sure. Neutralise any chlorine residual with sodium bisulphite solution, and ensure adequate contact time to accomplish complete dechlorination.

It is recommended that all RO membrane cleaning operations should be closely co-ordinated with Ion Exchange (I) Ltd., during RO membrane element warranty period. IEI Ltd field service personnel should be on site, at least for the first cleaning event.

The use of cationic surfactant should be avoided in cleaning solutions, as irreversible fouling of the membrane elements may occur.

7.2.7RO membrane element foulants

During normal operation over a period of time, RO membrane elements are subject to fouling by suspended or sparingly soluble materials that may be present in the feed water. Common examples of such foulants are calcium carbonates scale, calcium sulphates scale, metal oxides scale, silica coating and organic or biological deposits.

The nature and rapidity of fouling depends on the condition of the feed water. Fouling is progressive, and, if not controlled early, will impair the RO membrane element performance in a relatively short time.

Monitoring overall plant performance on a regular basis is an essential step in recognising when membrane elements are becoming fouled. Performance is affected progressively and in varying degrees, depending on the nature of the foulants. Table 7.1 provides a summary of the expected effects that common foulants have on performance of the RO system.

7.2.8Foulant removal

Foulant removal is achieved by cleaning and flushing. Further fouling is avoided by changing the operating conditions. As a general guide, foulant removal is required when any of the following conditions occur:

1. Permeate flow has dropped to 10-15 percent below rated flow at normal pressure.

2. Temperature corrected feedwater pressure has increased 10-15 percent to maintain rated product water flow.

3. Product water quality has decreased 10-15 percent, salt passage has increased 10-15 percent.

4. Applied pressure has increased about 10-15 percent.

5. The differential pressure across RO stage has increased noticeably (instrumentation may not be available to monitor this indication).

The following paragraphs provide a discussion of the common foulants and their removal:

Calcium carbonate scale

Calcium carbonate may be deposited from almost any feed water if there is a failure in the inhibitor addition or in the acid injection of pH control system that results in a high feed water pH. An early detection of the resulting calcium carbonate scaling is absolutely essential to prevent the damage that crystals can cause on the active membrane layers. Calcium carbonate scale that has been detected early can be removed by lowering the feed water pH to between 3.0 and 5.0 for one or two hours. Longer resident accumulations of calcium carbonate scale can be removed by recirculating a citric acid solution of 2 percent strength and a pH of no less than 4.0 through the RO membrane elements.

Ensure that the pH in any cleaning solution does not fall below 4.0 otherwise, damage to the RO membrane elements may occur, particularly at elevated temperatures. The maximum pH should be less than 10.0. Use sodium hydroxide to raise the pH, or sulphuric or hydrochloric acid to lower it.

Calcium sulphate scale

Solution 2 is the best choice for removal of calcium sulphate scale from the RO membrane.

Metal oxides scale

Precipitated hydroxides (e.g., ferric hydroxide) can usually be removed by using the techniques described above for calcium carbonate scale.

Silica scale

A silica coating not associated with either metal hydroxides or organic matter will usually respond only to very specialised cleaning methods. Contact Ion Exchange (I) Ltd., for instructions related to a specific problem.

Organic deposits

Organic deposits (e.g. microbiological slimes and moulds) are best removed by using solution 3. To inhibit additional growth, recirculate and soak the membranes with a IEI Ltds approved biocide solution. This requires extended exposures to be effective; a biocide solution is best employed when an RO block or train is to be left in a standby condition for more than three days. Contact Ion Exchange (I) Ltd., for the biocide best suited for specific conditions.

Cleaning solutions

The following chemical solutions are recommended for cleaning the RO membrane elements. The appropriate solutions to use can be determined by chemical analysis of the fouling material. A detailed examination of the results of the analysis will provide additional clues as to the best method of cleaning. Keeping records of the methods used and results obtained will provide data useful in developing the methods and solutions that work best under the feed water conditions at hand.

Solution 1 is recommended for inorganic fouling. Solution 2 is recommended for calcium sulphate and organics. Solution 3 is recommended for high organic fouling. All solutions are to be used the highest available temperature up to 400C or upto 60 minutes of cleaning. The quantities given are as per 100 litres of water. Prepare the solutions by proportioning the amount of chemicals to the amount of cleaning water to be used. Use chlorinefree permeate to mix the solutions. Mix thoroughly.

If additional information is needed, please contact Ion Exchange (I) Ltd.

RO membrane element cleaning and flushing

The RO membrane elements in place in the pressure tubes are cleaned by recirculating the cleaning solution across the high pressure side of the membrane at low pressure and relatively high flow. A cleaning unit is needed to do this.

The general procedure for cleaning the RO membrane is as follows:

1. Flush the pressure tubes by pumping clean, chlorinefree product water from the cleaning tank (or equivalent source) through the pressure tubes to drain for several minutes.

2. Mix a fresh batch of the selected cleaning solution in the cleaning tank, using clean product water.

3. Circulate the cleaning solution through the pressure tubes for approximately one hour or the desired period of time, at a flow rate of 133 to 151 l / min per pressure tube for 8.0 and 8.5 inch pressure tubes, or 34 to 38 l / min for 4.0 inch pressure tubes.

4. After completion of cleaning, drain and flush the cleaning tank; fill the cleaning tank with clean product water of the same pH as that of cleaning solution for rinsing. This is done to avoid precipitation of the matter which was dissolved during cleaning.

5. Repeat above step with permeate at neutral pH.

6. After the RO system is rinsed, operate it with the product dump valve open until the product water flows clean and is free of any foam or residues of cleaning agents (usually 15 to 30 minutes).

Table 7.2.9RO Membrane Element Foulant Symptoms

FoulantGeneral SymptomsResponse

1.Calcium precipitates (carbonates and phosphates, generally found at the concentrate end of the system.A marked decrease in salt rejection and a moderate increase in pressure between feed and concentrate. Also a slight decrease in system production.Chemically clean the system with solution 1.

2. Hydrated oxides (iron, nickel, copper etc)A rapid decrease in salt rejection and a rapid increase in pressure between feed and concentrate. Also a rapid decrease in system production.Chemically clean the system with solution 1.

3. Mixed colloids (iron, organic and silicates)A slight decrease in salt rejection and a gradual increase in pressure between feed and concentrate. Also a gradual decrease over several weeks in system production.Chemically clean the system with solution 2.

4. Calcium sulphates (generally found at the concentrate end of the system)A significant decrease in salt rejection and a moderate increase in pressure between feed and concentrate. Also a slight decrease in system production.Chemically clean the system with solution 2.

5. Organic depositsPossible decrease in salt rejection and a gradual increase in pressure between feed and concentrate. Also a gradual decrease in system production.Chemically clean the system with solution 2.

For heavy fouling, use Solution 3.

6. Bacterial foulingPossible decrease in salt rejection and a gradual increase in pressure between feed and concentrate. Also a gradual decrease in system production.Chemically clean the system with either of the solutions, depending on possible compound fouling.

The detailed trouble shooting guidelines and suggested treatment are attached herewith to be followed .All problems require the cause of the fouling to be corrected. Contact Ion Exchange (I) Ltd., for assistance.

Table 7.2.10Summary of Recommended Cleaning Solutions

SolutionIngredientsQuantitypH adjustment

1Citric Acid

RO product water(chlorine free)1.0 Kg

100 litresAdjust to 4.0 with sodium hydroxide (NaOH)

2Sodium tripolyphosphate

Tetra sodium EDTA

RO product water

(chlorine free)

2.0 kg

0.84 kg

100 litresAdjust to 10.0 with sulphuric acid (H2SO4)

3Sodium tripolyphosphate

Sodium Dodecylbenzene

RO product water(chlorine free)

2.0 kg

0.26 kg

100 litresAdjust to pH 10.0 with sulphuric acid (H2SO4)

INSTRUCTIONS FOR RO PLANT SERVICING / MEMBRANE CLEANING

1) Collect the details of particulars of client like previous field service report, contact person, address etc.

2) Discuss and review the operation of the plant with contact person/operator. Note down the problems if any.

3) Refer the logbook for product flow, reject flow, water quality and system pressure.

4) Check the pre-treatment and confirm the system is working as per design/requirements.

5) Identify the type of membrane.

6) Identify the plant problem from the trouble shooting guidelines.

7) Apply the appropriate treatment program as per guidelines .

8) Carry out the membrane cleaning.

9) Compare the product flow, reject flow, system pressure, treated water quantity. Collect all the details and put it in the log sheet.

10) Prepare field service report giving details of job carried out, list out essential spares required and the suggestions on plant monitoring and control. Propose the next servicing schedule and get it signed by the client. Forward the copy of the report to Branch in-charge/service in-charge.

7.3 MAINTENANCE OF MB UNIT7.3.1 General Maintenance

The Water Treatment Plant should be inspected externally every six months and any damaged paintwork on vessels, pipework and valves renewed.

An internal inspection of vessels is also recommended every six months, although this period can be extended if service experience indicates that a longer period would not jeopardise the performance.

When carrying out external examination of pipework, valves and vessels bear in mind that evidence of external corrosion may be due to underlying causes such as a damaged lining in a vessel or pipe subjected to hydrochloric acid or Caustic Soda.

Consequently when removing scale on such items (e.g. bulk storage tanks, measuring tanks) exercise caution. If there is any possibility of a break-through consult the Water Treatment Plant Chemist or Engineer. If the internal and external inspections are carried out systematically at regular intervals, and a record kept of any work carried out, there will be little likelihood of the unexpected happening.

In addition to the items specifically mentioned in the MAINTENANCE section, rectify leaking valves and joints immediately by loosened nuts and bolts or changing sealing joints (gasket). Replace gland packing when required. Don't let leaks persist. Keep the Water Treatment Plant dry and well swept.

If it is necessary for maintenance personnel to enter any of the treatment units, rubber or soft soled shoes must be worn and great care taken to avoid damage to any rubberlining and internal lateral systems. The feet should be placed on the lateral clamping bars, not on the laterals themselves and every effort taken to avoid standing on the small plastic strainers. Entry into the vessels should be discouraged, but if unavoidable, must be carried out under the supervision of the Water Treatment Plant Chemist or Engineer.

Valve should be inspected regularly and gland packing where used should be replaced regularly. Valves of the plug type and some diaphragm type which require lubrication should be attended to regularly.

Refer to the auxiliaty manuals for Maintenance instructions on other equipment that may be supplied such as pumps, blowers, instrumentation.

7.3.2 CATION, ANION & MIXED BED UNITS :

Inspect all units externally every 6 months including connecting pipework and valves. Chip away any loose paintwork, scale and make good with fresh paint. When the unit has been removed from service for internal inspection, close the manual inlet and outlet isolating valves as a safety measure and then open the AIR RELEASE and DRAIN Valves.

Remove the manhole cover and examine the internal lining in the unit. If the lining is damaged and shows signs of bulging or lifting, or is suspect, carry out a spark test and rectify. Check procedures involved with your maintenance department or refer the matter to this Company. If the condition of the lining below the level of the resin is suspected, the resin will have to be removed as described in the MAINTENANCE sheet entitled RESIN REMOVAL AND REPLACEMENT.

Carry out an extended backwah with the manhole cover open and observe the bed performance. The water should break through evenly. If it breaks through from one side of the vessel and floods over the bed surface, or the bed breaks into lumps, (indicating packing and channelling) backwash at the fastest possible flow rate without bringing resin over, and stir with a stout rod until the bed is level and of a consistent density. Remove any 'fines' etc. by skimming the top surface and then shovelling out.

After backwashing, drain the unit down and then note and record the bed level to some convenient point. Refer to the MAINTENANCE sheet entitled BED DEPTH. Compare this measurement with the last recorded level as a check for resin loss. Note that in order to obtain an accurate bed measurement, the level must always be taken immediately following a backwashing operation. If the condition or performance of the resin is suspected take samples (approximately 150 mm and again 450 mm and arrange for the samples to be analysed.

Refil the cation or anion unit by backwashing and double check bed depth, then refit the manhole cover.

On Mixed Bed units, carry out an air mix operation (see relevant sections in the OPERATION section) and observe the surface of the bed. The whole of the top water and resin should be in a fairly vigorous 'bubbling' stage.

7.3.4 BED DEPTH :

An ion exchange plant is designed to give a specified treated water quality when run on a particular raw water, the analysis of which has been used for the design. An economical quantity of resin required is decided upon and also an economical quantity of regenerant to achieve the required quality of treated water and capacity between regenerations.

The resin volume is a very important factor. If this is less, then a reduced capacity is obtained. A procedure is given below for measuring the ion exchange resin bed depth from which, by knowing the cross- section area of the pressure vessel, the resin volume can be computed.

Equipment :

A scale long enough to measure the distance from the bottom of the unit to the top flange of the manhole. A length of 25 mm x 25 mm wood may be used. Alternatively a length of PVC, GI or , MS pipe.

Note:

For rubber lined units, GI or MS pipes should not be used as they might cause damage to the lining or to the collecting systems.

If a pipe or length of wood is used, a separate scale is required to measure distance.

Method :

Open top manhole.

Open WASH OUTLET, then slowly open WASH INLET Valves. This will fluidise the resin bed.

After 3-5 minutes carefully insert the measuring pipe into the unit, through the resin until it reaches the bottom.

Note:

Where a SILEX underbed is employed, the pipe is to be inserted down to this level.

Where no SILEX is used, the collecting system may be one of several types-Header and lateral, strainer on plate-in both cases polypropylene strainers are employed. Hence care should be taken to see that no damage occurs to these or other components. This pipe should be carefully manoeuvred so that it reaches the bottom plate.

Hold the pipe vertical. Mark off the distance to a convenient reference point such as the manhole flange.

Remove the pipe and repeat procedure to check the depths at two other points, then remove pipe.

Measure the distance marked-off on the pipe (A).

Continue backwashing for 10 minutes then close WASH INLET Valve. This results in the resin settling down under