Water Treatment

Water Treatment

Hand Book

PREFACE

Aqua Designs was started with the mission of providing eco friendly solutions

which will be useful for individuals, industries and also to nature.

Since its inception, Aqua Designs has offered successful solutions on

environmental perspective which has created a unique place in the industrial

sector.

The vision of MD Mr. Suthakar is to spread the message of harvesting water,

reducing its usage, recycling and reuse. This vision transformed into collection

of data on water and its uses and sharing this knowledge with one and all in

order to make this world a lively place to live.

.......... and hence this book.

With best compliments from

S. Suthakar

Managing Director – Aqua Designs

ABOUT US

Aqua Designs – Offers A to Z solutions for water and waste water treatment. A

one Stop Shop for all types of consultancies in water and waste water

management.

Aqua Designs commitment to the environment, keeps it in the forefront of

product innovations, purification and recycling technologies.

Aqua Designs provides water solutions for Institutions, Industry, Municipal

Authorities, and Commercial and Public properties. The Company boasts of the

widest range of specialty water-related products and services that are ISO

9001:2000 certified by RINA of Italy.

Aqua Designs was the proud recipient of the prestigious Award for The “Best

Upcoming Water Company 2006 – 2007”given by the magazine Water Digest

in association with UNESCO, NDTV Profit & WES-Net India in order to

acknowledge those persons and Organizations, who have contributed toward

water and its industry.

Aqua Designs was also the proud winner of the Awards for “Best Water

Treatment Project – Industrial 2007-2008” & “Best Water R&D and

Technological Breakthrough 2007-2008” instituted by Water Digest.

For the year 2008-2009, Aqua Designs added one more feather in its cap. It

bagged two more Awards instituted by the Water Digest for the categories Best

Consultancy & Best Water Conservation IT Park showing its strength in IT

Sector using MBR Technology.

A proven track record of offering A – Z solutions was appreciated and the Best

Consultancy Award is the proof for that.

The Company has excellent marketing and sales team with a cumulative

experience beyond 100 years. It is one of the major reason for Aqua Designs

entering big corporate and Multi National Companies. Due to its expertise the

Company is able to offer competitive Designs and proposals, which keeps the

competitors at bay .This proven technology has made the company one of the

front runners in this field.

Aqua Designs success depends on its human resources. From Designs,

Proposals, Projects, Erection and commissioning to operation and

maintenance, it has proved its capability in the market which gives them a clear

edge over others in the market.

Aqua Designs is supported by its own State-of-the-Art Laboratory for testing

water, waste water, air & stack samples both for physiochemical and

microbiological parameters as per PCB norms and IS standards. We have the

facility to monitor stack emissions and ambient air quality...The facility is

certified under ISO 9001:2000. The Laboratory handles and supports all in

house requirements; specific client needs and also offers Pilot Plant studies.

Aqua Designs provides services starting from EIA to Designs to implementation

of Projects to Operation & Maintenance to Supply of Specialty Chemicals to run

the operations and finally to analyze the various products of the treatment

using its Laboratory facility.

Aqua Designs also has its own chemical manufacturing and fabrication facilities

to support its growing needs in business.

Aqua Designs was formed with the sole intention of suggesting eco friendly

solutions for Industries and Municipalities. The vision was to provide solutions

to varied sectors in par with the developed nations.

Aqua Designs not only offers the concepts and design to their customers, but

also stay with the customer and successfully operate the scheme for years.

The customer satisfaction has lead Aqua Designs to be successful in various

types of Industries ranging from Petrochemicals, Automobile, Food and

Beverages, Breweries and Distilleries, Chemicals, Electronics, Power Industries

etc.

Aqua Designs believes only in continual improvement. It keeps offering

innovative solutions to its customers. One such is the concept of Membrane Bio

Reactors technology for treating the Sewage. Aqua Designs has now set a trend

such that big IT Parks have started using MBR Technology.

Aqua Designs is leaping forward like a giant and nothing can stop it. In the near

future it aspires to be a Global leader. Aqua designs “believes in Better the Best”

and this has made everything possible.

CHAPTER 1

Impurities in Water ................................ ................................................................ ......................

CHAPTER 2

Filters ................................................................ ................................ ...........................................

CHAPTER 3

Iron Removal Filters ................................ ................................................................ .....................

CHAPTER 4

Ion Exchange ................................ ................................................................ ................................

CHAPTER 5

Softener ................................ ................................ ................................ .......................................

CHAPTER 6

Membrane System ................................ ................................................................ .......................

CHAPTER 7

Steam Boiler ................................ ................................................................ ................................

CHAPTER 8

Cooling Water Treatment................................ ................................ ................................ .............

CHAPTER 9

Pumps ................................ ................................ ................................ ..........................................

CHAPTER 10

Raw Water Treatment ................................ ................................ ................................ .................

CHAPTER 11

Industrial Waste Water Treatment ................................................................ ..............................

CHAPTER 12

Chemical Cleaning ................................ ................................................................ ........................

1

8

13

17

36

40

49

62

79

84

92

97

WATER SAMPLE TEST PROCEDURES ................................................................ ........................ 107

Phenolphthalein (P) Alkalinity Test Procedure ................................ ................................ ........ 109

Total (M) Alkalinity Test Procedures ................................................................ ....................... 110

Conductivity Test Procedure ................................ ................................ ................................... 112

pH-Electrometric Method Test Procedures ................................ ................................ ............. 113

Total hardness Test Procedures ................................ ................................ .............................. 114

Sulphite testing procedure ................................ ................................ ...................................... 115

Chloride Test Procedure ................................ ................................ ................................ .......... 116

Checking Acid Solution Strength for Cleaning ................................ ................................ .......... 117

UNITS AND MEASUREMENT CONVERSION ...................................................... 118

BASICS................................ ................................ ................................ ..................................... 119

CHAPTER 1

01

Impurities in WaterWater impurities

Impurity in water technology is a relative term. For example Hardness is not

considered as an impurity in drinking water but in industrial water treatment

it leads to scaling of equipment and hence considered as an impurity.

Common impurities in water, their effect and method of removal are as follows:

Impurities Effect Method of removal

Can clog pipelines and equipment can choke Ion exchange resin and RO membranes

Coagulation, setting and filtration

Color Indication of organic, iron etc. and can be harmful to the unit operation ahead.

Coagulation, settling filtration, followed by activated carbon filter.

Organic matter Can foul Ion exchange resins membranes and may be detrimental to process.

Coagulation, setting, filtration, followed by activated carbon filtration.

Bacteria Will depend upon the type of bacteria, can induce corrosion and also harmful to RO membrane.

Coagulation, filtration, setting and super chlorination, UV, ozonation

Iron Red water, corrosion, deposit, interferes with dyeing, bleaching etc.

Aeration, coagulation, fi ltration, fi ltration through Manganese Zeolite

pH High pH or low pH can both induce corrosion.

Ion exchange, addition of acid or alkali.

Calcium, Magnesium (Hardness)

Scaling, cruds with soap interfere with dyeing and also harmful to other process.

Ion exchangeLime Soda

TurbiditySuspended silica

02 WATER TREATMENT HAND BOOK


Sodium Unharmful when low in concentration, increase TDS, high concentration can induce corrosion.

Ion Exchange through cation H+ resin.Reverse Osmosis

Bicarbonates, Carbonates, Alkalinity, Hydroxide(Alkalinity)

Corrosion, foaming and carry over

Acid additionIon Exchange by WAC Resin Split stream by hydrogen cation resinDegassification after step 2 and 3

Sulphate Scaling if associated with Calcium, harmful in construction water.

Ion Exchange Reverse Osmosis EvaporationElectrolysis.

Chloride Corrosion Ion ExchangeReverse OsmosisEvaporationElectrodylasis.

Nitrate Normally not found in raw water. Harmful in food processes (especially baby food).

Ion ExchangeReverse Osmosis

Silica Scaling and deposition on equipment.

Ion Exchange

Carbon Dioxide Corrosion Open aeration, Degasification, and Vacuum deaeration.

Hydrogen Sulphide Corrosion Aeration, filtration through Manganese Zeolite, aeration plus chlorination.

Oxygen Corrosion DeaerationAddition of chemicals likes sodium sulphite or hydrazine.

03


Ammonia Corrosion especially of Copper and Zinc

AerationHydrogenations exchange if ammonia is present in Ionic form.

Free chlorine Corrosion By adding chemicalsActivated carbon

Definition of Terms

Total electrolyte:

Leakage:

Conductivity:

Resistivity:

Water Analysis Format

++ +Total Cations= TC= Ca + Na all as CaCO3

--Total Anions=TA=T Alkalinity + Cl + SO + NO all as CaCO4 3 3

++ ++Total Hardness=TH= Ca + Mg as CaCO3

- -- -Total Alkalinity=T.Alk= HCO + CO + OH all as CACO3 3 3

- -- - EMA= Cl + SO + NO all as CaCO4 3 3

Total Acid Ions=EMA + CO + SiO all as CaCO2 2 3

Total electrolyte=TE=TC=TA

Total dissolved solids=TDS=TE + SiO2

Electrolytes are strongly ionized compounds. TE is

numerically equal to either TC or TA (not some of both). SiO and CO being 2 2

weekly ionized are not included in total electrolyte.

Electrolyte or silica passing through the demineralizing unit due to

incomplete ion exchange.

The ability of a solution to carry current. Conductivity

measurement is used to indicate the purity of water. It is measured as micro

mhos or micro siemens/cm.

Resistivity is a measurement used for ultra pure water. Its unit is

megohm. Resistivity is reciprocal of conductivity

The following format which has been shown is for ease of designing

calculation where total cation or anion can be easily seen, matched for

correction of analysis and also for designing the Ion Exchange units. Water

testing laboratories normally do not give analysis for many ions in CaCO 3

units; example Chloride ion, given as Chloride (mg/liter) which should be

converted to CaCO ppm units, by multiplying by 1.41. Similar other ions, 3

which are not mentioned in CaCO units, should be converted to CaCO 3 3

units.


05

Substance Symbol Example Substance Symbol Example

Calcium

Magnesium

Sodium

Potassium

Ca++

Mg++

Na+

K+

125

105

100

0

Bicarbonates

Carbonates,Hydroxides

Chlorides

SulphateNitrate

HCO -3

CO --3

OH-

Cl-

SO --4

No -3

150

00

100

800

Total Cation TC 330 Total Anions TA 330

Total Hardness

Ca + Mg 230 Alkalinity HCO - + 3

CO -- + 3

OH-

150

Equivalent Mineral Acidity

Cl-So –4

No -3

180

All the above are expressed as ppm CaCO3

Iron Fe expressed in mg/liter as Fe

0.5 Silica Carbon Dioxide

SiO2

Co2

2015

Substance Unit Example

TurbidityColourTotal Dissolved SolidsSuspend SolidsAcidity/Alkalinity

NTUHazenPpmPpmpH

5 NTU5 Hazen Unit350 ppm20 ppm7.3

Conversion Factors for conversion to Calcium Carbonate (CaCO )3

Ions Symbol Ionic weight

Equivalent weight

To convert to CaCO 3

multiply by

CATIONS

Aluminum Al+++ 27.0 9.0 5.56

Ammonium Nh4 + 18.0 18.0 2.78

Barium Ba ++ 137.4 68.7 .728

Calcium Ca+ 40.1 20.0 2.49

Copper Cu++ 63.6 31.8 1.57

Hydrogen H+ 1.0 1.0 50.0

Iron (Ferrous)

Fe++ 55.85 27.8 1.80

Iron (Ferric) Fe+++ 55.85 18.6 2.69

Magnesium Mg++ 24.3 12.2 4.10

Manganese Mn++ 54.9 27.5 1.82

Potassium K+ 39.1 39.1 1.28

Sodium Na+ 23.0 23.0 2.17


07

ANIONS

Bicarbonate Hc0 -3 61.0 61.0 0.82

Bisulphate HSO -4 97.1 97.1 0.515

Bisulphite HSO -3 81.1 81.1 0.617

Carbonate Co –3 60.0 30.0 1.67

Chloride Cl- 35.5 35.5 1.41

Fluoride F- 19.0 19.0 2.63

Hydroxide OH- 17.0 17.0 2.94

Nitrate No -3 62.0 62.0 0.807

Phosphate (monovalent)

H PO -2 4 97.0 97.0 0.516

Phosphate (divalent)

HOP –4 96.0 48.0 1.04

Phosphate (trivalent)

Po —4 95.0 31.7 1.58

Sulphate So –4 96.1 48.0 1.04

Sulphide S– 32.1 16.0 3.12

Sulphite So –3 80.1 40.0 1.25

SymbolIons Ionicweight

Equivalentweight

To convertto CaCO3

multiply by

08

CHAPTER 2

WATER TREATMENT HAND BOOK

FiltersBasic Operation of Filter

Sequence of Operation

Service:

Backwash:

Rinse :

Note

The basic operation of Pressure Filter, Dual Media Filter and Activated Carbon

and iron removal filters is same.

All Units operate in down flow mode, where the water enters from the top,

percolates through the media and treated water is collected from the bottom.

u The water to be filtered enters from the top of the shell,

percolates downward through the media and is drawn off from the

bottom.

u The water enters from the bottom of the vessel, passes

through the media and is drained from the top. This is called

BACKWASH and it is done to carry the dirt accumulated on the top.

Generally back washing is done once in every 24 hrs or when the

pressure drop exceeds 8 psi. (0.5 kg/cm2).

The water enters from the top passed through the media and is drained

off from the bottom.

When activated carbon is installed in a vessel, it should be soaked for 12 to 24

hours to remove trapped air and back washed to remove fines and stratify the

bed. A necessary maintenance item, periodic back washing removes solids

trapped in the carbon bed, as well as fine carbon particles. Since the

dechlorination reaction oxidizes the carbon surface, which slowly breaks down

the carbon structure, back washing is especially important in de-chlorination

applications. Frequency is determined by the solids content of the feed water.

Tests on activated carbon dechlorination systems indicate that regular back

washing of carbon beds helps preserve the dechlorination and filtering

efficiency. By back washing regularly and expanding the carbon by at least 30

percent, fouling or binding of the carbon bed does not occur.

Raw Water

Filter Media

Collecting System

Treated Water

Filter Media

Collecting System

Raw Water

Backwash

Dirty Water

09

CAUTIONWet activated carbon removes oxygen from air. In closed or partially closed

containers and vessels, oxygen depletion may reach hazardous levels. If

workers must enter a vessel containing activated carbon, appropriate sampling

and work procedures for potentially low-oxygen spaces should be followed as

required by salutatory requirements.

Calculate area of vessel by required volumetric flow rate and the velocity as

mentioned in the following table.

Area (m2) = Volumetric Flow Rate (m3/hr)/ Velocity (m/hr) (1)

Based on above calculated area calculate diameter of the vessel by the

following formulae:½ Diameter (m) = [Area (m2)/ 0.785] (2)

Thumb rules for designing a filter

Other requirements

10

Parameters Sand FiltersDual MediaFilters

ActivatedCarbon

Velocity (m3/m2/hr) 7.5 – 12 12-20 15-20

Effective size ofMedia (mm)

0.45 - 0.6(fine sand)

0.65 - 0.76(Anthracite)

0.35 - 0.5

Uniform coefficient 1.6 max 1.85 <2(115 typical)

Density (kg/m3) 2650 1600

Parameters

Loss of head 0.03 M for clean bed to .2 to 3 M final

Length of runbetween cleaning

12 to 24 hours or when the pressure2drop across the bed reaches 0.5 Kg/cm

Method of cleaning

Back washing at rate of 36 M/Hr or24 m/hr with air scouring at 36 M/hrat 0.35 to 0.5 kg/Cm2 pressure

Amount of wash water 1 to 4 %

Time for back washing 10 to 20 minutes

Time for air scouring 2 to 5 minutes

WATER TREATMENT HAND BOOK

Important points on Filter:

Quantity of Media

uNormally, pressure sand filter is used to filter suspended solids upto

30 ppm and dual filter for 50-55 ppm and water with higher

suspended solids would require coagulation. Output quality of water

from Pressure Sand Filter is 25 to 50 microns.

uNormally, velocity for Sand velocity is taken for water treatment / 3 2residential filter are taken from 7.5 to 18 M /M /hr; for institutional

filters 20 to 30 3 2uM /M /hr. For recirculation of water like swimming pool velocities

3 2can be taken greater than 35 M /M /hr for low turbidity application

uHigher velocity will induce higher head loss through the bed and

frequency of backwash will increase.Back washing of filter should

always be carried out using clean water.

uWhenever air scouring is provided, it should be done before back

washing step.

uWhere strainers are provided at bottom, pebbles and gravels need

not be put.

3Quantity of media is Calculated in Cubic Meters (M ) and then converted to

Kgs

The depth for various media is

Sand/ Anthracite 540 mm

Crushed Gravels 100 mm

Pebbles (1/2 to1/4) 100 mm

Pebbles (1 to1/2) 100 mm

Pebbles (11/2 to 1/4) 160 mm

Volume = Area* (depth/1000)

PROBLEM CAUSE REMEDY

TurbidityBreakthrough

Change inRaw water

Analyze waterBackwash

Loss of mediaBroken LateralsHigh backwash flow

Change the laterals or rectify.Control Backwash

High Pressure Dropacross Bed

Media Dirty

Give Backwash If backwash doesnot solve problem give extendedbackwash Change Filter mediaif Step 1 & 2 does not work

Mud Ball Formation Change in RawWater Quality

Air Scour & Give extendedbackwash Check pretreatmentif any Decrease Velocity ChangeMedia if nothing of above works.

MediaHeight

11

Trouble Shooting of Filters

Filter Details2u Blower velocity is at 36 M / Hr at pressure is 0.5 Kg / cm

u minimum service Velocity is 7.5 M/ Hr

u Normal service Velocity is 9.0 M/Hr

u Maximum service Velocity is 7.5 M/ Hr

u Backwash velocity For Air scour type 24 M/Hr

u Backwash velocity For Non Air scour type 24 M/Hr

u Density of Media is 2600gm/cc

Model

Diameterin mm

Bed Area2in M

Height onstraight(HOS)inM HVT

Height onstraight(HOS) inM for Airscour type

Bed Depthin Meters

500

0.20

1500

1400

1

1.5

600

0.28

1500

1400

1

2.1 3.83

1

1400

1500

0.51

800 1000

0.79

1500

1400

1

5.93 8.48

1

1400

1500

1.13

1200 1400

1.54

1500

1400

1

11.5 15.08

1

1400

1500

2.01

1600 1800

2.54

15 00

1400

1

19.05 23.55

1

1400

1500

3.14

2000 2200

3.80

1500

1400

1

28.50

ServiceFlow (mini)M3/Hr

ServiceFlowNormal)M3/Hr

ServiceFlow (Maxi)M3/Hr

BW FlowM3/HrFor AirScouringtype

1.8 2.52 4.59 7.11 10.17

13.86

18.09

22.86

28.26

34.20

2.0 2.8 5.1 7.9 11.3 15.4 20.1 25.431.4 38.0

4.8 6.72 12.24

18.96

27.12

36.96

48.24

60.96

75.36

91.2


CHAPTER 3

13

Iron Removal Filters

Manganese Zeolite

(manganese Greensand)

Many water supplies contain quantities of iron & manganese that may be

detrimental to number of domestic and industrial use if not removed. Iron &

manganese removal is very important pretreatment step in Ion Exchange &

R.O. treatment.

uIron & manganese exists in water in the following forms

uInsoluble iron & manganese

uSoluble iron & manganese

uOrganic iron & manganese

uCombination of all three

Depending on the type of iron present in water different treatment methods are

adopted.

Manganese zeolite is a natural green

sand coated with manganese oxide

that removes Iron & manganese from

solution. The greensand is processed

by treating with manganous sulfate

and then with potassium

permanganate. This results in the

higher Oxides of manganese in and

on the green sand granules. The

resultant greensand is a manganese

zeolite with following characteristics.

S.No Type of impurity Removal method

1Insoluble iron& manganese

No oxidation required.Simple Coagulation insolid contact Unitfollowed by filtration

Soluble iron & manganese2Oxidation by air, chlorine& filtration Lime / Limesoda softening Ion Exchange

3 Organic bound iron Coagulation by alum, settling

4 Combination of three above Manganese zeolite

Parameter

Colour

Density

Effective size

Uniformity coefficient

Mesh size

Attrition loss perannum %

Bed Depth(minimum)

Freeboard

Service flow rate

Backwash flow rate3 220—25 M /hr/M

3 25 –12 M /hr/M

50% of bed depth

700 mm ofgreensand and300mm of anthracite

2—4 %

16—60

1.6

0.30- 0.35 mm

31360Kg/M

Black


Removal process

Batch process (intermediate Regeneration)

Continuous KMnO feed system:4

Reaction times

Manganese zeolite process is used in conjunction with above process when the

concentration is more or as a standalone process if the concentrations of Fe &

Mn are low.

There are two methods, which is normally employed for removal of Fe & Mn by

Manganese zeolite.

uBatch process (intermediate Regeneration)

uContinuous KMnO feed system4

The regenerative batch process uses Manganese zeolite both as oxidizing

source and also as filter media. After the zeolite is saturated with metal ions, it

is regenerated with KMnO (potassium per manganate).4

This process has its limitation. Batch process is employed when the

concentration of iron & manganese is small (i.e. < 2 PPM) and also if the

flowrate required is not very high. (Flow rate limited to about 5-6M/Hr)

The capacity of manganese zeolite is (0.09lbs iron or manganese / Cu Ft)

And the regeneration is done by 0.5 % KMnO . The amount of KMnO required is 4 43 2about (0.18lbs of KMnO / Cu Ft of media). Backwashing at 20-25 M /Hr /M is 4

done once in 24 hours or when the pressure drop across the bed reaches to 7-8

psi, whichever is earlier.

Batch process is still used but is being replaced quite rapidly by continuous feed

system. In this process KMnO solution is added before the pressure filter that 4

contains dual media and manganese zeolite. The Anthracite on the top of

Manganese zeolite acts as a filter and removes the iron & manganese oxidized

by permanganate. MnO oxidizes the residual ions that are not oxidized by 2

permanganate. MnO also removes excess KMnO . When the bed gets 2 4

saturated with metal oxides, it is backwashed to remove all particulate

matters.

Permanganate is fed as 1-2 % solution directly to the inlet line. Contact time for

oxidation is about 20—60 seconds; hence it is fed 20 '(50-60 mm) upstream

from the zeolite bed Alkali is added to low pH water for optimum removal but

utmost care should be taken during alkali addition due to precipitation problem

KMnO is used either in conjunction with chlorine or alone. KMnO dosage 4 4

differs depending on whether it is used alone or with chlorine.

15

Dosage of KMnO4With chlorine

Without Chlorine

Birm

1 mg/liter ofCl / 1ppm of Fe2

KMnO mg/liter = (0.2mg/literKMnO for 1ppm of Fe) + (2 mg/liter of4 4

KMnO for 1ppm Of Mn) + (5mg/liter of KMnO for1ppm of H S)4 4 2

KMnO mg/liter = (1.mg/literKMnO for 1ppm of Fe) + (2 mg/liter of KMnO for 4 4 4

1ppm Of Mn) + (5mg/liter of KMnO4 for 1ppm ofH S)2

Birm is another type of manganese dioxide. It is a silicon dioxide core that has

been coated with manganese dioxide. This makes Birm much lighter than its ore

counterpart, less than 400gms/liter. The benefit of this type of product is that it

can be backwashed at a flowrate of 0.8Kg. / Liter. Birm does require dissolved

oxygen in the water for the precipitation of iron, where the manganese dioxide ore

does not. Birm relies on its ability to act as a catalyst between iron and oxygen. It

has a limited amount of MnO available, so it does not have the ability to supply 2

oxygen through a redox reaction. The oxygen content should be, at least,

equivalent to 15% of the total iron content. If the oxygen content is less than

15%, aeration is required. Birm is recommended on levels of iron less than 10

ppm. It can be utilized on higher concentrations, but the frequency of

regeneration (backwashing) becomes excessive. Birm has a capacity of

approximately 900 -1100 grams/Cu meter. It can treat up to 3 cubic meters of

water containing 10 ppm Fe as CaCO3. Birm should not be used on waters that

have oil or hydrogen sulfide, and the organic matter should not exceed 5 ppm. As

with any product, consult the manufacturer for operational guidelines. (Sybron

Chemicals).


CHAPTER 4

17

Ion Exchange

Ion Exchange Load Calculation

Let us take the following examplesFeed water analysis as ppm CaCO3

Free CO - 15, Silica – 52

Ion Exchange load w.r.t different unit operation

Cations

Calcium

Magnesium

Sodium

Potassium

Iron

Total

Unit as ppm CaCO3

210

40

120

5

0

375

Anions

Bicarbonate

Chloride

Sulphate

Nitrate

Total

200

70

85

20

375

Unit Operation

Softening

Dealkaization

Strongly acidCation(TC)

Weakly Basic Anion

Strongly acid Cationafter dealkalization

Strongly Basic Anionafter WBA

Strongly Basic Anion

Strongly Basic Anionafter Degassing

Strongly basic Anionafter degassingand WBA

Total Anion – (T.Alk+ EMA ) +SiO2

(Cl+SO +NO +SiO ) -4 3 2

(Alkalinity + CO )2

Total Anions

Total Anions – EMA

Total Cations –Carbonate Hardness

EMA (SO +Cl+NO )4 3

Total Cations(Ca+Mg+Na+K)

HCO3

Total Hardness(Ca +Mg)

Ion Exchange LoadConcentration(as ppm CaCO )3

250

200

375

175

175

225

375

185 (assuming 5 ppmleakage of CO )2

10 ppm (assuming 5ppm leakage )


Ion Exchange load w.r.t different unit operation

uMatch total cations to total cations to total Anions. They should be equal.

(Error of +_ 5% can be considered)

uRefer to the table for calculating the Resin Quantity. The Ion Exchange

load can be taken as mentioned in the table.

Sizing consideration for Ion Exchange System

Approximate regenerate Level and operating Capacity

Design parameters

Ion Exchange Resin Quantity (liters) = [Flow (m3/hr)* IonExchange load(ppm)* Time] / Ex.capacity of Resin (gms/liter)

Parameters

Velocity*

Bed Depth

Free Board *

Type ofInternal

Cation

15-20 M/hr

900-2000 mm

60-100%

Hub/radialStrain on plate


60-100%

900-2000mm

15-20 M/hr

Anion Mixed bed

30-44 M/hr

1000-2000 mm

60-100%


Degassifier

50-70 M/hr

2400-3600mm

Rasching ringsPall rings

Parameters

Regenerantflowrate

Total rinse

DisplacementRinse

Backwashvelocity

Fast Rinse

Unit

3 3M /Hr/M

BV

BV

3 2M /Hr/M

3 3M /Hr/M 16

6

1.5

5

4

WAC SAC

4.8

5

1.5

9

16

WBA

2.1

5

1.5

6

8

SBA Type 1

4

5

1.5

6

8

SBA Type 2

4

5

1.5

6

8

Parameters

Regeneration levelgm/L Cation

Regeneration levelgm/L ANION

EC for CATIONgm CaCO3/L

EC for ANIONgm CaCO3/L

WAC

110

110

SAC

80

54

WBA

55

50

SBA Type 1

80

35

SBA Type 2

80

25

MB

80

80

40

20

19

4 % NaOH contains 41.75 gms NaOH per liter

50 % NaOH contains 763 gms NaOH per liter

99% NaOH contains 803 gms NaOH per liter

4 % HCl contains 40.72 gms HCl per liter

32 % HCl contains 479.2 gms HCl per liter

Following different schemes of DM / Ion exchange systems are possible

depending upon the application and the outlet water quality required

Detailed parameters on the quality of water required in various

industries is given in Chapter 9.

SA – Strong Acid Resin (H+)

SA*- Strong Acid Resin (Na+)

WB – Weak Base Anion Resin

D – Degasser

SB – Strong Base Anion Resin

WC – Weak Acid Cation Resin

MB – Mixed bed (mixture of Strong Acid Cation Resin (H+) and

strong base anion resin (OH-)

Ion exchange systems

Note:

u

u

u

u

u

u

u

u

u


# Type Of DM/ Ion Exchange Systems

Application Outlet Water Quality

1 Removal of silica, removal of CO2 is not required

Conductivity < 50 micro mhos

2 Where CO2 and silica removal is required, low alkalinity water

Conductivity < 30 micro mhos,silica < 0.5 ppm

3 Where CO2 content is high, i.e. high alkalinity water


4 EMA and alkalinity high in raw water


SA WB

SA SB

SA D SB

SA D WB SB

Service

Regeneration

Raw Water is passed through ion exchange unit till the required quality of water is

being produced. This is known as service cycle. When the resin stops producing

desired quality water, the Resin is said to be exhausted and will have to be

regenerated. Service flow can be down flow (top to bottom) or upflow (bottom to

top).

The restoration of resin back to its original form is called Regeneration.

Depending upon the resin, regeneration is usually done by using acid, alkali or

common salt. These chemicals are known as regenerant.

Sequence of Regeneration for down flow unit is :-

1. Backwash

2. Chemical injection

3. Displacement (slow rinse)

4. Fast rinse or Final rinse

In the up flow unit upward wash is only done for a minute or so.

5

High EMA and high alkalinity in raw water Hardness > =1 Alkalinity

Conductivity < 30 micro mhos, silica < 0.5 ppm

6

Softening, where only hardness to be removed

Hardness less than 5 ppm as CaCO3

7

Dealkalization when only temporary hardness is present

10 % of the influent alkalinity TDS reduction upto alkalinity removal

8

Dealkalization alkalinity with permanent hardness

10 % of the influent alkalinity TDS reduction alkalinity removal

9

Low conductivity water required MB is installed after SBA

Conductivity < 1 micro mhos, silica < 0.002 ppm

10

When ultrapure water is required for pharmaceutical or electronic industries

Conductivity < 0.02 micro mhos, resistivity 14-18 mega ohms silica < 0.002 ppm

WC SA D WB SB

SA*

WC D

SA* SA D

MB1

MB1 MB2

21

Operation of Ion Exchange unit

Backwash Chemical Injection

Downflow Coflow Regeneration

Regeneration Tank 1

2

3

4

5

4

5

Slow Rinse

3

Fast Rinse

5

1

1 Raw water 2 Backwash outlet 3 Chemical Injection inlet 4 Power water for ejector 5 Drain for chemical and

final rinse


Upflow Countercurrent Regeneration

Power Water

Regenerant Flow

Power Water Drain Drain

Raw water or feed water Final Rinse

1

Raw water or feed water

Final Rinse

1

2

3 3

4

5 5

6

6

2

Chemical Injection Slow Rinse

Final Rinse

23

Typical Regeneration Efficiencies for different type of resins

Typical Regeneration level ranges for single resin column

Resin Type /Configuration

Regeneration SystemTypical RegenerationEfficiencies (%)

Strong Acid Cation

Co-current HClCounter-current HClCo-current H SO2 4

Counter-current H SO2 4

200-250120-150250-300150-200

Weak Acid Cation

Weak Acid Cation+ Strong Acid Cation

Strong Base AnionType 1

Strong Base AnionType 2

Weak Base Anion

Co-current Counter current

Co-currentCounter-current

120-150

150-200125-140

250-300140-220

105-115

105-115

Regenerant SystemRegenerant Levelg/liter

Typical operatingcapacity mg/liter

Co-current Regeneration

Hcl

H SO2 4

NaOH

Counter current Regeneration

Hcl

H SO2 4

NaOH

60 - 80

60 - 80

60 - 80

60 - 80

60 - 80

60 - 80

40 – 60

45 – 65

30 – 40

50 – 70

55 – 75

55 – 75


Design Guide lines for Operating and Designing Resin

System

Note:-

Degasser

These are only for help. Actual data

should be obtained from the resin manufacturer.

Most resins have similar data.

The forced-draft degasifier blows an air stream

countercurrent to the water flow.

The undesirable gas escapes through the vent

on the top of the aerator. A disadvantage to this

process is that the water is saturated with

oxygen after aeration.

Parameter Guideline

Swelling

Strong Acid Cation Na → H

Weak Acid Cation H → Ca

Strong Base Anion Cl → OH

Weak Base Anion Free base → Cl

5-8 %

15-20 %

15-25 %

15-25 %

Bed Depth Minimum

Cocurrent single Resin

Counter current Single Resin

Backwash Flow Rate

SAC Resin

WAC Resin

SBA Resin

WBA Resin

Flow Rates

Service/Fast Rinse

Co-current Regeneration

Counter- current Regeneration

Total Rinse Requirements

SAC Resin

WAC Resin

SBA Resin

5-60M/hr

1-10 M/hr

5-20M/hr

2-6 Bed Volumes

3-6 Bed Volume

3-6 Bed Volume

2-4 Bed Volume

10-25 M/hr

10-20 m/hr

5-15 M/hr

3-10M/Hr

750 mm

1000 mm

25

Packing Data

Ceramic Raschig ring – There are 145 pieces of raschig ring per liter.

The ring size is 38 mm X 38 mm and weighs about 6 kg.

RingSizemm

Numberof ringsin 1 M3 ofrandompacking

FreeVolume

3 3M /M

PackingSurfaceArea

2 3M /M

Hydraulicradius ofpassage

EquivalentDiameterofPackingD=4r

Mass of3 1 M of

rings Kg

25 X 25X 3 53200 0.74 204 0.00363 0.01452 532

35 X 35X 4

20200 0.74 140 0.00555 0.02220 505

50 X 50X 4

6000 0.785 87.5 0.00900 5300.0360


Degassifier Height and Raschig rings Heights

3 2Degassifier Flow & Area (velocity taken is 60 m /h/m )

Inlet CO2

ppm

Outlet CO2

ppm

DegassifierHeights Meters

Raschig ringsHeights Meters

500

200

150

100

50

35

852

852

852

852

852

852

4.264.905.49

3.654.264.90

3.653.654.26

3.043.654.26

2.433.043.65

2.433.043.65

2.903.203.96

2.292.593.35

2.002.433.04

1.672.132.89

1.211.672.43

1.211.372.13

Degassifier3Flow M /Hour

Cross Sectional 2Area in M

Internal DiameterOf degasser in mm

Required air flow3rate in M /Hour

5

7.5

10

12.5

15

17.5

20

22.5

25

27.5

30

35

40

45

50

0.083

0.125

0.167

0.208

0.250

0.291

0.333

0.375

0.416

0.458

0.500

0.583

0.667

0.750

0.833

325

400

460

512

560

600

650

691

728

764

800

862

925

977

1030

75

112.5

150

187.5

225

262.5

300

337.5

375

412.5

450

525

600

675

750

27

Failure to produce specified quality of water

The failure to produce specified quality treated water will depend upon the specific

Ion Exchange unit. The causes for deteriorating water quality from each Ion

Exchanged bed are given in the tabulated form. Quality of water can also

deteriorate due to resin fouling. Various types of foulants which can contaminate

the Ion Exchange resin.

Defects Causes Remedies

1.Change inRaw waterComposition

ServicecycleExceedingSpecification

Faultyregeneration

Loss of ionexchangeResin

Increase in TDS

% change in Na/TCor Alk/TA

Flow meter not workingor out of calibration

Conductivity meter notworking or workinginaccurately

Check, rectify or replace

Check power to conductivitymeter Calibrate meterCell dirty, Replanitinize.

Insufficient chemicalWeak regenerant (lessChemical or too muchdilution water) Poordistribution of regenerantEjector not functioningor Chemical going veryslowly

Check and follow properregeneration Check and rectify.Faulty internal distributor orbroken strainer on top inpack bed system.Insufficientpower water flow at requiredpressure to ejector Checkrubber lining above ejector,check for chokage in ejector,air lock in vessel or if everything is ok change faultyejector.

Obtain new water analysis andSet water meter to new capacity.

Calculate new capacity tothe increased load.

High Backwash inDownflow systemChemical attack byOxidizing agent likechlorine Excessivehigh pressure flowrate Broken Strainersin Upflow system/Upset supporting bedor damaged underdrain.Air sucking throughejector in Pack bedsystem

Reduce Backwash flow rate.Dechlorinate. Check performanceof ACF Unit. If no ACF unitis there, use reducing agent(like sodium sulphite).Check & Rectify. Do notexceed specification Check forresin in effluent or resin or inresin trap.. Change strainerRectify bottom distributor.This happens sometime duringinjection. Take care


Fouling ofIon Exchangematerial

Channelingor shortCircuiting

High Pressuredrop acrossresin bed

Pump notdelivering

Excessive turbidity in rawwater Excessive Resin finesResin degraded Excessivehigh flow rates or operatingpressure CrossContamination of Resinin Mix bed

Oxidized iron or manganesein raw water(Normallyeffects cation)Excessiveturbidity in raw

See fouling of resins Shortcircuiting for possiblecause Resin Dirty

See in Fouling of ResinUse Clean regenerantchemical, Use DM waterfor dilution

See fouling of resinsShort circuiting for possiblecause Resin Dirty

Obstructions in pipelinespump Vesse ls e tc .,Damaged Rubber liningValves not properly openedStrainer clogged due to dirtand resin fines

1 Air, chlorine or otheroxidizing agent can oxidizeiron and manganesePretreatment with any ofthe above Cleaning by Hclfor cation or by Brinefor Anion

Restrictedflow

1. See pump troubleshooting chart for cause

1. See Pump TroubleShooting for solution

Inspect pipeline clean andremove obstruction. Replacepipe with good rubberlining or rectify Open valvefully (except control valve)Clean strainers (For removalof resin)

ExcessiveRinsing

Organic Fouling of AnionIon Exchange Resin

Brine Treatment. Forextreme Condition Sodiumhypochlorite dosing, Shouldbe done under supervision

29

ImproperRegeneration

Increased Concen--tration of sulphuricacid in cationregeneration Regen--erant dosage too lowor too weak Inadequatebackwash Damageunderdrain or internaldistributor

See method ofRegeneration Usecorrect method ofregeneration Giveextended backwash(30 minutes or more)to clean the resin bed.Replace or Rectify

Low serviceflow rate

Very slow service rateincreases leakage fromunit (will reflect onanion unit )

Have storage systemand operate at higherflow or use recyclesystem.Minimum linearvelocity should not fall

3 2below 2 M /Hr /M

Valve leakage Defective Valve

Replace Note :- ValveLeakage can givewrong reading ininstruments & wateranalysis

Nominal agingof Resin

Cation Life – 5 to10 yearsAnion Resin – 3 to5 years

1 Replace old resin

Attrition Loss 3 to 5 % perannum

1 Top up resin lost

Inadequatemixing of Resin.Applies toMixed Bed only

Improper Draindown Air Mixingtime too shortNot Enough air

Water should not betotally drained afterrinsing. The level ofwater should alwaysbe above resin bedAir mixing should bedone for minimum often minutes Check airrequirement & blowercapacity

Problem ofmiddle collectorin mixed bed

Can be caused byleakage of cationResin Improperdilution ofregenerantBroken collector

Add Cation Resin tomake up Loss or addinert resin CheckChange


Indian standard grade for the commonly used

regeneration chemicals

Hydrochloric Acid -- IS 265

Sulphuric Acid -- IS 266

Sodium Hydroxide -- IS 252 (Tech/Rayon Grade 46% lye)

IS 1021 (Pure Grade - Flakes)

Sodium Carbonate -- IS 251 (Tech Grade)

Sodium Sulphite -- IS 247 (Tech Grade)

Sodium chloride -- IS 297 (Tech Grade)

Alum -- IS 260 (Tech Grade)

Recommended impurity level for Hydrochloric Acid

Concentration and density of HCl solution

Impurity Maximum level

Fe 0.01%

Other metals(total) 10 ppm

Organic Matter 0.01 %

H SO as SO32 4 0.4 %

Oxidants(HNO ,Cl )3 25 ppm

Suspended matter as turbidity 0

Inhibitors none

Percent Sp.Gravity Grams/Liter1

2

46

8

10

12

14

16

18

20

22

24

26

28

30

32

34

36

1.0032 10.03 1.0082 20.16

1.0181 40.721.0279 61.67

1.0376 83.01

1.0474 104.7

1.0574 126.9

1.0675 149.5

1.0776 172.4

1.0878 195.8

1.0980 219.6

1.1083 243.8

1.1187 268.5

1.1290 293.5

1.1392 319.5

1.1493 344.8

1.1593 371.0

1.1691 397.5

1.1789 424.4

31

Recommended impurity level for Sodium Hydroxide

Concentration and density of NaOH solution

Recommended impurity level for Sodium Chloride

Concentration and density of NaCl solution


NaClNaClO3

Na CO2 3

FeHeavy metals(Total)SiO2

Na SO2 4 0.2 %50 ppm

5 ppm10 ppm0.75%30 ppm0.6%

Percent Sp.Gravity Grams/Liter123456789101620263036404650

1.00951.02071.03181.04281.05381.06481.07581.08691.09791.10891.17511.21911.28481.32791.39001.43001.48731.5253

10.1020.4130.9541.7152.6963.8975.3186.9598.81110.9188.0243.8334.0398.4500.4572.0684.2762.7


Sulphate 0.6%

Magnesium and Calcium 30 ppm

Specific Gravity Percent Grams/Liter1.0051.0121.0271.0411.0561.0711.0861.1011.1161.132 1.1481.1641.1801.197 26

2422201816 14121086421

311.2283.2256.0229.5203.7178.5154.1130.2107.184.4762.4741.0720.2510.05


Concentration and density of H SO solution2 4

Common conversion factors for ion exchange calculation

Flow Rate

Other Parameters

Percent Sp.Gravity Grams/Liter

1

1.5

2

3

4

5

10

15

20

30

40

50

98

100

1.005

1.008

1.012

1.018

1.025

1.032

1.066

1.109

1.140

1.219

1.303

1.395

1.906

1.944

10.05

15.12

20.24

30.54

41.00

51.60

106

166.1

228

365.7

521.2

1799

1831

697.5

To convert from To Multiply by

Kgr/ft3 as CaCO3 g CaO/Litre 1.28

Kgr/ft3 as CaCO3 g CaCO3/Litre 2.29

Kgr/ft3 as CaCO3 eq/litre 0.0458

g CaCO3/litre Kgr/ft3 (as CaCO3) 0.436

g CaO/litre Kgr/ft3 (as CaCO3) 0.780

To convert from3U.S. gpm/ft2U.S. gpm/ft

U.S. gpm

To

BV/hr

M/hr

M3/hr3U.S. gpm/ft

Multiply by

8.02

2.45

0.227

7.446BV/min

33

Parameter To convert from To Multiply by

Pressure drop PSI/ft MH O/M of Resin2 2.30

Regenerantconcentration

Ibs/ft3 g/litre 16.0

PSI/ft 2G/cm /M 230

Density Ibs/ft3 g/litre 16.0

Rinse requirement U.S. gal/ft3 BV 0.134

1 gallon of water weighs 8.33 pounds

1 Cubic foot of water weighs 62.4 pounds

1 cubic centimeter of water weighs 1 gram

1 liter of water weighs 1 kilogram

1 cubic meter of water weighs 1 metric ton

1 metric ton = 2240 lb.

Water analysis conversion factor

Anions

SubstanceAtomic /molecularweight

EquivalentWeight To CaCO3

Calcium

Magnesium

Sodium

Potassium

Iron (ferrous)

Iron (ferric)

Aluminium

Barium

Strontium

40.0

24.3

23.0

39.1

55.8

55.8

27.0

137.4

87.6

20

12.25

23.0

39.1

27.9

18.6

9.0

68.7

43.8

43.8

4.12

2.17

1.28

1.79

2.69

5.56

0.73

1.14

SubstanceAtomic /molecular weight

EquivalentWeight

To CaCO3

Bicarbonate

Carbonate

Chloride

Sulphate

Nitrate

Phosphate

Sulphide

Co2

Silica

61.0

60.0

35.5

95.1

62.0

95.0

32.1

44.0

60.1

61.0

60.0

35.5

48.0

62.0

31.7

16.0

44

60.1

0.82

0.83

1.41

1.04

0.81

1.58

3.13

1.14

0.83


Set-Points for Brine regeneration to remove organic fouling

Parameter Units

FirstCausticRegeneration

SaltRegeneration

SubsequentCausticRegeneration

Quantity ofRegenerant

Gm/liter 32 112 32

RegenerantStrength

% 3.5 15 5

640745.6912Grams/liter

Quantity ofdiluteRegenerant

Volume ofRegenerant

Liter/literof resin

0.9246 0.6968 0.6432

1.921.62.83 3M /Hr/Mof resin

Flow Rate ofRegenerant

202520MinutesTime forRegeneration

Flow Rate ofRinse Water

3 3M /Hr/Mof resin

1.6 4 1.6

Time forRinsing

Minutes 10 15 10

35

CHAPTER 5


Softener(Basic ion exchange process)

STEP 1 –

Note:

STEP 2 –

Important points on Softener

Thumb rules of designing a Softener

To select resin quantity (liters) for a particular hardness (ppm) for a

particular output (m3) per regeneration per hour based on regeneration level

160 gm/liter, ion exchange capacity = 55, TDS limit = 1500 ppm, refer TABLE 1

Resin Quantity = Load (ppm as CaCO ) * Flow * time3

Ex. Capacity

For example

Load = Hardness = 100 ppm as CaCO3

Flow = 5M3 /hr

Time = (Service cycle) = 12 hrs.

Ex. Capacity = 60 gm as CaCO3

Resin Quantity = 100 * 5 * 12

60

Na / TC and TDS and correction factor should be applied.

Actual Resin Quantity = 60 * correction due Na/TC factor * Correction due to TH

factor = 60 * 0.96 * 0.97 = 56 (approximately)

Hence Ion Exchange load for designing a softener is 56. These calculations are

based on Ion Exchange resin and will vary from manufacturer to manufacturer

resin.

To select vessel model for a selected resin quantity, approx. flow 3 2 3 2rates based on linear velocity- min (8 M /M /hr) and max (25 M /M /hr), and

free board 5-100 %, refer TABLE 2

Regeneration level, hardness leakage desired and correction factors can be

found from resin supplier's graph.

Suggested vessel selection chart for softeners

TABLE 1: STEP 1 – To select resin quantity ( liters) for a particular hardness(ppm) for a particular output(m3) per regeneration per hour based onregeneration level 160 gm/liter, ion exchange capacity = 55, TDSlimit=1500 ppm)

Outputb/wRegen--eration(OBR M3)

Resin Qtyin liters for various hardness

5

10

13.5

27.0

22.5

45.0

Hardness= 150ppm

Hardness= 250ppm

Hardness= 350ppm

Hardness= 500ppm

Hardness= 650ppm

Hardness= 800ppm

Hardness= 1000ppm

31.5 45.0 58.5 72.0 90.0

180.0144.0117.090.063.0

= 100 liters

37

152025

3530

45

55

75

65

40

50

85

95

60

70

80

100

90

39.052.566.079.591.5105.0118.5132.0144.0157.2171.0184.5 198.0210.0

223.0237.0250.5262.5

65.087.5110.0132.5152.5175.0197.5220.0240.0262.0285.0307.5330.0350.0

372.0395.0417.5437.5

91.0122.5154.0111.3213.5245.0276.5308.0336.0366.8399.0430.5462.0490.0

521.0553.0584.5612.5

135180225270315360405450495

540585630675720

765810855900

175.5234.0292.5351.0409.5468.0526.5585.0643.5

702.0760.5

877.5936.0

994.51053.01111.51170.5

819.0

216.0288.0360.0432.0504.0576.0648.0720.0792.0864.0936.01008.01080.01152.0

1224.01296.01368.01440.0

270.0360.0450.0540.0630.0720.0810.0900.0990.01080.01170.01260.0135001440.0

1530.01620.01710.01800.0

TABLE 2: STEP 2 – To select vessel model for a selected resin

quantity, approx. flow rates based on linear velocity min=8

m3/m2/hr and max=25 m3/m2/hr, and free board 5-30 %

ResinQty(liters)

Approx.Flow Rate Min-maxLPH

FreeBoard(%)

VesselModelCapacity(liters)

13.5

22.5

27.0

160-500

160-500

160-500

8 %

20 %

33 %

6 x 32(14.6 liters)

6 x 35(16. l liters)

6 x 35(18.0)

7 x 40(24.5 ltrs)

212-663 9 %

212-663 20 %7 x 44(27.1 ltrs)

276-865 16 %8x40(31.4 ltrs)

276-865 29 %8x44(34.9 ltrs)

350-1,093 26 %9x35(33.9 ltrs)

60415-1,295 6 %

10x54(63.8 ltrs)

584-1,825 30 %12x48(78.5 ltrs)

70584-1,825 12 %

12x48(78.5 ltrs)

704-2,200 50 %13x54(106 ltrs)

80 704-2,200 33 %13x54(106 ltrs)

90 704-2,200 18 %13x54(106 ltrs)

100 704-2,200 6 % 13x54(106 ltrs)

822-2,570 50 % 14x65(150 ltrs)

ResinQty(liters)

Approx.FlowRateMin-maxLPH

FreeBoard(%)

VesselModelCapacity(liters)


31.5 350-1,093 8 %9x35(33.9 ltrs)

415-1,295 27 %10x35(40.1 ltrs)

415-1,295 48 %10x40(46.5 ltrs)

39 415-1,295 3 %10x35(40.1 ltrs)

415-1,295 19 %10x40(46.5 ltrs)

415-1,295 33 %10x44(51.7 ltrs)

45 415-1,295 3 %10x40(46.5 ltrs)

415-1,295 15 %10x44(51.7 ltrs)

415-1,295 22 %10x47(55.0 ltrs)

415-1,295 42 % 10x54(63.8 ltrs)

>100<140

>140<180

>180<240

>240<300

>300<430

>430<650

>650<950

>950<1250

> 1250<1700

822-2,570

1,000-3,140

1,400-4,370

1,900-6,000

2,300-7,300

3,700-11,600

5,400-16,800

9,400-29,448

16,000-50,240

~

~

~

~

~

~

~

~

~

14x65(150 ltrs)

16x65(182 ltrs)

18x65(250 ltrs)

21x62(310 ltrs)

24x62(450 ltrs)

30x72(710 ltr)

36x72(1020 ltr)

48x72(1840 ltr)

63x64(2500 ltr)

39

CHAPTER 6


Membrane SystemConventional and membrane process solutions to common water problems

Pretreatment water quality for membrane processes

Suspended matter

Turbidity NTU

SDI

Ionic content

Iron, mg/L(ferrous)

Manganesemg/L

Silica mg/L(w/o)in concentrate

Chemical Feed

ResidualChlorine ppm

Scale inhibitormg/l inconcentrate

Acidification pH

Maximum feedotemperature C

Maximum LSIwith Scaleinhibitor

Spiral CA Spiral PA EDR

<1.0

<4.0

<2.0

<0.5

<160

<1.0

12-18

5.5-6.0

40

Note

<1.0

<4.0

<2.0

<0.5

<160

ND

12-18

4-10

45

+2.45-+2.8

<5

<15

<0.1

<0.1

<saturationin feed

ND

As required

As required

43

2.1

Turbidity Suspended solidsBiological contamination

Coagulation/flocculationMedia filtrationDisinfection

Microfiltration

Constituent ofconcern

Conventionalprocess

Membraneprocess

Color Odor Volatile organics

Activated carbonCl, + media filtrationaeration

Ultrafiltration

HardnessSulfatesManganeseIronHeavy metals

Lime softeningion exchangeOxidation, filtrationIon exchangeCoagulation/flocculation

Nanofiltration

Total dissolvedsolids Nitrate

DistillationIon exchange

Reverse osmosisElectrodialysis

41

Note:- Type of Membrane PA = polyamide, CA = Cellulose Acetate and EDR = Electrodialysis Reversal CA membranes work in Narrow pH range 5.5-6.0 and require acidification to prevent hydrolysis. Therefore, the Langelier Saturation Index of the existing concentrate tends to be low enough and scale inhibitor for calcium carbonate scale is not required.

Troubleshooting Guide

CHECK VERIFY EFFECT

Pressure dropbetweenfeed and reject.

Has not increasedby more than 15%.

More than 15% indicatesfouling of feed path andmembrane sur face .Requires cleaning

Pressure dropbetween feedand permeate

Has not increased bymore than 15%.

More indicates foulingof membrane surface.Requires cleaning.

Permeateconductivity

Has not increasedby more than 15%.

More indicates foulingof membrane surface.Requires cleaning.

Acid dosing Is withinrecommendedvalue.

More can cause membranedamage or sulfate scaling.Less can cause carbonatescaling or metal oxidefouling.

InstrumentsReading

Verify by calibrationand carry out of labcheck of the parameters theinstrument ismonitoring.

Wrong operation Falsesense of security thateverything is OK.

pH metercalibration& control

The pH controllergenerally controls aciddosing pumps. The pHcontroller should becalibrated periodicallyand tripping of dosingpump to the set pointshould be checked.

More or less acid dosingthan required.Effectof this has already beenmentioned earlier.


Foulants & Their Impact

FoulantsPossible Location

Pressure drop

PermeateFlow

Salt Passage

Metal Oxide

ColloidalFouling

Scaling

BiologicalFouling

OrganicFouling

2Oxidant(Cl )

Abrasion(carbon,Silt)

O-ring orglue leaks

Recovery toohigh

St1 Stage

St1 Stage

Last Stage

Any Stage

All Stages

St1 Stage(Most Severe)

st1 Stage

Random

All stages

Normal toincreased

Normal toincreased

Increased

Normal toincreased

Normal

Normal toincreased

Decreased

Normal todecreased

Decreased

Decreased

Decreased

Decreased

Decreased

Decreased

Increased

Increased

Normal toincreased

Normal toDecreased

Normal toincreased

Normal toincreased

Increased

Normal toincreased

Decreased toincrease

Increased

Increased

Increased

Increased

O ring

Probing with ¼ 'plastictube and by measuringhow far it has beeninserted.

Failure can lead to increasesalt passage, increasepermeate flow. Decreasepressure drop.

Brine valve Should not be closed fully.

If fully closed, 100%recovery will result andcause membrane damagedue to precipitation ofinorganic salt.

43

Cleaning of RO Membrane

Symptom of fouling

Indications that the system requires cleaning

Types of Foulants

Types of Membrane Cleaning Solutions

RO membranes get fouled with suspended solids contained in the feedwater or

with sparingly soluble salts, as minerals are concentrated. Pretreatment is

done to reduce the fouling potential of feedwater but inspite of that fouling

occurs over a period of time.

1. Decrease in Product flow.

2. Increase in salt passage.

3. Increase in differential pressure

4. Deterioration in permeate quality

5. Increase in the differential pressure across the RO stage.

1. A 10 to 15 % decline in normalized Product flow.

2. A 10 % increase in salt passage.

3. 15 % increase in differential pressure.

1. Inorganic fouling – Like Calcium Scales or Metal Oxides

2. Organic Fouling – Example Humic Acid

3. Particulate Deposition or colloidal fouling –Particulate matter

4. Biofouling

The number of formulation for cleaning solutions is varied but we are

mentioning only the common type of cleaners used for most common fouling

problems.

Foulant

Inorganic Salts

Metal Oxides (Iron)

Inorganic Colloids(silt)

Biofilms

Organics

Cleaning Chemicals

0.2 % HCl0.5 % Phosphoric Acid2.0 % Citric Acid

0.5 % Phosphoric Acid1.0 % Sodium Hydrosulphite

o0.1%Sodium Hydroxide,30 C0.025 % Sodium Dodecylsulphate

o0.1 % NaOH, 30 Co0.1 % NaOH, 30 C

1 % Sodium salt of ETDA and0.1 % NaOH

0.025 % Sodium Dodecylsulphateo0.1 % NaOH 30 C

0.1% sodium triphosphate 1.0 %Sodium salt of ETDA

Remarks


Flux

Number of Elements:

Osmotic pressure

Selection of Feed pumps

Scaling of Membrane Process

The throughput of a pressure-driven membrane filtration system expressed as

flow per unit of membrane area (e.g., gallons per square foot per day (gfd) or

liters per hour per square meter (Lmh).

If the water quality is better, higher flux that can be used without causing

excessive fouling.

When the flux has been set and the element area (a

function of the specific membrane selected) is known, the required number of

elements can be calculated:2Number of elements =Permeate Flow (LPD)/(LMH)*Active Membrane area (M )

Recovery Rate = (Permeate Flow rate / Feed flow rate)*100

Osmotic pressure can be defined as the pressure and potential energy

difference that exists between two solutions on either side of a semipermeable

membrane.

A rule of thumb for osmosis is that 1 psi of osmotic pressure is caused by every

100 ppm (mg/l) difference in total dissolved solids concentration (TDS).

Feed pumps should be selected on the basis of high efficiency. Variable

frequency drives now are commonplace in brackish water RO Plants. These

frequency drives should also be selected on similar basis. Typical feed pump

energy requirements for brackish water RO plants range from 0.5 to 2 kWh/M3

and for seawater it is less than 3 kWh/M3 with the use of energy recovery

device.

Scaling is predicted by Langelier Saturation Index (LSI) or at a higher ionic

strength the Stiff & Davis Index predicts the scaling tendency more accurately.

Type of Water System Operating Water

2 3 2Flux (gpd/ft ) & (M /M .d)

Municipal wastewater (sewerage)

Treated River or Canal water

Surface Water (lakes/Reservoir)

Deep Wells (low turbidity)

RO Permeate Water

Surface seawater

Beach well seawater

8-12 - or 0.33-0.49

8-14 – or 0.33-0.57

8-14 – or 0.33-0.57

14-18- or 0.33-0.73

20-30 –or 0.81-1.22

7-10 - or 0.29 –0.40

7-10 - or 0.29 –0.40

45

uIf pH >pHs (or pHsd) then water is saturated with calcium carbonate.

uIf pH <pHs (or pHsd) then water is unsaturated.

uA positive value of index indicates tendency towards scaling.

uWith the scale inhibitors available nowadays an LSI <+2.4 can be

easily controlled.

uCirculating a muriatic acid solution can easily redissolve carbonate

scale. Lowering the pH during operation can also dissolve it.

uIn predicting the solubility limits of sulphate two points are important.-

ua) Modern RO membranes reject divalent ions very well. Therefore it is

reasonable to assume a zero

percent salt passage when calculating the concentrating factor CF.

ub) Compounds are more soluble in the concentrate than in feed water.

The solubility product constant Ksp of each compound increases with

ionic strength.

uAs a rule of thumb, the scale inhibitor dosages for RO systems are

calculated as concentrations in the concentrate of 12 –18 Mg/liter. This

value is then converted to a feed water dosage using the CF for design

recovery and assuming zero percent salt passage.

uThere are four important pieces of information needed to predict

the product and concentrate composition and volume:

uRecovery rate, (Ret): -The recovery rate is limited by the

concentration of sparingly soluble salts in the feed water. Lowering the

pH and adding anti-scalants can increase the potential recovery rate.

The other determining factor is the configuration of the membrane

system. Each element can recover approximately 10 percent of the

feed flow as product. Generally, 50 percent recovery is assumed for a

6-element vessel.

uRejection rate: -Manufacturers lists a rejection rate for chloride and

one for sulfate or other divalent ions for NF membranes. For greater

accuracy, use a weighted average based on the feed water

composition. For instance, if the feed water has a ratio of 3: 1 mono-

valent to multi-valent ions and the rejection rates are 90 percent for

chloride and 99.5 percent for sulfate, the weighted average rejection

rate would be Rejection = (0.75*0.9)+(0.25*0.995) / (0.75+0.25)

=0.924 If the goal is to minimize concentrate volume, choose a

membrane with a very high rejection. However, if the goal is to

minimize concentrate TDS, choose a membrane that will produce the

target water quality. NF membranes are sufficient in many cases.

To predict the product and concentrate composition and

volume:


uFeed water-dissolved solids concentration, C, in mg/L.

uTarget delivery water concentration after blending, C, in mg/L.

uAccurate product and concentrate concentration prediction

calculations that take concentration polarization into consideration

can get quite complex, but do no provide that much more accuracy in a

first pass cost estimate.

Product concentration, Cp in mg/L:

Cp= Cf (1-Rejection) / Recovery

Concentrate concentration Cc in mg/L

Cc =Cf* Rejection / (1-Recovery)

The maximum amount of blend water that can be mixed with the membrane

product and still achieve the target water quality is calculated as follows,

assuming filtered feed water is used for the blend water:

Qb = Qt (Ct- Cp) / (Cf-Cp)

Where Qb is the maximum blend volume in m3/day, Q, is the target volume in

m3/day, and Ct is the target dissolved solids concentration in mg/L. If there is a

component of the blend water that is more limiting than the total dissolved

solids, there are two options. Either plan to remove that component from the

blend water or use the concentration of that component in the blend water for

Cf and the estimated remaining concentration of it in the membrane product

water for Cp.

As an example, consider the following situation:

Cf = 900 mg/L with 0.5 mg/L manganese

Rejection = 0.95

Recovery = 0.85

Ct = 300 mg/L with less than 0.05 mg/L manganese

Cp = 900*(l-0.95)/0.85 = 56 mg/L

Cb = (300-56)/ (900-56) = 0.29 or 29 percent blending with feed water.

When the manganese concentration is considered as the limiting component:

Cf = 0.5 mg/L manganese

Rejection = 0.95 Recovery = 0.85

Ct = Less than 0.05 mg/L manganese

Cp = 0.05*(l-0.95) / 0.85 = 0.03 mg/L

Cb = (0.05-0.03) / (0.5-0.03) = 0.04 or 4 percent blending with feed water.

47

If the blend water is filtered with greensand or the manganese is removed in

some other way, the higher level of blending is possible, otherwise not.

However it is decided, once the blend volume has been established, the

membrane process feed, product, and concentrate flows are set (all in

m3/day):

Qp = Qt- Qb

Qf = Qp / Recovery

Qc = Qp (1-Recovery) / (Recovery)

Using the following assumptions:

Feed water is being pumped from a tank of approximately the same height as

the membrane skid, 10 meters of pipe Pipe is a 10 cm (4 in.) in diameter for 20-

cm (8-in.) modules and 5 cm (2 in.) for 10 cm (4 in.) module.

Horsepower (Hp) without energy recovery

Hp = hg+0.5v2+p*Qf*1000/(746*Ef)

Horsepower (Hp) with energy recovery

Hp = (hg+0.5v2+p)(1-Er)*Qf*1000/746

Where h is height difference between top of tank and membrane inlet in m,

2g is gravitational constant, 9.81 m/s

v is velocity = Q / pipe area, m/s,

3Qf = membrane feed flow, m /sec,

1000 = mass of one m3 of water in kg,

746 = conversion factor from J/s to hp,

Ef= combined Efficiency of Pump and Motor

E recovery = energy recovery in decimal, 0.20 - 0.30 depending on concentrate

pressure.

Pump Horsepower for RO


CHAPTER 7

49

Steam Boiler

Steam Boiler System

List of Problems Caused by Impurities in Water

The principal components of a steam boiler system include a steam boiler,

condensate return tank, condensate pump, deaerator, feedwater pump, steam

traps, low water flame cut-off controller, chemical feeder, and make-up water

treatment equipment. However, depending on the size of the system and the

end use of the steam, other components may include a converter or heating

coils, unit heater, steam sparger, jacketed steam cooker, and/or steam

sterilizer

Impurity(ChemicalFormula)

ProblemsCommon ChemicalTreatment Methods

Alkalinity (HCO -,32- CO and CaCO )3 3

Carryover of feedwater intosteam,produce CO in steam2

leading to formation ofcarbonic acid (acid attack)

Neutralizing amines,filming amines,combination of both,and lime-soda.

Hardness (calciumand magnesiumsalts, CaCO )3

Primary source of scale inheat exchange equipment

Lime softening,phosphate, chelatesand polymers

3+Iron (Fe and2+Fe )

Causes boiler and waterline deposits

Phosphate, chelatesand polymers

Oxygen (O )2

Oxygen scavengers,filming amines anddeaeration

Corrosion of water lines,boiler, return lines, heatexchanger equipment,etc.(oxygen attack)

Corrosion occurswhen pH dropsbelow 8.5

pHpH can be lowered byaddition of acids andincreased by additionof alkalis

Hydrogen Sulfide(H S)2

Corrosion Chlorination

ChlorinationScale in boilersand cooling watersystems

Scale in boilers andcooling watersystems


Troubleshooting Water system for Boiler

Condition Possible Cause Action

Hardness inBoiler feedWater

Improper functioningof Water softener Infiltration of rawwater at converters.

Regenerate/repairwater softener.Take condensatesamples at allsteam convertersto pinpoint placeof infiltration. Makenecessary repair.

Dissolved oxygenin Feedwaterexceeds therecommendedrange.

Deaerator malfunction.Feedwater pumpsucking air at theseal.Insufficient sodiumsulfite residual.

Check deaerator press/temp.Check deaeratorvalve to ensure themost effective opening.Repair feedwater pumpseal.

Consistently lowChemical residualin system(General).

Testing reagentshelf life expired.Chemical feedpump inoperativeor out of adjustment.Restriction in thechemical feedline.Mistake in chemicalidentification.Inadequate amountof treatment chemical.Makeup water increasedue to lead in thesystem (boiler sectionor condensate).

Replenish test reagents.Repair or adjust chemicalfeed pump.Clean or replace chemicalfeedline.Make sure the chemicalyou are using is whatyou want. Increasechemical dosage. Inspectboiler and condensatepiping system for anyindication of leaks. Makesure drain valves oncondensate receivingtanks are closed.Check boiler blowdownvalves to ensure 100%shut-off. Check continuousblowdown valves setting.

Low phosphateresidual.

Increased hardnessin feedwater.Wrong type/choiceof phosphate.

Check water softener. Seeaction for “Hardness inboiler feed water.” Selectphosphate based on theneeded Po4 percent toensure the highest qualityfor the hardness content.

51

Boilers

Boilers use varying amounts of water to produce steam or hot water, depending

on their size. They require make up water to compensate for uncollected

condensate or to replace blow down water. These units have a tendency to

develop leaks as they age.

Low sulfiteresidual.

Chemicals feed pumpinoperative.An increase of oxygencontentin feedwater.Improper samplingor testing technique.

Check sulfite feedsystem and make necessaryadjustment/repair.Check deaerator operationand make necessaryadjustment/repair.Increase sodium sulfitefeed rate. “Collecting WaterSamples. Test for sulfitefirst. Stir sample smoothly.

Total dissolvedsolids exceedtherecommendedrange.

Insufficient boilerblowdown.Excessive chemicaladdition.

Increase blowdown rate.Adjust the surface blowdown valve.Analyze boiler water todetermine treatmentchemical residual andmake adjustments.

High totald i s s o l v e ds o l i d s i ncondensate.

Boiler water carryoverwith the steam.Too much amineinjected.Infiltration of rawwater at converters.Active corrosionoccurring in the system.

Reduce the total dissolvedsolids in the boiler byblowdown. Make sure waterlevel is not too high.Reduce amine injection,but maintain therecommended pH.Take condensate samplesat all steam converters andtest for hardness and TDSto find the point ofinfiltration. Make necessaryrepair.Analyze the condensate foriron/copper content. Ensureamine treatment is reachingall points in the condensatesystem.


Water Efficiency Opportunities:

1. Install a condensate return system

2. Locate and repair leaks

3. Limit blow down

4. Establish an effective corrosion and scale program

5. Install automatic controls to treat boiler make up water.

– A condensate returns system

reuses condensate water as make-up water. This can save up to 50-70

percent of the water used and can save energy as well.

– Boilers can develop leaks in steam traps and

the distribution system. Escaping steam wastes both water and energy.

– Adjust blow down limits to near the minimum required

to properly flush the system and maintain desired water quality.

–Regularly

inspect boiler water and fire tubes. Reducing scale by chemical treatment

or mechanical removal will increase heat transfer and energy efficiency

and will reduce the amount of blow down necessary to maintain water

quality.

Eliminate systems that mix condensate with cool fresh water for blow down to

the sewer.

Water Treatment Recommendation

A

1.The make-up water treatment to these systems depends on theboiler pressure and the end use of the steam. 2.The make-up should preferably be softened for low pressuresteam boiler. 3.The make-up must be softened & dealkalized for steam boilersystems when the total alkalinity concentration in the make-upis high (i.e., systems where the boiler is blown down to controlalkalinity rather than TDS).4. In boiler system where silica controls the blowdown, themake up water should be demineralized.

1.Sodium sulphite must be added at a point after mechanicaldeaeration such that a residual sulphite concentration of 30-60ppm (50 – 100 ppm Na SO ) is maintained in the boiler water.2 3

2.It does not matter if the sulphite concentration is more butit should not be less than 30 ppm SO or 50 ppm Na SO .3 2 3

3.The sulphite-oxygen reaction may be catalyzed by adding5 ml of cobaltous chloride solution per 100 g of sodium sulphite.

B

1. If the pH of the boiler water is less than 10.5, caustic must beadded to the boiler.2. If the pH of the boiler water is greater than 11.5, theblowdown rate must be increased and the caustic additionmust be decreased—the boiler water pH level must be10.5-11.5 pH.

C

53

Note:- For Details See Boiler Water Treatment Manual.

1. If the boiler water total alkalinity concentration is greater than700 ppmCaCO , then the blowdown rate must be increased and3

the caustic or trisodium phosphate addition must be decreased.2. The boiler water total alkalinity concentration must be lessthan 700 ppm CaCO ;3

1. If the boiler water hydroxide alkalinity concentration is lessthan 150 ppm CaCO , caustic or tri-sodium phosphate must be3

added to the boiler water.2. Alternately, if the boiler water hydroxide alkalinity concentrationis greater than 300 ppm CaCO , the blowdown rate must be3

increased and the caustic or tri-sodium phosphate additionmust be decreased—the boiler water hydroxide alkalinitymust be 150-300 ppm CaCO3

1. If the phosphate is added upstream of the boiler feed pumps,hexameta phosphate must be used since tri-sodium phosphatewould precipitate hardness salts, thus increasing the wear onpump seals. Hexameta phosphate on the other hand keepshardness in solution until it reaches the boiler, at which pointthe alkalinity and increased temperature there converts it totrisodium phosphate;2. If the phosphate is added directly to the boiler water, eitherhexameta or tri-sodium phosphate may be used;3. If the phosphate is being consumed more rapidly than tri-sodium phosphate is being added (i.e.,hardness in leakageinto the system), hexameta phosphate should be used at leasttemporarily because it has a higher phosphate concentrationand thus a higher capacity for hardness than tri-sodium phosphate;4. When hexameta phosphate is used, its conversion to tri-sodium phosphate in the boiler effectively reduces theOH alkalinity concentration and the pH level of the boilerwater;

1. If the pH level of the condensate return is less than 8.5, aneutralizing amine such as morpholine must be added to thefeedwater after the make-up location.2. If the pH level of the condensate return is greater than9.5, the amine addition must be decreased the condensatereturn pH level must be 8.5-9.5.3. If problems persist in achieving proper pH levels in thecondensate return system, seek the advice of the watertreatment consultant. If there is no condensate return,amine must not be added

In conjunction with the above controls and regulation of boilerblowdown, the boiler water neutralized total dissolved solidsmust be controlled within the limits of 1500-3000 ppm (or2000-4000 micromhos/cm).

H

F

E

D

G


Note

Hydrazine Sulphate oxygen scavenging should only be used with drum

type boilers. Drum boilers have blowdown facilities. TDS levels should be

monitored more rigorously when using hydrazine sulphate as an oxygen

scavenger, since TDS levels may increase with the formation of ferrous

sulphate.

Excessive oxygen

content in deaerator

effluent

Temperature in storage

tank does not correspond

within 5 º F of

saturation temperature

of the steam

The venting is not sufficient. Increase

venting by opening the manually

operating vent valve.

The steam pressure reducing valve

not working properly. Check valve for

free operation.

Check water and, if possible, steam

flow rates vs. design. Trays or scrubber

and inlet valves are designed for specific

flow ranges.

Spray nozzle not working. There couldbe deposit or sediment on the nozzleon the spring broken or seat. Leakingstuffing boxes of pump upstream ofdeaerator can be the cause Repairstuffing box or seal with deaerated water.

Excessive consumption

of oxygen scavenger

Trays collapsed-possibly from interrupted steam supply or sudden supply of coldwater causing a vacuum. Condensatemay be too hot. Water entering thedeaerating heater must usually be cooledif the temperature.

55

Chemical dosageOxygen scavenger

Sodium sulphite

Hydrazine

7.88 ppm of sodium sulphite is required to remove 1ppm of dissolved oxygen.

This requirement is for pure sodium sulphite. 93 % pure sodium sulphite will

require 10 ppm of sodium sulphite per ppm of oxygen. The amount of catalyst

required is 0.25 %

Theoretically 1 ppm of Hydrazine reacts with 1 ppm of dissolved oxygen. In

practice of 1.5 to 2 ppm is used for 1 ppm of dissolved oxygen

Amine Requirement

Amount of amine required for maintaining pH of 8.0 in water containing 10 ppm

CO2

Morpholine –37 ppm: - It has a specific gravity of 1.002 and has a pH of 9.7 for

100-ppm solution

Cyclohexylamine –15 ppm: - It has a specific gravity of 0.86 and has a pH of

10.7 for 100-ppm solution

Suggested dosage of Sodium sulphite & Hydrazine

Dosage of Sodium sulphite

Recommended Hydrazine Residual

2Boiler pressure (Kg/Cm ) Ppm Na SO .2 3

14.00

21.00

31.0042.00

52.00

64.00

70.00

105.00

80-90

60-70

45-60

30-4525-30

15-20

Not recommended

Not recommended

2Drum pressure (Kg/Cm ) Residual Hydrazine in ppm.

63.00 0.1-0.15

0.1-0.15

105.00 0.05-0.10

175.00 0.02-0.03

210.00 0.01-0.02

70.00


Notes

Amine Limits

Note:-

Cyclohexylamine is not for use in systems having a feedwater alkalinity

more than 75 ppm

These system lengths are for classification only and are not absolute. For

example a medium length system may have more of the characteristics of

a long system if lines are poorly insulated or because of bad design.

These should not come in contact with food products and hence any

steam in contact with milk and other such products should not have amine.

Amine Limitation

Cyclohexylamine Not to exceed 10 ppm in steam.

DEAE Not to exceed 10 ppm in steam.

Hydrazine Zero in steam

Morpholine Not to exceed 10 ppm in steam.

Octadecylamine Not to exceed 3 ppm in steam.

Type of Amine Conditions Amount needed

Ammonia Co Absent2 0.2 ppm to give pH 9.0

Cyclohexylamine Co Absent2

CO2 Present

1 ppm to give pH 9.02.3 parts per part of CO to give pH2

8.1 (corresponds to bicarbonate)2.0 parts per part of CO to give2

pH 7.41.4 ppm per ppm of Co2

to give pH of 7.0

57

Limits on Boiler water conditions for an effective

treatment program

NOTE

Chemical requirements for feed water and boiler for low and medium pressure boilers:Feed Water:

Ortho-Phosphate

Hydroxyl Alkalinity (Causticity)

Sodium Lignosulfonate (as tannic acid)

Range

BIS Standard for Feed water and Boiler Waterst1 Standard (10392-1982)

BoilerPressurepsig(kg/

2cm )

Maxi--mumTDS(ppm)

Maximum Conductivity( mho)

Maxi--mumSilica(ppm)

RangeSulfite(ppmSO )3

RangePhosphate(ppmPO )4

RangeAlkalinity(ppmCaCO )3

*Lignosulphonate(ppm)

1-15(1.05) 6000 9000 200 30-60 30-60 300-500 70-100

16-149(1.12-10.5) 4000 6000 200 30-60 30-60 220-500 70-100

70-100220-50030-6030-6015060004000150-299(10.5-20)

300-449(20-30)

450-599(31-40)

600-749(41-52)

750(>52)

3500

3000

2500

2000 3000

3750

4500

5250 90

40

30

20

20-40

20-40

15-30

15-30

30-60

30-60

30-60

30-60 170-425

170-425

170-425

180-450 70-100

60-90

50-80

40-90

Parameters

TotalHardness

pH Value

DissolvedOxygen

Silica

Upto20Kg2/cm

221 Kg/cm 2- 39Kg/cm

2 40Kg/cm2- 59Kg/cm

Unit

<10 <1.0 <0.5 ppm asCaCO3

8.5-9.5 8.5-9.5 8.5-9.5

0.1 0.02 0.01 As ppm

5 0.5As ppmSiO2


Boiler water

<0.4 ofCausticAlkalinity

15As ppmSiO2

<0.4 ofCausticAlkalinity

ParametersUpto20

2Kg/cm

221 Kg/cm to239 Kg/cm

240Kg/cm259Kg/cm Unit

TotalHardness

NotDetectable

NotDetectable

NotDetectable

TotalAlkalinity

700 500 300As ppmCaCO3

11.0to 12.0

11.0 to12.0

10.5 to11.0

pH Value

ResidualSodiumSulphite

30 to50

20 to30 --

ppm asNa SO2 3

0.1 to1.0

0.1 to0.5

0.05 to0.3

ppm asN H2 4

ResidualHydrazine

Ratio Na SO2 4

/Caustic Alkalinity (NaOH)

Ratio Na SO /2 4

Totallkalinity(as NaOH)

Above0.4

Above0.4

Above0.4

Phosphate

TotalDissolvedSolids

Silica

20 to40

15 to30

5 to20

ppm asPO 4

3500 2500

Causticalkalinity

350 200 60As ppmCaCO3

1500 ppm

Above2.5

Above2.5

Above2.5

59

ASME Guidelines for Water Quality in Modern Industrial

Water Tube Boilers for Reliable Continuous Operation

ABMA Standard Boiler Water Concentrations for Minimizing

Carryover

This value will limit the silica content of the steam to 0.25 ppm as a function of

selective.

Boiler Feed Water Boiler Water

DrumPressure(psi)

2(kg/cm )

Iron(ppmFe)

Copper(ppmCu)

TotalHardness(ppmCaCO )3

Silica(ppmSiO )2

TotalAlkalinity**(ppmCaCO )3

SpecificConductance(micro mhos/cm)(unneutralized)

0-300(0-20)

301-450(21-30)

451-600(31-42)

601-750(43 –52)

751-900(53-63)

901-1000(64-70)

1001-1500(71-105)

1001-1500(71-105)

0.100

0.050

0.030

0.025

0.020

0.020

0.010

0.010

0.050

0.025

0.020

0.020

0.015

0.015

0.010

0.010

0.300

0.300

0.200

0.200

0.100

0.050

0.0

0.0

150

90

40

30

20

8

2

1

700*

600*

500*

400*

300*

200*

0***

0***

7000

6000

5000

4000

3000

2000

150

100

DrumPressure(psig)

Boiler Water

TotalSilica*(ppmSiO )2

Specific**Alkalinity(ppm CaCO )3

Conductance(micromhos/cm)

0-300

301-450

451-600

601-750

751-900

901-1000

1001-1500

1501-2000

150

90

40

30

20

8

2

1

700

600

500

400

300

200

0

0

7000

6000

5000

5000

3000

2000

150

100


Boiler Water Limits

Silica Levels Allowed in Boiler Water

Boiler Pressurepsig TDS Alkalinity

Suspended Solids Silica*

0 to 300

301 to 450

451 to 600

601 to 750

751 to 900

901 to 1000

1001 to 1500

1501 to 2000

Over 2000

3500

3000

2500

2000

1500

1250

1000

750

500

700

600

500

400

300

250

200

150

100

300

250

150

100

60

40

20

10

5

125

90

50

35

20

8.0

2.5

1.0

0.5

Boiler Pressure (psi) Allowable Silica (as ppm SiO )2

0-15 150

16-149 150

150-299 150

300-449 90

450-599

40

600-749

30

750

20

61

CHAPTER 8


Cooling Water Treatment

Description of Process

Objective for Cooling Water Treatment

Factors important for cooling System

Cooling towers are heat exchangers that are used to dissipate large heat loads to the atmosphere. They are used in a variety of settings, including process cooling, power generation cycles, and air conditioning cycles. All cooling towers that are used to remove heat from an industrial process or chemical reaction are referred to as industrial process cooling towers (IPCT). Cooling towers used for heating, ventilation, and air conditioning (HVAC), are referred to as comfort cooling towers (CCT). Cooling towers are classified as either wet towers or dry towers. Dry towers use a radiator like cooling unit instead of water evaporation.

The following four basic objectives for Cooling Water Treatment are

1. Minimize problems from corrosion, scale, deposition, and growth to obtain

maximum efficiency.

2. Implementation and control must be "do-able" with a minimum input of

labor and money.

3. Cost effective as possible considering the total water system capital and

operating costs.

4. Must be environmentally acceptable.

Following steps are necessary to optimize the cycle of concentration (COC) for

a cooling tower and evaluate cooling water requirement or replacement

1. Evaluate the cooling system

2. Determine the water quality constituents sand concentration limits for

cooling system protection

3. Evaluate water treatment requirements

4. Choosing monitoring and maintenance requirement Create a plan to change chemistry or flow rates, if problem occurs.

63

Equipment Material of construction

Cooling tower Wood, Plastic, Metal and fiber glass

Heat exchangers(Chillers,Jacketed vessel, etc)

Copper, copper alloy, SS, &galvanized steel tubes

Covers of Heat exchangers &Support plates

Mild steel Water lines may beof copper

Piping for cold water Mild steel (MS), PVC, Stainless steel(SS) and fiber glass

Type of Material Effect of impurity

GI Pipes Corrosion (white rust) at High TDSand pH above 8.5 or less than 6.5

Stainless steel

Corrosion due to chloride, Chloride above200 ppm can create problem in Ss304when deposit forming conditions exist butif no deposit forming surface can withstandaround 1000 ppm Cl. 316 SS can withstandabout 5000 ppm Cl even with depositforming surface

Mild steel

Highly corrosive due to solids and alsodue to acidic or basic conditionsOxygen also corrosive to mild steel

Copper & Copperalloys

Corrosion to ammonia

Wood Natural decay. Can getchemically attacked.

PlasticCorrosion resistant. Biomass canget built up on plastic film


Cooling Tower Maintenance Schedule

Daily/Weekly Periodic Annual

1.Test water sample forproper concentration ofdissolved solids. Adjustbleed water flow as needed. 2.Measure the water treat--ment chemical residualin the circulating water.Maintain the residualrecommended by yourwater treatment specialist.3.Check the strainer onthe bottom of the collectionbasin and clean it ifnecessary. 4.Operate the make-upwater float switch manuallyto ensure proper operation. 5.Inspect all moving partssuch as drive shafts,pulleys,and belts.6.Check for excessivevibration in motors, fans,and pumps.7.Manually test the vibrationlimit switch by jarring it.8.Look for oil leaks ingearboxes. 9.Check for structuraldeterioration, looseconnectors, water leaks,and openings in the casing. 10.During periods of coldweather, check winterizationequipment. Make sure anyice accumulation is withinacceptable limits.

1.Check the distributionspray nozzles to ensureeven distribution overthe fill.2.Check the distributionbasin for corrosion,leaks,and sediment. 3.Operate flow controlvalves through theirrange of travel andre-set for even water flow through the fill.4.Remove any sludgefrom the collection basinand check for corrosionthat could develop intoleaks.5.Check the drift eliminators, air intake louvers,and fill for scale build-up.Clean as needed.6.Look for damaged orout- of-place fill elements.7.Inspect motor supports,fan lades, and othermechanical parts forexcessive wear or cracks.8.Lubricate bearings andbushings. Check the levelof oil in the gearbox. Addoil as needed.9.Adjust belts and pulleys.10.Make sure there is properclearance between the fanblades and the shroud. 11.Check for excessivevertical or rotational replay in the gearbox outputshaft to the fan.

1.Check the casingbasin,and pipingfor corrosion anddecay.Without proper mainte-nance,coolingtowers may sufferfrom corrosionand wood decay.Welded repairsare especiallysusceptible tocorrosion. Theprotective zinccoating on galva-nized steel towersis burned offduring the weldingprocess. Primeand paint anywelded repairswith a corrosionresistant coating.2.Leaks in thecooling towercasing may allowair to bypass thefill. All cracks,holes, gaps, anddoor access panelsshould be properlysealed.Removedust, scale, andalgae from thefill, basin, anddistribution spraynozzles tomaintain properwater flow.

65

Cooling Tower Inspection Process

Cooling Water Monitoring

Generally, the cooling tower structure and system should be inspected every

six months in temperate climates. In more tropical and desert climates the

interval should be more frequent, in accordance with equipment manufacturer

and engineering recommendations. A list of items that need to be inspected is

shown below:

uWooden structural members: - Look for rotten and broken boards,

loose hardware and excessive fungal growth. The plenum area after

the drift eliminators is the most likely to suffer wood rot, since biocides

added to the water do not reach this area. Pay particular attention to

structural members in this area.

uOther structural members: - Check concrete supports and

members for excessive weathering and cracking. Look for metal

corrosion. On fiberglass ductwork and piping, check for cracking and

splitting.

uWater distribution throughout the tower should be uniform. Check

piping for leaks.

uFans should be free of excessive vibration. Check mounts for

deterioration and looseness. Examine blade leading edges for fouling,

corrosion and dirt buildup. Check the fan stack for integrity, shape and

stack-to-blade clearance.

uInspect for broken fill, debris in the fill, scale on fill water outlet.

uLook for debris and plant growth in the drift eliminator. Make sure the

eliminator is not broken or missing altogether.

uCheck for alga growth, scale and plugged nozzles in the hot water bay

(cross flow towers). Nozzles should be checked monthly during the

cooling season.

uRecord all observations on the Operator Checklist. This should include

gearbox oil levels, oil additions (frequent refills could be a sign of

bearing wear or leaks), water data, chemical inventories and hot

water bay observations.

uBe sure to keep the water log sheet records up to date. Maintain a

record of necessary components, control ranges, control capabilities

(especially for calcium, pH, alkalinity, biocide, chemical feeds,

conductivity, possible phosphate content.) Follow water treatment

procedures closely.

uPeriodically check the water appearance for turbidity and foam.

uInspect wet surfaces for evidence of slime, algae or scale. Do the same

for submerged surfaces. Use a corrosion coupon to monitor system

corrosion rates where potential corrosion problems are indicated.

uMonitor chemical additions for visible and uniform flow and proper

rate.


Treatment

Chlorination Filtration

Sulphuric acid

Inhibitors Antiscalant

Antifoulant

Fouling in cooling system Reasons of Fouling

Silt introduced by the makeup water

Dirt from air

If fouling is not controlled, it will result in heavy deposits inside cooling water tubes, resulting in reduced tube diameter.

Reaction of residues from chemical treatment Microbiological debris

Products produced by corrosion such as hydroxides and insoluble salts

Fouling is controlled by filtration and by chemicals and oxidation by chlorine and or ozone

Selection of capacity of side stream filter

% reduction of undissolved solids Select 80 %

Time desired for reduction in hours = t= select maximum in 48 hours

48 hours maximum

Blowdown = b in M3/hrs b=100 M3/Hrs V= total volume of cooling system M3 6000

Filtration rate F= v/t Loge[(100)/(100-%reduction)]-b

Microorganism Bacteria, algae and fungi present in cooling water decreases the efficiency of heat transfer in cooling tower and condensers.

Chlorine is the most widely used chemical in industry as oxidizing agent for destruction and dissolution of microorganism

Chlorine is only effective when pH is between 6 to 7

Cooling water pH %of HOCl for effective oxidation

6 97 7 76

8 24

9 3 At pH 7 in CW system every 1 ppm Cl2 dosed only 0.76 ppm is used as oxidizing agent for control of microorganism

General guidelines for chlorine dosing of reasonably good water

Cooling Water System Estimated Chlorine dosage

uHeat exchangers can also be monitored for heat transfer performance

to give an early warning of water treatment deficiencies. Small side

stream test heat exchangers are available commercially for

monitoring cooling water site fouling. Biological growth can rapidly

cause systems to get fouled. Slime appearing on a submerged coupon

is a good indicator that there is a problem. Submerged coupons, which

are found in the cooling tower reservoir, indicate growth in less

accessible areas of the cooling tower.

67

Makeup water for CWcirculation water

Recirculation coolingwater system

Cooling Water SystemOnce Through inland Lake/river/seawater

Estimated Chlorine dosageContinuous dosing of 1-2 ppm + shockdosing of 3-5 ppm for 15 minutes afterevery 8 hour cycle

Continuous 1-2 ppm. Shock doseof 3-5 ppm

Continuous 1-2 ppm.

Calculation of H SO Dosing System2 4

CW circulation rate CWR=34000

Makeup water percentage P=2

M=150M Alkalinity to bemaintained ppm

A=140 M.Alkalinity in Makeupwater ppm

C=2Cycle of concentration

Acid dosingRequired AH

(CWR*P/100*Q) /1000=34000*0.02*130/1000=88.4kgs at 98 %

Quantum ofM.Alkalinity ppm

Q=[(A*C)-M]=[(140*2)-150]=130 H SO %2 4 Sp.Gr Dosing

98 1.826D=AH/Sp.Gr=88.4/1.826=48.4lph

oDosage Quantity at 30 C


Impact of Water quality Parameters on Cooling Systems

Iron

Water QualityParameters

TreatmentImpact on System

Hardness(Ca +Mg )

Scaling Calcium scalingmore troublesome becauseof inverse solubility ofs ome c a l c i um s a l t s )Magnesium salt problematicwhenn silica levels high.

Softening by externaltreatment AntiscalantDescaling if scalinghas taken place

Alkalinity mainlydue bicarbonate

Can be corrosive. Useful inp r e d i c t i n g C a l c i u mcarbonate scale potential

Dealkalization

SilicaDifficult to removesilica deposit

TSS Apart from makeup water,SS can also be present ascorrosion and deposit byproducts. Can be cause ofUnder deposit corrosion byadhering to bio film.

Pretreatment likecoagulation andclarification Sidestream filtration

Ammonia Ideal nutrient for Microorganism, Highly corrosiveto copper, Reduces chlorineeffectiveness as Disinfectant

B r o m i n e b e t t e r disinfectant in presenceof Ammonia Air stripping

Phosphate

Problem when in highconcentration (Ca>1000ppm) & (PO4 >20 ppm)Calcium Phosphate deposit

Close monitoring ofBlowdown. Properuse of dispersant

Chloride

Co r r o s i v e a t h i g he rconcentration For SS 300ppm considered corrosivebut for other metals >1000ppm considered corrosiveForms undesirable foulantswith Phosphate.Deactivatesspecialized polymers usedto inhibit calcium phosphatescaling.

BOD Indication of Bio growth Oxidizing Biocide

ZincGood at low levels but cancontribute to deposit athigher level

Manure for microorganismOrganism

Galvanized Corrosion Heavy Metal

69

Non Oxidizing Biocides

SS-suspension & Sol=Solution (Source –Technical Data sheet of Vulcan

Chemicals).

Material Formula Form%active

MinDoseppm

MaxDoseppm

FeedTime

MinpH

MaxpH

Methylene-bis-thiocya--nate

SCN-CH -2

SCN SS 10 25 50 1/wk 6 8

1

2

Tetrahydro3,5-Dimethyl-2H-1-3,5-Thiadia-zone-2-Thione

C H5 10

N S2 2 Sol 24 30 60 1/wk 6.5 14

Na Dime-thyl–Dithio-carbamate

C H NS3 6 2

Na Sol 30 20 40 1/wk 7 14

Dibromo-Nitrilo-Propion--amide

C H N3 2 2

OBr Sol 20 6 15 1/wk 6 8

(Chloro)Methyl-isothiazolinone

C H NOS4 4

Cl &C H NOS4 5

Sol 1.15 25 50 1/wk 6 9.5

Glutaraldehyde

O=CH(CH )2 3

CH=OSol 45 25 100 1/wk 6 14

14

14

6

6

1/wk

1/wk

120

120

30

30

9.4Sol

Sol

RC H6 5

(CH )3 3

NCl

Alkyl-Benzyl-DimethylAmmoniumChloride

Dioctyl-DimethylAmmoniumChlorite

50

(C H )6 17 2

(CH )3 2

NCl

3

4

5

6

7

8


Oxidizing Biocides:

C5H6N2O2ClBr

solid ––

––

0.2 0.5 C 7 10

NaBr varies

38%as NaBr

2.0 4.0 C 7 10

ChlorineDioxide

Chlorine

CalciumHypochl-orite

SodiumHypochl-orite(I)

SodiumHypochl-orite(D)

LithiumHypochlorite

TrichloroIsocyanuricacid

SodiumDichloroIsocyanuricacid

Bromo,Chloro,DimethylHydantion

Material Formula Form%FAC

FeedType

MinpH

MaxpH

ResidualRequire-ments

MinDoseppm

Max Doseppm

ClO2 sol 0.2 0.5 C 5 9

SodiumBromide-“Chlorine”

Cl2 gas 100 0.5 1.0 C 6 7.5

Ca(OCl)2 solid 0.5 1.0 C 6 7.565

NaOCl solution 12 0.5 1.0 C 6 7.5

NaOCl solution 5 0.5 1.0 C 6 7.5

LiOCl solid 35 0.5 1.0 C 6 7.5

(CONCl)3 solid 89 0.5 1.0 C 6 7.5

(CON)3Cl2 Na solid 56 0.5 1.0 C 6 7.5

71

Diagnostic Indicators for Cooling Systems

Metals:Copper>0.25 mg/lIron>1.0 mg/lZinc>0.5 mg/l ORMeasured corrosionratesCopper>0.2MPYMild steel piping>3 MPYMild steel Hex tubing>0.5 MPYGalvanized steel>4 MPY

Additives:Chlorine > 0.5 mg/lOzone >0.2 mg/l

Carbon dioxide>5 mg/l

pH < 7.0

Water velocity:> 3 feet/sec @ >150ºF> 5 feet/sec @ 120ºF> 8 feet/sec @ <90ºF

Conductivity outsidethe manufacturer'srecommended range

The water consumptionrate has increasedgreatly.

Possible Problem Possible Solution

High corrosion rateInadequate chemicaldosage control Use ofconditioning chemicalscontaining copper orzinc

Improve corrosionprotection throughuse of an additive orby o the r meansImprove addi t ivedosage control and/ormonitoring Eliminateuse o f add i t ivescontaining copperor z inc Considerrep lac ing coppercomponents or piping

Leaks or system failureHigh rate of corrosionof copper piping;couldcause leaks or systemfailure

Overuse of theseoxidizing chemicalsl e a d s t o h i g hcorrosion rates

Reduce or stabilizeaddit ive dosageImprove monitoringInstall an automaticconductivity probecontrolled oxidizingagent feed system.

C o p p e r o x i d eprotection is inhibited Raise pH

InadequatepH control

Implement pHcontrol Checkdosage of low-pHadditives

Reduce recirculationrate Increase line sizeR e p l a c e c o p p e relements with nonmetallic parts or othernon copper parts

System operat ionnot optimized Possiblemisuse of additivesImproper blowdownrate

Investigate: Systemsettings Chemicaldosing rates Blowdown system operation

The heat load to thesystem has greatlyincreased. Possiblemassive system leak.

Check if additional heatload has been addedon the system today.Check the system forleaks. Inspect sanitarysewer and storm sewermanholes on site forunusually high flows.

Indicator


Cooling water distribution headers in all plants are generally of carbon steel without any protective lining. In some places Hume pipe are also used to severe corrosion.

Fertilizers – Stainless steel and carbon steelOil refineries – general admiralty brass but in some cases combination of admiralty brass and carbon steelPetrochemicals- Combination of 90-10 Copper Nickel, admiralty brass, SS and carbon steelLPG Plants- mainly carbon steelAcrylic Fiber Plants – Stainless steel, Copper –Nickel and carbon steelChilling and refrigeration - 90-10 copper Nickel, Copper / SSAir compressor & Nitrogen Plants – Admiralty BrassPower plants – Copper-Nickel /Copper /SSControl limits for various cooling water treatments

Coolers and condensers (tube Bundles)

Table1

Characteristics Unit Normal Normal

SHMP + Zn SHMP+CrO +Zn4

Maximum Maximum

pH Mg/L 6.3 6.8 6.5-7.0 7.0

MO Alkalinity Mg/L*1 *1

Ca Hardness Mg/L 200-300 300 200-300 300

500300-500500300-500Mg/LTotal hardness

Chloride as Cl Mg/L 200-300 *2300 200-300 *2300

1000800-10001000800-1000Mg/LSulphate as SO4

Silica as SiO2 Mg/L 75-100 100 75-100 100

3020-30*330 (50)20-30(30-50)

Mg/LTSS

Organo Phosphate(HEDP) as PO4

Mg/L

Total InorganicPhosphate as PO4 Mg/L 15-20 *425 10-15 *415

*43020-25––

––

––

––

Mg/LChromate as CrO4

Zinc Sulphateas Zn

Mg/L 3-5 *4 5 2-3 *43

Polymericdispersant

TDS Mg/L 1200-1500 1500 1500-2000 2000

Mg/L 5-10 10

1

2

14

12

7

13

9

10

6

3

11

8

4

5

*1-MO Alkalinity will find its own level based on pH to be maintained.*2- In case of stainless steel exchangers, chloride levels will be lowdepending on design.*3- With polymeric dispersant*4 Actual inhibitors levels depend on operating conditions

73

Table2

*1-MO Alkalinity will find its own level based on pH to be maintained.*2- In case of stainless steel exchangers, chloride levels will be lowdepending on design.*3- With polymeric dispersant*4 Actual inhibitors levels depend on operating conditions

Zn+O-PO4+Polymer

Zn +HEDP Zn +HEDP +SHMP (max)

Characteristics

Unit NormalMaximum

NormalMaximum

Normal

Maximum

pH Mg/L 7.5–8.0 8.01

2 MO Alkalinity Mg/L*1*1 *1

Ca Hardness Mg/L300-400

400 300-400 400 300-400 4003

4 Total hardness Mg/L 600-800

800 600-800 800 600-800 800

5 Chloride as Cl Mg/L 200-300*1300 200-300 *2300 200-300 *2300

6Sulphate asSO4

Mg/L800-1000

1200 800-100 1200800-1000

1200

7 Silica as SiO2 Mg/L 75-100 125 75-100 125 75-100 125

8TSS Mg/L 30-50 50 20-30

*3(30-50)30

)*3(5020-30

*3(30-50)30

)*3(50

9

Organo Phosphate(HEDP)as PO4

––

––

–––– –– ––

––––––

––Mg/L *48-10 *410 *44-6 *44-6

10

Total Inorganic Phosp--hate as PO4

Mg/L *46-8 *48

11Orthophosphate as PO4 Mg/L *48-10 *415

12 Zinc Sulphateas Zn Mg/L 1-1.5 1.5 2-3 3 1.5-2 2

Polymericdispersant13 Mg/L 20-30 50 5-10 10 15-20 20

14 TDS Mg/L 1500-2000

2000 1500-2000

2000 1500-2000


Puckorius Scaling Index

Factor "A" FOR Total dissolved Solids

The Langelier Saturation Index and Ryznar Stability Index were originally

developed to identify scaling (calcium carbonate) and corrosion tendencies of

water in supply piping. These indexes, which are still in wide use today, are

considered very conservative. Most scaling and corrosion conditions identified

by these indexes can typically be controlled by specialty chemicals. Their

usefulness is therefore limited, but because of their common use, the following

calculation procedure is provided The Puckorius Scaling Index modifies the

Ryznar Stability Index by calculating the pH of the bulk water, and thus, more

accurately predicts scaling conditions.

LSI = (measured pH) - (pHs). A positive value indicates scale; a negative value,

no scale.

RSI = (2 pHs) - (measured pH). A value below 6 means scale; above 6, no

scale.

Calculating pH of saturation (pHs).

The pH of saturation (pHs) can be determined from the relationship between

various characteristics of water. The following factors and formula are used in

determining the pHs:

(1) Factors Needed to Calculate pHs:

A = Total Dissolved Solids (ppm), table B-1

B = Temperature (oF), table B-2

C = Calcium Hardness (ppm as CaCO3), table B-3

D = Total Alkalinity (ppm as CaCO3), table B-4

(2) pHs = 9.30 + A + B - (C + D)

Calculation of Calcium Carbonate Saturation Index

Factor "B" FOR Temperature

Total SolidMg /liter

Value of“A”

50

100

600

1000

2000

3000

4000

5000

0.07

0.1

0.18

0.2

0.22

0.24

0.25

0.26

oC oF Value of “B”0-1 32-34 2.6

2-6 36-42 2.5

7-9 44-48 2.4

10-13 50-56 2.3

14-17 58-62 2.2

18-21 64-70 2.1

2.1 72-80 2.0

28-31 82-88 1.9

32-37 90-98 1.8

38-43 100-110 1.7

44-50 112-122 1.6

51-55 124-132 1.5

56-64 134-146 1.4

65-71 148-160 1.3

72-81 162-178 1.2

75

Factors "C" for Calcium Hardness (as ppm CaCO3)* Zero

to 1000 ppm

Calcium HardnessAs CaCO3

Value of “C”

10-11

12-13

14-17

18-22

23-27

28-34

35-43

44-55

56-69

70-87

88-110

111-138

139-174

175-220

221-270

271-340

341-430

440-550

551-690

691-870

871-1000

2.0

1.8

2.2

2.1

1.3

1.1

1.2

1.0

0.7

0.8

0.6

0.9

1.4

1.5

1.6

1.7

1.9

2.6

2.3

2.5

2.4

Calcium HardnessAs CaCO3

Value of “C”

10-11

12-13

14-17

18-22

23-27

28-34

35-43

44-55

56-69

70-87

88-110

111-138

139-174

175-220

221-270

271-340

341-430

440-550

551-690

691-870

871-1000

1.0

1.1

1.2

1.3

1.4

1.5

1.6

1.7

1.8

1.9

2.0

2.1

2.2

2.3

2.4

2.5

2.6

2.7

2.8

2.+

3.0


Equilibrium pH Value (pHeq) determined from Total

Alkalinity

Example 1

Example 2

Water from a cooling tower has a TDS of 1,000 ppm, calcium hardness of 500

ppm (as CaCO ), total alkalinity of 100 ppm (as CaCO ) and measured pH of 3 3

8.2. The hottest temperature on the waterside of the heat exchanger is 120oF.

pHs = 9.30 + A + B - (C + D)

pHs = 9.30 + 0.20 + 1.57 - (2.30+2.00) = 6.77

Water from a cooling tower has a total alkalinity of 100 ppm (as CaCO ) and a 3

measured pH of 8.2 (same as example 1). From table 5, the pHeq is 7.47.

PSI = (2pHs) - (pHeq) = 2 (6.77) - 7.47

= 13.54 - 7.47 = 6.07

RSI = (2pHs) - (measured pH) = 13.54 -

8.2 = 5.34

LSI = (measured pH) - (pHs) = 8.2 -

6.77 = +1.43

The pHeq may also be calculated as follows:pH eq = 1.485 log TA + 4.54 where TA denotes total alkalinity.

7.14

7.77

8.08

8.29

8.44

8.57

8.67

8.76

8.84

8.91

7.24

7.81

8.10

8.30

8.46

8.58

8.67

8.77

8.85

8.92

7.33

7.84

8.15

8.32

8.47

8.59

8.68

8.78

8.85

8.92

7.44

7.88

8.15

8.34

8.48

8.60

8.70

8.79

8.86

8.93

6.89

7.68

8.03

8.25

8.41

8.54

8.65

8.74

8.82

8.90

Alkalinityppm Alkalinity, ppm CaCO3, tens

hundreds 0 10 20 30 40 50 60 70 80 90

0

100

200

300

400

500

600

700

800

900

––

7.47

7.91

8.17

8.35

8.49

8.61

8.71

8.79

8.87

6.00

7.53

7.94

8.19

8.37

8.51

8.62

8.72

8.80

8.88

6.45

7.59

7.97

8.21

8.38

8.52

8.63

8.73

8.81

8.89

6.70

7.64

8.00

8.23

8.40

8.53

8.64

8.74

8.82

8.89

7.03

7.73

8.05

8.27

8.43

8.56

8.66

8.75

8.83

8.90

77

Scaling Indices versus conditions

Selection of capacity for side stream Filter for cooling tower

F=V/t log [(100) / (100-% reduction)]-be

% of reduction of undissolved solids (select 80 %)

t= time desired for reduction in hours (select maximum of 48 hours)

b= blowdown rate in m3/hr

V= total volume of cooling system in M3

Example for V=6000 M3, t=48 hours and b=100 M3/HrF=100 M3/H

LSI

3.0

2.0

1.0

0.5

0.2

0.0

-0.2

-0.5

-1.0

-2.0

-3.0

PSI/RSI

3.0

4.0

5.0

5.5

5.8

6.0

6.5

7.0

8.0

9.0

10.0

Condition

Extremely severe scaling

Very severe scaling

Severe scaling

Moderate scaling

Slight scaling

Stable water, no scaling, no tendency to dissolve scale

No scaling, very slight tendency to dissolve scale

No scaling, slight tendency to dissolve scale

No scaling, moderate tendency to dissolve scale

No scaling, strong tendency to dissolve scale

No scaling, very strong tendency to dissolve scale


CHAPTER 9

79

Pumps

Introduction

Types of Pump

Characteristics of different types of pumps

Pumps play a vital role in any water treatment system. Pump moves liquid from

one place to another. Hence selection of pump is very critical in all water

treatment system. Here we are giving general guideline, which will help, in

discussing with the pump manufacturer or supplier.

The three types of pump most commonly employed are Centrifugal, Rotary and

Reciprocating. Each class of pump is further divided into.

Pump Class Type

Centrifugal

VoluteDiffuserRegenerative turbineVertical TurbineMixed Axial FlowAxial flow (Propeller)

Single stage andMultistage. Seemanual on pumps

Rotary

GearVaneCam & Piston ScrewLobeShuttle Block

Reciprocating

Direct actingPower(including Crank& Flywheel)DiaphragmPiston

SimplexDuplexTriplex

Characteristics Centrifugal Rotary Reciprocating

Discharge Flow Steady steady steady

Usual Maximumsuction lift (Meters) 4.6 6.7 6.7

Liquid handled

Clean, clear dirtyabrasive and liquidswith high solidcontent.

Viscous,Nonabrasive Clean and clear

DischargePressure range Low to high Medium Low to high


0.87 1.34 1.77 2.54 4.46 8.18 11.8 18.9 36.3 71.0

1.44 2.23 2.94 4.23 7.43 13.6 19.6 31.5 60.5 118

2.02 3.12 4.12 5.92 10.4 19.1 27.5 44.0 84.8 166

2.88 4.46 5.88 8.45 14.9 27.3 39.2 63.0 121 236

5.77 8.92 11.8 16.9 29.7 54.5 78.4 126 242 473

8.65 13.4 17.7 25.4 44.6 81.8 118 189 363 710

14.4 22.3 29.4 42.3 74.3 136 196 315 605 1180

Liter/sec 1 2 3 5 10 20 30 50 100 200

Averageefficiency

Total headin meters

5

7

10

20

30

50

70

100

200

300

500

34 44 50 58 66 72 75 78 81 83

0.15 1.23 0.30 0.43 0.75 1.47 1.96 3.15 6.05 11.8

0.20 0.31 0.41 0.59 1.04 1.91 2.75 4.4 8.48 16.6

0.29 0.45 0.59 0.85 1.49 2.73 3.92 6.3 12.1 23.6

0.58 0.89 1.18 1.69 2.97 5.45 7.84 12.6 24.2 47.3

Usual capacityrange

Smallest tolargestavailable

Small tomedium

Relativelysmall

How increasedhead affects capacity Decrease None

Decrease and Nonefor duplex and triplex

Power input Depends onspecific speed

Increase Increase

How decreasedhead affectscapacity

Increase None Increasesmarginally

Power inputDepends onspecific speed Decrease Decrease

81

Basic guideline for selecting Pump

Specific speed of impeller

Pressure and Specific Gravity

Power Absorbed by pump

1. Sketch the proposed piping layout. Base the sketch on actual job condition.

Single line diagram can be used

2. Determine the required capacity of pump. The required capacity is the flow

rate, which has to be handled at a particular pressure. Once the flow rate

has been determined a suitable factor of safety is applied. In any case it

should not be less than 10 %

3. Compute the total head on pump

4. Analyze the liquid conditions. Obtain complete data on liquid to be

pumped.

5. Select the class and type as given in the table

6. Evaluate the pump chosen for installation. Check specific speed, impeller

type and operating efficiency.

½ ¾, Nq=3.65*n*Q / H Where n= speed in rpm

H= head in meters,

Q= discharge in Cubic meter /sec

This calculation allows comparison of all types of rotodyanmic pump on equal

footing.

Pressure developed by pump is proportional to specific gravity of liquid.

P=H, Where Y is the specific gravity

H in meters = Pressure in absolute atmosphere/ Sp.Gravity

H in Feet = Pressure psi/Sp.

Power = *Q*H /C *n, Where Y is Sp.Gravity1

Q –Discharge rate (capacity) in Cubic meter /sec

H= head in Meter

C = 75 for power in Metric HP1

= 76.04 for power in British HP

= 101.98 for power in Kw3=1000 kgf/M at 4C

Motor, brake, and water horsepower can be calculated as follows:

Mhp = Brake horsepower / Motor efficiency

Bhp = Water horsepower / pump efficiency

Whp = head (ft) x flow (gpm) /3960

To better understand the performance and operating characteristics of pumps,

operators should become familiar with the pump curve that is supplied by the

manufacturer for each pump.

Formulas required for pump Calculation


Pump curves usually show three curves on one sheet:

uThe head-capacity curve shows the discharge in gallons per minute

(gpm) the pump will deliver against various heads when operated at

the proper speed. This curve shows that as the head increases, the

discharge decreases, until there is no further discharge. Conversely,

as head decreases, flow increases.

uThe second curve, also plotted against flow, shows the efficiency at

which the pump operates at various points on the head capacity curve.

This curve shows that no pump is 100% efficient, due to internal

friction losses. The highest efficiency that can be hoped for is around

85%. Efficiency can be expected to decrease with age and wear.

uThe third curve, the brake horsepower curve, shows power consumed

plotted against flow. If we know the total head at which the pump is

operating, we can use the curve to find the gallons pumped. The power

required by the pump, as well as the pump efficiency, can also be read

from the curve for any set of conditions. This curve shows that it

usually takes more horsepower to pump more water: the lower the

flow, the lower the horsepower required, and the higher the flow, the

higher the horsepower required.

83

CHAPTER 10


Raw Water TreatmentObjectives

Selection of Water Treatment Processes

The objectives of a public water supply water system are to provide safe and

aesthetically appealing water to the customers without interruption and at a

reasonable cost- an adequate quantity of water at sufficient pressure for fire

protection and industrial water for manufacturing.

Selection of a suitable water treatment process for a given utility is always a

complex and diverse task. Conditions are likely to be different for different water

utility. Adoption of an appropriate water treatment process by a water utility is

influenced by the necessity to meet the regulatory guidelines, the desire of the

utility and its customers to meet other water quality standards and objectives and

the need to provide water service at the lowest reasonable cost. A water

treatment plant should be designed considering the fact that it should supply

continuous and safe water to the customers regardless of the raw water

characteristics and the environmental conditions. Hence, the selection of

treatment process is important in the plant design. The ultimate plant design has

a system that is proven to be simple, effective, reliable, durable and cost-

effective.

The design of water treatment plant starts with the preliminary studies that

include:

1. Design period;

2. Water supply areas – identifying the areas to be served;

3. Population – estimating the present and future population;

4. Estimating maximum daily water demand;

5. Evaluation and selection of the water source;

6. Size of the treatment plant;

7. Location of the treatment plant site; and

8. Financing.

The selection of package treatment plants and special proprietary devices or

processes should be based on proper consideration of:

Raw water condition and demand variability;

1. Operation and maintenance;

2. Servicing, repairs or replacement; and

Operational flexibility.

85

Water Treatment Processes

Aeration

Coagulation

Flocculation

Aeration is the process of bringing water and air into close contact in order to

remove dissolved gases, such as carbon dioxide, and to oxidize dissolved

metals such as iron. It can also be used to remove volatile organic chemicals

(VOC) in the water. Aeration is often the first major process at the treatment

plant. During aeration, constituents are removed or modified before they can

interfere with the treatment processes. Examples of aeration processes include

diffused mechanical nozzle spraying, multiple tray cascading and packed

power type.

The first step destabilizes the particle's charges. Coagulants with charges

opposite those of the suspended solids are added to the water to neutralize the

negative charges on dispersed non-settlable solids such as clay and color-

producing organic substances.

Once the charge is neutralized, the small-suspended particles are capable of

sticking together. The slightly larger particles formed through this process and

called microflocs, are not visible to the naked eye. The water surrounding the

newly formed microflocs should be clear. If it is not, all the particles' charges

have not been neutralized, and coagulation has not been carried to completion.

More coagulant may need to be added.

Following the first step of coagulation, a second process called flocculation

occurs. Flocculation, a gentle mixing stage, increases the particle size from

submicroscopic microfloc to visible suspended particles.

The microflocs are brought into contact with each other through the process of

slow mixing. Collisions of the microfloc particles cause them to bond to produce

larger, visible flocs called pinflocs. The floc size continues to build through

additional collisions and interaction with inorganic polymers formed by the

coagulant or with organic polymers added. Macroflocs are formed. High

molecular weight polymers, called coagulant aids, may be added during this

step to help bridge, bind, and strengthen the floc, add weight, and increase

settling rate. Once the floc has reached it optimum size and strength, the water

is ready for the sedimentation process.


Sedimentation

Filtration

Disinfection

Sedimentation basins are used to settle out the floc before going to the filters.

Some type of sludge collection device should be used to remove sludge from

the bottom of the basin.

Removal of suspended solids by filtration plays an important role in the natural

treatment of groundwater as it percolates through the soil. It is also a major

part of most water treatment. Groundwater that has been softened or treated

through iron and manganese removal will require filtration to remove floc

created by coagulation or oxidation processes. Since surface water sources are

subject to run-off and do not undergo natural particles and impurities.

Iron and manganese in water also promote the growth of iron bacteria, a group

of organisms that obtains its energy for growth from the chemical reaction that

occurs when iron and manganese mix with dissolved oxygen. These bacteria

form thick slime growths on the walls of the piping system and on well screens.

Such shines are rust-colored from the iron and black-colored from the

manganese. Variations in flow can cause these slime growths to come loose,

resulting in dirty water in the system.

The object of disinfection is to kill disease-causing organisms present in the

water. With regard to water treatment, disinfection refers to the destruction of

most intestinal or fecal bacteria. Sometimes disinfection is not complete. Some

viruses and especially some protozoa, such as Giardia or cryptosporidium,

could survive the disinfection process. The only method of complete protection

is to sterilize the water by boiling it for a period of 15 to 20 minutes

The methods of disinfection practical in public water supplies are chlorination,

ozonation, use of ultra-violet light, and over-liming. Potassium permanganate,

iodine, bromine, and silver are also used, but less frequently. Chlorination is so

widely used that the term disinfection and chlorination are almost the same in

waterworks practice.

Coarse Screen

Coarse screens, often termed bar screens or racks, and must be provided

to intercept large, suspended or floating material. Such screens or racks

are made of l/2-inch to 3/4-inch metal bars spaced to provide 1- to

3-inch openings.

Fine Screen

Surface waters require screens or strainers for removal of material too

small to be intercepted by the coarse rack, These may be basket-type,

in-line strainers, manually or hydraulically cleaned by back washing

or of the traveling type, which are cleaned by water jets. Fine screen,

clear openings should be approximately 3/8 inch.

87

Design Parameters for Water Treatment Processes

Forced or induced draft aeration devices should be designed to ensureeven water distribution, adequate counter currents of air and properexternal exhausting. As a guide, the loading should be within the rangeof 0.7 to 3.4 L/s per m² of total tray area (0.8 to 4 gpm/ft.) and 5 ormore trays used with separations not less than 150 mm (6 inches).Where pressure aeration is proposed for oxidation purposes,consideration should be given to compressed air quality and mixing, thescaling potential of the water and subsequent air release. Aeratorsshould have a bypass and provisions should be made for inspectionand cleaning of the devices. Exhaust gases should be vented outsidethe building.

To achieve proper coagulation, high intensity rapid mixing is considerednecessary. It is recommended that rapid mixing be accomplished byeither an in- line-mixing device or mixing in a separate process tank.Typical energy gradients (G values) would be in the range of 1000sec-1. It is recommended that some flexibility be provided in rapidmix design if possible.

The design of flocculation systems should allow for low velocities andavoidance of rapid acceleration to ensure maintenance of a good floc.When designing a flocculation process, selection of the mode of mixingand determination of the physical relations and characteristics of theflocculation tanks and clarifiers (sedimentation tanks) are among thefirst decisions to be made; either hydraulic mixing or mechanical mixingmay be chosen. Where sedimentation follows flocculation, theretention time for floc formation should be at least 30 minutes.

This process is designed to remove a majority of the settleable solidsby gravitational settling, thereby maximizing the downstream unitprocesses such as filtration. The factors that influence sedimentationefficiency include: Surface overflow rate (also known as surfaceloading rate); Inlet and outlet arrangements; type of sedimentationtank; Raw water characteristics and local climate conditions. There arethree main configurations for sedimentation tanks: horizontalrectangular basins; upflow sedimentation tanks; and upflow clarifierswith sludge blanket.

Aeration

Coagulation

Flocculation

Sedimentation


Design Data

EquipmentDesignParameter

TypicalDesignValues

Unit Remarks

CoarseScreen

CoarseScreen

0.05–0.08 Meter /sec

Design shouldhave provisionfor disposingDebris removedby screens

Fine Screen Velocity 0.4 –0.8 Meter /sec

Aeration Tray typeWater velocityAir requirementTray spacingArea requiredCascade TypeHeadAreaFlow velocitySpray TypeHeadNozzle diameterNozzle spacing Nozzle dischargeBasin areSpray pressure

0.8-1.57.5 30-7550-160

1.0-3.085-1050.3

1.2-92.5-4.00.6-3.65-10105-320about 70

3 2m /m /minm3/m3water cm

2 3m /m .s

meter2 3m /m .s

m/s

metercmmeterliter/sec

2 3m /m .skPa

Coagulation

Rapid MixDetentiontime Velocitygradient Gt

0.2-5700-1000

43X104–6X10

Min-1S

Flocculation

Slow MixDetentiontime VelocitygradientGt

0.2-515-60

41X104–15X10

89

Sedime--ntation

Rectangular TanksSurface overflow rate:Detention time:Water depth:Width/LengthWeir loading:Upflow ClarifiersSurface overflow rate:Detention(settling)time:Water depth:Weir loading:Upflow velocitySludge BlanketClarifiersSurface overflow rate:Detention (settling)time:Weir loading:Upflow velocity:Flocculation time

0.8 – 2.5 1.5 – 3 3 – 5 > 1/5< 11 1.3 – 1.91 – 33 – 57< 3 1– 31 – 27 - 15< 0.620

Meter/HrHourMeter

3M /Hr.MMeter/HrHourMeter

3M /Hr.Mm/hMeter/HrHour

3M /Hr.Mm/hminutes

Filtration

Rapid sandfilter FiltrationRate Backwashrate Air scoursystem Minimumfiltration cycleFilter mediadepths DualMedia SilicaAnthracitePressure Filters Filtration rate

120-14037-5037-7324

>24(600)

>200 >450

<15

3 2M /M .day3 2M /M .Hr3 2M /M .Hr

Hour

Inches(mm)

mmmmM/hour

Taste &OdourControl

A e r a t i o n a sdescribed before.KMnO Dosage4

PAC dosage

0.5-2.50.5-5

Mg/literMg/liter

PAC isPowderedactivatedcarbon. Thedosage ofPAC can attimes go upto50 mg/L

Disinfe--ction

Chlorine DoseChlorine residualOzone dose

1-50.5-11-5

Mg/literMg/literMg/liter

Fluoride Fluoride Dose 0.7-1.2 Mg/liter


Detention Parameters for Sedimentation for various

coagulants in Water treatment

Type of TreatmentOverflow Rate

3 2M /M /dayDetentionTime hours

Channel LoadingsM3/M/Day

Alum coagulation

Iron coagulation

Lime-sodacoagulation

20-30

28-40

28-45

2-8

2-8

4-8

150-220

200-275

200-275

MembraneProcesses

Microfiltration(MF)Pore sizePressureUltrafiltration(UF)Pore sizePressureNanofiltration(NF)Pore sizePressureReverse osmosis(RO)Pore sizePressure

0.1– 0.2 0.7 – 1.4 (10 – 20)

0.003 – 0.010.7 – 7.8 (10-40)

0.001 – 0.0055.3 – 10.6 (150)

<1 nm> > 14 (200)

mkg/cm2psig

m mmkg/cm2psig

m mmkg/cm2psig

kg/cm2(psi)

Distribution Velocity in mainsPressure

1-2 138-1000

M/seckPa

91

CHAPTER 11


Industrial Waste Water Treatment

Industrial Pretreatment Processes

Wastewater Unit operation

Physical

The treatment of industrial wastewater involves the same processes as

those used in the treatment of civil water. However, because of specific

compositions, the systems tend to vary. The chemical-physical type

processes are especially important for the removal of inorganic matter. The

basic processes used are

Screening is removal of coarse solids by use of a straining device.Sedimentation is gravity settling of pollutants out of the wastewater.Flotation is the use of small gas bubbles injected into the wastewater,

which causes pollutant particles in the wastewater to rise to the

surface for subsequent removal.Air stripping is removal of volatile and semi-volatile organic

compounds from wastewater by use of airflow.

u

u

u

u

Unit Operation

Physical

Chemical

Biological

ScreeningComminutionFlow equalizationSedimentationFlotationGranular –medium Filtration

PrecipitationAdsorptionDisinfectionDechlorinationOther Chemical Processes

Activated sludge ProcessAerated LagoonTrickling FiltersRBCPond StabilizationAnaerobic digestionBiological nutrient removal

93

Chemical

Biological

u

u

u

u

u

u

u

u

u

u

u

u

Neutralization is adjustment of alkalinity and acidity to the same

concentration (pH 7).

Precipitation is addition of chemicals to wastewater to change the

chemical composition of pollutants so that the newly formed

compounds settle out during sedimentation.

Coagulation is use of chemicals to cause pollutants to agglomerate

and subsequently settle out during sedimentation.

Adsorption is use of a chemical, which causes certain pollutants to

adhere to the surface of that chemical.

Disinfection is use of a chemical (or other method such as ultraviolet

radiation) to selectively destroy disease-causing organisms.

(Sterilization is the destruction of all organisms.)

Breakpoint chlorination is the addition of chlorine to the level that

chloramines will be oxidized to nitrous oxide and nitrogen, and

chlorine will be reduced to chloride ions.

Air activated sludge is an aerobic process in which bacteria consume

organic matter, nitrogen and oxygen from the wastewater and grow

new bacteria. The bacteria are suspended in the aeration tank by the

mixing action of the air blown into the wastewater. This is shown

schematically in Figure 1. There are many derivations of the activated

sludge process, several of which are described in this section.

High purity oxygen activated sludge is an aerobic process very similar

to air activated sludge except that pure oxygen rather than air is

injected into the wastewater.

Aerated pond/lagoon is an aerobic process very similar to air activated

sludge. Mechanical aerators are generally used to either inject air into

the wastewater or to cause violent agitation of the wastewater and air

in order to achieve oxygen transfer to the wastewater. As in air

activated sludge, the bacteria grow while suspended in the

wastewater.

Trickling filter is a fixed film aerobic process. A tank containing media

with a high surface to volume ratio is constructed. Wastewater is

discharged at the top of the tank and percolates (trickles) down the

media. Bacteria grow on the media utilizing organic matter and

nitrogen from the wastewater.

Rotating biological contactor (RBC) is a fixed film aerobic process

similar to the trickling filter process except that the media is supported

horizontally across a tank of wastewater. The media upon whom the

bacteria grow is continuously rotated so that it is alternately in the

wastewater and the air.

Oxidation ditch is an aerobic process similar to the activated sludge

process. Physically, however, an oxidation ditch is ring-shaped and is

equipped with mechanical aeration devices.


Bio-ChemicalOxygen Demand (BOD)

Activated SludgeTrickling filter or RBCAerated lagoonOxidation ditch

Total SuspendedSolids (TSS)

SedimentationScreeningFlotationChemical precipitation

Nitrogen

Nitrification/denitrificationAir strippingBreakpoint chlorination

Phosphorus

Chemical precipitationBiological treatmentAir stripping

Heavy metals

Biological treatmentChemical precipitationEvaporationMembrane process

Fats, Oil andGrease (FOG)

CoagulationFlotationBiological treatmentMembrane process

Volatile OrganicCompounds

Air strippingBiological treatmentCarbon adsorption

Pathogens

Chemical disinfectionUV radiationozonation

Pollutant Pretreatment Processes

95

PretreatmentProcess

Items to Look for in the Fieldfor Efficient Operation

Physical

ScreeningNo blinding or clogging of screens, noexcessive build-up of material on the screen

SedimentationLow flow rate, no short circuiting of flow, nofloating sludge, scum removal if appropriate

Centrifugation

Air strippingNo scaling of packing and piping, or freezingproblems at low temperatures

Chemical

NeutralizationpH monitoring, automated chemicalfeed, adequate mixing

PrecipitationAutomated chemical feed system, adequatemixing & contact timer

CoagulationAutomated chemical feed system, adequatemixing & contact timer

AdsorptionEfficient means of regeneration is keyto performance

DisinfectionAutomated chemical feed system, adequatemixing & contact timer

Biological

Activated sludge

Fine bubble aeration, even distribution of airand mixing, dissolved oxygen concentrationmonitoring, air flow turndown capability, nobulking/floating sludge

Trickling filterMethod for positive air circulation, even& periodic dousing of filter media

Rotating biologicalcontactor (RBC) Steady shaft rotation


CHAPTER 12

97

Chemical CleaningGeneral Guidance

Pre-Operational Cleaning

Chemical cleaning of water systems can be divided into two classifications: pre-

operational and remedial. Pre-operational cleaning is performed to prepare the

water-contacted metal surfaces to receive chemical treatment, which provides

protection from scale, corrosion, and microbiological growth. Remedial

cleaning is performed to restore water systems that have been fouled with

scale, corrosion products, and microbiological growth due to inadequate or

ineffective water treatment. Cleaning, particularly remedial cleaning is often

performed by outside contractors familiar with cleaning procedures,

techniques, and safety. It should be noted that if the water system is

significantly scaled, the chemical treatment program was obviously inadequate

and was not properly designed, set-up, controlled, or applied. After cleaning

has been completed, the chemical treatment program and QC program must

be improved so the same problem does not recur. Use of a well-designed QA

program would have produced identification and notification of potential and

developing problems before they became serious. Pre-operational cleaning is

often performed by contractors responsible for the fabrication of the water

system before turning it over to the military installation. Water system

operations personnel must assess the effectiveness of any cleaning process

that has been performed.

Pre-operational cleaning can be performed on all new systems or pieces of

equipment installed in any existing system, including new boiler tubes or new

chiller copper tube bundles. New piping and coils will usually be contaminated

with materials such as mill scale, rust, oil, and grease resulting from the

fabrication, storage, and installation of the equipment. Pre-operational

cleaning is performed to remove these materials and prepare metal surfaces to

receive corrosion protection from chemical treatment. Pre-operational

cleaning agents that are used include detergents, wetting agents, rust

removers, and dispersants. These cleaning agents have a pH in the range of 9

to 11. Water systems containing piping or components constructed of

galvanized steel and aluminum should not be subjected to procedures that

require high pH (greater than 8.5) because this would contribute to initiating

corrosion of these surfaces.

The requirement for performing a pre-operational cleaning process is usually

written into the specification for new construction of a water system that must

be performed by a mechanical contractor. The mechanical contractor is

required to perform the work as directed in the specifications. However, if the

specifications are not appropriate for the specific system, including

consideration of all system metallurgy, the cleaning process may contribute to

corrosion to mild steel, galvanized steel, copper, or aluminum, or it may result

in incomplete cleaning of dirty and corroded metal surfaces. A qualified

inspector should review the specifications or qualified independent consultant

to ensure that cleaning agents and procedures have been specified

appropriately.


Remedial Cleaning

Safety and Environmental Issues

Contracting Cleaning Services

Reasons for Cleaning

Types of Deposits

Remedial cleaning is performed to restore a water system that is fouled with

scale, corrosion products, or microbiological biomass due to inadequate or

ineffective waters treatment. The problem could have resulted from using

improper chemical technology, failure to maintain treatment levels within

control parameters or the failure of pretreatment equipment. The cleaning

agents used for remedial cleaning usually include acids, chelants, neutralizing

agents, and specialty cleaning chemicals.

Remedial cleaning may pose safety issues for personnel handling acids,

caustics, and various chemicals. There could also be environmental concerns

associated with chemical disposal. Inexperienced personnel should not

perform the chemical cleaning of an industrial water system.

For some cleaning jobs, such as large boilers and cooling towers, it may be

advisable to engage a service company specializing in chemical cleaning. If the

cleaning service is contracted, it is vital that adequate lines of communication

be established, and that safety procedures employed by the service company

comply with military regulations. An orientation meeting should be scheduled

between military installation personnel and the service company

representatives. At that time, the scope of the work can be defined, proper

procedures initiated, and the nature of the hazards described thoroughly. The

use of proprietary cleaning chemicals or chemical formulations may be

involved; disclosure of the use and nature of these chemicals should be made

at the orientation meeting. Military policies and restrictions can also be

explained.

Maintenance of an effective water treatment program is essential to minimize

scale and corrosion problems in industrial water systems; however, scale and

deposits that form will require remedial cleaning (descaling). If not removed,

these scale and water-caused deposits may impact the safety of operations

personnel, interfere with heat transfer, and cause excessive damage to, or

destruction of, the water-using equipment. Cleaning is not appropriate for the

removal of deposits when corrosion of the system has advanced to the point

where a large number of leaks may result from the removal of the deposits.

The deposits that occur in water systems can be inorganic mineral salts and

corrosion products or organic (oily) or biological in nature. Deposits range in

composition from very dense crystalline structures, to very porous and loosely

bound materials, to gelatinous slimes. Most of the deposits formed from water

constituents consist of corrosion products such as iron and copper oxides,

mineral scales, or mixtures of these materials.

99

Waterside Deposits Located in Heat Exchangers

Boiler Deposits

Remedial Cleaning Procedure

Cleaning Methods

Mechanical Methods

Chemical Methods

Water deposits located in heat exchangers are usually carbonate-based scales,

while steamside deposits may be a mixture of metallic oxides and organic

residuals from lubricating oil, particularly where reciprocating-type engines are

used. In steam systems, the oxides are usually iron and copper, resulting from

aggressive condensate. Microbiological deposits may form in cooling systems

from bacterial or algae growths, or from decomposition products of various

microorganisms.

Boiler deposits may take various forms. In low-pressure boilers using a

relatively hard feedwater, deposits are essentially calcium and magnesium,

silicates, sulfates, carbonates, phosphates and hydroxides, plus some

organics. Deposits may also contain considerable amounts of silica, iron, and

copper. These deposits can be spongy or porous or relatively hard and glass-

like. Deposits of the latter characteristic occur where silica is present in

appreciable quantities in the boiler water. Deposits in medium-pressure to

high-pressure boiler systems usually are mixtures of iron and copper oxides

and phosphates. Dense deposits may tend to form in high-heat transfer areas.

Considerable quantities of sludge-type accumulations may be found in

downcomers, mud drums, waterwall headers, crossover tubes, and areas of

low water circulation in the boiler.

Cleaning procedure information and procedures presented in this Chapter are

general in nature and must be modified to fit specific applications. Because

contractors perform most cleanings, these procedures are provided only for

general information.

There are two methods generally adopted for cleaning

1. Mechanical

2. Chemical

Mechanical methods are the oldest techniques used for removing deposits. To

perform an adequate mechanical-type cleaning, the equipment to be cleaned

may need to be partially or entirely dismantled. Even when equipment is

dismantled, some areas may be extremely difficult to reach and clean.

Chemical cleaning has largely replaced mechanical process equipment

cleaning as the most satisfactory method of removing deposits; however,

mechanical methods such as wire brushing, tumbling, scraping, and abrasive

blasting with sand and grit are still employed in special applications.

In this method acid or alkali is generally used for cleaning. At times there are

other chemicals which are also used for cleaning.


Cleaning Agents

General Guidance and Procedures for Preparing Cleaning Solutions

Hydrochloric (Muriatic) Acid

Example Procedure for 10% Solution

Cleaning agents may be broadly classified as being acid, alkaline, organic, or

solvent cleaners. There is no general or universal cleaner that removes all

deposits. The selection of a solvent or cleaning agent is based on the material's

ability to remove or dissolve the deposit, as well as on cost considerations,

safety hazards, and the effect of the cleaning material on the metals involved.

General guidance and procedures for preparing cleaning solutions of inhibited

hydrochloric (muriatic) acid and inhibited sulfamic acids are provided in

paragraphs below. Inhibited acid contains special chemical inhibitors that

prevent the acid cleaner from attacking the base metal while allowing the acid

to remove the unwanted corrosion product or scale deposit.

Inhibited hydrochloric (muriatic) acid in strengths of 5 to 20% is very effective

for removing calcium scale and iron oxide; however, for most applications, a

10% solution is adequate. The following formulation is for a 10% hydrochloric

acid solution. It can be used for removing scale consisting primarily of

carbonates with lesser amounts of phosphates, sulfates, and silicates. This

type of scale is typically found in a steam boiler system containing copper alloys

that has been treated with a phosphate-based program. Depending on the

specific descaling application, some of these ingredients can be omitted from

the formulation.

The following is an example procedure that can be used to make 3785 liters

(1000 gallons) of a 10% solution:

1. Add 1079 liters (285 gallons) concentrated (36% strength) hydrochloric

acid, American Society for Testing and Materials (ASTM) E 1146,

Specification for Muriatic Acid (Technical Grade Hydrochloric Acid), to

approximately 2271 liters (600 gallons) of water.

2. Add the proper amount of a corrosion inhibitor, Military Specification MIL-I-

17433, Inhibitor, Hydrochloric Acid, Descaling and Pickling, recommended

by the manufacturer to the diluted acid solution. The inhibitor must be

compatible with hydrochloric acid and must not precipitate under any

condition during the cleaning operation.

3. In a separate tank containing about 284 liters (75 gallons) of water:

4. Add 39 kilograms (85 pounds) of the chemical (1,3) diethylthiourea to

complex any copper and keep it from depositing. Do not use the

diethylthiourea as the corrosion inhibitor required in paragraph 9-

2.2.1(step 2) above.

5. Add 55 kilograms (120 pounds) of ammonium bifluoride, technical grade,

to help dissolve certain iron and silica scales.

6. Add 3.79 liters (1 gallon) of wetting agent,

Add the dissolved diethylthiourea, ammonium bifluoride, and wetting agent to

the diluted acid solution. Add sufficient water to obtain 3785 liters (1000

gallons).

101

Carbonate Deposits.

Phosphate Deposits

Metallic Oxides

Silica and Sulfate Scale

Hydrochloric Acid Limitations

Sulfamic Acid

Carbonate deposits dissolve rapidly in hydrochloric acid, with evolution of free

carbon dioxide. The escaping carbon dioxide tends to create some circulation or

agitation of the acid, which ensures the continual contact of fresh acid with the

scale. Once the carbonate has been dissolved from a mixed deposit, a loose,

porous structure may be left behind. This residual material can be effectively

removed from the equipment either mechanically or by washing with high-

pressure water.

The removal of phosphate deposits can usually be accomplished by using

hydrochloric acid; however, phosphate deposits have a tendency to dissolve

rather slowly. To minimize the total cleaning time, a temperature of 49 to 60 °C

(120 to 140 °F) is usually necessary to remove a predominantly phosphate scale.

Most metallic oxides found in deposits can be removed with hydrochloric acid. The

rate of dissolution is a function of temperature and solution velocity. If copper

oxides are present on steel surfaces, special precautions are needed to prevent

copper metal plate-out on the steel.

Heavy silica and sulfate scale is almost impossible to remove with hydrochloric

acid. Special chemicals and procedures are required to remove this scale.

Hydrochloric acid is not used to clean stainless steel because the chloride ion in

the acid solution may cause pitting or stress corrosion cracking. Hydrochloric acid

is not used for removing scale from galvanized steel surfaces since the galvanizing

will corrode. Aluminum is not cleaned using hydrochloric acid.

Sulfamic acid is an odorless, white, crystalline solid organic acid that is readily

soluble in water. An inhibited sulfamic acid compound, in a dry powder form, is

available. A 5 to 20% solution (2 to 9 kilograms to approximately 38 liters of water

[5 to 20 pounds to approximately 10 gallons of water]) is used for removing scale

from metal surfaces. The following information pertaining to sulfamic acid should

be considered.

u?Carbonate deposits are dissolved in sulfamic acid in a similar manner as

in hydrochloric acid. All the common sulfamate salts (including calcium)

are very soluble in water.

uThe dry powder form of sulfamic acid is safer to handle than a liquid

solution of hydrochloric acid; however, aqueous solutions of sulfamic acid

are much slower in action and require heating to remove scale. The

sulfamic acid solution is heated to a temperature in the range of 54 to 71

oC (130 to 160 oF) to obtain the same fast cleaning time that is achieved

by using hydrochloric acid at room temperature. Sulfamic acid is more

effective on sulfate scale than hydrochloric acid.


uInhibited sulfamic acid, used at temperatures up to 43 oC (110 oF),

will not corrode galvanized steel. Its use is recommended for

removing scale in cooling towers, evaporative condensers, and other

equipment containing galvanized steel. In general, sulfamic acid can

be applied to equipment while it is operating but should be drained

from the system after a few hours, and the concentration of the

normally used corrosion inhibitor should be increased several-fold to

protect the metal surfaces.

u?Commercially prepared descaling compounds consisting of

concentrated or diluted inhibited acid (containing 7 to 28% of the acid

and inhibitor) may be purchased under various trade names at prices

4 to 30 times the cost of the ingredients themselves if purchased as

generic chemicals.

u?Advertisements of some of these products may contain claims that

the acid does not attack cotton clothing and skin. These claims are

usually based on a very dilute solution of the acid that causes a

minimal attack on clothes and skin; however, the cost of the cleaning

process may be increased because a higher quantity of dilute product

may be needed. Be aware that handling acid in any strength must be

performed with considerable care, caution, and adherence to safety

procedures.

uThe cost of diluted acid is expensive; therefore, concentrated acid of

government specifications should be purchased and diluted to usable

strengths. The necessary corrosion inhibitors can be added to the

dilute acid solution. Users of small quantities of acid cleaners (possibly

less than 38 liters [10 gallons] of diluted acid per year) may not be

able to justify purchasing undiluted acid and spending the time, cost,

and effort to prepare the cleaning solution.

uThe unit to be cleaned must be isolated from other parts of the system.

For systems that cannot be isolated by the closing of valves, isolation

may be accomplished using rubber blankets, wooden bulkheads with

seals, inflatable nylon or rubber bags, rubber sponge-covered plugs,

or blind flanges and steel plates with rubber seals.

uDecide whether to clean using a soaking process or by circulating the

cleaning solution. In either case, temporary piping or hose lines will be

required to connect the cleaning solution mixing tanks or trucks to the

unit, with return lines to tanks or drains. Proper precautions and

adequate provisions must be made to protect equipment, isolate

control lines, replace liquid level sight glasses with expendable

materials, and provide suitable points for checking temperatures.

uThe entire cleaning procedure/process must be developed in detail

before starting chemical cleaning operations. Factors to be considered

include: the methods for controlling temperatures; the means of

mixing, heating, and circulating the chemical solution; proper venting

of dangerous gases from equipment to a safe area.

Cleaning Preparation

103

Methods for Removing Scale

Recirculating Cleaning Process for Boilers

Removing scale may be accomplished by circulating the inhibited acid solution

through the equipment or by soaking the equipment in a tank of inhibited acid.

Before starting any descaling process, check the acid to make sure it is properly

inhibited. You may check the acid by placing a mild steel coupon into a beaker

containing the prepared, diluted acid. You should notice no reaction around the

coupon. If you observe a reaction generating hydrogen gas bubbles around the

coupon, add more inhibitor.

The following example is an appropriate procedure for cleaning small boilers or

other systems using a hot recirculating inhibited acid solution:

1. Fill the boiler or system with preheated (71 to 77 oC [160 to 170 oF])

dilutes inhibited acid solution.

2. Allow the dilute inhibited acid solution to remain in place for 8 hours.

Circulate the acid solution for approximately 15 minutes each hour at a

rate of about 3.15 liters per second (50 gallons per minute) to ensure good

mixing.

3. Keep the temperature of the acid solution preheated at 71 to 77 oC (160 to

170 oF). Measure and record the temperature at least once every 30

minutes.

4. Check and record the acid strength at least every hour

5. Drain the system by forcing the acid solution out using 276 to 345

kilopascals (40 to 50 pounds per square inch gauge) nitrogen; follow

Specification A-A-59503, Nitrogen, Technical, Class 1. If leaks develop

when the system is under nitrogen pressure, you must use an alternate

method for removing the acid, such as pumping.o o6. Fill the boiler with preheated (65 to 71 C [150 to 160 F]) water and soak at

this temperature for 15 minutes.

7. Drain under nitrogen pressure of 276 to 345 kilopascals (40 to 50 pounds

per square inch gauge).

8. Prepare this mild, acid-rinse solution: Add 7.57 liters (2 gallons) of

hydrochloric acid (ASTM E 1146 or IS 226) for each 3785 liters (1000

gallons) of water. Also add corrosion inhibitor, in the amount recommended

by the manufacturer.o o9. Fill the boiler with the preheated (71 to 77 C [160 to 170 F]) mild acid-

rinse solution and soak for 30 minutes.

10. Drain the mild acid-rinse solution under nitrogen pressure at 276 to 345

kilopascals (40 to 50 pounds per square inch gauge). Maintain a positive

pressure of nitrogen in the boiler to prevent outside air from leaking inside.o11. Fill the boiler with the passivating solution preheated to 65 to 71 C (150 to

o o160 F), circulate for 10 minutes, and hold in the boiler at 65 to 71 C for an

additional 30 minutes.

Drain and rinse boiler until the pH of the rinse water is pH 8 to 10.


Circulating Method without Heat

Fill and Soak Method

The steps below describe a typical process for descaling smaller equipment,

such as enclosed vessels or hot water heater coils, without heating the inhibited

acid solution:

1. Note that an acid cleaning assembly may consist of a small cart on which is

mounted a pump and an 18.9- to 189-liter (5- to 50-gallon) steel or

polyethylene tank with a bottom outlet to the pump.

2. Install sill cocks at the bottom of the water inlet of the heat exchanger and

the top of the water outlet so that a return line can be connected directly

from the acid pump and from the heat exchanger to the acid tank.

3. Prepare an inhibited acid cleaning solution

4. Pump the acid solution into the heat exchanger through the hose

connection. Continue circulation until the reaction is complete, as

indicated by foam subsidence or acid depletion.

5. If the scale is not completely removed, check the acid strength in the

system If the acid strength is less than 3%, add fresh acid solution and

continue circulation until the remaining scale is removed. Usually an hour

of circulation is adequate.

6. Drain the heat exchanger.

7. Neutralize remaining acid by circulating a 1-% sodium carbonate (soda

ash) solution {about 3.6 kilograms per 38 liters (8 pounds per 100

gallons)}for about 10 minutes.

8. Rinse thoroughly with water until the pH of the rinse water is pH 8 to 10.

1. Prepare an inhibited dilute acid solution in a container of suitable size.

2. Depending on the item to be cleaned and the types of scale involved, you

may want to place an agitator (mixer) in the tank or install a pump outside

the tank to circulate the acid solution. A method to heat the acid may be

required, such as a steam coil. All equipment must be explosion-proof and

acid-resistant.

3. Immerse the item to be cleaned in the dilute acid solution. Continue

soaking until the reaction is complete as indicated by foam subsidence or

acid depletion.

4. If the scale is not completely removed, check the acid strength. If it is less

than 3%, add additional acid and continue soaking the items until the

remaining scale is dissolved. Usually 1 to 2 hours of soaking is adequate.

5. Remove item from tank.

6. To neutralize remaining acid, immerse the item in a 1% sodium carbonate

(soda ash) solution (about 3.6 kilograms per 38 liters [8 pounds per 100

gallons]) for 2 to 3 minutes.

Rinse the item thoroughly with water.

105

Checking Acid Solution Strength

Apparatus:

Reagents:

Method:

Results:

The initial strength of the dilute inhibited acid will vary from 5 to 20%, although

10% is typical. The strength of the acid decreases since acid is consumed in

dissolving the scale. The strength of the acid solution should be measured

periodically during a cleaning operation. When the acid strength falls below

3%, the solution may be discarded since most of its scale-dissolving capability

will have been used. Use the following procedure to check the acid strength:

1. Burette, 25 milliliters (0.8 ounce) automatic (for sodium hydroxide

solution)

2. Bottle, with dropper, 50 milliliters (2 ounces) (for phenolphthalein

indicator solution)

3. Graduated cylinder, 10 milliliters (0.3 ounce)

4. Casserole, porcelain, heavy duty, 210-milliliter (7.1-ounce) capacity

5. Stirring rod

1. Sodium hydroxide solution, 1.0 normality (N)

2. Phenolphthalein indicator solution, 0.5%

1. Measure 10 milliliters of acid solution accurately in the graduated cylinder.

2. Pour into the casserole.

3. Add 2 to 4 drops of phenolphthalein indicator solution to the casserole and

stir.

4. Fill the automatic burette with the 1.0 N sodium hydroxide solution; allow

the excess to drain back into the bottle.

5. While stirring the acid solution constantly, add sodium hydroxide solution

from the burette to the casserole until color changes to a permanent faint

pink. This is the endpoint. Read the burette to the nearest 0.1-milliliter

(0.003-ounce).

For hydrochloric acid: Percent hydrochloric acid = milliliter of 1.0 N sodium

hydroxide x 0.36.

For sulfamic acid: Percent sulfamic acid = milliliter of 1.0 N sodium hydroxide

x 0.97


WATER SAMPLE

TEST

PROCEDURES

107

WATER SAMPLE TEST PROCEDURES

Purpose of Testing

Testing Techniques

Testing of industrial water is done to determine the amount of treatment

chemicals in the water so that dosage levels can be properly regulated. These

tests are the only known means of having reliable operations, as far as the

water is concerned.

Accurate test results depend on following good basic laboratory procedures and

techniques.

1. Water analyses require certain chemical apparatus. These are scientific

instruments and are to be treated as such. The apparatus should be

HANDLED WITH CARE!

2. It is necessary to keep everything in GOOD ORDER at all times. Have a

place for everything and everything in its place! Be sure all bottles are

properly labeled and avoid mixing bottles! All bottles should be tightly

closed. Keep any reserve stock of solutions and reagents in cool, dark

place.

3. All equipment and apparatus should be kept CLEAN! Unless this is done,

the tests will not be reliable and errors will be introduced. Thoroughly rinse

and dry all glassware immediately after use. If color apparatus are

employed, do not expose to heat or to direct sunlight. If any liquid is spilled

on any of the equipment or apparatus, wipe off at once and dry.

4. MEASURE CAREFULLY! The apparatus are precision instruments that are

capable of very fine measurements. The results will be “off” if improper

amounts of samples are taken, if incorrect volumes of solution are added, if

the burette is not read correctly, of if the methods prescribed on the

following pages are not performed exactly as written.

5. The SUSPENDED MATTER OR SLUDGE will generally settle to the bottom if

the sample is allowed to stand before testing. The clear water can then be

used for the tests, making it unnecessary to filter (except for specific otests). Theoretically, all water analyses should be made at 77oF (25 C);

however, no appreciable error will be introduced if the test is made o obetween 68 and 86 F (20 to 30 C). In general, the shorter the time

between the collection and the analysis of the sample, the more reliable

will be the results.

When the water sample color interferes with the analysis, it may be necessary

to filter the sample through activated charcoal, except for the sulfite and nitrite

tests.


Phenolphthalein (P) Alkalinity Test Procedure

APPARATUS:

METHOD:

EXAMPLE:

Graduated Cylinder, 50 ml, Plastic

Bottle, w/Dropper (for Phenolphthalein Indicator) 2 oz

Casserole, Porcelain, Heavy Duty, 200 ml Capacity

Stirring Rod, Plastic

REAGENTS:

Standard Sulfuric Acid Solution, N/50

Phenolphthalein Indicator Solution, 1 percent

Measure the amount of water to be tested in the graduated cylinder. The

amount should be based on the expected results of the test according to the

following:

Pour into the casserole.

Add 6 drops of Phenolphthalein Indicator Solution to the casserole and

stir. If the water does not change to a red color, there is no

phenolphthalein alkalinity present and the “P” reading is reported as

“zero.” If the water does change to red color, “P” alkalinity is present

and the test should be continued.

Squeeze the rubber bulb to force the Standard Sulfuric Acid Solution

from the bottle to fill the burette just above the zero mark; then allow

the excess to drain back automatically into the bottle.

While stirring the water constantly, add Standard Sulfuric Acid slowly

from the burette to the casserole until the red color disappears and the

water resumes the original color of the sample before the

Phenolphthalein Indicator Solution was added. This is the end point.

Read the burette to the nearest 0.1-ml.

RESULTS: The P alkalinity (ppm as CaCO3) is calculated as follows: P

alkalinity (ppm as CaCO3) = (ml acid) x (factor)

4.3 ml of N/50 sulfuric acid were required to change the color of a 50 ml sample

of water from red to colorless:

P alkalinity = 4.3 x 20 = 86 ppm as CaC

u

u

u

u

u

P Alkalinity Expected,As CaCO3

Less than 100

More than 100

Sample Size

50ml

20ml

Factor

20

50

109

Total (M) Alkalinity Test ProceduresAPPARATUS:

METHOD:

RESULTS:

Burette, 10 ml, Automatic (for N/50 Sulfuric Acid) (item 1001)

Graduated Cylinder, 50 ml, Plastic (item 1004)

Bottle, w/Dropper (for Mixed Indicator) 2 oz (item 1005)

Casserole, Porcelain, Heavy Duty, 200 ml Capacity (item 1003)

Stirring Rod, Plastic (item 1006)

REAGENTS:

Standard Sulfuric Acid Solution, N/50 (item 2001)Mixed Indicator Solution, (item 2036)

Measure the amount of water to be tested in the graduated cylinder. The

amount should be based on the expected results of the tests according to the

following:


Add 10 drops of Mixed Indicator Solution to the casserole and stir. If

the water changes to a light pink color, free mineral acid is present.

There is no mixed indicator alkalinity, and the “M” reading is reported

as “zero.” If the water changes to a green or blue color, “M” alkalinity is

present and the test should be continued.

Squeeze the rubber bulb to force the Standard Sulfuric Acid Solution

to fill the burette to just above the zero mark; then allow the excess to

drain back automatically into the bottle.While stirring the water constantly, add Standard Sulfuric Acid Solution slowly from the burette to the casserole until the green or blue color changes to light pink. This is the end point. Read the burette to the nearest 0.1-ml.

The M alkalinity (ppm as CaCO3) is calculated as follows:

M alkalinity (ppm as CaCO3) = (ml acid) x (factor)

u

u

u

u

M Alkalinity Expected,As CaCO3 Sample Size Factor

Less than 100

More than 100

50ml

20ml

20

50


EXAMPLE:

NOTES:

5.9 ml of N/50 sulfuric acid were required to change the color of a 50 ml sample

of water from green to light pink:

M alkalinity = 5.9 x 20 = 118 ppm as CaCO3

u If the end point color is difficult to see, repeat the entire test using 15

drops of Mixed Indicator Solution.

u Just before the end point is reached, the green or blue color fades to a

light blue color and then becomes light pink. The end point is the first

appearance of a permanent pink color.

Value of P & M

Alkalinity

Bicarbonate

Alkalinity

Carbonate

Alkalinity

Hydroxide

Alkalinity

Total

Alkalinity

P= Zero

P< 1/2M

P=1/2M

P>1/2M

M

M-2P

Nil

Nil

Nil

2P

2P

2(M-P)

Nil

Nil

Nil

2P – M

M

M

M

M

111

Conductivity Test Procedure

Apparatus

Conductivity Meter & cell

Procedure

Results

In general, there are two types of conductivity meters. One has an electrode

that is put into a cell containing the water to be tested. The other has a small

cup mounted on the meter into which the water to be tested is poured. Either

type of meter may be automatically temperature compensated, or the meter

may require a temperature correction. The meter may indicate TDS or

conductivity as micromhos, but either measurement represents the same

characteristic of the water sample. Where the meter is designed to give either

measurement, it is important to always use the same measurement to avoid an

error.

Thermometer

Beaker

Graduated cylinder

Determine the cell constant if necessary, either directly with a standard

potassium chloride solution (say 0.002N) or by comparison with a cell the

constant of which is known accurately. (In the later case, the concentration

and nature of the electrolytes in the liquid which is used for the comparison

should be the same and should be similar respectively to those of the liquids

with which the cell is likely to be used in practice.

Use some of the samples to washout the conductivity cell thoroughly. Fill the

conductivity cell with the sample. Measure the conductivity in accordance with

the instruction of the instrument manufacturer.

Depending upon the type of meter used, the results are read as either

conductivity in micromhos or TDS in ppm. The relationship between these

measurements when these procedures are used is as follows:

TDS, ppm = 0.66 x Conductivity, micromhos

Conductivity, micromhos = 1.5 x TDS, ppm.


pH-Electrometric Method Test ProceduresApparatus

METHOD:

Notes:

pH Meter, Complete

Beaker, 150 ml,

Heavy Duty Plastic (3 each)

Wash Bottle, 500 ml, Heavy Duty Plastic

Reagents

Standard pH Buffer Solution, pH-4



Carefully follow the procedures provided with the pH meter. They should be

similar to the following:uTurn the meter from “standby” to “on” position.

uStandardize instrument by immersing the electrode(s) into two

different Standard pH buffer Solutions in the test beaker as follows:

(a.) Place electrode(s) in pH-7 Buffer Solution and adjust the meter to

read pH-7.(b). Place electrode(s) in the second pH Buffer Solution,

either the pH-4 or pH-10, depending on the suspected range of the

unknown sample to be tested, and adjust the meter to the same pH.

uRemove electrode(s) and thoroughly wash with distilled or condensate

water.

uImmerse the electrode(s) in the water sample and turn the meter to

“test” or “pH” position and read meter.uRinse the electrodes with distilled or condensate water and turn the

instrument to the “standby” position. Do not turn off.

uWhen not in use, keep the glass electrodes soaking in a pH-4 Buffer

Solution.

uWhen not in use, keep the plastic cap on the reference electrode.

Some reference electrodes must be kept full of electrolyte. Follow the

instrument instructions on this.

113

Total hardness Test ProceduresIntroduction

Reagent required

Procedure

Calculation

Hardness is defined as the sum of the calcium and magnesium ions in water

expressed in milligrams per liter (or ppm) as calcium carbonate. Hardness tests

should be done on softeners to make sure they are functioning and deaerator

water to make sure no contamination is occurring.

This test is based on the determination of the total calcium and magnesium

content of simple by titration with a sequestering agent in the presence of

organic dye sensitive to calcium and magnesium ions. The red to blue color

change endpoint is observed when all calcium and magnesium ions are

sequestered.

Hardness tests should be conducted on water softeners and condensate but not

on boiler water as elevated iron concentrations can lead to chemical

interference and poor test results.

Hardness Reagent 0.01 M

Hardness Buffer

Hardness Indicator Powder

Rinse the graduated cylinder and beaker or a test tube with the sample

to be tested. Fill the graduated cylinder to 50 mL and add this water to

the beaker or a test tube

If hardness is expected to be greater than 100 take a 50 ml sample

and if less than 100 then the sample can be of 20 ml

Add 5 drops of Hardness Buffer to the beaker using the plastic pipette.

Swirl to mix.

Add 1 spoon of Hardness Indicator Powder. Swirl to dissolve

completely. The sample will turn red if hardness is present. If the

sample is blue, the hardness level is completed to be zero.

If the sample colour is purple or red, add standard hardness titrating

solution slowly from the burette to the beaker until the purple or red

colour changes to blue. This is the end point. Read to nearest 0.1 ml

For a 50 mL sample, ppm Hardness as CaCO = mL of Hardness 3

Reagent X 20.

For a 20 mL sample, ppm Hardness as CaCO = mL of Hardness 3

Reagent X 50.

u

u

u

u

u

u

u


Sulphite testing procedureIntroduction

Reagents required

Procedure

Calculation

Sulfite is used in boiler feedwater conditioning to prevent oxygen pitting by the

removal of dissolved oxygen. It is necessary to maintain an excess sulfite level

to ensure rapid and complete oxygen removal. This test is based on the

reaction of sulfite with iodine in acidic solution. The iodide-iodate titrant

generates iodine in the acidic solution. This iodine is consumed in a reaction

with excess sulfite. At the endpoint, excess iodine combines with the indicator

to form a blue colour.

Iodide-Iodate Reagent N/40

Acid Starch Indicator Powder

Phenolphthalein Indicator

Rinse the graduated cylinder and beaker or a test tube with the sample

to be tested. Fill the graduated cylinder to 50 mL and add this water to

the beaker or a test tube

If sulphite is expected to be greater than 100ppm take a 50-ml sample

and if less than 100 ppm then the sample can be of 20 ml

Add 1 drops of Phenolphthalein Indicator to the beaker using the

plastic pipette. Swirl to mix.

If the sample remains colourless proceed with step 5. If the sample

turns pink add Acid Starch indicator Powder one, 1gram at a time until

the sample becomes colorless. Swirl to mix between each addition of

indicator.

Fill the Titration Burette to the zero mark with Iodide-Iodate Reagent

N/40. Add the reagent slowly to the Erlenmeyer flask with constant

stirring. Continue to titrate until a permanent blue color develops in

the sample. Read the titrated volume from the burette.

For a 50 mL sample,

Ppm sulphite as CaCO = mL of Iodide-Iodate Reagent X 20.3

For a 20 mL sample,

Ppm sulphite as CaCO = mL of Iodide-Iodate Reagent X 50.3

u

u

u

u

u

115

Chloride Test Procedure Apparatus:

Reagents

Procedure

Results

Example

Burette, 10 ml Automatic (for Mercuric Nitrate Solution)

Graduated Cylinder, 50 ml, Plastic

Casserole, Porcelain, Heavy Duty, 200 ml Capacity

Stirring Rod, Plastic

Bottle, w/Dropper, 2 oz (for Chloride Indicator Solution)

Standard Mercuric Nitrate Solution, 0.0141 N

Chloride Indicator Solution

Standard Sulfuric Acid Solution, N/50

Measure the amount of water to be tested in the graduated cylinder.

The amount should be based on the expected results of the tests

according to the following:


Add 1.0 ml of Chloride Indicator Solution to the water in the casserole

and stir for 10 seconds. The color of the water should be a green-blue

color at this point.

Add the standard Sulfuric Acid Solution a drop at a time until the water

turns from greenblue to yellow.

Squeeze the rubber bulb to force the Standard Mercuric Nitrate

Solution from the bottle to fill the burette just above the zero mark;

then allow the excess to drain back automatically into the bottle.

While stirring the sample constantly, add Standard Mercuric Nitrite Solution

slowly from the burette to the casserole until a definite purple color appears.

This is the end point.(The solution will turn from green-blue to blue a few drops

from the end point.) Read the burette to the nearest 0.1-ml.

The Chloride, in ppm C1, is calculated as follows:

Chloride, ppm C1 = (ml of Mercuric Nitrate – 0.2) x factor.

11.2 ml of 0.0141 N Mercuric Nitrate Solution was required to change the color

of a 50-ml sample of water from a green-blue to purple.

Chloride = (11.2 – 0.2) x 20 = 220 ppm)

u

u

u

u

u

Chloride Expected as Cl

Less than 20 ppm

More than 20 ppm

Sample Size

50ml

20ml

Factor

10

20


Checking Acid Solution Strength for Cleaning

Apparatus:

Reagents:

Method:

Results:

The initial strength of the dilute inhibited acid will vary from 5 to 20%, although

10% is typical. Since the acid is consumed by dissolving the scale, the strength

of the acid decreases. The strength of the acid solution should be measured

periodically during a cleaning operation. When the acid strength falls below

3%, the solution may be discarded since most of its scale-dissolving capability

will have been used. Use the following procedure to check the acid strength:

Burette, 25 milliliters (0.8 ounce) automatic (for sodium hydroxide solution)

Bottle, with dropper, 50 milliliters (2 ounces) (for phenolphthalein indicator

solution)

Graduated cylinder, 10 milliliters (0.3 ounce)

Casserole, porcelain, heavy duty, 210-milliliter (7.1-ounce) capacity

Stirring rod

Sodium hydroxide solution, 1.0 normality (N)

Phenolphthalein indicator solution, 0.5%

Measure 10 milliliters of acid solution accurately in the graduated

cylinder.


Add 2 to 4 drops of phenolphthalein indicator solution to the casserole

and stir.

Fill the automatic burette with the 1.0 N sodium hydroxide solution;

allow the excess to drain back into the bottle.

While stirring the acid solution constantly, add sodium hydroxide

solution from the burette to the casserole until color changes to a

permanent faint pink. This is the endpoint. Read the burette to the

nearest 0.1-milliliter (0.003-ounce).

For hydrochloric acid:

Percent hydrochloric acid = milliliter of 1.0 N sodium hydroxide x 0.36

For sulfamic acid:

Percent sulfamic acid = milliliter of 1.0 N sodium hydroxide x 0.97

u

u

u

u

u

117

Units and

Measurement

conversion


BASICS

Length

Area

Volume

Density

Mass

Velocity

Volume Flow

Mass Flow

1 m = 39. 37 " | in = 3,281 ' | feet-2 1 in | " = 25.40 mm = 2,540·10 m

1 ft | ' = 304. 8 mm = 0.3048 m

1 m² = 10.76 ft² = 1550 in²-21 ft² = 9,290·10 m²-41 in² = 6,452·10 m²

1 m³ = 6,102·104 in³

1 m³ = 35.31 cf | ft³ = 264.2 US Gallon-2 1 cf | ft³ = 2,832·10 m³ = 28.32 Liter | dm³

-21 in³ = 1,639·105m³ = 1,639·10 Liter | dm³-31 US Gallon = 3,785·10 m³ = 3,785 Liter | dm³-31 UK Gallon = 4,546·10 m³ = 4,546 Liter | dm

31 mn Air=38.04 SCF Air=1.292 kg Air-2 3 -21 SCF Air =2,629·10 mn Air=3,397·10 kg Air

-21 kg/m³ = 6.243·10 lb/ft³

1 lb/ft³ = 16.02 kg/m³

1 kg = 2.205 lb | lbs

1 lb | lbs = 0.4536 kg

1 m/s = 3.281 ft/s

1 m/s = 196.9 ft/min | FPM-31 FPM = 5.080·10 m/s

1 ft/sec. = 0.3048 m/s

1 m³/h = 0.5885 CFM | ft³/min

1 CFM = 1.699 m³/h31 SCFM = 1.577 mn /h Air (only)

1 kg/h = 2.205 lb/h

1 lb/h = 0.4536 kg/h

119

Pressure

Kinematic Viscosity

Temperature

Heat Load | Power

Specific Heat

1 bar = 14.50 psi

1 bar = 100.0 kPa

1 bar = 0.9869 Atm.

1 mbar = 0.7501 mm Hg | Torr

1 mbar = 10.20 mm WG

1 mbar = 100.0 Pa-21 psi | lbf/in² = 6,895·10 bar-21 psi | lbf/in² = 6,804·10 Atm.

1 psi | lbf/in² = 6,895 kPa

1 Pa·s = 1.000 cP

1 Pa·s = 0. 6720 lb/ (ft·s)

1 cP = 1,000·10-3 Pa·s | Ns/m²

1 cP = 1,000·10-3 kg/ (m·s)

1 lb/ (ft·s) = 1.488 Pa·s

1 lb/ (ft·s) = 1488 cP | mPa·s

°C | Celsius = 5 · (°F – 32) / 9

°F | Fahrenheit = 32 + 9 · °C / 5

Heat Content & Energy

1 kJ | KN·m = 0.9478 Btu

1 kJ | KN·m = 0.2388 Kcal

1 Btu = 1.055 kJ

1 Btu = 0.2520 Kcal

1 kcal = 4,187 kJ

1 kcal = 3.968 Btu

1 kWh = 859.8 Kcal

1 kW = 3412 Btu/h

1 kW = 859.8 Kcal/h

1 Btu/h = 2,931·10-4 kW

1 Btu/h = 0.2520 Kcal/h

1 kcal/h = 1,163·10-3 kW

1 kcal/h = 3.968 Btu/h

1 Boiler HP = 9.81 kW

1 kJ/ (kg·K) = 0.2388 Btu/ (lb·°F)

1 kJ/ (kg·K) = 0.2388 kcal/ (kg·°C)

1 Btu/ (lb·°F) = 4,187 kJ/ (kg·K)

1 kcal/ (kg·°C) = 4,187 kJ/ (kg·K)


Common conversion factors for ion exchange

calculation

To Convert To Multiply by

Kgr/ft3 (as CaCO3)Kgr/ft3 (as CaCO3)Kgr/ft3 (as CaCO3)g CaCO3/litreg CaO/litre

g CaO/Litreg CaCO3/Litreeq/litreKgr/ft3 (as CaCO3)Kgr/ft3 (as CaCO3)

1.282.290.04580.4360.780


U.S.gpm/ft3U.S.gpm/ft2U.S gpmBV/min

BV/hrM/hr

3M /hrU.S. gpm/ft3

8.022.450.2277.46

Capacity

Flow Rate

Pressure drop

Density

Rinse requirement


PSI/ftMH O/M of Resin2

G/cm/M2.30230

U.S. gal/ft3 BV 0.134



Lbs/ft3 gm/litre 16.0

121

Water Equivalents

One U.S. gallon - 0.1337 cubic foot

One U.S. gallon - 231 cubic inches

One U.S. gallon - 0.833 British Imp gallons

One U.S. gallon - 3.785 Liters

One U.S. gallon - 3785 cubic cm (Milliliters)

One U.S. gallon water - 8.33 Pounds (Lb)

One cubic foot - 7.48 U.S. gallons

One cubic foot of water - 62.43 Pounds

One litre/second - 15.9 (US) gal/Min

One cubic meter per hour - 4.4 (US) gal/min

One kgr / sq. cm - 14.2 pounds/sq. inch

One Pound/1000 gel - 120 parts per million

One inch/minute rise rate - 0.625 gpm/sq.ft

One cubic meter - 1000 liter

One cubic meter - 264.2 U.S gallons

One cubic meter - 220 British Imp gallons

.001

.001

.1

.1

.0583

.0583

.07

.07

.0004

.0004

1 Part permillion (1 ppm)

1 milligram perlitre (1mg/litre)

1

1

1

1

WaterAnalysisConver--siontable

Partspermillion(ppm)

Milli--gramsperlitermg/L

GramsperLitergms/L

Partsperhund--redthousandpts/100000

Grainsper U.S.gallonsgrs/U.Sgal

GrainsperBritishImpgallongrs/Imgal

KilograinspercubicfootKgr/cu.ft

1

.01

100

1

58.3

.583

70

.7

.435

.00436

1 gramperlitre(1m/litre)

1 Partsperhundredthousand1pt /1000000)

1000

10

1000

10


Water Analysis Conversion Table for Units Employed: Equivalents

.017

.014

2.294

.0583

0.583

1

.833

.583

1.04

1.71

1.43

229.4

.07

0.7

1.2

1

.7

1.24

1

.833

134

.1

1

1.71

1.43

1

1.79

1.2

1

161

.0560

0.560

0.958

0.800

0.560

1

.0075

.0052

1

.020

.20

.343

.286

.20

.357

1 Grainper U.Sgallon(1 gr/U.S gal)

1 GrainperBritishImp gal--lon (1gr /Impgal)

1 Kilograinper cubicfoot (1 kgr/cu.ft)

1 Parts permillion (1 ppm)

1 Part perhundredthousand(1 pt/100000)

1 Grain perUS gallon(1 gpg)

1 Englishor Clarkdegree

1 FrenchDegrees(1.French)

1 GermanDegrees (1 German)

17.1

14.3

2294

1

10

17.1

14.3

10

17.9

17.1

14.3

2294

0.1

1

1.71

1.43

1

1.79

WaterAnalysisConver--siontable

Partspermillion(ppm)

Milli--gramsperlitermg/L

GramsperLitergms/L

Partsperhund--redthousandpts/100000

Grainsper U.S.gallonsgrs/U.Sgal

GrainsperBritishImpgallongrs/Imgal

KilograinspercubicfootKgr/cu.ft

123

Indian standard grade for the commonly used

regeneration chemicals

Regeneration Chemicals

Hydrochloric Acid

Sulphuric Acid

Sodium Hydroxide

Sodium Carbonate

Sodium Sulphite

Sodium chloride

Alum

IS Number

IS 265

IS 266

IS 252 (Tech/Rayon Grade 46% lyes)IS1021 (Pure Grade - Flakes)

Is251 (Tech Grade)

Is251 (Tech Grade)

IS 297 (Tech Grade)

Is260 (Tech Grade)


Brief List of Reference

Betz Handbook

Demineralization by Ion exchange – S. Applebaum – Academic press

Reverse osmosis by Zahid Amjad – Van Nostrand Reinhold (NY)

Membrane Manual –Dow Chemical Company

Army Engineering Publications- Public bulletin No. 420-49-05

CIBO Energy efficiency handbook

WARE Boiler book on-line

“Chemical Treatment of Cooling Water in Industrial Plants”by Timothy Keister

(Basic Principals and Technology) ProChemTech International, Inc.

Brockway, Pennsylvania

Glegg handbook

Water and Wastewater by Hammer and Hammer

Dorfner, K., Ion Exchangers, Properties and Applications, Ann Arbor Science,

Ann Arbor, Michigan, 972

Kunin, R., Ion Exchange Resins, Robert E. Krieger Publ. Co., Huntington, N.Y.,

1957

Nachod, F. C. and Schubert, J., editors, Ion Exchange technology, Academic

Press, New York, N.Y., 1957

Water treatment technology program Report no 29

Pure water handbook by osmonics

"Pretreatment of Industrial Wastes," Manual of Practice No. FD-3

Public Works Technical Bulletin 420-49-21 Boiler water treatment lessons

learned

Public Works Technical Bulletin 420-49-22 Cooling water treatment lessons

learned

(Published by the U.S. Army Installation Support Center)

International site for Spirax Sarco

Industrial Water Treatment Primer TYNDALL AFB, FL 32403-6001

Sedifilt.com

Web site of N.E.M Business Solutions

Website of Portland water bureau

How to Manage Cooling Tower Water Quality by Ken Mortensen in RSES journal

_5-03pd

And many more

125

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Phone : +91 44 37171717Fax : +91 44 37171737Email : [email protected] : www.aquadesigns.in

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