This document provides an overview of cooling water systems training. It begins with an agenda and then discusses the basic types of cooling water systems - once through, closed recirculating, and open recirculating. For open recirculating systems, it describes the components and operation of cooling towers. It also covers fundamentals of cooling water, including important chemical properties like conductivity, hardness, alkalinity and pH. Maintaining proper control and treatment of these properties is key to optimal cooling water system operation.

1. COOLING WATER
TRAINING PROGRAM

2. CWT-2
Agenda
• Introduction
• Basic Types of Cooling Systems
• Fundamentals of Cooling Water
• Lunch
• Cooling System Problems
• Treatment Programs
• Questions

3. CWT-3
TYPES OF COOLING
WATER SYSTEMS

4. CWT-4
• The purpose of cooling
systems is to transfer heat
from one substance to
another
• The substance that gives
up its heat is “cooled”
• The substance that
receives the heat is the
“coolant”
THE COOLING PROCESS

5. CWT-5
Simple Heat Transfer
Hot Process In
Hot Cooling
Water Out
Cooled Process Out
Cold Cooling
Water In
BTU's
BTU's
Common Measurement of Heat
A BTU is the amount of heat required to
raise the temperature of 1 lb. of water 1°F
Heat Exchangers are
used for industrial
process cooling

6. CWT-6
Basic Types of Cooling
Water Systems
There are three basic types of cooling
water systems commonly used in
industry...
1. Once Through
2. Closed Recirculating
3. Open Recirculating

7. CWT-7
ONCE THROUGH
COOLING WATER
SYSTEMS

8. CWT-8
Once Through Systems
• Simplest type of system
• Water passes water through heat
exchangers only one time
• Discharged back to original source
• No recirculation occurs - mineral
content of water remains unchanged

9. CWT-9
Once Through Systems
Intake
Pump
Discharge
EXAMPLES
 Potable Water Systems
 Process Water
 General Service
CHARACTERISTICS
 Avg. Temp. Change: 8-10°F [4.4-5.6°C]
 Amount of Water Used: Large 
Heat Exchanger

10. CWT-10
Once Through Systems
A once-through cooling water
system uses large volumes of
water to achieve the cooling
process...

11. CWT-11
Once Through Systems
Large volumes of water used
Large volumes of water discharged
• Water intake source typically seawater,
lake water, or river water
• Discharge water returned to the same
source, but in a different location to
prevent recycling

12. CWT-12
Once Through Systems
Advantages
• Low capital/operating costs: Pumps+HX
• Water undergoes minimal temperature
change
Disadvantages
• Large volumes of water required
• Environmental concerns: Thermal pollution
• Cost: Expensive to treat large volumes

13. CWT-13
Once Through Systems
Considerations
Environmental
• Intake/Discharge restrictions
• Plants under increased pressure to reduce
water usage
Seasonal
• Water must meet minimal requirements
• Availability: Reliable supply needed
• Quality: Degrades during ‘dry times’

14. CWT-14
CLOSED RECIRCULATING
WATER SYSTEMS

15. CWT-15
Closed Recirculating Systems
A closed recirculating system (closed
loop) removes heat from a process by
using a fixed volume of cooling water that
is not open to the atmosphere. No water
is evaporated.

16. CWT-16
Closed Recirculating Systems
Heating or Cooling
Equipment
Pump
Cold
EXAMPLES
 Diesel Engine Jackets
 Automobile Radiators
 Chilled Water Systems
CHARACTERISTICS
 Avg. Temp. Change: 10-18°F [5.6-10°C]
 Amount of Water Used: Low
Heat Exchanger
Hot

17. CWT-17
Closed Recirculating Systems
Situations When Closed Loops are Useful…
• Critical Processes: High heat flux systems
• Discharge Restrictions: Volume/thermal
• Water Source Limitations: When water is not
plentiful
• Extended Equipment Life: Easier to control
corrosion in closed systems (e.g. chillers)

18. CWT-18
Secondary
Exchanger
Process
Exchanger
Pump
Makeup
TYPICAL
SYSTEM
Closed Recirculating Systems
Three Basic Parts of a
Closed Loop...
• Pump
• Primary Heat
Exchanger
• Secondary Heat
Exchanger

19. CWT-19
Closed Recirculating Systems
• Water temperatures range from 30°F [-1°C] in
a chiller system to 350°F [662°C] in a hot
water heating system.
• No theoretical water loss from the system
• Water losses occur from leaks around
expansion tanks, seals and valves
• Losses average 0.1-0.5% of system capacity
per day

20. CWT-20
Closed Recirculating Systems
Major Problems
• Corrosion
• Corrosion Product Build-up
• Plugging: Small orifices, ports, valves
• Microbiological Growth/Fouling
...Scale is generally not a
concern in closed loops

21. CWT-21
OPEN RECIRCULATING
WATER SYSTEMS

22. CWT-22
Open Recirculating Systems
Open recirculating systems are open to the
atmosphere at the tower. As the water flows over
the tower, heat picked up by the process is
released by evaporation. The cooling water then
returns to the heat exchangers to pick up more
heat.

23. CWT-23
Open Recirculating System
Makeup
Water
Pump
Blowdown
EXAMPLES
 Spray Ponds
 Cooling Towers
 Evaporative Condensers
CHARACTERISTICS
 Avg. Temp. Change: 20-30°F [11.1-16.7°C]
 Amount of Water Used: Moderate
Heat Exchanger
Cooling Tower

24. CWT-24
Heat Transfer Principle
Process In
Cold Chilled
Water Out
Process Out
Warm Chilled
Water In
BTU's
Open recirculating systems work on the basis
of two principles...
 HEAT TRANSFER
 EVAPORATION

25. CWT-25
Open Recirculating Systems
Heat Transfer
• Process in which
heat is transferred
from one substance
to another.
Evaporation
• Process by which
the hot cooling
water releases its
heat to the
atmosphere so that
it can return cool
water back to the
heat exchangers

26. CWT-26
Open Recirculating Systems
Cooling tower provides two conditions that
enhance the evaporation process...
• Break water into tiny droplets, thus providing
more escape routes for water molecules to
evaporate.
• Fans provide rapid flow of air through the
tower which removes evaporated water
molecules and allows even more to escape.

27. CWT-27
Open Recirculating Systems
Three Classifications of Open
Recirculating Cooling Towers…
1. Natural Draft
2. Mechanical Draft
3. Evaporative Condensers

28. CWT-28
Natural Draft Cooling Tower
• Hot air rises...
• Draws cool, dry, outside air
through the water, which
enhances evaporation
• Moist, warm air naturally
rises up & out of the tower
• Shape causes air to move
more quickly through the
lower section, where the
water is flowing
Hot Air & Water Vapor
Chimney
Hot-Water
Sprays
Hot Water
Cool
Water
Makeup
Water
Water
Basin &
Support

29. CWT-29
Hyperbolic Natural Draft
Cooling Tower

30. CWT-30
Mechanical Draft Towers
Use mechanically operated fans to move air
through the cooling tower…
Forced Draft Towers
Induced Draft Towers

31. CWT-31
Forced Draft Towers
• Push air through
tower
• Use limited to
smaller systems due
to high horsepower
required
Draft
Eliminator
Hot Air
Hot Water In
Solid Sides
Makeup
Water
Cooled
Water
Basin Cooled
Water
Fans

32. CWT-32
Induced Draft Towers
• Pull air through tower
• Classified as either counterflow or crossflow
• Classification depends on flow of air with
respect to cooling water
Counterflow Crossflow
Solid
Sides
Air Air
Louvered
Sides
Air Air

33. CWT-33
Evaporative Condenser
• A cooling tower that combines a closed
recirculating cooling system with an
open recirculating one
• Instead of having the recirculating water
open to atmosphere at the tower, the
water is carried inside of cooling coils

34. CWT-34
Evaporative Condensers
Vapor
In
Liquid
out
Water Makeup
Condenser Coil
Water Distribution System
Fan
Air Inlet
Pump
Air Discharge
Air Discharge
Fan
Pump
Air Flow
Condensing
Coil
Eliminator
Bleed
Tube
Blow-Through Type Draw-Through Type

35. CWT-35
Cooling Tower Components
• Basin
• Cold Well
• Drift Eliminators
• Louvers
• Cells
• Fill
• Spray Nozzles
Hot Air & Vapor
Drift
Eliminators
Cross
Flow
Air
Makeup
Water
Cool
Water
Basin
Louvers
Air
Hot
Water
In
Fan

36. CWT-36
Cooling Tower Components
• TOWER BASIN: Area under the cooling tower where CW is
collected and held until it is pumped back to the exchangers.
• COLD WELL: Deeper part of tower basin where the screens &
pumps are installed to circulate the water.
• DRIFT ELIMINATORS: Removes entrained water droplets from
the air leaving the tower. The moisture laden air is forced to
change direction and water droplets are removed.
• LOUVERS: Sloping boards on the outside of the towers where
air enters. Prevent water spray from leaving the tower.
• CELLS: Cooling towers are divided by partitions that separate it
into distinct sections. Each cell has its own fan system.

37. CWT-37
Tower Fill
• Increases contact
between air & water
• Breaks water into
small drops or a film
as it cascades
through the tower
• Two types of fill
Splash Fill
Film Fill

38. CWT-38
Tower Fill
Splash-Type Fill:
• Bars made of wood or plastic are used to
break water into droplets
Film-Type Fill:
• Plastic, wood or metal packing that divide
inlet water into thin films which maximize
exposed surface area
• Film packing allows greater air flow and
generally results in improved tower
efficiency

39. CWT-39
Control Valve
Water Inlet Orifices Deck
Water Depth Ceramic
Nozzle
Deck
Water Distributor
Header
Structural
Supports
Spray
Nozzles
Laterals
Spray Nozzles
Inlet Water Distribution System
Pressurized spray headers
Spreads hot water uniformly across the top of the tower
Tower deck with gravity
distribution through holes

40. CWT-40
Open Recirculating Water
Systems
• Efficient operation of the cooling water
system is critical to the production process in
any industrial plant.
• Optimal operation of cooling water systems
are dependent on two things:
 Maintain good mechanical control
 Maintain good chemical control

41. CWT-41
FUNDAMENTALS
OF
COOLING WATER

42. CWT-42
Why Use Water for Cooling?
• Plentiful; Readily Available; Cheap
• Easily Handled: Pumpable
• Can carry large amounts of heat
• Does not expand/contract much at
normally encountered temperatures
• Does not decompose

43. CWT-43
Why Use Water for Cooling?
• Specific Heat: Measure of how well a
substance absorbs heat
• Water can absorb more heat than virtually
any other substance that would be
considered for industrial cooling
• Minor increases in temperature
• Minimal environmental impact
• Everything is compared to water: Specific
Heat = 1.0

44. CWT-44
Why Isn’t Water Perfect for
Cooling?
• Dissolves everything it touches: Metal;
earth; stone
• Unique dissolving ability has earned
water the title...

45. CWT-45
Precipitation
Rain
Vegetation
(Evaporation)
Soil
Ponds and Lakes
Rivers
Moist Air
to Continent
Hydrologic Cycle
• Rain falls to earth
• Becomes ground water
• Enters ponds, lakes, rivers, oceans
• Evaporates back into air
• Rain again

46. CWT-46
Water contains 3 types of impurities
MINERALS
AIR
EARTH
Calcium
Magnesium
Sodium
Iron
Oxygen
Carbon
Monoxide
Carbon
Dioxide
Clay
Silt
Sand
(1) Dissolved Solids (2) Dissolved Gases (3) Suspended Matter
RAIN  Water in purest natural form

47. CWT-47
Two Sources of Water
Surface Water
• Low in dissolved solids
• High in suspended solids
• Quality changes quickly with seasons & weather
Ground Water
• High in dissolved solids
• Low in suspended solids
• High in iron & manganese
• Low in oxygen, may contain sulfide gas
• Relatively constant quality & temperature

48. CWT-48
What Chemical Properties of
Water Are Important?

49. CWT-49
Important Properties of Water
1. Conductivity
2. Hardness
3. Alkalinity
4. pH

50. CWT-50
Pure
Distilled
Water
Distilled
Water with
Salt
Conductivity
• Measure of water’s ability
to conduct electricity
• Pure water will not
conduct an electrical
current
• As minerals accumulate,
conductivity increases
NA+
NA+
CL-
CL-

51. CWT-51
Conductivity
• Proportional to amount
of dissolved solids in
the water
• Used to measure TDS
• Micromhos (umhos)
• Calcium, magnesium,
alkalinity, silica, sodium
•  Conductivity
•  Corrosion/Scale
Potential
Did you know?
The oceans alone contain
enough dissolved matter to
bury all of the land on earth
under 112 feet [34 meters] of
mineral deposits

52. CWT-52
Hardness
• Amount of Calcium & Magnesium present
• Hardness reacts with other minerals such as
carbonate alkalinity, phosphate, & sulfate
• Tendency to come out of solution & form hard
deposits in heat exchangers
• Ca/Mg inversely soluble with temperature
• Potential for hardness deposition affected by
alkalinity levels

53. CWT-53
Alkalinity
• Carbonate & Bicarbonate Ions
• React with hardness to form scale (e.g.
Calcium Carbonate)
• Must maintain within specified range
•  Alkalinity: Scale/deposition
•  Alkalinity: Corrosion

54. CWT-54
pH
ACIDIC BASIC
Hydrogen Ions Increase
1 2 4 5 6 7 8 9 10 11 12 13 14
3
Measure of hydrogen ions present in water...
H+ ions  -- pH 
H+ ions  -- pH 
pH SCALE

55. CWT-55
pH
• pH 7.0  ‘Neutral’ not ‘pure’ water
• Balance between hydrogen & hydroxyl
ions in the water
• Maintaining good pH control critical to
cooling system operation
• Short pH excursions can be detrimental
• Low pH: Corrosion
• High pH: Scale

56. CWT-58
Concentration of Dissolved
Solids
• Only pure water can evaporate
• No dissolved solids leave the
liquid water
• If there are no other water losses
from the system, the evaporation
process causes an increase in
the concentration of dissolved
solids in the recirculating cooling
water.
6
1
3
2
5
4
Constant
Evaporation

57. CWT-59
Concentration of Dissolved
Solids
• Mineral scale will form if the dissolved
solids concentration in the cooling water
becomes too high
• Supersaturation

58. CWT-60
Impact of Blowdown on
Concentration Ratio
Blowdown:
• Deliberate
discharge of
water to prevent
the dissolved
solids from
getting to high
6
1
3
2
5
4
Constant Evaporation
6
3
2
5
4
Constant Evaporation
1
With
Zero
Blowdown
With
Continuous
Blowdown
Maintaining
4 Cycles

59. CWT-61
Makeup Water
• Amount of water
required to replace
water lost by
evaporation and
blowdown
Evaporation
Makeup
Blowdown
Makeup =
Evaporation +
Blowdown

60. CWT-62
Holding Time Index
• Amount of time
required for the
concentration of any
ion to reach one-half
of it’s original
concentration
• Important for proper
selection & dosing
of treatment
chemicals
0
1
2
3
4
5
6
7
8
9
10
0 24 48 72 96 120
Time (hours)
Concentration
(ppm)
T½ = 60 hours

61. CWT-63
LUNCH
BREAK

62. CWT-64
COMMON COOLING
SYSTEM PROBLEMS

63. CWT-65
CORROSION
MICROBIO
Cooling System Problems
Left unchecked these
problems cause
• Loss of heat transfer
• Reduced equipment life
• Equipment failures
• Lost production
• Lost profits
• Increased maintenance
costs
• Plant shutdown

64. CWT-66
MINERAL SCALE

65. CWT-67
Mineral Scale
• Cooling Water contains many different
minerals -- normally these minerals are
dissolved in the water
• Under certain conditions minerals can
come out of solution and form into hard,
dense crystals called SCALE

66. CWT-68
Scaled Heat Exchanger Tubes
Mineral Scale
Common Scales
• Calcium Carbonate
• Magnesium Silicate
• Calcium Phosphate
• Calcium Sulfate
• Iron Oxide
• Iron Phosphate
• Others...
CaPO4
CaCO3

67. CWT-69
Mineral Scale
The Following Factors Affect
Scale Formation...
Mineral Concentration
Water Temperature
Water pH
Suspended Solids
Water Flow Velocity

68. CWT-70
Temperature & Scale Tendency
Scaling Tendency
Temperature

69. CWT-71
Mineral Scale
• Scale forms in hot areas of cooling
systems
• Reduces heat transfer efficiency
• Mechanical/Chemical cleaning
• Under deposit corrosion (pitting)
• Plant shutdown
• Equipment replacement

70. CWT-72
Preventing Mineral Scale
• Limit concentration of scale forming
minerals: Blowdown, clarify/filter MU
• Feed acid to reduce pH & alkalinity:
Reduces scaling -- increases corrosion
• Mechanical design changes: Increase
HX water velocity, backflush, air rumble
• Apply chemical scale inhibitors

71. CWT-73
Mineral Scale
Three Classifications Of Scale
Inhibiting Chemicals Are…
• Crystal Modifiers
• Sequestrants
• Dispersants

72. CWT-74
Organophosphates & organic dispersants
distort the crystal structure of scale so that it
does not become tightly adherent
Crystal Modifiers
Minerals do not align in
a tight matrix

73. CWT-75
Polyphosphates & anionic dispersants form a
complex with troublesome minerals to
prevent them from forming scale
Sequestrants
Treated Untreated

74. CWT-76
Dispersants
Compounds such as polyacrylates are
large molecules that impart a charge
causing scale forming minerals to repel
each other
-
Particle
-
-
-
-
-
- -
-
-
-
-
Particle
-
-
-
-
-
- -
-
-
-
-

75. CWT-77
CORROSION

76. CWT-78
CORROSION
Corrosion is the mechanism by which
metals are reverted back to
their natural “oxidized” state

77. CWT-79
Battery Analogy
• Anode
• Cathode
• Electrical Circuit
• Metal lost at anode
Corrosion
e-
Electrolyte
Anode
Cathode

78. CWT-80
Simplified Corrosion Cell
Fe 2+
CATHODE
ANODE
O2
OH-
e-
STEP 1
STEP 2
STEP 3
STEP 4
Water with
Dissolved
Minerals
Base Metal
O2
e-
e- e-

79. CWT-81
Four Step Corrosion Model
• Step 1: At the anode, pure iron begins to break down
in contact with the cooling water. This step leaves
behind electrons.
• Step 2: Electrons travel through the metal to the
cathode.
• Step 3: At the cathode, a chemical reaction occurs
between the electrons and oxygen carried by the
cooling water. This reaction forms hydroxide.
• Step 4: Dissolved minerals in the cooling water
complete the electrochemical circuit back to the
anode.

80. CWT-82
Factors Influencing Corrosion
• pH
• Temperature
• Dissolved Solids
• System Deposits
• Water Velocity
• Microbiological Growth

81. CWT-83
100
10
0
5 6 7 8 9 10
Corrosion
Rate,
Relative
Units
pH
Corrosion Vs. pH

82. CWT-84
Corrosion Vs. Temperature
Corrosion Rate
Temperature
In general, for every 18°F in
water temperature, chemical
reaction rates double.

83. CWT-85
Other Causes of Corrosion
Dissolved Solids
• Complete circuit from cathode to anode
System Deposits
• Anodic pitting sites develop under deposits
Water Velocity
• Too low = deposits
• Too high = Erosion
Microbiological Growth
• Deposits; Produce corrosive by-products

84. CWT-86
Types of Corrosion
All cooling system metallurgy experiences some degree
of corrosion. The objective is to control the corrosion
well enough to maximize the life expectancy of the
system...
1. General Corrosion
2. Localized Pitting Corrosion
3. Galvanic Corrosion

85. CWT-87
Base Metal
General Etch Uniform Attack
Water
Original
Thickness
General Corrosion
• Preferred
situation
• Take a small
amount of metal
evenly throughout
the system
• Anode very large

86. CWT-88
Base Metal
Localized Pitting Attack
Water
Original
Thickness
Pitting Corrosion
• Metal removed at
same rate but from
a much smaller area
• Anode very small
• Often occurs under
deposits or weak
points
• Leads to rapid
metal failure

87. CWT-89
Galvanic Corrosion
Active End
Passive End
Magnesium
Galvanized Steel
Mild Steel
Cast Iron
18-8 Stainless Steel Type 304 (Active)
18-12-3 Stainless Type 316 (Active)
Lead Tin
Muntz Steel
Nickel (Active)
76-Ni-16 Cr-7 Fe Alloy (Active)
Brass
Copper
70:30 Cupro Nickel
67-Ni-33 Cu Alloy (Monel)
Titanium
18-8 Stainless Steel Typ 304 (Passive)
18-12-3 Stainless Steel Type 316 (Passive)
Graphite
Gold
Platinum
• Occurs when two
different metals are
in the same system
• More reactive metal
will corrode in
presence of less
reactive metal
• Potential for galvanic
corrosion increases
with increasing
distance on chart

88. CWT-90
Galvanic Corrosion

89. CWT-91
Affects of Corrosion
• Destroys cooling system metal
• Corrosion product deposits in heat exchangers
• Heat transfer efficiency is reduced by deposits
• Leaks in equipment develop
• Process side and water side contamination occurs
• Water usage increases
• Maintenance and cleaning frequency increases
• Equipment must be repaired and/or repaired
• Unscheduled shutdown of plant

90. CWT-92
Methods To Control Corrosion
• Use corrosion resistant alloys: $
• Adjust (increase) system pH: Scale
• Apply protective coatings: Integrity
• Use “sacrificial anodes”: Zn/Mg
• Apply chemical corrosion
inhibitors

91. CWT-93
Anodic Corrosion Inhibitors
• Stop corrosion cell
by blocking the
anodic site
• Severe localized
pitting attack can
occur at an
unprotected anodic
sites if insufficient
inhibitor is present
Anodic Inhibitors
• Chromates
• Nitrites
• Orthophosphates
• Silicates
• Molybdates

92. CWT-94
Cathodic Corrosion Inhibitors
• Stop corrosion cell
by blocking the
electrochemical
reaction at the
cathode
• Corrosion rate is
reduced in direct
proportion to the
reduction in the size
of the cathodic area.
Cathodic Inhibitors
• Bicarbonates
• Polyphosphates
• Polysilicates
• Zinc

93. CWT-95
General Corrosion Inhibitors
• Protect metal by
filming all surfaces
whether they are
anodic or cathodic
General Inhibitors
• Soluble Oils
• Tolyltriazoles
• Benzotriazoles

94. CWT-96
FOULING

95. CWT-97
Fouling
FOULING is the accumulation of solid
material, other than scale, in a way that
hampers the operation of equipment or
contributes to its deterioration

96. CWT-98
Common Foulants
Suspended Solids
• Silt, Sand, Mud and Iron
• Dirt & Dust
• Process contaminants, e.g. Oils
• Corrosion Products
• Microbio growth
• Carryover (clarifier/lime softener)

97. CWT-99
• Water Characteristics
• Water Temperature
• Water Flow Velocity
• Microbio Growth
• Corrosion
• Process Leaks
Factors Influencing Fouling

98. CWT-100
Affects of Fouling
• Foulants form deposits in hot and/or low flow
areas of cooling systems
• Shell-side heat exchangers are the most
vulnerable to fouling
• Deposits ideal for localized pitting corrosion
• Corrosive bacteria thrive under deposits
• Metal failure results

99. CWT-101
Economic Impact of Fouling
• Decreased plant efficiency
• Reduction in productivity
• Production schedule delays
• Increased downtime for maintenance
• Cost of equipment repair or replacement
• Reduced effectiveness of
chemical inhibitors

100. CWT-102
Fouling
Three Levels Of Attack Can Be Employed
To Address The Effects Of Fouling...
1. Prevention
2. Reduction
3. Ongoing Control

101. CWT-103
Preventing Fouling
Prevention
• Good control of makeup clarification
• Good control of corrosion, scale, & microbio
Reduction
• Increase blowdown
• Sidestream filter
Ongoing Control
• Backflushing, Air rumbling, Vacuum tower basin
• Chemical treatment

102. CWT-104
Fouling
Chemical Treatment
• Charge Reinforcers
• Wetting Agents

103. CWT-105
Charge Reinforcement Mechanism
Slightly anionic
suspended
particle
Suspended Solid
which has adsorbed
highly anionic
chemical
Highly
Anionic
Chemical
• Anionic polymers increase strength of charge
already present on suspended solids
• Keep particles small enough so they do not
settle out

104. CWT-106
Wetting Agents
Particle Build-up
With Wetting Agent
• Surfactants
• Penetrate existing
deposits
• Wash away from
metal surfaces

105. CWT-107
MICROBIOLOGICAL
GROWTH

106. CWT-108
Microbiological Growth
• Water treatment is
about managing
three fouling
processes...
Corrosion
Scale
Microbio
The microbial fouling
process is...
• The most complex
• The least understood
• The hardest to measure
and monitor
• Controlled using the
least desirable, most
expensive, & potentially
hazardous products

107. CWT-109
Microbiological Growth
Three Kinds Of Troublesome
Microorganisms In Cooling Water...
1. Bacteria
2. Algae
3. Fungi

108. CWT-110
Bacteria
Sears
Tower
• Bacteria extremely small
• Compared to a
human, a bacteria is
like a grain of sand
to the Sears Tower
• Size allows many
(millions) to fit into a
small volume of
water...

109. CWT-111
Bacteria
• There are as many
bacteria in 12 oz. of
cooling water as there
are people living in the
United States
• There are 40,000 times
as many bacteria in a
50,000 gallon cooling
system as there are
people in the world!
12oz.
Cooling Water
40,000 X
50MGAL
Cooling System

110. CWT-112
Bacteria
Types of Bacteria
1. Slime Forming
2. Anaerobic Corrosive
3. Iron Depositing
4. Nitrifying
5. Denitrifying

111. CWT-113
Bacteria
Slime Formers
Iron Depositing
Anaerobic
Typical Rods

112. CWT-114
Bacteria
• Produce acidic waste that lowers pH and
causes corrosion
• Produce large volumes of iron deposits that
foul
• Produce acids from ammonia that increase
corrosion & lower pH
• Form sticky slime masses that foul & cause
reduced heat transfer

113. CWT-115
Two Classifications of Bacteria
Planktonic:
• Free-floating bacteria in bulk water
Sessile:
• Bacteria attached to surfaces
• Over 95% of bacteria in a cooling system are
sessile and live in BIOFILMS

114. CWT-116
Biofilms
• Contribute to all cooling
water problems
• Underdeposit corrosion
• Trap silt & debris which
foul heat exchangers
and tower fill
• Provide nucleation sites
for scale formation
Biofilm Formation




115. CWT-117
FLOW
Thermal
Foulant Conductivity
CaCO3 1.3-1.7
CaSO4 1.3
CaPO4 1.5
MgPO4 1.3
Fe Oxide 1.7
Biofilm 0.4
P P
Common
biofilms are 4
times more
insulating
than CaCO3
scale!
Biofilms
• More insulating than
most common scales 
• Reduce heat transfer
efficiency
• Increase dP across
heat exchangers &
reduce flow
• Health risks (legionella)

116. CWT-118
Algae
• Require sunlight to grow
• Found on tower decks & exposed areas
• Form “algae mats”
• Plug distribution holes on tower decks
• Plug screens/foul equipment
• Consume oxidants
• Provide food for other organisms

117. CWT-119
Fungi
• Use carbon in wood
fibers for food
• Destroy tower
lumber by either
surface or internal
rotting (deep rot)
• Loss of structural
integrity of tower

118. CWT-120
Factors Affecting Growth of
Microorganisms
• Microorganism Sources: Air or Makeup water
• Cooling systems provide the ideal
environment for microbiological growth
• Nutrients: Ammonia, oil, organic contaminants
• Temperature: 70-140°F acceptable
• pH: 6.0 - 9.0 ideal
• Location: Light/No Light
• Atmosphere: Aerobic/Anaerobic

119. CWT-121
Controlling Microbiological
Growth
Water Quality
• Eliminate organic contaminants (food)
• No food = No bugs
System Design Considerations
• Clean basin, plastic, cover decks
Chemical Treatment with Biocides

120. CWT-122
Microbiological Growth
Chemical Treatment With Biocides
• Oxidizing Biocides
• Non-oxidizing Biocides
• Biodispersants

121. CWT-123
COOLING WATER
TREATMENT
PROGRAMS

122. CWT-124
Treatment Programs
• Moly-Phosphonate
• Alkaline Zinc
• Stabilized Phosphate
• Dispersants
• All Organic
• Oxidizing Biocides
• Non-Oxidizing Biocides

123. CWT-125
MOLYBDATE-
PHOSPHONATE
PROGRAM
(Moly/Phosphonate)

124. CWT-126
Moly/Phosphonate Program
• Designed for system with corrosive (low
hardness &/or alkalinity) waters
• Molybdate-based corrosion inhibitor
• Phosphonate for scale inhibition
• Dispersant polymer for fouling
protection

125. CWT-127
Moly/Phosphonate Program
• Well suited to aluminum industry
• Works well in high heat flux systems
where heat transfer surfaces experience
high skin temperatures
• Provides protection over a wide range
of operating parameters
Calcium: 0-500 ppm
M-Alkalinity up to 2,000 ppm

126. CWT-128
• Molybdate workhorse of program
• Surface active anodic corrosion inhibitor
• Does not depend on controlled deposition
• Promotes rapid oxidation of metal surfaces to
form a tightly adherent layer of metal oxides
• Protective layer impermeable to other anions,
especially chlorides and sulfates
Moly/Phosphonate Programs

127. CWT-129
Moly/Phosphonate Program
General Control Guidelines
• Molybdate: 6-16 ppm (as MoO4)
• Phosphonate: 1-2 ppm (as PO4)
• Calcium: 0-500 ppm
• M-Alkalinity: 50 -2,000 ppm
• HTI: 120 Hours max.
• Temperature: 135-180°F [57-82°C]
• Conductivity: 2,000 micromhos max.

128. CWT-130
Moly/Phosphonate
Program Benefits
Improved Heat Transfer
• Reduced energy costs
Reduced Corrosion
• Extended equipment Life & reliability
No impact on quenchability
• Production not negatively impacted

129. CWT-131
ALKALINE/ZINC
PROGRAM

130. CWT-132
Alkaline/Zinc Program
• Uses low levels of zinc together with
ortho phosphate for corrosion control
• Polymeric dispersant used for general
dispersancy & scale control
• Attractive cost performance under high
stress conditions
• Basic program can be customized to fit
system needs

131. CWT-133
Alkaline/Zinc Program
• Zinc provides cathodic corrosion
protection
• Ortho phosphate provides anodic
corrosion protection
• The key to the success of the alkaline
zinc program is the polymer dispersant

132. CWT-134
Alkaline/Zinc Program
Polymer Dispersant
• Maintains zinc & phosphate in soluble form at
higher pH’s than they would under normal
circumstances
• Operating at higher pH’s allow program to
provide excellent corrosion protection at very
low levels of zinc (< 1.0 ppm)
• Also provides scale control

133. CWT-135
Alkaline/Zinc Program
General Application Ranges
• Dependent on Calcium & M-Alkalinity
• Ca 200 ppm M-Alkalinity 1,500 ppm
• Ca 1,000 ppm M-Alkalinity 300 ppm

134. CWT-136
Alkaline/Zinc Program
General Control Guidelines
• Zinc (soluble): 0.5-2.0 ppm
• Ortho PO4: Extremely variable
• Insoluble PO4: 1.5 ppm or 40% of total PO4
• Calcium: 15-1,000 ppm
• M-Alkalinity: 50 -1,500 ppm
• HTI: 120 Hours max.
• Temperature: 160°F [71°C] max.
• Conductivity: 6,000 micromhos max.

135. CWT-137
STABILIZED PHOSPHATE
PROGRAM

136. CWT-138
Stabilized Phosphate Program
• Uses high levels of orthophosphate to
provide corrosion protection
• Polymeric dispersant provides calcium
phosphate stabilization
• Supplemental Tolyltriazole (TT) used
for yellow metal protection

137. CWT-139
Stabilized Phosphate Program
• Operates at near-neutral pH
• High levels of ortho phosphate (10 -17
ppm) provide anodic corrosion inhibition
• Poly phosphate & calcium complex
provide cathodic corrosion protection
• Dispersant polymer for CaPO4
stabilization

138. CWT-140
Polymer Dispersant
• Key to program is polymeric dispersant
• Inhibit inorganic scales such as calcium
carbonate & calcium phosphate
• Keep particles suspended in water --
control foulants such as:
Manganese & iron oxides
Suspended solids like mud & silt

139. CWT-141
Polymer Dispersant
• Mechanism: Charge Reinforcement
• Polymer adsorbs onto particles &
increases the ± charge naturally present
• Treated particles repel each other
• Reduces chances of collision &
agglomeration
• Prevents formation of deposits

140. CWT-142
Stabilized Phosphate Program
Excellent choice when...
• Restrictions on use of heavy metals
• Bulk water temperature < 150°F
• Low make-up calcium &/or M-alkalinity
• High incoming O-PO4 levels

141. CWT-143
Stabilized Phosphate Program
General Control Guidelines
• Total O-PO4: 8 -17 ppm (Ca dependent)
2.0 ppm insoluble max.
• Calcium: 15 -1,000 ppm
• pH: 6.8-8.4 (Ca dependent)
• HTI: 96 Hours max.
• Temperature: 150°F [66°C] max.
• Conductivity: 7,500 micromhos max.

142. CWT-144
Stabilized Phosphate Program
Properly controlled programs
• Excellent protection against corrosion
and scaling
Poorly controlled program causes
• Severe Corrosion
• Scaling
• Fouling

143. CWT-145
ALL ORGANIC
PROGRAM

144. CWT-146
All Organic Program
• Non-heavy metal/phosphate program
• All Organic programs use high pH &
alkalinity conditions to provide corrosion
protection in a scale forming cooling
system environment
• Organic scale inhibitors prevent mineral
deposits

145. CWT-147
All Organic Program
• All organic components make this a
very environmentally acceptable
program
• Contains no heavy metals that can be
precipitated (e.g. zinc sulfide)
• Contains no inorganic phosphates to
precipitate with iron in low-pH localized
leak areas

146. CWT-148
All Organic Program
• Operates under alkaline conditions at pH’s
between 8.5-9.4
• Designed for systems where makeup calcium
& M-Alkalinity cycle naturally to within
program guidelines
• Supplemental acid/caustic feed may be
required to maintain proper M-Alk.
• Maintaining the proper calcium-alkalinity
relationship is critical

147. CWT-149
All Organic Program
General Control Guidelines
• Calcium: 80-900 ppm
• M-Alkalinity: 300-500 ppm
Temperature dependent
• pH: 8.5-9.4
• HTI: 48 Hours max.
• Temperature: 110-140°F [43-60°C]
• Conductivity: 4,500 micromhos max.

148. CWT-150
All Organic Program
Properly controlled programs
• Excellent protection against corrosion
and scaling
Poorly controlled program causes
• Severe Corrosion
• Scaling
• Fouling

149. CWT-151
OXIDIZING BIOCIDES

150. CWT-152
Oxidizing Biocides
• Penetrate microorganism’s cell wall and
burn-up the internals of the organism
• Effective against all types of bacteria
• No microorganism resistant to oxidizers
• Kill everything given sufficient
concentration levels & contact time

151. CWT-153
Oxidizing Biocides
• Broad-spectrum
effectiveness
makes oxidizers
primary biocide in
large cooling
water applications
Oxidizers
• Gas Chlorine
• Bleach
• Acti-Brom
• BCDMH
• Stabilized Bromine

152. CWT-154
Oxidizing Biocides
• Biocide effectiveness
pH dependent
• Cl2  HOCl & OCl-
• Br  HOBr & OBr-
• HOCl/HOBr Biocidal
• @ pH=8.0
HOCl: 22%
HOBr: 83%
Bromine more
biocidal
HOCl
or
HOBr
0
10
20
30
40
50
60
70
80
90
100
4 5 6 7 8 9 10 11 12
pH
0
10
20
30
40
50
60
70
100
OCl-
or
OBr-
HOCl
HOBr
80
90

153. CWT-155
Chlorine Advantages
• Economical
• Traditional technology

154. CWT-156
Chlorine Disadvantages
• Slower kill at high pH
• Consumed by ammonia, sulfides, iron, manganese, &
hydrocarbons
• Volatile and easily stripped, thus high usage rates
• High residuals (or slug feeding) cause wood delignification
• High feed rates and residuals can cause higher corrosion rates
• Poor control (or slug treatment) leads to degradation of water
treatment compounds -- e.g. organic phosphate and tolyltriazole
• Chlorinated organics, e.g., THM’s, are toxic, regulated, and
persistent in the environment

155. CWT-157
Bromine Advantages
• Higher biocidal activity at significantly lower dosages than
chlorine
• Increased kill rate - better recoverability from upsets
• More active over a higher, wider pH range
• No decrease in biocidal activity in the presence of ammonia
since bromamines are as active as HOBr
• Lower halogen residuals in the effluent
• Brominated organics are less persistent than chlorinated
organics in receiving water
• Lower residuals: less wood delignification, less tolytriazole and
organic phosphate degradation, and less corrosion
• Less mechanical stripping (at pH <8.0)

156. CWT-158
Bromine Disadvantages
• Bromine is more aggressive to HEDP
• A chlorine source is needed to generate
ACTI-BROM on site.
• Dry products have fixed bromine to chlorine
ratio.
• Low residual can be difficult to control.
• Lower residual or intermittent feed can result
in lack of algae control

157. CWT-159
NON-OXIDIZING
BIOCIDES

158. CWT-160
Non-Oxidizing Biocides
• Organic compounds that react with
specific cell components
• Interfere with metabolism or destroy
cell wall

159. CWT-161
Non-oxidizing Biocides
• Generally not used as the primary
biocide in larger systems due to cost
• Typically slug fed at high dosages
• Often used for clean-up or contingency
reasons

160. CWT-162
Non-Oxidizing Biocides
• Different microorganisms exhibit
different levels of resistance to various
non-oxidizing biocides
• Specific to type of microorganism
• Work within specific (limited) pH ranges
• Carefully regulated by EPA
• Safety/Handling issues

161. CWT-163
Non-Oxidizing Biocides
Common Non-Oxidizers
• Isothiazoline
• Glutaraldehyde
• DBNPA
• Quaternary Amines
• Glut/Quat Combo

162. CWT-164
Non-Oxidizing Biocides
• No practical method of directly testing
levels of non-oxidizing biocides in CW
• Optimal dosage & application frequency
should be determined through indirect
measurement
• Microbio counts, sessile monitoring,
ATP, toxicity testing, biofouling monitors

163. CWT-165
Before Biodispersant
After Biodispersant
Biodispersants
Do not kill -- Penetrate deposits and
increase the effectiveness of oxidizing
& non-oxidizing biocides.