ISO 22449-1:2020

INTERNATIONAL ISO
STANDARD 22449-1
First edition
2020-01
Use of reclaimed water in industrial
cooling systems —
Part 1:
Technical guidelines
Utilisation de l'eau recyclée dans les systèmes de refroidissement
industriels —
Partie 1: Lignes directrices techniques
Reference number
ISO 22449-1:2020(E)
©
ISO 2020

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ISO 22449-1:2020(E)

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Published in Switzerland
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ISO 22449-1:2020(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and abbreviated terms . 1
3.1 Terms and definitions . 1
3.2 Abbreviated terms . 3
4 Technical guidelines for the use of reclaimed water in industrial cooling systems .3
4.1 General . 3
4.2 Water quality specifications . 3
4.3 Water quantity and temperature requirements . 5
4.4 Wastewater treatment technologies for reuse . 6
4.5 Treatment for inhibition of corrosion, scaling and biological fouling . 6
Annex A (informative) Types and characteristics of industrial cooling systems .9
Annex B (informative) Water quantity requirements .15
Annex C (informative) Make-up water quality requirements in closed-circuit hybrid cooling
system .16
Bibliography .17
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ISO 22449-1:2020(E)

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso .org/
iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 282, Water reuse, Subcommittee SC 4,
Industrial water reuse.
A list of all parts in the ISO 22449 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
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ISO 22449-1:2020(E)

Introduction
Industries can use large quantities of water in their production processes. Among various industrial
water uses, cooling water is a significant proportion of the total used. Industrial wastewater reuse is
one of the promising ways to solve water shortage and to provide a non-conventional water source
for cooling systems. In addition, for cooling systems, the most common water conservation method to
optimize water use is increasing the cycles of concentration inherently. Information about different
types and characteristics of industrial cooling systems is included in Annex A. In many countries such
as the United States, Japan, Israel and Indonesia, industrial wastewater reuse in industrial cooling
systems has been developed rapidly.
Reclaimed water originates not only from industrial wastewater but also from domestic wastewater.
In consideration of diverse water quality of industrial wastewater and water from other sources, it is
necessary to describe different types of industrial cooling systems which can use industrial wastewater
or most of industrial wastewater mixed with domestic wastewater, as make-up water and to give their
characteristics. However, there are no relevant ISO standards to guide the use of industrial wastewater
or mainly of industrial wastewater mixed with domestic wastewater, as make-up water and solve the
common problems such as corrosion and scaling in water reuse. This document is designed to promote
the use of reclaimed water by providing technical guidelines for the use of industrial wastewater in
industrial cooling systems. This should drive the design and operation of industrial cooling systems. The
document should lead worldwide water reuse in industrial cooling systems and is of great significance
to promote the reuse of water resources, to improve the water use efficiency, and to practice the concept
of industrial circular economy.
The design of a cooling system is a complex matter balancing the cooling requirements of the process,
the site-specific factors and the environmental requirements using technologies which allows
implementation under economically and technically viable conditions. The process of designing
industrial cooling systems is completed by the assessment of the best choice considering the other
environmental issues and the constraints linked to the industrial process. However, as a non-
conventional water source, reclaimed water can reduce the replenishment of freshwater when it is
used as make-up water. If technically and economically possible, the use of reclaimed water improves
environmental performances of the system.
This document renders technical guidelines for the use of reclaimed water in industrial cooling systems.
It provides a basic framework for industrial cooling systems using reclaimed water.
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INTERNATIONAL STANDARD ISO 22449-1:2020(E)
Use of reclaimed water in industrial cooling systems —
Part 1:
Technical guidelines
1 Scope
This document defines terms related to industrial cooling water systems and specifies technical
guidelines for the use of reclaimed water for make-up water purposes water in industrial cooling
systems. It provides a basic framework for consideration in the design and operation of industrial
cooling systems using reclaimed water. The aim of the document is to promote and to help the
implementation of the use of reclaimed water in industrial cooling systems.
It provides:
— Terms and definitions;
— Technical guidelines for the use of reclaimed water in industrial cooling systems.
This document is applicable to cooling systems that are considered to work as auxiliary systems for
the normal operation of an industrial process. However, the operation of a cooling system in relation
to process safety is not covered in this document. In addition, some environmental concerns also need
to be taken into consideration, for example the drift control or the use of some persistent biocides.
This document can be used to encourage consistency within any organization engaged in the use of
reclaimed water.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 20670, Water reuse — Terminology
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 20670 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1.1
blowdown (purge) water
water discharged from the system to control the concentration of salts or other impurities in the
circulating water, which requires treatment either in a municipal treatment system or onsite
[SOURCE: ISO 16345:2014, 2.11]
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ISO 22449-1:2020(E)

3.1.2
coolant
heat-absorbing medium or process
[SOURCE: ISO 8573-1:2010, 3.3]
3.1.3
cooling water
water which is used to absorb and remove heat
[SOURCE: ISO 6107-1:2004, 15]
3.1.4
cooling tower
tower used for evaporative cooling of circulating cooling water (3.1.3), normally constructed of wood,
plastic, galvanized metal or ceramic materials
[SOURCE: ISO 16784-2:2006, 3.4]
3.1.5
corrosion
gradual destruction or slow degradation of a substance or surface by a chemical effect
[SOURCE: ISO 16797:2004, 2.7]
3.1.6
cycles of concentration
ratio of the concentration of specific ions in the circulating cooling water (3.1.3) to the concentration of
the same ions in the make-up water (3.1.8)
[SOURCE: ISO 16784-2:2006, 3.6]
3.1.7
heat transfer medium
medium (water, air, etc.) used for the transfer of the heat without change of state
Note 1 to entry: The fluid cooled by the evaporator, the fluid heated by the condenser, and the fluid circulating in
the heat recovery heat exchanger.
[SOURCE: ISO 13612-2:2014, 3.22]
3.1.8
make-up water
water which is added to the system to compensate for the loss of water due to evaporation, blow-down,
leakage and drift loss
[SOURCE: ISO 16784-2:2006, 3.9]
3.1.9
non-conventional water source
sources of water not originating from natural fresh surface water or groundwater, including seawater
desalination, use of brackish water (directly or via desalination), and reuse of urban or industrial
wastewaters with varying levels of treatment
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ISO 22449-1:2020(E)

3.1.10
Ryznar Stability Index
RSI
index to help monitor the scaling and corrosion (3.1.5) potential of water
Note 1 to entry: Ryznar values are always positive, which attempts to correlate an empirical database of scale
thickness observed in municipal water systems and to quantify the relationship between calcium carbonate
saturation state and scale formation. The Ryznar index takes the form: RSI = 2 pH --pH (pH is the pH at saturation
s s
in calcite or calcium carbonate; pH is the measured water pH). The application of RSI in water treatment plant
demonstrated that RSI was fit in estimating the treated water chemical stability and appeared to be promising in
the field of treated water quality management.
3.1.11
scaling
surface film and corrosion (3.1.5) products produced on the surface by high temperature corrosion
[SOURCE: ISO 13573:2012, 3.1]
3.2 Abbreviated terms
BOD Biochemical Oxygen Demand
COD Chemical Oxygen Demand
HPC Heterotrophic Plate Count
TDS Total Dissolved Solid
TN Total Nitrogen
TOC Total Organic Carbon
TP Total Phosphorus
TSS Total Suspended Solid
4 Technical guidelines for the use of reclaimed water in industrial cooling systems
4.1 General
Considerations for using industrial wastewater as a source of makeup water for cooling water purposes
will likely require either an upgrade to the existing wastewater treatment system, or an additional
treatment process to improve effluent water quality and remove constituents of concern for reuse as
make-up water for cooling water systems. Industry and facility may have specific requirements that
include the space, design and choice of materials for the selection of a cooling system. A new installation
also should have an upgrading in water treatment process and take economic factors into consideration
to optimize the cost on operation and maintenance and balance the environmental efficiency. For
the purpose of water reuse in industrial cooling systems, the following factors should be taken into
consideration: water quality, water quantity and temperature, wastewater treatment technologies for
reuse, treatment for inhibition of corrosion, scaling and biological fouling, based on the industrial water
reuse experience among different regions.
4.2 Water quality specifications
The quality of reclaimed water is of great importance for the design, operation and maintenance of
industrial cooling systems. The water quality of reclaimed water can be influenced by the type of industry
and type of process; specific requirements for pipes, heat exchangers and cooling towers with the influence
of construction material and risk of direct human contact requiring disinfection and chlorine residual,
etc. Reclaimed water quality and treatment requirements may become a significant part of the local
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ISO 22449-1:2020(E)

regulations and guidelines for water reuse. Water quality parameters of interest and their specifications
of make-up water in most commonly used cooling system are listed in Table 1. Besides, make-up water
quality specifications for a closed-circuit hybrid cooling system are listed in annex Table C.1. The
recommended range of make-up water quality can be changed by controlling the reclaimed water volume
and quality, which is important for the operation of recirculating cooling water system.
[9][10][11]
Table 1 — Typical water quality specifications in most commonly used cooling systems
[12][13]
Typical values and Impact on Cooling Water
Parameter Unit
recommended range Systems
— Metal corrosion and scaling
increases when pH is below
pH / 6,5-9
and above recommended
ranges, respectively.
— Calcium is more troublesome
than magnesium in
contributing to scaling.
Total hardness (CaCO mg/l) ≤250
3
Magnesium is not as much
of problem unless the silica
levels are also high.
Alkalinity (CaCO mg/l) 100-500 — Scaling
3
— Reflect the organic content
BOD mg/l ≤10 and associated demand for
5
oxidizing biocide.
— Bio-fouling, biomass growth,
COD mg/l ≤30
cr
disinfection by-products
TSS mg/l ≤10 — Corrosion, fouling, scaling
TDS mg/l ≤5 000 — Scaling, fouling
a
Conductivity μs/cm ≤3 000 — Scaling, fouling
— Disinfection by products,
b
Residual chlorine mg/l End 0,1~0,2
corrosion
≤300 (stainless steel) — Corrosive to most metals,
Chloride mg/l
especially mild steel
≤1 000 (other metals)
— Nutrient element, biomass
Fecal Coliform CFU/100ml ≤200 growth, disinfection by-
products.
a
The range will depend upon the particular cooling water system’s design and characteristics, the type of chemical
program and the industrial process.
b
Total chlorine residual should be met after a minimum contact time of 30 minutes.
c
Iron may be a concern if it combines with phosphate to form undesirable foulants. It may also deactivate specialized
polymers used to inhibit calcium phosphate scaling. Reclaimed water may have a high concentration at 0,12 to 0,32 of
[14]
iron . Specialized treatment of iron is required for this concentration to avoid fouling the heat exchangers.
d [15]
The concentration of phosphate is limited to be less than 3 mg/l according to Chinese standard GB/T 31329-2014 ;
In a water pollution control plant owned by San Jose and Santa Clara (US), it indicates that phosphate is a common anionic
[14]
inhibitor and may also provide a mild steel corrosion protection at the levels equal to or less than 4 mg/l .
NOTE
—  Parameters such as chemical stability (e.g., Mn, silica) and biological stability (e.g., HPC) could be considered on a case-
by-case basis if specific risks are identified or required by local regulations.
—  Specific metals and anions are considered for selection depending on reclaimed water source characteristics and
use facilities. For example, copper and nickel can plate out on steel, causing localized galvanic corrosion that can rapidly
penetrate thin steel heat exchanger tubes.
—  Monitoring sites of biological stability could be considered at distribution and storage system outlets and point-of-use
with long hydraulic retention time.
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ISO 22449-1:2020(E)

Table 1 (continued)
Typical values and Impact on Cooling Water
Parameter Unit
recommended range Systems
— Combine with chloride to
form chloramines which can
negate the disinfecting effect
of chlorine and some non-
≤5
NH -N mg/l oxidizing biocides.
3
≤1 (if copper presents)
— Corrosive to copper alloys
at concentrations as low as
2,0 ppm.
2−
Sulfate (SO ) mg/l ≤800 — Scaling
4
— Form undesirable foulants if
c
Fe mg/l ≤0,3
combines with phosphate.
— At higher concentrations
(calcium greater than
1 000 mg/l and phosphate
3−d
PO mg/l ≤3 greater than 20 mg/l), there
4
is a potential for calcium
phosphate scaling in the heat
exchanger.
a
The range will depend upon the particular cooling water system’s design and characteristics, the type of chemical
program and the industrial process.
b
Total chlorine residual should be met after a minimum contact time of 30 minutes.
c
Iron may be a concern if it combines with phosphate to form undesirable foulants. It may also deactivate specialized
polymers used to inhibit calcium phosphate scaling. Reclaimed water may have a high concentration at 0,12 to 0,32 of
[14]
iron . Specialized treatment of iron is required for this concentration to avoid fouling the heat exchangers.
d [15]
The concentration of phosphate is limited to be less than 3 mg/l according to Chinese standard GB/T 31329-2014 ;
In a water pollution control plant owned by San Jose and Santa Clara (US), it indicates that phosphate is a common anionic
[14]
inhibitor and may also provide a mild steel corrosion protection at the levels equal to or less than 4 mg/l .
NOTE
—  Parameters such as chemical stability (e.g., Mn, silica) and biological stability (e.g., HPC) could be considered on a case-
by-case basis if specific risks are identified or required by local regulations.
—  Specific metals and anions are considered for selection depending on reclaimed water source characteristics and
use facilities. For example, copper and nickel can plate out on steel, causing localized galvanic corrosion that can rapidly
penetrate thin steel heat exchanger tubes.
—  Monitoring sites of biological stability could be considered at distribution and storage system outlets and point-of-use
with long hydraulic retention time.
4.3 Water quantity and temperature requirements
Compared with fresh water, reclaimed water is more likely to contain higher concentrations of
constituents during evaporation. Evaporation rate is influenced by water temperature and flow rate,
which will further affect the blowdown volume and evaporation volume, therefore it is necessary to
emphasize the water temperature and quantity requirements for using reclaimed water as make-up
water. The minimal flow and quantity vary among the various cooling water systems as performance
depends on the concentration factor applied, evaporation and to a lesser extent to the ambient
temperature. Higher ambient temperatures can cause the cooling water temperature to increase.
Increasing temperature may increase the scaling and corrosion tendency. The organisms that make up
microbial tend to flourish between 40 °F and 150 °F, and increasing microbial will reduce the efficiency
of heat transfer.
Table 2 shows the impact factors and formula of makeup volume, which creates opportunities
for appropriate conservation methods to achieve water savings. An example of water quantity
requirements for different industrial cooling systems under assumed conditions is shown in Table B.1
in Annex B. Additionally, scaling and corrosion in heat exchanger tubes are very velocity dependent.
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ISO 22449-1:2020(E)

At lower cooling water velocities, or in stagnant regions, biofilms increase and deposits occur from
suspended solids or inorganic scale. The survey results show that it will lead to scaling and corrosion
when the flow rate is lower than 0,3 m/s. In addition, the fouling thermal resistance value of water has
[10]
a big difference between the flow rate above 1 m/s and below 1 m/s .
The temperature of make-up water is also an important factor because many chemical and industrial
processes are temperature-critical applications and also correlated with the efficiency of the removal
of waste heat. Some compounds have an inverse solubility at high temperatures (above 140 °F) which
can cause increased scale formation. Because equipment designers usually incorporate one or more
factors to accommodate less-than-ideal heat transfer conditions, heat exchangers are frequently over-
designed so that the operation at the anticipated cooling water flow rates would lower the process fluid
temperature below acceptable values. As a result, operators reduce the cooling tower water flow rates
to certain heat exchangers as a means of controlling process temperatures.
Table 2 — The impact factors and formula for the makeup volume
Impact factors Calculation formula
Evaporation rate (ER) ER = Recirculated flow rate × (Warm water temperature-Desired
a
cool temperature) × 0,01/10 °F
Cycles of concentrations (COC) COC = Cooling water concentration/Makeup water concentration
Blowdown Volume (BL) BL = Evaporation Volume/(COC-1)
Makeup Volume = Blowdown Volume + Evaporation Volume
a
As a rule of thumb, for each 10 °F that the circulated water needs to be cooled, one percent of the cooling water is
evaporated in the cooling tower.
4.4 Wastewater treatment technologies for reuse
To meet the requirements of reused water quality in industrial cooling systems, applicable treatment
technologies are needed. According to the origins (industrial wastewater or blowdown), conventional
wastewater, wastewater with high salinity and wastewater with toxic and non-biodegradable
compounds should be treated at different treatment levels. Usually, many industrial wastewaters
contain high concentrations of total dissolved solids, which may be a result of neutralization or other
chemical treatment processes. TDS cause toxicity through increases in salinity, changes in the ionic
composition of water and toxicity of individual ions. Wastewater with a high TDS level can have adverse
impacts on the efficiency of biological treatment and exacerbate corrosion in water networks. In
general, it is better to ensure water and makeup water chemistry are treated properly to avoid this
issue, as once scale is formed, it is difficult and costly to remove. Lower dissolved solids will provide
the right quality of makeup water and correct circulation chemistry, allowing the cooling system to run
efficiently. This helps increase cycles for water and maintain a manageable amount of blowdown, which
in turn, helps conserve the amount of any makeup water or chemicals needed.
4.5 Treatment for inhibition of corrosion, scaling and biological fouling
Corrosion and scaling are common problems in cooling water systems. The characteristic of industrial
wastewater with complex constituents and a large amount of toxic and non-biodegradable substances
calls for more specific requirements when using the reclaimed water originated from industrial
wastewater as make-up water in cooling systems. For example, many schemes for reuse of treated
industrial wastewater, particularly in the electronics industry, provide a soft water for use as cooling
tower makeup. Besides, alkalinity of the treated effluent has a close connection with pH, which will
indirectly impact the water stability when reusing in cooling systems. Therefore, it is required to
identify water corrosion and scaling tendency in industrial cooling systems so as to cost-effectively
reuse the industrial wastewater. A general method determining the tendency of scale or corrosion
inhibitors is based on water stability index, which is listed in Table 3.
Treatments towards scaling and corrosion mainly include chemical and physical methods. Chemical
agents are commonly used as scale and corrosion inhibitors. Scale and corrosion inhibitors should
have low toxicity and be chemically stable, and the product should be confirmed based on the dynamic
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ISO 22449-1:2020(E)

simulation testing. An economic analysis would also be needed for different products. It is also feasible
to choose the chemical agents according to experience on water quality and site conditions. Dynamic
simulated tests should follow an evaluation of make-up water qualities, stability and environmental
influence of chemical agents, fouling resistance, corrosion rate, adhesion rate, concentration multiple of
cooling water, materials of heat transfer equipment, water flow velocity in heat transfer equipment and
temperature of circulating cooling water. Most successful treatment programs use several corrosion
inhibitors blended together such as molybdate-silicate-azolepolydiol and phosphonate-phosphate-
azole to take advantage of a synergistic effect, where the net reduction in corrosion from the use of a
mixture is greater than the sum obtained from individual components.
In addition, some chemical programs designed to prevent scale can work only when the hardness level
stays within the specified range. Some corrosion control programs require a certain hardness level
to function correctly. For example, the most commonly used corrosion inhibitors, polyphosphates and
phosphonates, do not work if less than 50 mg/l calcium hardness is present in the cycled cooling water.
Physical technologies such as ultrasonic and electronic descaling are also effective methods to mitigate
the fouling. The adoption of an appropriate physical technology depends on the operation efficiency,
costs a
...