ISO 4789:2023
(Main)Guidelines for wastewater treatment and reuse in thermal power plants
Guidelines for wastewater treatment and reuse in thermal power plants
This document specifies guidelines for wastewater treatment and reuse in thermal power plants, including the types and characteristics of wastewater and the technologies of wastewater treatment and reuse. In this document, thermal power plant drainage systems are divided into fuel supply, chemical water treatment, boiler and auxiliary, recirculating cooling, flue gas processing, gasification scrubber and ash handling. Wastewater from these systems is classified in accordance with its system sources. In addition, technical guidelines for wastewater treatment and reuse are provided according to the water requirements of systems in the thermal power plant. This document is formulated to provide feasible technical guidance for the treatment and reuse of wastewater in thermal power plants. It is applicable to coal-fired, oil-fired, gas-fired (including gas turbine), biomass-fired, waste incineration and integrated gasification combined cycle (IGCC) thermal power plants.
Lignes directrices pour le traitement et la réutilisation des eaux usées dans les centrales électriques thermiques
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INTERNATIONAL ISO
STANDARD 4789
First edition
2023-06
Guidelines for wastewater treatment
and reuse in thermal power plants
Lignes directrices pour le traitement et la réutilisation des eaux usées
dans les centrales électriques thermiques
Reference number
ISO 4789:2023(E)
© ISO 2023
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ISO 4789:2023(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2023
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
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ISO 4789:2023(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 . 2
4 General principles . 3
5 Types and characteristics of wastewater in thermal power plants .3
6 Wastewater treatment and reuse technologies . 7
6.1 Water quality requirements for reuse water in thermal power plants . 7
6.2 Fuel supply system wastewater treatment and reuse . 8
6.2.1 Coal wastewater . 8
6.2.2 Oily wastewater . 9
6.2.3 Leachate . 9
6.3 Chemical water treatment system wastewater treatment and reuse . 10
6.3.1 RO concentrated water . 10
6.3.2 Membrane washing wastewater and resin reclaimed wastewater
treatment and reuse . 11
6.4 Boiler and auxiliary system wastewater treatment and reuse . 11
6.4.1 Boiler blowdown . . . 11
6.4.2 Boiler chemical cleaning wastewater .12
6.4.3 Auxiliary equipment cooling water blowdown .12
6.5 Recirculating cooling system wastewater treatment and reuse .12
6.6 Flue gas processing system wastewater treatment and reuse .13
6.6.1 WESP blowdown .13
6.6.2 FGD wastewater . 14
6.7 Gasification scrubber system wastewater treatment and reuse . 14
6.8 Ash handling system wastewater treatment and reuse . 15
Annex A (informative) Cases of water balance in thermal power plants .16
Annex B (informative) Cases of wastewater reuse in thermal power plants .25
Bibliography .28
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ISO 4789:2023(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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use
of (a) patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed
patent rights in respect thereof. As of the date of publication of this document, ISO had not received
notice of (a) patent(s) which may be required to implement this document. However, implementers are
cautioned that this may not represent the latest information, which may be obtained from the patent
database available at www.iso.org/patents. ISO shall not be held responsible for identifying any or all
such patent rights.
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.
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 4789:2023(E)
Introduction
Global water scarcity is becoming increasingly pronounced as a result of the massive demand for water
caused by population growth, public life and industrial growth. Due to the increasing cost of water and
sewage disposal, wastewater reuse in thermal power plants is being initiated. The number of wastewater
recycling projects in thermal power plants is increasing and water treatment and reuse technologies
are being developed. Studies have shown that electric power plants account for approximately half the
[1]
global industrial water withdrawal , which means the problem of water shortage will be aggravated
with the expansion of thermal power plants.
Although the generation of electricity from renewable sources (e.g. wind, hydro and solar photovoltaic)
with almost zero water consumption is growing, the proportion of world gross electricity generated
[2]
by combustible fuels still accounted for 64,1 % in 2020 . In addition, the wastewater from thermal
power plants (power plants that generate electricity from combustible fuels) is diverse, with a high
[3]
volume and complex pollutant components , and its discharge poses a threat to the ecology of water
environments. Therefore, the reuse of wastewater from thermal power plants has dual benefits of
water saving and environmental protection.
The increasing efforts to control water scarcity and water pollution in some countries have made
industrial wastewater reuse a valuable means of augmenting the existing water supply and reducing
wastewater discharge to the environment. In terms of wastewater treatment and reuse in thermal
[4] [5] [6] [7]
power plants, the United States , China , Japan and International Energy Agency (IEA) have all
introduced relevant policies to encourage wastewater reuse or even zero discharge in thermal power
plants.
However, the reclaimed water quantity of wastewater in thermal power plants is not high, and the
different characteristics of wastewater generated from different systems are ignored. Therefore, it
is necessary to strengthen the classification and characteristic analysis of wastewater, adopt more
reasonable and efficient treatment and reuse technologies in thermal power plants to optimize the
reclaimed water quantity of wastewater, to realize zero liquid discharge of wastewater and to improve
the benefits of water saving and environmental protection and ultimately achieve the sustainable
development goals (see www.un.org/sustainabledevelopment).
v
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INTERNATIONAL STANDARD ISO 4789:2023(E)
Guidelines for wastewater treatment and reuse in thermal
power plants
1 Scope
This document specifies guidelines for wastewater treatment and reuse in thermal power plants,
including the types and characteristics of wastewater and the technologies of wastewater treatment
and reuse.
In this document, thermal power plant drainage systems are divided into fuel supply, chemical water
treatment, boiler and auxiliary, recirculating cooling, flue gas processing, gasification scrubber and
ash handling. Wastewater from these systems is classified in accordance with its system sources. In
addition, technical guidelines for wastewater treatment and reuse are provided according to the water
requirements of systems in the thermal power plant. This document is formulated to provide feasible
technical guidance for the treatment and reuse of wastewater in thermal power plants.
It is applicable to coal-fired, oil-fired, gas-fired (including gas turbine), biomass-fired, waste incineration
and integrated gasification combined cycle (IGCC) thermal power plants.
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 — Vocabulary
3 Terms, definitions and abbreviated terms
For the purposes of this document, the terms and definitions given in ISO 20670 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1 Terms and definitions
3.1.1
advanced treatment for TDS
advanced treatment for total dissolved solids
process of further reducing the salt content in wastewater by using advanced treatment technology
after pretreatment to achieve certain reuse water targets
3.1.2
ash handling system
system that includes all the equipment, pipelines and monitoring devices for collecting bottom ash and
fly ash from combustion or gasification of fuel in boilers and transferring it out of the power plant
3.1.3
boiler and auxiliary system
system that includes primary production equipment for the combustion or gasification of fuel and other
auxiliary machinery
1
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ISO 4789:2023(E)
3.1.4
chemical water treatment system
system that treats the raw water to achieve water quality requirements for the different water
applications in the power plant
Note 1 to entry: A chemical water treatment system includes the raw water pretreatment, boiler replenishment
water treatment, condensate polishing treatment and wastewater treatment
3.1.5
flue gas processing system
system that purifies boiler flue gas and reduces pollutants such as sulfur dioxide, nitrogen oxides,
particulate matter and organic gas in flue gas
3.1.6
fuel supply system
system that collects, stores, pre-treats and transports combustible fuels for power generation
3.1.7
gasification scrubber system
system that purifies gaseous fuel after gasification of solid or liquid fuel
3.1.8
recirculating cooling system
system that circularly uses a cooling medium (e.g. water, air) to transfer heat
Note 1 to entry: A recirculating cooling system consists of heat exchange equipment, cooling equipment,
treatment facilities, pumps, pipelines and other related facilities.
3.1.9
reclaimed water quantity
amount of water that is directly cascade-utilized or reused after proper treatment in the production
process of the thermal power plant
3.1.10
thermal power plant
power plant that converts heat, such as that released by the combustion of carbonaceous fuels, into
electricity
Note 1 to entry: Carbonaceous fuels include coal and coal products, oil and oil products, natural gas, biofuels
from biomass, industrial waste and municipal waste.
[SOURCE: ISO 27919-1:2018, 3.1.42, modified — Definition revised and note to entry added.]
3.2 Abbreviated terms
A/O anoxic/oxic
BOD biochemical oxygen demand after 5 days
5
COD chemical oxygen demand
EDTA ethylene diamine tetraacetic acid
FGD flue gas desulfurization
IGCC integrated gasification combined cycle
MBR membrane bioreactor
MVR mechanical vapor recompression
2
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ISO 4789:2023(E)
NF nanofiltration
NTU nephelometric turbidity unit
PAHs polycyclic aromatic hydrocarbons
RO reverse osmosis
TDS total dissolved solids
TP total phosphorus
TSS total suspended solids
UASB upflow anaerobic sludge blanket
UF ultrafiltration
WESP wet electrostatic precipitator
4 General principles
The following principles should be followed for the treatment and reuse of wastewater in thermal
power plants.
a) The wastewater should be treated and reused separately if its water quality and reuse target are
different.
b) If wastewater has similar water quality and the same reuse target, similar treatment processes can
be adopted.
c) Wastewater that meets the water quality requirements of the reuse target can be directly utilized
in the target system.
d) The process flow of wastewater treatment and reuse in thermal power plants should be determined
taking requirements of the effluent water quantity and quality, influent water quality of reuse
targets, site conditions, environmental protection and other factors into account during the
technical and economic review.
e) The entire plant water balance should be optimized before designing a water reuse plan. The water
withdrawal, consumption and drainage of each system should be considered through a water
balance. The water quality requirements of each system should also be considered (see Annex A).
5 Types and characteristics of wastewater in thermal power plants
Wastewater in thermal power plants can be classified based on the following systems: fuel supply,
chemical water treatment, boiler and auxiliary, recirculating cooling, flue gas processing, gasification
[8]
scrubber and ash handling. The types of wastewater in each system are shown in Table 1.
3
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ISO 4789:2023(E)
Table 1 — Types of wastewater in thermal power plants
System source Type Involved power plants
a
Coal wastewater Coal-fired power plants, IGCC
b
Oily wastewater All power plants
Fuel supply
Biomass-fired power plants, waste incineration
c
Leachate
power plants
d
RO concentrated water
Chemical water treat-
e
Membrane washing wastewater All power plants
ment
f
Resin reclaimed wastewater
a
Coal wastewater has high TSS, COD, chroma and turbidity. The TSS concentration can be between 200 mg/l and
5,000 mg/l. Coal wastewater includes the leakage caused by the spraying and dustproofing in the coal yard, the washing
waste water caused by the washing of the coal transporting trestle, the rain water in the coal yard and the effluent water
after dust removal in the coal conveying system.
b [9]
Oily wastewater includes oil slick, disperse oil, emulsified oil and dissolved oil . It can come from the oil storage
facilities, the leakage of the oil system in the main plant during the operation of the steam engine and the power generation
turning machine bearings, and the oily wastewater generated during the operation, cleaning or overhaul of the equipment.
c [10]
Leachate has high COD, BOD , ammonia nitrogen, TSS and heavy metals, with a pH of 5~7 . It comes from the
5
biochemical degradation during the stacking process of biomass or waste. Its quantity and quality are different due to the
types of waste generated from various sites, fuel composition and climatic conditions at the power plants.
d
RO-concentrated water is of high salinity, and its quality is related to the quality of raw water. It is concentrated
wastewater generated during the operation of the RO membrane filtration system in the chemical water treatment system
[11]
of the power plants .
e
Membrane washing wastewater is acidic or alkaline and has a high salinity. It comes from the physical and chemical
cleaning of membrane components in chemical water treatment system. Its quantity and quality are related to the quality
of raw water and the concentration of chemical cleaning agent.
f
Resin reclaimed wastewater is the acid or alkali wastewater from the regeneration of ion-exchange resin in the
chemical water treatment system. It is of high TDS and TSS. Its quantity and quality are related to resin regeneration time
and acid and base dosage.
g
Boiler blowdown can be divided into boiler continuous blowdown and boiler regular blowdown. The boiler continuous
3−−2 2−
+ 2+ 3+
blowdown contains only a small amount of Na , PO ,CO ,SiO , Fe , Fe and other salts. The iron content in the boiler
4 3 3
[12]
regular blowdown is high and contains ammonia nitrogen, TSS and COD .
h
Boiler chemical cleaning wastewater has high TDS, COD and TSS. Major pollutants are dependent on the type of acid
cleaning agent, such as hydrochloric acid, citric acid, complex acid and EDTA, used in the process of boiler chemical cleaning.
i
Auxiliary equipment cooling water blowdown contains a small amount of TDS and the water quality is high. It comes
from the cooling water system of auxiliary equipment of the power plant.
j
Cooling tower blowdown has high salinity, which has the largest flow rate in thermal power plants. Its quantity and
quality are related to the concentration ratio. The common pollutants include TSS, colloid, organic matter, inorganic salts,
microorganisms and algae. These pollutants come mainly from supplemental water and chemicals added to the water cycle,
as well as pollutants that grow in the system.
k
WESP blowdown can be split into WESP continuous blowdown and WESP regular blowdown since the cleaning types
of WESP include continuous-flow water cleaning and spray cleaning. The WESP blowdown is acidic wastewater, including
TSS, TDS and heavy metal. Its quantity is related to the cleaning type of WESP.
l
FGD wastewater is acidic, with a pH value between 4 and 6, containing a large number of TSS (e.g. gypsum particles,
SiO , CaF ) and a certain amount of COD. TSS is about 10,000 mg/l or more, TDS ranges between 30,000 mg/l to 65,000 mg/l.
2 2
-
The hardness is relatively high. The anions in wastewater are mainly Cl and sulfate radical ions, and there are many kinds
of heavy metal cation, such as mercury, lead, zinc, nickel and arsenic.
m
Tar-containing wastewater is the organic wastewater with tar as the main pollutant produced by wet gas purification
equipment. Tar can be considered a mixture of several acidic, alkaline and neutral compounds. The acidic components
include acids and phenols, the basic components include nitrogen-containing compounds and the neutral components
[12]
include PAHs . In addition, the wastewater also contains ammonia nitrogen, chloride and other inorganic substances.
n
The quality of ash handling wastewater is determined by the chemical composition of ash. Since the fuel source is not
fixed, the water quality of ash handling wastewater is also unstable. In general, ash wastewater is of high pH and TDS.
The pH value is generally greater than 9 and sometimes more than 10,5. It contains heavy metal elements and fluoride
dissolved from ash residue. The TSS of ash handling wastewater in the slurry concentration pool is higher.
4
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ISO 4789:2023(E)
TTaabbllee 11 ((ccoonnttiinnueuedd))
System source Type Involved power plants
g
Boiler blowdown
Boiler chemical cleaning waste-
h
Boiler and auxiliary water All power plants
Auxiliary equipment cooling
i
water blowdown
j
Recirculating cooling Cooling tower blowdown All power plants
k
WESP blowdown Coal-fired power plants
Coal-fired power plants, oil-fired power plants,
Flue gas processing
l
FGD wastewater biomass-fired power plants, waste incineration
power plants
a
Coal wastewater has high TSS, COD, chroma and turbidity. The TSS concentration can be between 200 mg/l and
5,000 mg/l. Coal wastewater includes the leakage caused by the spraying and dustproofing in the coal yard, the washing
waste water caused by the washing of the coal transporting trestle, the rain water in the coal yard and the effluent water
after dust removal in the coal conveying system.
b [9]
Oily wastewater includes oil slick, disperse oil, emulsified oil and dissolved oil . It can come from the oil storage
facilities, the leakage of the oil system in the main plant during the operation of the steam engine and the power generation
turning machine bearings, and the oily wastewater generated during the operation, cleaning or overhaul of the equipment.
c [10]
Leachate has high COD, BOD , ammonia nitrogen, TSS and heavy metals, with a pH of 5~7 . It comes from the
5
biochemical degradation during the stacking process of biomass or waste. Its quantity and quality are different due to the
types of waste generated from various sites, fuel composition and climatic conditions at the power plants.
d
RO-concentrated water is of high salinity, and its quality is related to the quality of raw water. It is concentrated
wastewater generated during the operation of the RO membrane filtration system in the chemical water treatment system
[11]
of the power plants .
e
Membrane washing wastewater is acidic or alkaline and has a high salinity. It comes from the physical and chemical
cleaning of membrane components in chemical water treatment system. Its quantity and quality are related to the quality
of raw water and the concentration of chemical cleaning agent.
f
Resin reclaimed wastewater is the acid or alkali wastewater from the regeneration of ion-exchange resin in the
chemical water treatment system. It is of high TDS and TSS. Its quantity and quality are related to resin regeneration time
and acid and base dosage.
g
Boiler blowdown can be divided into boiler continuous blowdown and boiler regular blowdown. The boiler continuous
3−−2 2−
+ 2+ 3+
blowdown contains only a small amount of Na , PO ,CO ,SiO , Fe , Fe and other salts. The iron content in the boiler
4 3 3
[12]
regular blowdown is high and contains ammonia nitrogen, TSS and COD .
h
Boiler chemical cleaning wastewater has high TDS, COD and TSS. Major pollutants are dependent on the type of acid
cleaning agent, such as hydrochloric acid, citric acid, complex acid and EDTA, used in the process of boiler chemical cleaning.
i
Auxiliary equipment cooling water blowdown contains a small amount of TDS and the water quality is high. It comes
from the cooling water system of auxiliary equipment of the power plant.
j
Cooling tower blowdown has high salinity, which has the largest flow rate in thermal power plants. Its quantity and
quality are related to the concentration ratio. The common pollutants include TSS, colloid, organic matter, inorganic salts,
microorganisms and algae. These pollutants come mainly from supplemental water and chemicals added to the water cycle,
as well as pollutants that grow in the system.
k
WESP blowdown can be split into WESP continuous blowdown and WESP regular blowdown since the cleaning types
of WESP include continuous-flow water cleaning and spray cleaning. The WESP blowdown is acidic wastewater, including
TSS, TDS and heavy metal. Its quantity is related to the cleaning type of WESP.
l
FGD wastewater is acidic, with a pH value between 4 and 6, containing a large number of TSS (e.g. gypsum particles,
SiO , CaF ) and a certain amount of COD. TSS is about 10,000 mg/l or more, TDS ranges between 30,000 mg/l to 65,000 mg/l.
2 2
-
The hardness is relatively high. The anions in wastewater are mainly Cl and sulfate radical ions, and there are many kinds
of heavy metal cation, such as mercury, lead, zinc, nickel and arsenic.
m
Tar-containing wastewater is the organic wastewater with tar as the main pollutant produced by wet gas purification
equipment. Tar can be considered a mixture of several acidic, alkaline and neutral compounds. The acidic components
include acids and phenols, the basic components include nitrogen-containing compounds and the neutral components
[12]
include PAHs . In addition, the wastewater also contains ammonia nitrogen, chloride and other inorganic substances.
n
The quality of ash handling wastewater is determined by the chemical composition of ash. Since the fuel source is not
fixed, the water quality of ash handling wastewater is also unstable. In general, ash wastewater is of high pH and TDS.
The pH value is generally greater than 9 and sometimes more than 10,5. It contains heavy metal elements and fluoride
dissolved from ash residue. The TSS of ash handling wastewater in the slurry concentration pool is higher.
5
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ISO 4789:2023(E)
TTaabbllee 11 ((ccoonnttiinnueuedd))
System source Type Involved power plants
m
Gasification scrubber Tar-containing wastewater Biomass gasification power plants, IGCC
Coal-fired power plants, biomass-fired power
n
Ash handling Ash handling wastewater
plants, waste incineration power plants
a
Coal wastewater has high TSS, COD, chroma and turbidity. The TSS concentration can be between 200 mg/l and
5,000 mg/l. Coal wastewater includes the leakage caused by the spraying and dustproofing in the coal yard, the washing
waste water caused by the washing of the coal transporting trestle, the rain water in the coal yard and the effluent water
after dust removal in the coal conveying system.
b [9]
Oily wastewater includes oil slick, disperse oil, emulsified oil and dissolved oil . It can come from the oil storage
facilities, the leakage of the oil system in the main plant during the operation of the steam engine and the power generation
turning machine bearings, and the oily wastewater generated d
...
ISO/DISFDIS 4789:20222023(E)
2022-08-23
2023-02-07
ISO/TC 282/SC 4/WG 6
Secretariat: SAC
Guidelines for wastewater treatment and reuse in thermal power plants
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ISO/DISFDIS 4789:20222023(E)
© ISO 20222023
All rights reserved. Unless otherwise specified, or required in the context of its implementation,
no part of this publication may be reproduced or utilized otherwise in any form or by any means,
electronic or mechanical, including photocopying, or posting on the internet or an intranet,
without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.orgwww.iso.org
Published in Switzerland
ii © ISO 20222023 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/DIS FDIS 4789:20222023(E)
Contents
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 . 2
4 General principles . 3
5 Types and characteristics of wastewater in thermal power plants . 3
6 Wastewater treatment and reuse technologies . 6
6.1 Water quality requirements for reuse water in thermal power plants . 6
6.2 Fuel supply system wastewater treatment and reuse . 7
6.2.1 Coal wastewater . 7
6.2.2 Oily wastewater . 8
6.2.3 Leachate . 8
6.3 Chemical water treatment system wastewater treatment and reuse . 9
6.3.1 RO concentrated water . 9
6.3.2 Membrane washing wastewater and resin reclaimed wastewater treatment and
reuse . 10
6.4 Boiler and auxiliary system wastewater treatment and reuse . 10
6.4.1 Boiler blowdown . 10
6.4.2 Boiler chemical cleaning wastewater . 10
6.4.3 Auxiliary equipment cooling water blowdown . 11
6.5 Recirculating cooling system wastewater treatment and reuse . 11
6.6 Flue gas processing system wastewater treatment and reuse . 12
6.7 Gasification scrubber system wastewater treatment and reuse . 13
6.8 Ash handling system wastewater treatment and reuse . 14
Annex A (informative) Cases of water balance in thermal power plants . 15
A.1 A coal-fired power plant . 15
A.2 An IGCC power plant . 18
A.3 A waste incineration plant . 21
Annex B (informative) Cases of wastewater reuse in thermal power plants . 25
B.1 A gas-fired power plant . 25
B.2 A coal-fired power plant . 26
Bibliography . 28Foreword iv
Introduction. v
1 Scope . 1
2 Normative references . 1
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ISO/DISFDIS 4789:20222023(E)
3 Terms, definitions and abbreviated terms . 1
3.1 Terms and definitions . 1
3.2 Abbreviated terms . 2
4 General principles . 3
5 Types and characteristics of wastewater in thermal power plants . 3
6 Wastewater treatment and reuse technologies . 6
6.1 Water quality requirements for reuse water in thermal power plants . 6
6.2 Fuel supply system wastewater treatment and reuse . 7
6.2.1 Coal wastewater . 7
6.2.2 Oily wastewater . 8
6.2.3 Leachate . 8
6.3 Chemical water treatment system wastewater treatment and reuse . 9
6.3.1 RO concentrated water . 9
6.3.2 Membrane washing wastewater and resin reclaimed wastewater treatment and
reuse . 10
6.4 Boiler and auxiliary system wastewater treatment and reuse . 10
6.4.1 Boiler blowdown . 10
6.4.2 Boiler chemical cleaning wastewater . 10
6.4.3 Auxiliary equipment cooling water blowdown . 11
6.5 Recirculating cooling system wastewater treatment and reuse . 11
6.6 Flue gas processing system wastewater treatment and reuse . 12
6.7 Gasification scrubber system wastewater treatment and reuse . 13
6.8 Ash handling system wastewater treatment and reuse . 14
Annex A (informative) Cases of water balance in thermal power plants . 15
A.1 A coal-fired power plant . 15
A.2 An IGCC power plant . 18
A.3 A waste incineration plant . 21
Annex B (informative) Cases of wastewater reuse in thermal power plants . 25
B.1 A gas-fired power plant . 25
B.2 A coal-fired power plant . 26
Bibliography . 28
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ISO/DIS FDIS 4789:20222023(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/directiveswww.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/patentswww.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.htmlwww.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 282, Water reuse, Subcommittee SC 4,
Industrial water reuse.
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.htmlwww.iso.org/members.html.
© ISO 20222023 – All rights reserved v
---------------------- Page: 5 ----------------------
ISO/DISFDIS 4789:20222023(E)
Introduction
Global water scarcity is becoming increasingly pronounced as a result of the massive demand for water
brought aboutcaused by population growth, public life and industrial growth. Due to the increasing cost
of water and sewage disposal, wastewater reuse in thermal power plants is being initiated. The number
of wastewater recycling projects in thermal power plants is increasing and water treatment and reuse
technologies are being developed. Studies have shown that electric power plants account for
[[1]]
approximately half the global industrial water withdrawal, , which means the problem of water
shortage will be aggravated with the expansion of thermal power plants.
Although the generation of electricity from renewable sources (e.g. wind, hydro and solar photovoltaic)
with almost zero water consumption is growing, the proportion of world gross electricity generated by
[[2]]
combustible fuels still accounted for 64.,1 % in 2020. . In addition, the wastewater from thermal
power plants (power plants that generate electricity from combustible fuels) is diverse, with a high
[[3]]
volume and complex pollutant components, , and its discharge poses a threat to the ecology of water
environments. Therefore, the reuse of wastewater from thermal power plants has dual benefits of water
saving and environmental protection.
The increasing efforts to control water scarcity and water pollution in some countries have made
industrial wastewater reuse a valuable means of augmenting the existing water supply and reducing
wastewater discharge to the environment. In terms of wastewater treatment and reuse in thermal
[[4]] [[5]] [6] [7]
power plants, the United States, , China, , Japan and International Energy Agency (IEA) have all
introduced relevant policies to encourage wastewater reuse or even zero discharge in thermal power
plants.
However, the reclaimed water quantity of wastewater in thermal power plants is not high, and the
different characteristics of wastewater generated from different systems are ignored. Therefore, it is
necessary to strengthen the classification and characteristic analysis of wastewater, adopt more
reasonable and efficient treatment and reuse technologies in thermal power plants to optimize the
reclaimed water quantity of wastewater, to realize zero liquid discharge of wastewater and to improve
the benefits of water saving and environmental protection and ultimately achieve the sustainable
development goals (see www.un.org/sustainabledevelopment).www.un.org/sustainabledevelopment).
vi © ISO 20222023 – All rights reserved
---------------------- Page: 6 ----------------------
ISO/DIS 4789:2022(E)
Guidelines for wastewater treatment and reuse in thermal power
plants
1 Scope
This document specifies guidelines for wastewater treatment and reuse in thermal power plants,
including the types and characteristics of wastewater and the technologies of wastewater treatment
and reuse.
In this document, thermal power plant drainage systems are divided into fuel supply, chemical water
treatment, boiler and auxiliary, recirculating cooling, flue gas processing, gasification scrubber and ash
handling. Wastewater from these systems is classified in accordance with its system sources. In
addition, technical guidelines for wastewater treatment and reuse are provided according to the water
requirements of systems in the thermal power plant. This document is formulated to provide feasible
technical guidance for the treatment and reuse of wastewater in thermal power plants.
It is applicable to coal-fired, oil-fired, gas-fired (including gas turbine), biomass-fired, waste
incineration and integrated gasification combined cycle (IGCC) thermal power plants.
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 — Vocabulary
3 Terms, definitions and abbreviated terms
For the purposes of this document, the terms and definitions given in ISO 20670 and the following
apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obphttps://www.iso.org/obp
— IEC Electropedia: available at https://www.electropedia.org/https://www.electropedia.org/
3.1 Terms and, definitions and abbreviated terms
3.1.1
advanced treatment for TDS
advanced treatment for total dissolved solids
process of further reducing the salt content in wastewater by using advanced treatment technology
after pretreatment to achieve certain reuse water targets
3.1.2
ash handling system
system that includes all the equipment, pipelines and monitoring devices for collecting bottom ash and
fly ash from combustion or gasification of fuel in boilers and transferring it out of the power plant
3.1.3
boiler and auxiliary system
© ISO 2022 – All rights reserved 1
---------------------- Page: 7 ----------------------
ISO/DISFDIS 4789:20222023(E)
system that includes primary production equipment for the combustion or gasification of fuel and other
auxiliary machinery
3.1.4
chemical water treatment system
system that treats the raw water to achieve water quality requirements for the different water
applications in the power plant
Note 1 to entry: A chemical water treatment system includes the raw water pretreatment, boiler replenishment
water treatment, condensate polishing treatment and wastewater treatment
3.1.5
flue gas processing system
system that purifies boiler flue gas and reduces pollutants such as sulfur dioxide, nitrogen oxides,
particulate matter and organic gas in flue gas
3.1.6
fuel supply system
system that collects, stores, pre-treats and transports combustible fuels for power generation
3.1.7
gasification scrubber system
system that purifies gaseous fuel after gasification of solid or liquid fuel
3.1.8
recirculating cooling system
system that circularly uses a cooling medium (e.g. water, air) to transfer heat
Note 1 to entry: A recirculating cooling system consists of heat exchange equipment, cooling equipment, treatment
facilities, pumps, pipelines and other related facilities.
3.1.9
reclaimed water quantity
amount of water that is directly cascade-utilized or reused after proper treatment in the production
process of the thermal power plant
3.1.10
thermal power plant
power plant that converts heat, such as that released by the combustion of carbonaceous fuels, into
electricity
Note 1 to entry: Carbonaceous fuels include coal and coal products, oil and oil products, natural gas, biofuels from
biomass, industrial waste and municipal waste.
[SOURCE: ISO 27919-1:2018, 3.1.42, modified — Definition revised and note to entry added.]
2 © ISO 2022 – All rights reserved
---------------------- Page: 8 ----------------------
ISO/DIS FDIS 4789:20222023(E)
3.2 Abbreviated terms
A/O anoxic/oxic
BOD biochemical oxygen demand after 5 days
5
COD chemical oxygen demand
EDTA ethylene diamine tetraacetic acid
FGD flue gas desulfurization
IGCC integrated gasification combined cycle
MBR membrane bioreactor
MVR mechanical vapor recompression
NF nanofiltration
NTU nephelometric turbidity unit
PAHs polycyclic aromatic hydrocarbons
RO reverse osmosis
TDS total dissolved solids
TP total phosphorus
TSS total suspended solids
UASB upflow anaerobic sludge blanket
UF ultrafiltration
WESP wet electrostatic precipitator
4 General principles
The following principles should be followed for the treatment and reuse of wastewater in thermal
power plants:.
a) The wastewater should be treated and reused separately if its water quality and reuse target are
different.
b) If wastewater has similar water quality and the same reuse target, similar treatment processes can
be adopted.
c) Wastewater that meets the water quality requirements of the reuse target can be directly utilized in
the target system.
d) The process flow of wastewater treatment and reuse in thermal power plants should be
determined taking requirements of the effluent water quantity and quality, influent water quality of
reuse targets, site conditions, environmental protection and other factors into account during the
technical and economic review.
e) The entire plant water balance should be optimized before designing a water reuse plan. The water
withdrawal, consumption and drainage of each system should be considered through a water
balance. The water quality requirements of each system should also be considered. (See Annex A)
© ISO 2022 – All rights reserved 3
---------------------- Page: 9 ----------------------
ISO/DISFDIS 4789:20222023(E)
5 Types and characteristics of wastewater in thermal power plants
Wastewater in thermal power plants can be classified based on the following systems: fuel supply,
chemical water treatment, boiler and auxiliary, recirculating cooling, flue gas processing, gasification
[8 ]
scrubber and ash handling [. ]. The types of wastewater in each system are shown in Table 1.
Table 1 — Types of wastewater in thermal power plants
System source Type Involved power plants
a
Coal wastewater Coal-fired power plants, IGCC
b
Oily wastewater All power plants
Fuel supply
Biomass-fired power plants, waste incineration power
c
Leachate
plants
d
RO concentrated water
e
Chemical water treatment Membrane washing wastewater All power plants
f
Resin reclaimed wastewater
g
Boiler blowdown
h
Boiler chemical cleaning wastewater
Boiler and auxiliary All power plants
Auxiliary equipment cooling water
i
blowdown
j
Recirculating cooling Cooling tower blowdown All power plants
k
WESP blowdown Coal-fired power plants
Flue gas processing
Coal-fired power plants, oil-fired power plants, biomass-
l
FGD wastewater
fired power plants, waste incineration power plants
m
Gasification scrubber Tar-containing wastewater Biomass gasification power plants, IGCC
Coal-fired power plants, biomass-fired power plants,
n
Ash handling Ash handling wastewater
waste incineration power plants
4 © ISO 2022 – All rights reserved
---------------------- Page: 10 ----------------------
ISO/DIS FDIS 4789:20222023(E)
a
Coal wastewater has high TSS, COD, chroma and turbidity. The TSS concentration can be between 200 mg/l and
5,000 mg/l. Coal wastewater includes the leakage caused by the spraying and dustproofing in the coal yard, the washing
waste water caused by the washing of the coal transporting trestle, the rain water in the coal yard and the effluent water
after dust removal in the coal conveying system.
b [9]
Oily wastewater includes oil slick, disperse oil, emulsified oil and dissolved oil. It can come from the oil storage
facilities, the leakage of the oil system in the main plant during the operation of the steam engine and the power generation
turning machine bearings, and the oily wastewater generated during the operation, cleaning or overhaul of the equipment.
c [[10]]
Leachate has high COD, BOD , ammonia nitrogen, TSS and heavy metals, with a pH of 5~7. . It comes from the
5
biochemical degradation during the stacking process of biomass or waste. Its quantity and quality are different due to the
types of waste generated from various sites, fuel composition and climatic conditions at the power plants.
d
RO-concentrated water is of high salinity, and its quality is related to the quality of raw water. It is concentrated
wastewater generated during the operation of the RO membrane filtration system in the chemical water treatment system of
[[11]]
the power plants. .
e
Membrane washing wastewater is acidic or alkaline and has a high salinity. It comes from the physical and chemical
cleaning of membrane components in chemical water treatment system. Its quantity and quality are related to the quality of
raw water and the concentration of chemical cleaning agent.
f
Resin reclaimed wastewater is the acid or alkali wastewater from the regeneration of ion-exchange resin in the chemical
water treatment system. It is of high TDS and TSS. Its quantity and quality are related to resin regeneration time and acid and
base dosage.
g
Boiler blowdown can be divided into boiler continuous blowdown and boiler regular blowdown. The boiler continuous
3− 2− 2−
+ 3- 2- 2- 2+ 3+ Field Code Changed
blowdown contains only a small amount of Na , PO , CO , SiO , PO ,CO ,SiO , Fe , Fe and other salts. The iron
4 3 3
4 4 4
[[12]]
content in the boiler regular blowdown is high and contains ammonia nitrogen, TSS and COD. .
h
Boiler chemical cleaning wastewater has high TDS, COD and TSS. Major pollutants are dependent on the type of acid
cleaning agent, such as hydrochloric acid, citric acid, complex acid and EDTA, used in the process of boiler chemical cleaning.
i
Auxiliary equipment cooling water blowdown contains a small amount of TDS and the water quality is high. It comes
from the cooling water system of auxiliary equipment of the power plant.
j
Cooling tower blowdown has high salinity, which has the largest flow rate in thermal power plants. Its quantity and
quality are related to the concentration ratio. The common pollutants include TSS, colloid, organic matter, inorganic salts,
microorganisms and algae. These pollutants come mainly from supplemental water and chemicals added to the water cycle,
as well as pollutants that grow in the system.
k
WESP blowdown can be split into WESP continuous blowdown and WESP regular blowdown since the cleaning types of
WESP include continuous-flow water cleaning and spray cleaning. The WESP blowdown is acidic wastewater, including TSS,
TDS and heavy metal. Its quantity is related to the cleaning type of WESP.
l
FGD wastewater is acidic, with a pH value between 4 and 6, containing a large number of TSS (e.g. gypsum particles,
SiO2, CaF2) and a certain amount of COD. TSS is about 10,000 mg/l or more, TDS ranges between 30,000 mg/l to
-
65,000 mg/l. The hardness is relatively high. The anions in wastewater are mainly Cl and sulfate radical ions, and there are
many kinds of heavy metal cation, such as mercury, lead, zinc, nickel and arsenic.
m
Tar-containing wastewater is the organic wastewater with tar as the main pollutant produced by wet gas purification
equipment. Tar can be considered a mixture of several acidic, alkaline and neutral compounds. The acidic components
include acids and phenols, the basic components include nitrogen-containing compounds and the neutral components
[ [12] ]
include PAHs . . In addition, the wastewater also contains ammonia nitrogen, chloride and other inorganic substances.
n
The quality of ash handling wastewater is determined by the chemical composition of ash. Since the fuel source is not
fixed, the water quality of ash handling wastewater is also unstable. In general, ash wastewater is of high pH and TDS. The pH
value is generally greater than 9 and sometimes more than 10.,5. It contains heavy metal elements and fluoride dissolved
from ash residue. The TSS of ash handling wastewater in the slurry concentration pool is higher.
6 Wastewater treatment and reuse technologies
6.1 Water quality requirements for reuse water in thermal power plants
To ensure the proper operation of each system, it is recommended that the reuse water quality after
treatment meet the requirements of influent water for the given target. The required water quality
parameters of various types of industrial reuse water are given in Table 2.
© ISO 2022 – All rights reserved 5
---------------------- Page: 11 ----------------------
ISO/DISFDIS 4789:20222023(E)
Table 2 — Required water quality parameters of reuse water
Chemical
Recirculating
Ash
water Boiler and Flue gas processing
Gasification
Fuel supply system cooling
handling
treatment auxiliary system system
scrubber
system-
system-
system-
No. Parameter system-
Ash
Process
Dust- Boiler WESP
handling
Washing Influent Coolin
...
FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 4789
ISO/TC 282/SC 4
Guidelines for wastewater treatment
Secretariat: SAC
and reuse in thermal power plants
Voting begins on:
2023-02-21
Voting terminates on:
2023-04-18
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
ISO/FDIS 4789:2023(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN-
DARDS TO WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS. © ISO 2023
---------------------- Page: 1 ----------------------
ISO/FDIS 4789:2023(E)
FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 4789
ISO/TC 282/SC 4
Guidelines for wastewater treatment
Secretariat: SAC
and reuse in thermal power plants
Voting begins on:
Voting terminates on:
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© ISO 2023
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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or ISO’s member body in the country of the requester.
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Reference number
Email: copyright@iso.org
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO
ISO/FDIS 4789:2023(E)
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LOGICAL, COMMERCIAL AND USER PURPOSES,
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ii
© ISO 2023 – All rights reserved
NATIONAL REGULATIONS. © ISO 2023
---------------------- Page: 2 ----------------------
ISO/FDIS 4789:2023(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and abbreviated terms . 1
3.1 Terms, definitions and abbreviated terms . 1
3.2 Abbreviated terms . 2
4 General principles . 3
5 Types and characteristics of wastewater in thermal power plants .3
6 Wastewater treatment and reuse technologies . 7
6.1 Water quality requirements for reuse water in thermal power plants . 7
6.2 Fuel supply system wastewater treatment and reuse . 8
6.2.1 Coal wastewater . 8
6.2.2 Oily wastewater . 9
6.2.3 Leachate . 9
6.3 Chemical water treatment system wastewater treatment and reuse . 10
6.3.1 RO concentrated water . 10
6.3.2 Membrane washing wastewater and resin reclaimed wastewater
treatment and reuse . 11
6.4 Boiler and auxiliary system wastewater treatment and reuse . 11
6.4.1 Boiler blowdown . . . 11
6.4.2 Boiler chemical cleaning wastewater .12
6.4.3 Auxiliary equipment cooling water blowdown .12
6.5 Recirculating cooling system wastewater treatment and reuse .12
6.6 Flue gas processing system wastewater treatment and reuse .13
6.6.1 WESP blowdown .13
6.6.2 FGD wastewater . 14
6.7 Gasification scrubber system wastewater treatment and reuse . 14
6.8 Ash handling system wastewater treatment and reuse . 15
Annex A (informative) Cases of water balance in thermal power plants .16
Annex B (informative) Cases of wastewater reuse in thermal power plants .25
Bibliography .28
iii
© ISO 2023 – All rights reserved
---------------------- Page: 3 ----------------------
ISO/FDIS 4789:2023(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 nongovernmental, 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.
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.
iv
© ISO 2023 – All rights reserved
---------------------- Page: 4 ----------------------
ISO/FDIS 4789:2023(E)
Introduction
Global water scarcity is becoming increasingly pronounced as a result of the massive demand for water
caused by population growth, public life and industrial growth. Due to the increasing cost of water and
sewage disposal, wastewater reuse in thermal power plants is being initiated. The number of wastewater
recycling projects in thermal power plants is increasing and water treatment and reuse technologies
are being developed. Studies have shown that electric power plants account for approximately half the
[1]
global industrial water withdrawal , which means the problem of water shortage will be aggravated
with the expansion of thermal power plants.
Although the generation of electricity from renewable sources (e.g. wind, hydro and solar photovoltaic)
with almost zero water consumption is growing, the proportion of world gross electricity generated
[2]
by combustible fuels still accounted for 64,1 % in 2020 . In addition, the wastewater from thermal
power plants (power plants that generate electricity from combustible fuels) is diverse, with a high
[3]
volume and complex pollutant components , and its discharge poses a threat to the ecology of water
environments. Therefore, the reuse of wastewater from thermal power plants has dual benefits of
water saving and environmental protection.
The increasing efforts to control water scarcity and water pollution in some countries have made
industrial wastewater reuse a valuable means of augmenting the existing water supply and reducing
wastewater discharge to the environment. In terms of wastewater treatment and reuse in thermal
[4] [5] [6] [7]
power plants, the United States , China , Japan and International Energy Agency (IEA) have all
introduced relevant policies to encourage wastewater reuse or even zero discharge in thermal power
plants.
However, the reclaimed water quantity of wastewater in thermal power plants is not high, and the
different characteristics of wastewater generated from different systems are ignored. Therefore, it
is necessary to strengthen the classification and characteristic analysis of wastewater, adopt more
reasonable and efficient treatment and reuse technologies in thermal power plants to optimize the
reclaimed water quantity of wastewater, to realize zero liquid discharge of wastewater and to improve
the benefits of water saving and environmental protection and ultimately achieve the sustainable
development goals (see www.un.org/sustainabledevelopment).
v
© ISO 2023 – All rights reserved
---------------------- Page: 5 ----------------------
FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 4789:2023(E)
Guidelines for wastewater treatment and reuse in thermal
power plants
1 Scope
This document specifies guidelines for wastewater treatment and reuse in thermal power plants,
including the types and characteristics of wastewater and the technologies of wastewater treatment
and reuse.
In this document, thermal power plant drainage systems are divided into fuel supply, chemical water
treatment, boiler and auxiliary, recirculating cooling, flue gas processing, gasification scrubber and
ash handling. Wastewater from these systems is classified in accordance with its system sources. In
addition, technical guidelines for wastewater treatment and reuse are provided according to the water
requirements of systems in the thermal power plant. This document is formulated to provide feasible
technical guidance for the treatment and reuse of wastewater in thermal power plants.
It is applicable to coal-fired, oil-fired, gas-fired (including gas turbine), biomass-fired, waste incineration
and integrated gasification combined cycle (IGCC) thermal power plants.
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 — Vocabulary
3 Terms, definitions and abbreviated terms
For the purposes of this document, the terms and definitions given in ISO 20670 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1 Terms, definitions and abbreviated terms
3.1.1
advanced treatment for TDS
advanced treatment for total dissolved solids
process of further reducing the salt content in wastewater by using advanced treatment technology
after pretreatment to achieve certain reuse water targets
3.1.2
ash handling system
system that includes all the equipment, pipelines and monitoring devices for collecting bottom ash and
fly ash from combustion or gasification of fuel in boilers and transferring it out of the power plant
3.1.3
boiler and auxiliary system
system that includes primary production equipment for the combustion or gasification of fuel and other
auxiliary machinery
1
© ISO 2023 – All rights reserved
---------------------- Page: 6 ----------------------
ISO/FDIS 4789:2023(E)
3.1.4
chemical water treatment system
system that treats the raw water to achieve water quality requirements for the different water
applications in the power plant
Note 1 to entry: A chemical water treatment system includes the raw water pretreatment, boiler replenishment
water treatment, condensate polishing treatment and wastewater treatment
3.1.5
flue gas processing system
system that purifies boiler flue gas and reduces pollutants such as sulfur dioxide, nitrogen oxides,
particulate matter and organic gas in flue gas
3.1.6
fuel supply system
system that collects, stores, pre-treats and transports combustible fuels for power generation
3.1.7
gasification scrubber system
system that purifies gaseous fuel after gasification of solid or liquid fuel
3.1.8
recirculating cooling system
system that circularly uses a cooling medium (e.g. water, air) to transfer heat
Note 1 to entry: A recirculating cooling system consists of heat exchange equipment, cooling equipment,
treatment facilities, pumps, pipelines and other related facilities.
3.1.9
reclaimed water quantity
amount of water that is directly cascade-utilized or reused after proper treatment in the production
process of the thermal power plant
3.1.10
thermal power plant
power plant that converts heat, such as that released by the combustion of carbonaceous fuels, into
electricity
Note 1 to entry: Carbonaceous fuels include coal and coal products, oil and oil products, natural gas, biofuels
from biomass, industrial waste and municipal waste.
[SOURCE: ISO 27919-1:2018, 3.1.42, modified — Definition revised and note to entry added.]
3.2 Abbreviated terms
A/O anoxic/oxic
BOD biochemical oxygen demand after 5 days
5
COD chemical oxygen demand
EDTA ethylene diamine tetraacetic acid
FGD flue gas desulfurization
IGCC integrated gasification combined cycle
MBR membrane bioreactor
MVR mechanical vapor recompression
2
© ISO 2023 – All rights reserved
---------------------- Page: 7 ----------------------
ISO/FDIS 4789:2023(E)
NF nanofiltration
NTU nephelometric turbidity unit
PAHs polycyclic aromatic hydrocarbons
RO reverse osmosis
TDS total dissolved solids
TP total phosphorus
TSS total suspended solids
UASB upflow anaerobic sludge blanket
UF ultrafiltration
WESP wet electrostatic precipitator
4 General principles
The following principles should be followed for the treatment and reuse of wastewater in thermal
power plants.
a) The wastewater should be treated and reused separately if its water quality and reuse target are
different.
b) If wastewater has similar water quality and the same reuse target, similar treatment processes can
be adopted.
c) Wastewater that meets the water quality requirements of the reuse target can be directly utilized
in the target system.
d) The process flow of wastewater treatment and reuse in thermal power plants should be determined
taking requirements of the effluent water quantity and quality, influent water quality of reuse
targets, site conditions, environmental protection and other factors into account during the
technical and economic review.
e) The entire plant water balance should be optimized before designing a water reuse plan. The water
withdrawal, consumption and drainage of each system should be considered through a water
balance. The water quality requirements of each system should also be considered. (See Annex A)
5 Types and characteristics of wastewater in thermal power plants
Wastewater in thermal power plants can be classified based on the following systems: fuel supply,
chemical water treatment, boiler and auxiliary, recirculating cooling, flue gas processing, gasification
[8]
scrubber and ash handling. The types of wastewater in each system are shown in Table 1.
3
© ISO 2023 – All rights reserved
---------------------- Page: 8 ----------------------
ISO/FDIS 4789:2023(E)
Table 1 — Types of wastewater in thermal power plants
System source Type Involved power plants
a
Coal wastewater Coal-fired power plants, IGCC
b
Oily wastewater All power plants
Fuel supply
Biomass-fired power plants, waste incineration
c
Leachate
power plants
d
RO concentrated water
Chemical water treat
e
Membrane washing wastewater All power plants
ment
f
Resin reclaimed wastewater
a
Coal wastewater has high TSS, COD, chroma and turbidity. The TSS concentration can be between 200 mg/l and
5,000 mg/l. Coal wastewater includes the leakage caused by the spraying and dustproofing in the coal yard, the washing
waste water caused by the washing of the coal transporting trestle, the rain water in the coal yard and the effluent water
after dust removal in the coal conveying system.
b [9]
Oily wastewater includes oil slick, disperse oil, emulsified oil and dissolved oil. It can come from the oil storage
facilities, the leakage of the oil system in the main plant during the operation of the steam engine and the power generation
turning machine bearings, and the oily wastewater generated during the operation, cleaning or overhaul of the equipment.
c [10]
Leachate has high COD, BOD , ammonia nitrogen, TSS and heavy metals, with a pH of 5~7 . It comes from the
5
biochemical degradation during the stacking process of biomass or waste. Its quantity and quality are different due to the
types of waste generated from various sites, fuel composition and climatic conditions at the power plants.
d
RO-concentrated water is of high salinity, and its quality is related to the quality of raw water. It is concentrated
wastewater generated during the operation of the RO membrane filtration system in the chemical water treatment system
[11]
of the power plants .
e
Membrane washing wastewater is acidic or alkaline and has a high salinity. It comes from the physical and chemical
cleaning of membrane components in chemical water treatment system. Its quantity and quality are related to the quality
of raw water and the concentration of chemical cleaning agent.
f
Resin reclaimed wastewater is the acid or alkali wastewater from the regeneration of ion-exchange resin in the
chemical water treatment system. It is of high TDS and TSS. Its quantity and quality are related to resin regeneration time
and acid and base dosage.
g
Boiler blowdown can be divided into boiler continuous blowdown and boiler regular blowdown. The boiler continuous
3−−2 2−
+ 2+ 3+
blowdown contains only a small amount of Na , PO ,CO , , Fe , Fe and other salts. The iron content in the boiler
SiO
4 4 4
[12]
regular blowdown is high and contains ammonia nitrogen, TSS and COD .
h
Boiler chemical cleaning wastewater has high TDS, COD and TSS. Major pollutants are dependent on the type of acid
cleaning agent, such as hydrochloric acid, citric acid, complex acid and EDTA, used in the process of boiler chemical cleaning.
i
Auxiliary equipment cooling water blowdown contains a small amount of TDS and the water quality is high. It comes
from the cooling water system of auxiliary equipment of the power plant.
j
Cooling tower blowdown has high salinity, which has the largest flow rate in thermal power plants. Its quantity and
quality are related to the concentration ratio. The common pollutants include TSS, colloid, organic matter, inorganic salts,
microorganisms and algae. These pollutants come mainly from supplemental water and chemicals added to the water cycle,
as well as pollutants that grow in the system.
k
WESP blowdown can be split into WESP continuous blowdown and WESP regular blowdown since the cleaning types
of WESP include continuous-flow water cleaning and spray cleaning. The WESP blowdown is acidic wastewater, including
TSS, TDS and heavy metal. Its quantity is related to the cleaning type of WESP.
l
FGD wastewater is acidic, with a pH value between 4 and 6, containing a large number of TSS (e.g. gypsum particles,
SiO , CaF ) and a certain amount of COD. TSS is about 10,000 mg/l or more, TDS ranges between 30,000 mg/l to 65,000 mg/l.
2 2
The hardness is relatively high. The anions in wastewater are mainly Cl and sulfate radical ions, and there are many kinds
of heavy metal cation, such as mercury, lead, zinc, nickel and arsenic.
m
Tar-containing wastewater is the organic wastewater with tar as the main pollutant produced by wet gas purification
equipment. Tar can be considered a mixture of several acidic, alkaline and neutral compounds. The acidic components
include acids and phenols, the basic components include nitrogencontaining compounds and the neutral components
[12]
include PAHs. In addition, the wastewater also contains ammonia nitrogen, chloride and other inorganic substances.
n
The quality of ash handling wastewater is determined by the chemical composition of ash. Since the fuel source is not
fixed, the water quality of ash handling wastewater is also unstable. In general, ash wastewater is of high pH and TDS.
The pH value is generally greater than 9 and sometimes more than 10,5. It contains heavy metal elements and fluoride
dissolved from ash residue. The TSS of ash handling wastewater in the slurry concentration pool is higher.
4
© ISO 2023 – All rights reserved
---------------------- Page: 9 ----------------------
ISO/FDIS 4789:2023(E)
TTaabbllee 11 ((ccoonnttiinnueuedd))
System source Type Involved power plants
g
Boiler blowdown
Boiler chemical cleaning waste
h
Boiler and auxiliary water All power plants
Auxiliary equipment cooling
i
water blowdown
j
Recirculating cooling Cooling tower blowdown All power plants
k
WESP blowdown Coal-fired power plants
Coal-fired power plants, oil-fired power plants,
Flue gas processing
l
FGD wastewater biomass-fired power plants, waste incineration
power plants
a
Coal wastewater has high TSS, COD, chroma and turbidity. The TSS concentration can be between 200 mg/l and
5,000 mg/l. Coal wastewater includes the leakage caused by the spraying and dustproofing in the coal yard, the washing
waste water caused by the washing of the coal transporting trestle, the rain water in the coal yard and the effluent water
after dust removal in the coal conveying system.
b [9]
Oily wastewater includes oil slick, disperse oil, emulsified oil and dissolved oil. It can come from the oil storage
facilities, the leakage of the oil system in the main plant during the operation of the steam engine and the power generation
turning machine bearings, and the oily wastewater generated during the operation, cleaning or overhaul of the equipment.
c [10]
Leachate has high COD, BOD , ammonia nitrogen, TSS and heavy metals, with a pH of 5~7 . It comes from the
5
biochemical degradation during the stacking process of biomass or waste. Its quantity and quality are different due to the
types of waste generated from various sites, fuel composition and climatic conditions at the power plants.
d
RO-concentrated water is of high salinity, and its quality is related to the quality of raw water. It is concentrated
wastewater generated during the operation of the RO membrane filtration system in the chemical water treatment system
[11]
of the power plants .
e
Membrane washing wastewater is acidic or alkaline and has a high salinity. It comes from the physical and chemical
cleaning of membrane components in chemical water treatment system. Its quantity and quality are related to the quality
of raw water and the concentration of chemical cleaning agent.
f
Resin reclaimed wastewater is the acid or alkali wastewater from the regeneration of ion-exchange resin in the
chemical water treatment system. It is of high TDS and TSS. Its quantity and quality are related to resin regeneration time
and acid and base dosage.
g
Boiler blowdown can be divided into boiler continuous blowdown and boiler regular blowdown. The boiler continuous
3−−2 2−
+ 2+ 3+
blowdown contains only a small amount of Na , PO ,CO , , Fe , Fe and other salts. The iron content in the boiler
SiO
4 4 4
[12]
regular blowdown is high and contains ammonia nitrogen, TSS and COD .
h
Boiler chemical cleaning wastewater has high TDS, COD and TSS. Major pollutants are dependent on the type of acid
cleaning agent, such as hydrochloric acid, citric acid, complex acid and EDTA, used in the process of boiler chemical cleaning.
i
Auxiliary equipment cooling water blowdown contains a small amount of TDS and the water quality is high. It comes
from the cooling water system of auxiliary equipment of the power plant.
j
Cooling tower blowdown has high salinity, which has the largest flow rate in thermal power plants. Its quantity and
quality are related to the concentration ratio. The common pollutants include TSS, colloid, organic matter, inorganic salts,
microorganisms and algae. These pollutants come mainly from supplemental water and chemicals added to the water cycle,
as well as pollutants that grow in the system.
k
WESP blowdown can be split into WESP continuous blowdown and WESP regular blowdown since the cleaning types
of WESP include continuous-flow water cleaning and spray cleaning. The WESP blowdown is acidic wastewater, including
TSS, TDS and heavy metal. Its quantity is related to the cleaning type of WESP.
l
FGD wastewater is acidic, with a pH value between 4 and 6, containing a large number of TSS (e.g. gypsum particles,
SiO , CaF ) and a certain amount of COD. TSS is about 10,000 mg/l or more, TDS ranges between 30,000 mg/l to 65,000 mg/l.
2 2
The hardness is relatively high. The anions in wastewater are mainly Cl and sulfate radical ions, and there are many kinds
of heavy metal cation, such as mercury, lead, zinc, nickel and arsenic.
m
Tar-containing wastewater is the organic wastewater with tar as the main pollutant produced by wet gas purification
equipment. Tar can be considered a mixture of several acidic, alkaline and neutral compounds. The acidic components
include acids and phenols, the basic components include nitrogencontaining compounds and the neutral components
[12]
include PAHs. In addition, the wastewater also contains ammonia nitrogen, chloride and other inorganic substances.
n
The quality of ash handling wastewater is determined by the chemical composition of ash. Since the fuel source is not
fixed, the water quality of ash handling wastewater is also unstable. In general, ash wastewater is of high pH and TDS.
The pH value is generally greater than 9 and sometimes more than 10,5. It contains heavy metal elements and fluoride
dissolved from ash residue. The TSS of ash handling wastewater in the slurry concentration pool is higher.
5
© ISO 2023 – All rights reserved
---------------------- Page: 10 ----------------------
ISO/FDIS 4789:2023(E)
TTaabbllee 11 ((ccoonnttiinnueuedd))
System sou
...
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