ISO/FDIS 20468-10
(Main)Performance evaluation of treatment technologies for water reuse systems — Part 10: Guidelines for evaluation of dependability of treatment systems
Performance evaluation of treatment technologies for water reuse systems — Part 10: Guidelines for evaluation of dependability of treatment systems
This document provides guidelines for evaluating the dependability of treatment systems for water reuse. The dependability of a treatment system is evaluated mainly from the availabilities of unit processes composing the system facility to perform functional requirements related to water quality performance over a long period of time in operation. The document specifies methodologies for both qualitative and quantitative assessments of availability on a life cycle basis by using two influencing factors, reliability as the ability to prevent a failure, and maintainability as the ability to recover from a failure.
Titre manque — Partie 10: Titre manque
General Information
Standards Content (Sample)
FINAL DRAFT
International
Standard
ISO/TC 282/SC 3
Performance evaluation of
Secretariat: JISC
treatment technologies for water
Voting begins on:
reuse systems —
2025-09-23
Part 10:
Voting terminates on:
2025-11-18
Guidelines for evaluation of
dependability of treatment systems
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
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
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.
Reference number
FINAL DRAFT
International
Standard
ISO/TC 282/SC 3
Performance evaluation of
Secretariat: JISC
treatment technologies for water
Voting begins on:
reuse systems —
Part 10:
Voting terminates on:
Guidelines for evaluation of
dependability of treatment systems
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.
© ISO 2025
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
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 Reference number
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions, and list of abbreviated terms . 1
3.1 Terms and definitions .1
3.2 Abbreviated terms .3
4 Concept of dependability evaluation of treatment systems . 3
4.1 Dependability evaluation by availability .3
4.2 Treatment system and critical unit processes as performance control points (PCPs) .3
5 Evaluation procedure for dependability of treatment systems . 4
5.1 General .4
5.1.1 Setting boundary for dependability evaluation .4
5.1.2 Setting PCPs .4
5.1.3 Availability assessment of PCPs .4
5.1.4 Availability assessment of treatment system .4
5.2 Setting PCPs, confirming requirements and defining failure state .5
5.3 Qualitative assessment of availability .5
5.4 Quantitative assessment of availability .6
Annex A (informative) Examples of maintenance strategy as benchmark for qualitatively
assessing availability applied to key technologies . 7
Annex B (informative) Example of quantitative assessment of availability .11
Bibliography .12
iii
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).
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 3, Risk and
performance evaluation of water reuse systems.
A list of all parts in the ISO 20468 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.
iv
Introduction
The purpose of this document is to define a methodology to evaluate the dependability of treatment systems,
which is listed as one of “treatment technology non-functional requirements” in ISO 20468-1. Although the
targeted performance requirement can be selected depending on the purpose, functional requirements
related to water quality should be targeted with high priority in conventional water reuse projects.
As a consequence, the dependability of a treatment system can be represented and evaluated by availability
as the ability to perform long-term operation without a failure and the fulfilment of functional requirements
related to the water quality target to be conformed with. As well, dependability as a “non-functional
requirement” can be evaluated by benchmarking for making comparisons or improving treatment system
performance.
Performance indicators other than dependability for the non-functional requirements of treatment systems
have already been specified in ISO 20468-2 for environmental performance based on greenhouse gas
(GHG) emissions and in ISO 20468-8 for economic evaluations based on life cycle cost (LCC). If functional
requirements related to water quality performance are satisfied, dependability can provide appropriate
information on operation and maintenance used for calculating GHG emissions and LCC.
A comprehensive evaluation of dependability, environmental, and economic performance can be used to
select an appropriate and cost-effective treatment system in the planning phase and to identify improvement
for operations and optimization opportunities on a life cycle basis. A variety of stakeholders, including
managers of water reuse projects and owners of water infrastructure and facilities can find beneficial
opportunities and options through a comprehensive performance evaluation using the guidelines in the
ISO 20468 series.
v
FINAL DRAFT International Standard ISO/FDIS 20468-10:2025(en)
Performance evaluation of treatment technologies for water
reuse systems —
Part 10:
Guidelines for evaluation of dependability of treatment systems
1 Scope
This document provides guidelines for evaluating the dependability represented by the availability of
treatment systems for water reuse.
The document specifies methodologies for both qualitative and quantitative assessments of availability on a
life cycle basis.
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 list of 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
availability
ability of a treatment technology to be in a state to perform a required function under given conditions at a
given instant of time or over a given time interval
Note 1 to entry: This ability depends on the combined aspects of reliability (3.1.11) performance, maintainability (3.1.7)
performance, and maintenance support performance (3.1.8). Preventive maintenance (3.1.10) can extend reliability and
improve availability.
[SOURCE: ISO 20468-1:2018, 3.1.1, modified — “assuming that the required external resources are provided”
was removed from the definition; “Preventive maintenance can extend reliability and improve availability”
was added to Note 1 to entry; Note 2 to entry was removed.]
3.1.2
benchmarking
tool for performance improvement through systematic search and adaptation of leading practices
[SOURCE: ISO 20468-1:2018, 3.1.2]
3.1.3
corrective maintenance
maintenance carried out after fault detection to effect restoration
[SOURCE: IEC 60050-192:2015, 192-06-06, modified — Note 1 to entry was removed.]
3.1.4
dependability
ability of a system represented by the availability (3.1.1) performance and its influencing factors, namely
reliability (3.1.11) performance, maintainability (3.1.7) performance and maintenance support performance (3.1.8)
[SOURCE: ISO 20468-1:2018, 3.1.5, modified — “collective term used to describe” was replaced with “ability
of a system represented by”; the list of influencing factors was added to the definition.]
3.1.5
downtime
amount of time that a system or a component is not able to operate or meet required functions
[SOURCE: ISO 20468-1:2018, 3.1.6]
3.1.6
failure
state in which a treatment technology does not meet a functional or a non-functional requirement (3.1.9)
[SOURCE: ISO 20468-1:2018, 3.1.7]
3.1.7
maintainability
ability of a treatment technology, under given conditions of use, to be retained in, or restored to, a state in
which it can perform a required function, when maintenance is performed under given conditions and using
stated procedures and resources
...
ISO/DISFDIS 20468-10
ISO/TC 282/SC 3
Secretariat: JISC
Date: 2025-02-0309-09
Performance evaluation of treatment technologies for water reuse
systems —
Part 10:
Guidelines for evaluation of dependability of treatment systems
FDIS stage
Warning for WD’s and CD’s
This document is not an ISO International Standard. It is distributed for review and comment. It is subject to change
without notice and may not be referred to as an International Standard.
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 supporting documentation.
ISO/DISFDIS 20468-10:20242025(en)
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
E-mail: copyright@iso.org
Website: www.iso.org
Published in Switzerland
iii
ISO/DISFDIS 20468-10:20242025(en)
Contents
Foreword . v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms, definitions, and list of abbreviated terms . 1
3.1 Terms and definitions . 1
3.2 Abbreviated terms . 3
4 Concept of dependability evaluation of treatment systems . 3
4.1 Dependability evaluation by availability . 3
4.2 Treatment system and critical unit processes as performance control points (PCPs) . 4
5 Evaluation procedure for dependability of treatment systems . 4
5.1 General . 4
5.2 Setting PCPs, confirming requirements and defining failure state . 5
5.3 Qualitative assessment of availability . 6
5.4 Quantitative assessment of availability . 7
Annex A (informative) Examples of maintenance strategy as benchmark for qualitatively
assessing availability applied to key technologies . 8
Annex B (informative) Example of quantitative assessment of availability . 12
Bibliography . 13
iv
ISO/DISFDIS 20468-10:20242025(en)
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).
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.
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 ).
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 3, Risk and
performance evaluation of water reuse systems.
A list of all parts in the ISO 20468 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.
v
ISO/DISFDIS 20468-10:20242025(en)
Introduction
The purpose of this document is to define a methodology to evaluate the dependability of treatment systems,
which is listed as one of “treatment technology non-functional requirements” in ISO 20468-1:2018. . Although
the targeted performance requirement can be selected depending on the purpose, “functional requirements”
related to water quality should be targeted with high priority in conventional water reuse projects.
As a consequence, the dependability of a treatment system can be represented and evaluated by availability
as the ability to perform long-term operation without a failure and the fulfilment of “functional requirements”
related to the water quality target to be conformed with. As well, dependability as a “non-functional
requirement” can be evaluated by benchmarking for making comparisons or improving treatment system
performance.
Performance indicators other than dependability for the “non-functional requirements” of treatment systems
have already been specified in ISO 20468-2 for environmental performance based on greenhouse gas (GHG)
emissions and in ISO 20468-8 for economic evaluations based on life cycle cost (LCC). If “functional
requirements” related to water quality performance are satisfied, dependability can provide appropriate
information on operation and maintenance used for calculating GHG emissions and LCC.
A comprehensive evaluation of dependability, environmental, and economic performance can be used to select
an appropriate and cost-effective treatment system in the planning phase and to identify improvement for
operations and optimization opportunities on a life cycle basis. A variety of stakeholders, including managers
of water reuse projects and owners of water infrastructure and facilities can find beneficial opportunities and
options through a comprehensive performance evaluation using the guidelines in the ISO 20468 series.
vi
ISO/DISFDIS 20468-10:20242025(en)
Performance evaluation of treatment technologies for water reuse
systems —
Part 10:
Guidelines for evaluation of dependability of treatment systems
1 Scope
This document provides guidelines for evaluating the dependability represented by the availability of
treatment systems for water reuse.
The document specifies methodologies for both qualitative and quantitative assessments of availability on a
life cycle basis.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitute
theconstitutes requirements inof 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 20670:2018, Water reuse — Vocabulary
3 Terms, definitions, and list of 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
availability
ability of a treatment technology to be in a state to perform a required function under given conditions at a
given instant of time or over a given time interval
Note 1 to entry: This ability depends on the combined aspects of the reliability (3.1.11) performance, the maintainability
(3.1.7) performance, and the maintenance support performance (3.1.8.). Preventive maintenance (3.1.10) can extend
reliability and improve availability.
[SOURCE: ISO 20468-1:2018, 3.1.1, modified — “assuming that the required external resources are provided”
was removed from the definition; “Preventive maintenance can extend reliability and improve availability”
was added to Note 1 to entry; Note 2 to entry was removed.]
3.1.2
benchmarking
tool for performance improvement through systematic search and adaptation of leading practices
[SOURCE: ISO 20468-1:2018, 3.1.2]
ISO/DISFDIS 20468-10:20242025(en)
3.1.3
corrective maintenance
maintenance carried out after fault detection to effect restoration
[SOURCE: IEC 60050-192:2015, 192-06-06, modified — Note 1 to entry was removed.]
3.1.4
dependability
ability of a system represented by the availability (3.1.1) performance and its influencing factors:, namely
reliability (3.1.11) performance, maintainability (3.1.7) performance and maintenance support performance
(3.1.8)
[SOURCE: ISO 20468-1:2018, 3.1.45, modified — “collective term used to describe” was replaced with “ability
of a system represented by”]”; the list of influencing factors was added to the definition.]
3.1.5
downtime
amount of time that a system or a component is not able to operate or meet required functions
[SOURCE: ISO 20468-1:2018, 3.1.6]
3.1.6
failure
state in which a treatment technology does not meet a functional or a non-functional requirement (3.1.9)
[SOURCE: ISO 20468-1:2018, 3.1.7]
3.1.7
maintainability
ability of a treatment technology, under given conditions of use, to be retained in, or restored to, a state in
which it can perform a required function, when maintenance is performed under given conditions and using
stated procedures and resources
[SOURCE: ISO 20468-1:2018, 3.1.9]
3.1.8
maintenance support performance
ability of a maintenance organisation, under given conditions and maintenance policy, to provide, upon
demand, the resources required to maintain the treatment technology
[SOURCE: ISO 20468-1:2018, 3.1.10, modified — Notes to entry were removed.]
3.1.9
non-functional requirement
requirement that specifies criteria or constraints on the design or implementation of a treatment technology
[SOURCE: ISO 20468-1:2018, 3.1.12]
3.1.10
preventive maintenance
maintenance carried out to mitigate degradation and reduce the probability of failure (3.1.6)
[SOURCE: IEC 60050-192:2015, 192-06-05, modified — Notes to entry were removed.]
ISO/DISFDIS 20468-10:20242025(en)
3.1.11
reliability
ability that a device, system or process will perform its prescribed function without failure (3.1.6) for a given
time when operated correctly in a specified environment
[SOURCE: ISO 20670:2023, 3.79, modified ― “probability“” was replaced with “ability“]”.]
3.1.12
uptime
amount of time that a system or a component is able to operate or meet required functions
3.2 List of abbreviatedAbbreviated terms
AVI inherent availability
AVO operational availability
LCC life cycle cost
MTBF mean time between failures
MTTR mean time to recovery
NF nanofiltration
PCP performance control pointreverse osmosistransmembrane pressureultraviolet
RO
TMP
UV
RO reverse osmosis
TMP transmembrane pressure
UV ultraviolet
4 Concept of dependability evaluation of treatment systems
4.1 Dependability evaluation by availability
The dependability of a treatment system is evaluated mainly from the availabilities of unit processes, which
make up the system facility, to achieve functional requirements, related to water quality over the course of
operation. In plannin
...
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