Service activities relating to drinking water supply, wastewater and stormwater systems — Guidelines for the implementation of continuous monitoring systems for drinking water quality and operational parameters in drinking water distribution networks

This document specifies guidelines for the implementation of continuous monitoring systems for drinking water quality and operational parameters in drinking water distribution networks. It provides guidance for determining the: — effective number of continuous monitoring stations in the drinking water distribution network; — location of monitoring stations in the drinking water distribution network; — types of operational and drinking water quality parameter measuring devices (MDs) that can be installed in a continuous monitoring station; — quality control, maintenance and calibration requirements of the continuous monitoring system. This document excludes guidance on the design, structure, number and type of MDs to be installed in a continuous monitoring system.

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TECHNICAL ISO/TS
SPECIFICATION 24541
First edition
2020-11
Service activities relating to drinking
water supply, wastewater and
stormwater systems — Guidelines for
the implementation of continuous
monitoring systems for drinking water
quality and operational parameters in
drinking water distribution networks
Reference number
ISO/TS 24541:2020(E)
ISO 2020
---------------------- Page: 1 ----------------------
ISO/TS 24541:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

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 © ISO 2020 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/TS 24541:2020(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Principles ..................................................................................................................................................................................................................... 6

5 Considerations for the justification of need for continuous monitoring ...................................................7

5.1 General ........................................................................................................................................................................................................... 7

5.2 Cost-benefit ................................................................................................................................................................................................ 7

5.3 Risks of continuous monitoring ............................................................................................................................................... 8

5.4 Local contexts .......................................................................................................................................................................................... 9

6 Choosing parameters to be monitored .......................................................................................................................................... 9

7 Locating the continuous monitoring stations in the drinking water distribution

network .......................................................................................................................................................................................................................12

7.1 General .......................................................................................................................................................................................................12

7.1.1 Network layout ...............................................................................................................................................................12

7.1.2 Development or implementation of an existing hydraulic or statistical

model of the drinking water distribution network (preferred) ...........................................12

7.1.3 The pragmatic approach ........................................................................................................................................12

7.2 Locations for monitoring stations .......................................................................................................................................13

7.2.1 General...................................................................................................................................................................................13

7.2.2 The pragmatic approach ........................................................................................................................................13

7.2.3 The hydraulic model approach .........................................................................................................................14

7.3 Network alert definition ..............................................................................................................................................................14

7.4 Decision support tools ...................................................................................................................................................................14

7.5 Periodic evaluation of the continuous monitoring system ............................................................................14

8 Installation, maintenance, operation, calibration and data transmission of MDs ........................14

8.1 Installation considerations ........................................................................................................................................................14

8.1.1 General...................................................................................................................................................................................14

8.1.2 Geographical location ...............................................................................................................................................15

8.1.3 Site installation location .........................................................................................................................................15

8.2 Maintenance and operational considerations ...........................................................................................................15

8.3 Calibration considerations .........................................................................................................................................................16

8.4 Communication considerations ............................................................................................................................................16

Annex A (informative) Examples of positives and negatives of continuous monitoring systems ......17

Annex B (informative) Examples of commonly deployed drinking water quality parameter

measuring devices ...........................................................................................................................................................................................19

Annex C (informative) Evaluation of the performance of measuring devices ........................................................23

Bibliography .............................................................................................................................................................................................................................24

© ISO 2020 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO/TS 24541:2020(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 224, Service activities relating to drinking

water supply, wastewater and stormwater systems.

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 2020 – All rights reserved
---------------------- Page: 4 ----------------------
ISO/TS 24541:2020(E)
Introduction

Cases of drinking water contamination around the world have raised awareness of water utilities'

exposure to risk. Contamination can arise from many causes, including societal mishaps, errors in

operation, maintenance or management by the water utility, natural disasters, vandalism, sabotage,

criminality and terrorist activity. The distributed nature of drinking water systems makes them

especially vulnerable to contamination and can permit the rapid dispersion of a contaminant. The

velocities and volumes of water in a drinking water distribution network can result in contamination

affecting significant numbers of users in a short time (e.g. tens of minutes). Recognition of these risks

has raised awareness of the need to consider the use of continuous monitoring systems to rapidly detect

potential contamination events.

The occurrence of an event can rarely be predicted. However, the more frequently relevant data can

be collected and examined, the greater is the chance of quickly detecting an event's occurrence. This

supports consideration of the adoption of continuous monitoring systems to provide the data streams

that can be used in event detection.

A contamination event can make a waterworks or a drinking water distribution network unusable for a

time and require implementation of contingency plans. Such plans could involve, for example, accessing

an alternative source water or providing an alternative water service other than via the drinking water

distribution network.

To date, very few water utilities have installed continuous monitoring systems either in part or

throughout their drinking water distribution network(s). This situation can result from a rational

decision based on risk assessment and, in some cases, a cost-benefit analysis. However, it should be

acknowledged that circumstances can change – gradually over time or rapidly in the face of events.

Water utilities wishing to explore such an option can face uncertainties and gaps in their knowledge on

how to proceed. In such circumstances water utilities typically face three main challenges:

— which types of measuring devices (MDs) to install in each continuous monitoring station;

— how many continuous monitoring stations to install per drinking water system;

— where to locate the continuous monitoring stations in the drinking water distribution network in

order to achieve the best results.

The installation of continuous monitoring systems could reduce the risk to public health and mitigate

the impact on users and other stakeholders during a contamination event. The value of continuous

monitoring systems can be determined using appropriate risk assessment and cost-benefit analysis.

Such an evaluation should take into account existing controls and establish the additional risk

mitigation that might be achieved and likely costs.

Advances in MD technology have recently made the adoption and deployment of continuous monitoring

more practicable. MDs are not limited to the measurement of drinking water quality alone. Continuous

measurement of operational parameters such as water flow and water pressure can improve the water

utility's capability to interpret results from the measurement of drinking water quality.

This document provides water utilities, their contractors, consultants and regulators with guidelines

for the installation of continuous monitoring systems in drinking water systems, including guidance on

their appropriate selection, maintenance and optimal calibration.

These guidelines can aid a water utility's processes for risk assessment and cost-benefit analysis. Taken

together these can help a water utility's top management take informed, risk-based decisions on the

worthwhileness of investment in a continuous monitoring system.

The guidance provided in this document is intended to be universally applicable, regardless of the

structure and size of a water utility's drinking water system. An event detection process (EDP) that

relies upon grab samples and intermittent data inputs could be implemented at lower cost. However,

where a water utility's assets, finances, management system and technical capability make it

practicable, the ability to provide continuous data streams offers advantages for event detection.

© ISO 2020 – All rights reserved v
---------------------- Page: 5 ----------------------
ISO/TS 24541:2020(E)

To gain experience, initial deployment could be limited to higher-risk areas within a wider drinking

water system.
vi © ISO 2020 – All rights reserved
---------------------- Page: 6 ----------------------
TECHNICAL SPECIFICATION ISO/TS 24541:2020(E)
Service activities relating to drinking water supply,
wastewater and stormwater systems — Guidelines for
the implementation of continuous monitoring systems
for drinking water quality and operational parameters in
drinking water distribution networks
1 Scope

This document specifies guidelines for the implementation of continuous monitoring systems for

drinking water quality and operational parameters in drinking water distribution networks.

It provides guidance for determining the:

— effective number of continuous monitoring stations in the drinking water distribution network;

— location of monitoring stations in the drinking water distribution network;

— types of operational and drinking water quality parameter measuring devices (MDs) that can be

installed in a continuous monitoring station;

— quality control, maintenance and calibration requirements of the continuous monitoring system.

This document excludes guidance on the design, structure, number and type of MDs to be installed in a

continuous monitoring system.
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 24513, Service activities relating to drinking water supply, wastewater and stormwater systems —

Vocabulary
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 24513 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
accuracy
measurement accuracy
accuracy of measurement

closeness of agreement between a measured quantity value and a true quantity value of a measurand

[SOURCE: ISO/IEC Guide 99:2007, 2.13, modified]
© ISO 2020 – All rights reserved 1
---------------------- Page: 7 ----------------------
ISO/TS 24541:2020(E)
3.2
capability
quality of being able to perform a given activity
[SOURCE: ISO 15531-1:2007, 3.63, modified]
3.3
continuous monitoring
continuous near-real-time measurements of one or more sampling characteristics

Note 1 to entry: To determine the status, it is possible that one or more relevant parameters need to be checked,

supervised, critically observed or measured compared with one or more pre-defined indicators.

Note 2 to entry: Measuring device (3.14) which provides a non-continuous but regular output signal at a given

frequency can be used for the purpose of continuous monitoring.

Note 3 to entry: The location where a measuring device is installed shall be defined as a continuous monitoring

station.
[SOURCE: ISO 2889:2010, 3.22, modified]
3.4
drinking water
DEPRECATED: potable water
water intended for human consumption

Note 1 to entry: Requirements for drinking water quality specifications are generally laid down by the national

relevant authorities. Guidelines are established by the World Health Organization (WHO).

3.5
drinking water distribution network
asset system for distributing drinking water (3.4)

Note 1 to entry: Drinking water distribution networks can include pipes, valves, hydrants, washouts, pumping

stations, reservoirs, and other metering and ancillary infrastructure and components.

Note 2 to entry: Pumping stations and reservoirs can be sited either in the waterworks (3.23) or in the drinking

water distribution network.
3.6
drinking water system

asset system providing the functions of abstracting, treating, storing, distributing or supplying of

drinking water (3.4)
3.7
event
situation when a behaviour deviates from the normal

Note 1 to entry: An event can be one or more occurrences and can have several causes.

Note 2 to entry: An event can consist of something not happening.

Note 3 to entry: An event can sometimes be referred to as an “incident” or “accident”.

Note 4 to entry: An event without consequences can also be referred to as a “near miss”, “incident”, “near hit” or

“close call”.
3.8
event detection
recognition of event indicator or information about a new situation, or both
Note 1 to entry: New situations can be sorted into one of the following:
— event indicator or situation, or both, are considered known and non-hazardous;
2 © ISO 2020 – All rights reserved
---------------------- Page: 8 ----------------------
ISO/TS 24541:2020(E)

— event indicator or situation, or both, are considered hazardous, but a procedure to handle them already exists;

— event indicator or situation, or both, are considered unknown, and a procedure for them does not yet exist.

3.9
event detection process
EDP

set of interrelated or interacting activities which transforms inputs (data or information on an actual or

suspected event (3.7)) into outputs (to support the water utility's (3.22) operational activities)

3.10
event indicator

signal to the water utility (3.22) or one or more stakeholders (3.20) of expectations of service

performance
Note 1 to entry: The signal can exist yet remain unobserved for a period.
3.11
maintenance

combination of all technical, administrative and managerial actions during the life cycle of an asset

intended to retain it in, or restore it to, a state in which it can perform the required function

3.12
management
coordinated activities to direct and control a water utility (3.22)

Note 1 to entry: Management can include establishing policies and objectives, and processes (3.17) to achieve

these objectives.

Note 2 to entry: The word “management” sometimes refers to people, i.e. a person or group of people with

authority and responsibility for the conduct and control of a service. When “management” is used in this sense, it

should always be used with some form of qualifier to avoid confusion with the concept “management” as a set of

activities defined above. For example, “management should …” is deprecated whereas “crisis management team

should …” is acceptable. Otherwise different words should be adopted to convey the concept when related to

people, e.g. managerial or managers.

Note 3 to entry: The term “management” can be qualified by a specific domain it addresses. Examples include

public health management, environmental management and risk (3.18) management.
3.13
measurement
process (3.17) to determine a value
3.14
measuring device

component, or a group of components, used in an in-line or online operating position, which continuously

(or at a given frequency) gives an output signal proportional to the value of one or more measurands in

waters which it measures
Note 1 to entry: The device can be portable or fixed in position.

Note 2 to entry: The term “in-line measuring device” is often used for a measuring device used in an in-line

position. The term “online measuring device” is often used for a measuring device used in an online position.

[SOURCE: EN 17075:2018, 3.1]
3.15
monitoring
determining the status of a system, a process (3.17) or an activity

Note 1 to entry: To determine the status, there can be a need to check, supervise or critically observe.

© ISO 2020 – All rights reserved 3
---------------------- Page: 9 ----------------------
ISO/TS 24541:2020(E)
3.16
operation

action(s) taken in the course of normal functioning of drinking water (3.4) or wastewater systems

EXAMPLE Monitoring and regulation or diversion of drinking water or wastewater.
3.17
process

set of interrelated or interacting activities that use inputs to deliver an intended result

Note 1 to entry: Whether the “intended result” of a process is called an output, product or service depends on the

context of the reference.

Note 2 to entry: Inputs to a process are generally the outputs of other processes and outputs of a process are

generally the inputs to other processes.

Note 3 to entry: Two or more interrelated and interacting processes in series can also be referred to as a process.

Note 4 to entry: Processes in an organization are generally planned and carried out under controlled conditions

to add value.

Note 5 to entry: A process where the conformity of the resulting output cannot be readily or economically

validated is frequently referred to as a “special process”.

Note 6 to entry: In benchmarking, organizational and technical processes and combinations of both are

considered. A process within the meaning of benchmarking comprises a combination of one task with one plant

or object (e.g. operate sewer network, treat wastewater, treat drinking water (3.4), provide domestic connection,

further train staff, purchase material).

Note 7 to entry: In service standards, the term “process” can have a broader meaning than its narrower

interpretation in management system standards. For example, it can also include some elements.

3.18
risk

combination of the likelihood of a hazardous event (3.7) and the severity of consequences, if the hazard

occurs in the drinking water system (3.6), wastewater system or stormwater system

Note 1 to entry: Risk is often characterized by reference to potential events and consequences or a combination

of these.

Note 2 to entry: The English term “likelihood” does not have a direct equivalent in some languages; instead, the

equivalent of the term “probability” is often used. However, in English, “probability” is often narrowly interpreted

as a mathematical term. Therefore, in risk management terminology, “likelihood” is used with the intent that it

should have the same broad interpretation as the term “probability” has in many languages other than English.

Note 3 to entry: Risk can also be defined as the effect of uncertainty on objectives, where uncertainty is the state,

even partial, of deficiency of information related to understanding or knowledge of an event, its consequence or

likelihood.
3.19
sensor

electronic device that senses a physical condition or chemical's presence and delivers an electronic

signal proportional to the observed characteristic
[SOURCE: ISO/IEC TR 29181-9: 2017, 3.14, modified]
4 © ISO 2020 – All rights reserved
---------------------- Page: 10 ----------------------
ISO/TS 24541:2020(E)
3.20
stakeholder
interested party

person or organization that can affect, be affected by or perceive itself to be affected by a decision or

activity

EXAMPLE Users (3.21) and building owners, relevant authorities, responsible bodies, operators, employees

of the operator, external product suppliers and providers of other services, contractors, communities, customers

and environmental associations, financial institutions, scientific and technical organizations, laboratories.

Note 1 to entry: Stakeholders will typically have an interest in the performance or success of an organization.

Note 2 to entry: For the application of this document, environment is considered as a specific stakeholder.

3.21
user
DEPRECATED: consumer

person, group or organization that benefits from drinking water (3.4) delivery and related services,

wastewater service activities, stormwater service activities or from reclaimed water delivery and

related services
Note 1 to entry: Users are a category of stakeholder.

Note 2 to entry: Users can belong to various economic sectors: domestic users, commerce, industry, tertiary

activities or agriculture.

Note 3 to entry: The term “consumer” can also be used, but in most countries the term “user” is more common

when referring to public services.
3.22
water utility

whole set of organization, processes, activities, means and resources necessary for abstracting,

treating, distributing or supplying drinking water (3.4) or for collecting, conveying, treating, disposing

or reusing of wastewater or for the control, collection, storage, transport and use of stormwater and for

providing the associated services
Note 1 to entry: Some key features of a water utility are:

— its mission, to provide drinking water services or wastewater services or the control, collection, storage,

transport and use of stormwater services or a combination thereof;
— its physical area of responsibility and the population within this area;
— its responsible body;

— the general organization with the function of operator being carried out by the responsible body, or by legally

distinct operators;

— the type of physical systems used to provide the services, with various degrees of centralization.

Note 2 to entry: Drinking water utility addresses a utility dealing only with drinking water; wastewater utility

addresses a utility dealing only with wastewater; stormwater utility addresses a utility dealing only with

stormwater.

Note 3 to entry: When it is unnecessary or difficult to make a distinction between responsible body and operator,

the term “water utility” covers both.

Note 4 to entry: In common English, “water service” can be used as a synonym for “water utility”, but this

document does not recommend using the term in this way.
© ISO 2020 – All rights reserved 5
---------------------- Page: 11 ----------------------
ISO/TS 24541:2020(E)
3.23
waterworks
asset system for collecting, treating, pumping and storing drinking water (3.4)

Note 1 to entry: asset types can include catchments, impounding reservoirs, dams, springs, wells, intakes,

transmission mains, filters, tanks, dosing equipment, metering and ancillary infrastructure.

Note 2 to entry: Pumping stations and reservoirs can be sited either in the waterworks or in the drinking water

distribution network (3.5).
4 Principles

Compliance with the requirements for monitoring of drinking water quality and operational

parameters is predominantly achieved using spot sampling and laboratory analysis. The use of MDs

for the continuous monitoring of the drinking water distribution network can be an effective means for

the real-time identification of changes indicating potential contamination of drinking water quality or

events interfering with the operation of a drinking water system. Such real-time identification of events

can improve drinking water supply integrity.

Some MDs can measure several parameters at the same time and can use data analysis tools to facilitate

the reading and understanding of the measurements.

The use of MDs for the continuous monitoring of the drinking water system can provide an effective

supplementary measure within the organization and management of water services.

Although the cost of acquiring MDs will typically be reduced with wider uptake, it should be recognized

that their deployment can be costlier than using sampling and laboratory analysis. Any

...

TECHNICAL ISO/TS
SPECIFICATION 24541
First edition
Service activities relating to drinking
water supply, wastewater and
stormwater systems — Guidelines for
the implementation of continuous
monitoring systems for drinking water
quality and operational parameters in
drinking water distribution networks
PROOF/ÉPREUVE
Reference number
ISO/TS 24541:2020(E)
ISO 2020
---------------------- Page: 1 ----------------------
ISO/TS 24541:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

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 PROOF/ÉPREUVE © ISO 2020 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/TS 24541:2020(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Principles ..................................................................................................................................................................................................................... 6

5 Considerations for the justification of need for continuous monitoring ...................................................7

5.1 General ........................................................................................................................................................................................................... 7

5.2 Cost-benefit ................................................................................................................................................................................................ 7

5.3 Risks of continuous monitoring ............................................................................................................................................... 8

5.4 Local contexts .......................................................................................................................................................................................... 9

6 Choosing parameters to be monitored .......................................................................................................................................... 9

7 Locating the continuous monitoring stations in the drinking water distribution

network .......................................................................................................................................................................................................................11

7.1 General .......................................................................................................................................................................................................11

7.1.1 Network layout ...............................................................................................................................................................11

7.1.2 Development or implementation of an existing hydraulic or statistical

model of the drinking water distribution network (preferred) ...........................................12

7.1.3 The pragmatic approach ........................................................................................................................................12

7.2 Locations for monitoring stations .......................................................................................................................................12

7.2.1 General...................................................................................................................................................................................12

7.2.2 The pragmatic approach ........................................................................................................................................13

7.2.3 The hydraulic model approach .........................................................................................................................13

7.3 Network alert definition ..............................................................................................................................................................13

7.4 Decision support tools ...................................................................................................................................................................14

7.5 Periodic evaluation of the continuous monitoring system ............................................................................14

8 Installation, maintenance, operation, calibration and data transmission of MDs ........................14

8.1 Installation considerations ........................................................................................................................................................14

8.1.1 General...................................................................................................................................................................................14

8.1.2 Geographical location ...............................................................................................................................................14

8.1.3 Site installation location .........................................................................................................................................14

8.2 Maintenance and operational considerations ...........................................................................................................15

8.3 Calibration considerations .........................................................................................................................................................15

8.4 Communication considerations ............................................................................................................................................16

Annex A (informative) Examples of positives and negatives of continuous monitoring systems ......17

Annex B (informative) Examples of commonly deployed drinking water quality parameter

measuring devices ...........................................................................................................................................................................................19

Annex C (informative) Evaluation of the performance of measuring devices ........................................................23

Bibliography .............................................................................................................................................................................................................................24

© ISO 2020 – All rights reserved PROOF/ÉPREUVE iii
---------------------- Page: 3 ----------------------
ISO/TS 24541:2020(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 224, Service activities relating to drinking

water supply, wastewater and stormwater systems.

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 PROOF/ÉPREUVE © ISO 2020 – All rights reserved
---------------------- Page: 4 ----------------------
ISO/TS 24541:2020(E)
Introduction

Cases of drinking water contamination around the world have raised awareness of water utilities'

exposure to risk. Contamination can arise from many causes, including societal mishaps, errors in

operation, maintenance or management by the water utility, natural disasters, vandalism, sabotage,

criminality and terrorist activity. The distributed nature of drinking water systems makes them

especially vulnerable to contamination and can permit the rapid dispersion of a contaminant. The

velocities and volumes of water in a drinking water distribution network can result in contamination

affecting significant numbers of users in a short time (e.g. tens of minutes). Recognition of these risks

has raised awareness of the need to consider the use of continuous monitoring systems to rapidly detect

potential contamination events.

The occurrence of an event can rarely be predicted. However, the more frequently relevant data can

be collected and examined, the greater is the chance of quickly detecting an event's occurrence. This

supports consideration of the adoption of continuous monitoring systems to provide the data streams

that can be used in event detection.

A contamination event can make a waterworks or a drinking water distribution network unusable for a

time and require implementation of contingency plans. Such plans could involve, for example, accessing

an alternative source water or providing an alternative water service other than via the drinking water

distribution network.

To date, very few water utilities have installed continuous monitoring systems either in part or

throughout their drinking water distribution network(s). This situation can result from a rational

decision based on risk assessment and, in some cases, a cost-benefit analysis. However, it should be

acknowledged that circumstances can change – gradually over time or rapidly in the face of events.

Water utilities wishing to explore such an option can face uncertainties and gaps in their knowledge on

how to proceed. In such circumstances water utilities typically face three main challenges:

— which types of measuring devices (MDs) to install in each continuous monitoring station;

— how many continuous monitoring stations to install per drinking water system;

— where to locate the continuous monitoring stations in the drinking water distribution network in

order to achieve the best results.

The installation of continuous monitoring systems could reduce the risk to public health and mitigate

the impact on users and other stakeholders during a contamination event. The value of continuous

monitoring systems can be determined using appropriate risk assessment and cost-benefit analysis.

Such an evaluation should take into account existing controls and establish the additional risk

mitigation that might be achieved and likely costs.

Advances in MD technology have recently made the adoption and deployment of continuous monitoring

more practicable. MDs are not limited to the measurement of drinking water quality alone. Continuous

measurement of operational parameters such as water flow and water pressure can improve the water

utility's capability to interpret results from the measurement of drinking water quality.

This document provides water utilities, their contractors, consultants and regulators with guidelines

for the installation of continuous monitoring systems in drinking water systems, including guidance on

their appropriate selection, maintenance and optimal calibration.

These guidelines can aid a water utility's processes for risk assessment and cost-benefit analysis. Taken

together these can help a water utility's top management take informed, risk-based decisions on the

worthwhileness of investment in a continuous monitoring system.

The guidance provided in this document is intended to be universally applicable, regardless of the

structure and size of a water utility's drinking water system. An event detection process (EDP) that

relies upon grab samples and intermittent data inputs could be implemented at lower cost. However,

where a water utility's assets, finances, management system and technical capability make it

practicable, the ability to provide continuous data streams offers advantages for event detection.

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To gain experience, initial deployment could be limited to higher-risk areas within a wider drinking

water system.
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TECHNICAL SPECIFICATION ISO/TS 24541:2020(E)
Service activities relating to drinking water supply,
wastewater and stormwater systems — Guidelines for
the implementation of continuous monitoring systems
for drinking water quality and operational parameters in
drinking water distribution networks
1 Scope

This document specifies guidelines for the implementation of continuous monitoring systems for

drinking water quality and operational parameters in drinking water distribution networks.

It provides guidance for determining the:

— effective number of continuous monitoring stations in the drinking water distribution network;

— location of monitoring stations in the drinking water distribution network;

— types of operational and drinking water quality parameter measuring devices (MDs) that can be

installed in a continuous monitoring station;

— quality control, maintenance and calibration requirements of the continuous monitoring system.

This document excludes guidance on the design, structure, number and type of MDs to be installed in a

continuous monitoring system.
2 Normative references
There are no normative references in this document.
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 24513 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
accuracy
measurement accuracy
accuracy of measurement

closeness of agreement between a measured quantity value and a true quantity value of a measurand

[SOURCE: ISO/IEC Guide 99:2007, 2.13, modified]
3.2
capability
quality of being able to perform a given activity
[SOURCE: ISO 15531-1:2007, 3.63, modified]
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3.3
continuous monitoring
continuous near-real-time measurements of one or more sampling characteristics

Note 1 to entry: To determine the status, it is possible that one or more relevant parameters need to be checked,

supervised, critically observed or measured compared with one or more pre-defined indicators.

Note 2 to entry: Measuring device (3.14) which provides a non-continuous but regular output signal at a given

frequency can be used for the purpose of continuous monitoring.

Note 3 to entry: The location where a measuring device is installed shall be defined as a continuous monitoring

station.
[SOURCE: ISO 2889:2010, 3.22, modified]
3.4
drinking water
DEPRECATED: potable water
water intended for human consumption

Note 1 to entry: Requirements for drinking water quality specifications are generally laid down by the national

relevant authorities. Guidelines are established by the World Health Organization (WHO).

3.5
drinking water distribution network
asset system for distributing drinking water (3.4)

Note 1 to entry: Drinking water distribution networks can include pipes, valves, hydrants, washouts, pumping

stations, reservoirs, and other metering and ancillary infrastructure and components.

Note 2 to entry: Pumping stations and reservoirs can be sited either in the waterworks (3.23) or in the drinking

water distribution network.
3.6
drinking water system

asset system providing the functions of abstracting, treating, storing, distributing or supplying of

drinking water (3.4)
3.7
event
situation when a behaviour deviates from the normal

Note 1 to entry: An event can be one or more occurrences and can have several causes.

Note 2 to entry: An event can consist of something not happening.

Note 3 to entry: An event can sometimes be referred to as an “incident” or “accident”.

Note 4 to entry: An event without consequences can also be referred to as a “near miss”, “incident”, “near hit” or

“close call”.
3.8
event detection
recognition of event indicator or information about a new situation, or both
Note 1 to entry: New situations can be sorted into one of the following:
— event indicator or situation, or both, are considered known and non-hazardous;

— event indicator or situation, or both, are considered hazardous, but a procedure to handle them already exists;

— event indicator or situation, or both, are considered unknown, and a procedure for them does not yet exist.

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3.9
event detection process
EDP

set of interrelated or interacting activities which transforms inputs [data or information on an actual or

suspected event (3.7)] into outputs [to support the water utility's (3.22) operational activities]

3.10
event indicator

signal to the water utility (3.22) or one or more stakeholders (3.20) of expectations of service

performance
Note 1 to entry: The signal can exist yet remain unobserved for a period.
3.11
maintenance

combination of all technical, administrative and managerial actions during the life cycle of an asset

intended to retain it in, or restore it to, a state in which it can perform the required function

3.12
management
coordinated activities to direct and control a water utility (3.22)

Note 1 to entry: Management can include establishing policies and objectives, and processes (3.17) to achieve

these objectives.

Note 2 to entry: The word “management” sometimes refers to people, i.e. a person or group of people with

authority and responsibility for the conduct and control of a service. When “management” is used in this sense, it

should always be used with some form of qualifier to avoid confusion with the concept “management” as a set of

activities defined above. For example, “management should …” is deprecated whereas “crisis management team

should …” is acceptable. Otherwise different words should be adopted to convey the concept when related to

people, e.g. managerial or managers.

Note 3 to entry: The term “management” can be qualified by a specific domain it addresses. Examples include

public health management, environmental management and risk (3.18) management.
3.13
measurement
process (3.17) to determine a value
3.14
measuring device

component, or a group of components, used in an in-line or online operating position, which continuously

(or at a given frequency) gives an output signal proportional to the value of one or more measurands in

waters which it measures
Note 1 to entry: The device can be portable or fixed in position.

Note 2 to entry: The term “in-line measuring device” is often used for a measuring device used in an in-line

position. The term “online measuring device” is often used for a measuring device used in an online position.

[SOURCE: EN 17075:2018, 3.1]
3.15
monitoring
determining the status of a system, a process (3.17) or an activity

Note 1 to entry: To determine the status, there can be a need to check, supervise or critically observe.

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3.16
operation

action(s) taken in the course of normal functioning of drinking water (3.4) or wastewater systems

EXAMPLE Monitoring and regulation or diversion of drinking water or wastewater.
3.17
process

set of interrelated or interacting activities that use inputs to deliver an intended result

Note 1 to entry: Whether the “intended result” of a process is called an output, product or service depends on the

context of the reference.

Note 2 to entry: Inputs to a process are generally the outputs of other processes and outputs of a process are

generally the inputs to other processes.

Note 3 to entry: Two or more interrelated and interacting processes in series can also be referred to as a process.

Note 4 to entry: Processes in an organization are generally planned and carried out under controlled conditions

to add value.

Note 5 to entry: A process where the conformity of the resulting output cannot be readily or economically

validated is frequently referred to as a “special process”.

Note 6 to entry: In benchmarking, organizational and technical processes and combinations of both are

considered. A process within the meaning of benchmarking comprises a combination of one task with one plant

or object (e.g. operate sewer network, treat wastewater, treat drinking water (3.4), provide domestic connection,

further train staff, purchase material).

Note 7 to entry: In service standards, the term “process” can have a broader meaning than its narrower

interpretation in management system standards. For example, it can also include some elements.

3.18
risk

combination of the likelihood of a hazardous event (3.7) and the severity of consequences, if the hazard

occurs in the drinking water system (3.6), wastewater system or stormwater system

Note 1 to entry: Risk is often characterized by reference to potential events and consequences or a combination

of these.

Note 2 to entry: The English term “likelihood” does not have a direct equivalent in some languages; instead, the

equivalent of the term “probability” is often used. However, in English, “probability” is often narrowly interpreted

as a mathematical term. Therefore, in risk management terminology, “likelihood” is used with the intent that it

should have the same broad interpretation as the term “probability” has in many languages other than English.

Note 3 to entry: Risk can also be defined as the effect of uncertainty on objectives, where uncertainty is the state,

even partial, of deficiency of information related to understanding or knowledge of an event, its consequence or

likelihood.
3.19
sensor

electronic device that senses a physical condition or chemical's presence and delivers an electronic

signal proportional to the observed characteristic
[SOURCE: ISO/IEC TR 29181-9: 2017, 3.14, modified]
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3.20
stakeholder
interested party

person or organization that can affect, be affected by or perceive itself to be affected by a decision or

activity

EXAMPLE Users (3.21) and building owners, relevant authorities, responsible bodies, operators, employees

of the operator, external product suppliers and providers of other services, contractors, communities, customers

and environmental associations, financial institutions, scientific and technical organizations, laboratories.

Note 1 to entry: Stakeholders will typically have an interest in the performance or success of an organization.

Note 2 to entry: For the application of this document, environment is considered as a specific stakeholder.

3.21
user
DEPRECATED: consumer

person, group or organization that benefits from drinking water (3.4) delivery and related services,

wastewater service activities, stormwater service activities or from reclaimed water delivery and

related services
Note 1 to entry: Users are a category of stakeholder.

Note 2 to entry: Users can belong to various economic sectors: domestic users, commerce, industry, tertiary

activities or agriculture.

Note 3 to entry: The term “consumer” can also be used, but in most countries the term “user” is more common

when referring to public services.
3.22
water utility

whole set of organization, processes, activities, means and resources necessary for abstracting,

treating, distributing or supplying drinking water (3.4) or for collecting, conveying, treating, disposing

or reusing of wastewater or for the control, collection, storage, transport and use of stormwater and for

providing the associated services
Note 1 to entry: Some key features of a water utility are:

— its mission, to provide drinking water services or wastewater services or the control, collection, storage,

transport and use of stormwater services or a combination thereof;
— its physical area of responsibility and the population within this area;
— its responsible body;

— the general organization with the function of operator being carried out by the responsible body, or by legally

distinct operators;

— the type of physical systems used to provide the services, with various degrees of centralization.

Note 2 to entry: Drinking water utility addresses a utility dealing only with drinking water; wastewater utility

addresses a utility dealing only with wastewater; stormwater utility addresses a utility dealing only with

stormwater.

Note 3 to entry: When it is unnecessary or difficult to make a distinction between responsible body and operator,

the term “water utility” covers both.

Note 4 to entry: In common English, “water service” can be used as a synonym for “water utility”, but this

document does not recommend using the term in this way.
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3.23
waterworks
asset system for collecting, treating, pumping and storing drinking water (3.4)

Note 1 to entry: asset types can include catchments, impounding reservoirs, dams, springs, wells, intakes,

transmission mains, filters, tanks, dosing equipment, metering and ancillary infrastructure.

Note 2 to entry: Pumping stations and reservoirs can be sited either in the waterworks or in the drinking water

distribution network (3.5).
4 Principles

Compliance with the requirements for monitoring of drinking water quality and operational

parameters is predominantly achieved using spot sampling and laboratory analysis. The use of MDs

for the continuous monitoring of the drinking water distribution network can be an effective means for

the real-time identification of changes indicating potential contamination of drinking water quality or

events interfering with the operation of a drinking water system. Such real-time identification of events

can improve drinking water supply integrity.

Some MDs can measure several parameters at the same time and can use data analysis tools to facilitate

the reading and understanding of the measurements.

The use of MDs for the continuous monitoring of the drinking water system can provide an effective

supplementary measure within the organization and management of water services.

Although the cost of acquiring MDs will typically be reduced with wider uptake, it should be recognized

that their deployment can be costlier than using sampling and laboratory analysis. Any decision made

to apply MDs should be based on a cost-benefit analysis to ensure that no unjustified cost is transferred

to users. While their deployment should reduce the risk of harm for users, it will not remove the risk

entir
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