ISO/TS 24541:2020

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 2020
© ISO 2020
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ii © ISO 2020 – All rights reserved

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
Foreword
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This document was prepared by Technical Committee ISO/TC 224, Service activities relating to drinking
water supply, wastewater and stormwater systems.
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iv © ISO 2020 – All rights reserved

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.
To
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