ISO/TR 24524:2019

Service activities relating to drinking water supply, wastewater and stormwater systems - Hydraulic, mechanical and environmental conditions in wastewater transport systems

ISO/TR 24524:2019 details the hydraulic, mechanical and environmental conditions generally found in wastewater transport systems from toilets through to wastewater treatment plants, the general powers of wastewater services to manage discharges to sewers, and the responsibilities imposed on wastewater services by applicable local, regional or national legislation.

Activités de service relatives aux systèmes d'alimentation en eau potable, aux systèmes d'assainissement et aux systèmes de gestion des eaux pluviales — Conditions hydrauliques, mécaniques et environnementales dans les systèmes de collecte des eaux usées

Le présent document détaille les conditions hydrauliques, mécaniques et environnementales généralement présentes dans les systèmes de collecte des eaux usées à partir des toilettes vers les stations de traitement des eaux usées, les prérogatives dont disposent les services d'assainissement pour gérer les rejets dans les égouts, et les responsabilités imposées aux services d'assainissement par la législation locale, régionale ou nationale en vigueur.

General Information

• Status: Published
• Publication Date: 21-Feb-2019
• ICS: 03.080.30 - Services for consumers
• ICS: 13.060.30 - Sewage water
• ICS: 97.020 - Home economics in general
• Technical Committee: ISO/TC 224 - Drinking water, wastewater and stormwater systems and services
• Drafting Committee: ISO/TC 224 - Drinking water, wastewater and stormwater systems and services
• Current Stage: 6060 - International Standard published
• Start Date: 22-Feb-2019
• Completion Date: 13-Dec-2025

Overview

ISO/TR 24524:2019 is a Technical Report from ISO/TC 224 that describes the hydraulic, mechanical and environmental conditions typically found in wastewater transport systems - from toilets and household drain lines through sewers, pumping stations and on to wastewater treatment plants. It is a guidance document (a technical report, not an International Standard) intended to help wastewater services, product manufacturers and regulators understand operating conditions, the powers of wastewater services to manage discharges, and responsibilities imposed by local, regional or national legislation.

Key Topics

• Toilets and flush characteristics
  • Purpose and function of toilets; variation in toilet designs and flush volumes (examples in the report include northern Europe ~2–4 L, Japan ~6–10 L).
  • How toilet configuration affects the ability of materials to pass into drain lines.
• Drain lines and intermittent flow hydraulics
  • Typical drain-line configurations and intermittent-flow behaviour.
  • Clearance issues that lead to stranding, settling and snagging of solids.
• Wastewater transport hydraulics
  • Typical transit times, flow regimes and indicators such as Reynolds number that describe laminar vs. turbulent flow in pipes.
• Screening and mechanical protection
  • Role of screens, grilles and other devices to collect solids and protect pumps and downstream infrastructure from clogging.
• Treatment process interactions
  • Primary settlement, biodegradation of settled solids and the liquid phase characteristics relevant to treatment performance.
• Environmental considerations
  • Impacts of discharged materials (including plastics and microplastics), compatibility with treatment processes and receiving environments.
• Definitions and legal/operational context
  • Terms (aligned with ISO 24513 vocabulary), and summary of wastewater services’ general powers and legislative responsibilities.

Applications

ISO/TR 24524:2019 is practical guidance for:

• Wastewater utilities and operators - diagnosing root causes of sewer blockages, setting operational limits, and designing screening and pumping arrangements.
• Product manufacturers (toilet paper, wipes, personal-care items) - evaluating whether products are likely to disintegrate, transport through sewers, and be compatible with treatment processes (i.e., assessing “flushability”).
• Plumbing and civil engineers - designing drain lines, sewers and pump stations with realistic hydraulic and mechanical loads in mind.
• Regulators and policy makers - informing discharge rules, by-laws and public guidance to reduce sewer blockages and environmental impacts.
• Environmental consultants and asset managers - assessing impacts of discharged material (e.g., microplastics) on treatment performance and the receiving environment.

Related Standards

• ISO 24513 - Vocabulary for service activities relating to drinking water supply, wastewater and stormwater systems (normative reference used by ISO/TR 24524:2019).

Keywords: ISO/TR 24524:2019, wastewater transport systems, sewer blockages, toilet flushable, drain line hydraulics, Reynolds number, wastewater treatment, screening, microplastics.

Standards Content (Sample)

TECHNICAL ISO/TR
REPORT 24524
First edition
2019-02
Service activities relating to drinking
water supply, wastewater and
stormwater systems — Hydraulic,
mechanical and environmental
conditions in wastewater transport
systems
Reference number
©
ISO 2019
© ISO 2019
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: [phone]
Fax: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Toilets . 2
4.1 General . 2
4.2 Typical toilet types . 2
4.3 Usage patterns . 3
5 Drain lines . 3
5.1 General . 3
5.2 Drain line hydraulic conditions — intermittent flow . 3
5.2.1 General. 3
5.2.2 Drain line clearance — stranding . 3
5.2.3 Drain line clearance — settling . 4
5.2.4 Drain line clearance — snagging . 4
5.3 Typical drain line configurations . 4
6 Wastewater transport systems . 5
6.1 General . 5
6.2 Typical transit times in transport systems . 6
6.3 Typical hydraulic conditions in flowing pipes (Reynolds number) . 6
7 Screening . 6
8 Treatment processes . 6
8.1 General . 6
8.2 Settlement . 7
8.3 Liquid phase of treatment plants . 7
8.4 Biodegradation of settled solids . 7
9 Environmental considerations . 7
Bibliography . 8
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 2019 – All rights reserved

Introduction
This document addresses the hydraulic, mechanical and environmental conditions generally found in
wastewater transport and treatment systems (which will be referred to collectively as the “wastewater
systems”) based on information that was available at the time of publication.
Wastewater transport and treatment systems have been and are designed to treat sanitary waste
streams from toilets and urinals – comprising faeces, urine and toilet paper, along with other sanitary
waste streams from bathing, laundry and kitchen activities. Most also treat industrial and commercial
discharges containing chemicals. However, in recent years a number of products have been introduced
in the market place that are claimed to be compatible with sanitary objectives, which are then either
identified as being toilet flushable or which by their location of use and usage, are likely to be flushed
down the toilet as the means of disposal. Many of these products are not compatible with current
infrastructure.
The principal objectives for managers of wastewater systems are to protect public health and the
environment and the occupational health and safety of their workers, along with promoting sustainable
[1]
development . Management of the wastewater system should also consider impacts on any outputs
arising from wastewater treatment. There are many factors that contribute to the successful operation
of wastewater systems, including adequate capacity and proper design, along with the necessary capital
expenditure and maintenance to maintain and expand the infrastructure as necessary. Another factor
for the successful operation of wastewater systems is the prevention of blockages. When blockages
occur, there is an unacceptable risk that wastewater may spill from the system and, in doing so, flood
property and the surrounding land, and pollute watercourses and the surrounding environment.
A major problem for wastewater operators is the disposal/flushing to sewers of inappropriate and
[2]–[4]
unsuitable items . Wastewater system blockages and clogged pumps can also come from a variety
of sources, including debris and other materials creating barriers to the entry or free flow of water into
or through the system including outside drains, industrial and commercial discharges.
Further, there may be fouling and damage to wastewater treatment systems from blocked grilles,
gratings, and screens that are intended to:
a) collect and restrict the passage of materials;
b) protect other equipment from being damaged;
c) protect the operation of the treatment systems themselves;
d) minimize the potential for the untreated or partially treated material to enter the environment.
These problems may result in:
— health risk and inconvenience to customers, including that their properties may be flooded with
wastewater;
— damage to the environment, including watercourses;
— otherwise unnecessary expenditure in rectifying the issues in order to maintain efficient operations
and to prevent sewer backups or sewer overflows;
— exposure of workers to health and safety risks.
The presence of inappropriate materials can compound problems of aging infrastructure and hydraulic
capacity of the wastewater infrastructure. It should be noted that sewer overflows may occur for a
number of reasons unrelated to blockages, for example: system design constraints; infrastructure
failure; and weather.
To protect the wastewater system, a discharged material or product that is disposed via the wastewater
system should be able to:
— be flushed from the toilet bowl;
— pass through the drain line (pipes inside/immediately outside property);
— be transported through the wastewater system (sewers and pumping stations);
— not adversely affect the intended performance of wastewater treatment systems;
— not adversely affect the receiving environment when in a disintegrated state.
The physical characteristics that a product should achieve in order to avoid these issues include:
— being able to disintegrate to a sufficient degree and in a timely manner so as to not cause problems
in the drain line, sewer system or when passed through pumps;
— to be transported in the flow through the piped system, yet settle in the primary settlement process
of wastewater treatment;
— for the material to be compatible with both the wastewater treatment process and the receiving
environment.
The conditions listed in this document may be taken into account when designing and evaluating the
performance of products which could potentially be flushed via the toilet. It can also assist stakeholders
in communicating with consumers and communities about the compatibility of materials flushed via
the toilet.
vi © ISO 2019 – All rights reserved

TECHNICAL REPORT ISO/TR 24524:2019(E)
Service activities relating to drinking water supply,
wastewater and stormwater systems — Hydraulic,
mechanical and environmental conditions in wastewater
transport systems
1 Scope
This document details the hydraulic, mechanical and environmental conditions generally found in
wastewater transport systems from toilets through to wastewater treatment plants, the general
powers of wastewater services to manage discharges to sewers, and the responsibilities imposed on
wastewater services by applicable local, regional or national legislation.
2 Normative references
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
discharged material
material deposited into a toilet as a means of disposal
Note 1 to entry: Some solid materials that are discharged will be contaminated with human excreta such as
faeces, urine, vomit, menses, blood, saliva and nasal or throat discharges.
Note 2 to entry: Discharges to wastewater transport systems come also from other sanitary equipment such as
showers, laundries, kitchen sinks, and industrial and commercial entities.
3.2
grille
assembly of bars at an environmental exit point from a wastewater transport system to minimise
release of solid materials to the environment and exclude entry
Note 1 to entry: In some parts of the world grilles are called grates.
3.3
microplastics
small pieces of plastic less than five millimetres in diameter
Note 1 to entry: Microplastics can be in the form of a sphere (microbeads), or as fibres or fragments.
[SOURCE: Adapted from Gesamp Reports and Studies No. 90 – Microplastics in the Ocean (2015), p.14.]
3.4
plastic
solid material which contains, as an essential ingredient, one or more synthetic organic high polymers
and which is formed (shaped) during either manufacture of the polymer or the fabrication into a
finished product by heat and/or pressure
[SOURCE: ISO 13617:2001, 3.12, modified — NOTE removed.]
3.5
Reynolds number
R
e
dimensionless ratio of the inertial flow forces to the viscous forces within a fluid
Note 1 to entry: An indicator of the flow characteristics (laminar or turbulent) of a moving fluid.
[SOURCE: ISO 28520:2009, 3.4]
3.6
screen
device of rigid bars, mesh, perforated plate or other configurations installed in wastewater systems
Note 1 to entry: Screens are used to collect solids from within wastewater systems to, for example, protect
pumps and downstream infrastructure from clogging or blocking.
3.7
toilet
fixed receptacle into which a person may urinate or defecate, typically consisting of a large bowl
connected to a cistern for flushing
Note 1 to entry: Also known as a water closet (WC).
[SOURCE: Adapted from the Oxford English Dictionary. Oxford: OUP; 2018.]
4 Toilets
4.1 General
The purpose of the toilet is to dispose of human excreta (urine, menses, vomit and faeces) by using
water to flush it through a drain line to another location for disposal, thus providing safe, sanitary
disposal of human waste.
Any material discharged via a toilet should not adversely affect the intended operation of the toilet.
4.2 Typical toilet types
There are a range of toilet configurations found in different parts of the world. Toilet design,
configuration and installation may impact on the ability of material to pass through the toilet and into
the drain line.
Table 1 shows the commonly found variations in the configuration of toilets as found in a review of the
countries listed in 2015.
Table 1 — Typical toilet design configurations in different geographic locations
Country or region Toilet flush volume Toilet bowl design
Australia/ NZ 4,5 l and 6,0 l Wash down
Canada 4,8 l and 6,0 l Siphonic
Chile 4,8 l to 7,0 l Siphonic
2 © ISO 2019 – All rights reserved

Table 1 (continued)
Country or region Toilet flush volume Toilet bowl design
Europe (southern) 3,0 l to 6,0 l Wash down
Europe (northern) 2,0 l to 4,0 l Wash down
Israel 4,5 l to 6 l Wash down
Japan 6.0 l to 10 l Wash down/siphonic
UK and Ireland 4,5 l to 6,0 l Wash down
USA 3,0 l to 6,0 l Siphonic
As indicated in Table 1, there are a range of flush volumes to be taken into account.
For global considerations, a volume for toilets of 4,5 l to 6,0 l may be used as a reference.
4.3 Usage patterns
The frequency and nature of the usage of toilets varies considerably. Some of these uses will involve
faecal material and urine with or without toilet paper, others involve urine alone (with or without toilet
paper). The sequence of these uses in any one day will depend on the region, the number, gender and
age of the persons
...

TECHNICAL REPORT    ISO/TR 24524:2019(E)
Deleted: PRF
Deleted: 2018
2019-02
ISO TC 224/ WG 10
Secretariat: AFNOR
Service activities relating to drinking water supply, wastewater and stormwater systems —
Deleted:
Hydraulic, mechanical and environmental conditions in wastewater transport systems
Deleted: WD stage¶
Warning for WDs and CDs¶
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.¶
Deleted: 2018
© ISO 2019 – All rights reserved 1

Deleted: PRF
Deleted: 2018
© ISO 2018, Published in Switzerland
All rights reserved. Unless otherwise specified, 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
Ch. de Blandonnet 8 • CP 401
CH‐1214 Vernier, Geneva, Switzerland
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
[e-mail]
www.iso.org
Deleted: www.iso.org¶
Deleted: 1
Deleted: 2018
ii © ISO 2019 – All rights reserved

Deleted: PRF
Deleted: 2018
Contents
Deleted: Foreword iv¶
Foreword . 4
Introduction v¶
1 Scope 1¶
Introduction. 5
2 Normative references 1¶
1  Scope . 1
3 Terms and definitions 1¶
4 Toilets 2¶
2  Normative references . 1
4.1 General 2¶
4.2 Typical toilet types 2¶
3  Terms and definitions . 1
4.3 Usage patterns 3¶
4  Toilets . 2  5 Drain lines 3¶
5.1 General 3¶
4.1  General . 2
5.2 Drain line hydraulic
4.2  Typical toilet types . 2
conditions — intermittent
4.3  Usage patterns . 3
flow 3¶
5.2.1 General 3¶
5  Drain lines . 3
5.2.2 Drain line clearance —
5.1  General . 3
stranding 4¶
5.2  Drain line hydraulic conditions — intermittent flow . 3
5.2.3 Drain line clearance —
5.2.1  General . 3  settling 4¶
5.2.4 Drain line clearance —
5.2.2  Drain line clearance — stranding . 4
snagging 4¶
5.2.3  Drain line clearance — settling . 4
5.3 Typical drain line
5.2.4  Drain line clearance — snagging . 4
configurations 4¶
5.3  Typical drain line configurations . 5
6 Wastewater transport
systems 5¶
6  Wastewater transport systems . 5
6.1 General 5¶
6.1  General . 5
6.2 Typical transit times in
6.2  Typical transit times in transport systems . 6
transport systems 6¶
6.3 Typical hydraulic
6.3  Typical hydraulic conditions in flowing pipes (Reynolds number) . 6
conditions in flowing pipes
7  Screening . 6
(Reynolds number) 6¶
7 Screening 6¶
8  Treatment processes . 7
8 Treatment processes 6¶
8.1  General . 7
8.1 General 6¶
8.2  Settlement . 7
8.2 Settlement 7¶
8.3 Liquid phase of
8.3  Liquid phase of treatment plants . 7
7¶
treatment plants
8.4  Biodegradation of settled solids . 7
8.4 Biodegradation of
settled solids 7¶
9  Environmental considerations . 7
9 Environmental
Bibliography . 9
considerations 7¶
Bibliography 8¶
... [1]
Deleted: 2018
© ISO 2019 – All rights reserved iii

Deleted: PRF
Deleted: 2018
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).
Deleted: 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).
Deleted: 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.
Deleted: www.iso.org/iso/forewor
d.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.
Deleted: www.iso.org/members.ht
ml.
Deleted: 1
Deleted: 2018
iv © ISO 2019 – All rights reserved

Deleted: PRF
Deleted: 2018
Introduction
This document addresses the hydraulic, mechanical and environmental conditions generally found in
wastewater transport and treatment systems (which will be referred to collectively as the “wastewater
systems”) based on information that was available at the time of publication.
Wastewater transport and treatment systems have been and are designed to treat sanitary waste
streams from toilets and urinals – comprising faeces, urine and toilet paper, along with other sanitary
waste streams from bathing, laundry and kitchen activities. Most also treat industrial and commercial
discharges containing chemicals. However, in recent years a number of products have been introduced
in the market place that are claimed to be compatible with sanitary objectives, which are then either
identified as being toilet flushable or which by their location of use and usage, are likely to be flushed
down the toilet as the means of disposal. Many of these products are not compatible with current
infrastructure.
The principal objectives for managers of wastewater systems are to protect public health and the
environment and the occupational health and safety of their workers, along with promoting sustainable
[1]
development . Management of the wastewater system should also consider impacts on any outputs
arising from wastewater treatment. There are many factors that contribute to the successful operation
of wastewater systems, including adequate capacity and proper design, along with the necessary capital
expenditure and maintenance to maintain and expand the infrastructure as necessary. Another factor
for the successful operation of wastewater systems is the prevention of blockages. When blockages
occur, there is an unacceptable risk that wastewater may spill from the system and, in doing so, flood
property and the surrounding land, and pollute watercourses and the surrounding environment.
A major problem for wastewater operators is the disposal/flushing to sewers of inappropriate and
[2]–[4]
unsuitable items . Wastewater system blockages and clogged pumps can also come from a variety of
sources, including debris and other materials creating barriers to the entry or free flow of water into or
through the system including outside drains, industrial and commercial discharges.
Further, there may be fouling and damage to wastewater treatment systems from blocked grilles,
gratings, and screens that are intended to:
a) collect and restrict the passage of materials;
b) protect other equipment from being damaged;
c) protect the operation of the treatment systems themselves;
d) minimize the potential for the untreated or partially treated material to enter the environment.
These problems may result in:
— health risk and inconvenience to customers, including that their properties may be flooded with
Deleted: a)
wastewater;
— damage to the environment, including watercourses;
Deleted: b)
— otherwise unnecessary expenditure in rectifying the issues in order to maintain efficient operations
Deleted: c)
and to prevent sewer backups or sewer overflows;
— exposure of workers to health and safety risks.
Deleted: d)
The presence of inappropriate materials can compound problems of aging infrastructure and hydraulic
capacity of the wastewater infrastructure. It should be noted that sewer overflows may occur for a
number of reasons unrelated to blockages, for example: system design constraints; infrastructure
failure; and weather. Deleted: 2018
© ISO 2019 – All rights reserved v

Deleted: PRF
Deleted: 2018
To protect the wastewater system, a discharged material or product that is disposed via the wastewater
system should be able to:
— be flushed from the toilet bowl;
Deleted: a)
— pass through the drain line (pipes inside/immediately outside property);
Deleted: b)
— be transported through the wastewater system (sewers and pumping stations);
Deleted: c)
— not adversely affect the intended performance of wastewater treatment systems;
Deleted: d)
— not adversely affect the receiving environment when in a disintegrated state.
Deleted: e)
The physical characteristics that a product should achieve in order to avoid these issues include:
— being able to disintegrate to a sufficient degree and in a timely manner so as to not cause problems
Deleted: a)
in the drain line, sewer system or when passed through pumps;
— to be transported in the flow through the piped system, yet settle in the primary settlement process
Deleted: b)
of wastewater treatment;
— for the material to be compatible with both the wastewater treatment process and the receiving
Deleted: c)
environment.
The conditions listed in this document may be taken into account when designing and evaluating the
Deleted: report
performance of products which could potentially be flushed via the toilet. It can also assist stakeholders
Deleted: should
in communicating with consumers and communities about the compatibility of materials flushed via the
toilet.
Deleted: 1
Deleted: 2018
vi © ISO 2019 – All rights reserved

TECHNICAL REPORT    ISO/TR 24524:2019(E)
Service activities relating to drinking water supply, wastewater
and stormwater systems — Hydraulic, mechanical and
environmental conditions in wastewater transport systems
1 Scope
This document details the hydraulic, mechanical and environmental conditions generally found in
wastewater transport systems from toilets through to wastewater treatment plants, the general powers
of wastewater services to manage discharges to sewers, and the responsibilities imposed on
wastewater services by applicable local, regional or national legislation.
2 Normative references
ISO 24513, Service activities relating to drinking water supply, wastewater and stormwater systems —
Vocabulary 1
Deleted:
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
Deleted: https://www.iso.org/ob
p
— IEC Electropedia: available at http://www.electropedia.org/
Deleted: http://www.electropedi
a.org/
3.1
discharged material
material deposited into a toilet as a means of disposal
Note 1 to entry: Some solid materials that are discharged will be contaminated with human excreta such as faeces,
urine, vomit, menses, blood, saliva and nasal or throat discharges.
Note 2 to entry: Discharges to wastewater transport systems come also from other sanitary equipment such as
showers, laundries, kitchen sinks, and industrial and commercial entities.
3.2
grille
assembly of bars at an environmental exit point from a wastewater transport system to minimise
release of solid materials to the environment and exclude entry
Note 1 to entry: In some parts of the world grilles are called grates.
3.3
microplastics
small pieces of plastic less than five millimetres in diameter
Note 1 to entry: Microplastics can be in the form of a sphere (microbeads), or as fibres or fragments.
Deleted: 2018
© ISO 2019 – All rights reserved 1

Deleted: PRF
Deleted: 2018
[SOURCE: Adapted from Gesamp Reports and Studies No. 90 – Microplastics in the Ocean (2015), p.14.]
3.4
plastic
solid material which contains, as an essential ingredient, one or more synthetic organic high polymers
and which is formed (shaped) during either manufacture of the polymer or the fabrication into a
finished product by heat and/or pressure
[SOURCE: ISO 13617:2001, 3.12, modified — NOTE removed.]
3.5
Reynolds number
R
e
dimensionless ratio of the inertial flow forces to the viscous forces within a fluid
Note 1 to entry: An indicator of the flow characteristics (laminar or turbulent) of a moving fluid.
[SOURCE: ISO 28520:2009, 3.4]
3.6
screen
device of rigid bars, mesh, perforated plate or other configurations installed in wastewater systems
Note 1 to entry: Screens are used to collect solids from within wastewater systems to, for example, protect pumps
and downstream infrastructure from clogging or blocking.
3.7
toilet
fixed receptacle into which a person may urinate or defecate, typically consisting of a large bowl
connected to a cistern for flushing
Note 1 to entry: Also known as a water closet (WC).
[SOURCE: Adapted from the Oxford English Dictionary. Oxford: OUP; 2018.]
4 Toilets
4.1 General
The purpose of the toilet is to dispose of human excreta (urine, menses, vomit and faeces) by using
water to flush it through a drain line to another location for disposal, thus providing safe, sanitary
disposal of human waste.
Any material discharged via a toilet should not adversely affect the intended operation of the toilet.
4.2 Typical toilet types
There are a range of toilet configurations found in different parts of the world. Toilet design,
configuration and installation may impact on the ability of material to pass through the toilet and into
the drain line.
Table 1 shows the commonly found variations in the configuration of toilets as found in a review of the
countries listed in 2015.
Deleted: 2018
2 © ISO 2019 – All rights reserved

Deleted: PRF
Deleted: 2018
Table 1 — Typical toilet design configurations in different geographic locations
Country or region Toilet flush Toilet bowl design
volume
Australia/ NZ 4,5 l and 6,0 l Wash down
Canada 4,8 l and 6,0 l Siphonic
Chile 4,8 l to 7,0 l Siphonic
Europe (southern) 3,0 l to 6,0 l Wash down
Europe (northern) 2,0 l to 4,0 l Wash down
Israel 4,5 l to 6 l Wash down
Japan 6.0 l to 10 l Wash down/siphonic
UK and Ireland 4,5 l to 6,0 l Wash down
USA 3,0 l to 6,0 l Siphonic
As indicated in Table 1, there are a range of flush volumes to be taken into account.
For global considerations, a volume for toilets of 4,5 l to 6,0 l may be used as a reference.
4.3 Usage patterns
The frequency and nature of the usage of toilets varies considerably. Some of these uses will involve
faecal material and urine with or without toilet paper, others involve urine alone (with or without toilet
paper). The sequence of these uses in any one day will depend on the region, the number, gender and
age of the persons in the building and the nature of the building.
5 Drain lines
5.1 General
There are a range of drain line configurations found in different parts of the world (see Table 2). Drain
line design, configuration, construction and maintenance may impact the ability of waste to pass
through the drain line. Typically, material introduced into a drain line moves along the drain line with
water from toilet flushing. Failure of flushed material to exit the drain line may result in blocked
plumbing and the generation of unacceptable odours or allow material to dry out and adhere to the pipe
surface.
When material moves down the drain line it may occasionally become snagged on a damaged or broken
pipe. Depending on the severity of the damage to the pipe, it should then either self‐release, tear off the
snag or break up within a certain number of flushes. When such material does not release, tear off or
break up, it may result in issues for the drain line. Any material discharged via a toilet should not
adversely affect the intended operation of the drain line or sewer system. It should exit a drain line
within a timeframe/number of flushes.
5.2 Drain line hydraulic conditions — intermittent flow
5.2.1 General
The hydraulic condition commonly observed in drain lines associated with residences is the
[5]
intermittent flow of wastewater which influences the motion of solids in the drain line .
Deleted: 2018
© ISO 2019 – All rights reserved 3

Deleted: PRF
Deleted: 2018
Solids discharged into drain lines can move by either being entrained in the flush wave or by a sliding
dam action. The movement within the flush wave is often short‐lived and will only occur close to the
discharge point. Further downstream, often after between 5 m and 10 m from the discharge point, the
[5]
flush wave will have dissipated and any movement will be as a sliding dam as described by Butler .
5.2.2 Drain line clearance — stranding
The modes of movement of solid materials in drain lines or small sewers is complex and has been
[5]
documented extensively by Butler . Material discharged into a drain line will normally move throug
...

RAPPORT ISO/TR
TECHNIQUE 24524
Première édition
2019-02
Activités de service relatives
aux systèmes d'alimentation
en eau potable, aux systèmes
d'assainissement et aux systèmes
de gestion des eaux pluviales —
Conditions hydrauliques, mécaniques
et environnementales dans les
systèmes de collecte des eaux usées
Service activities relating to drinking water supply, wastewater and
stormwater systems — Hydraulic, mechanical and environmental
conditions in wastewater transport systems
Numéro de référence
©
ISO 2019
DOCUMENT PROTÉGÉ PAR COPYRIGHT
© ISO 2019
Tous droits réservés. Sauf prescription différente ou nécessité dans le contexte de sa mise en œuvre, aucune partie de cette
publication ne peut être reproduite ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique,
y compris la photocopie, ou la diffusion sur l’internet ou sur un intranet, sans autorisation écrite préalable. Une autorisation peut
être demandée à l’ISO à l’adresse ci-après ou au comité membre de l’ISO dans le pays du demandeur.
ISO copyright office
Case postale 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Genève
Tél.: [phone]
Fax: [phone]
E-mail: [e-mail]
Web: www.iso.org
Publié en Suisse
ii © ISO 2019 – Tous droits réservés

Sommaire Page
Avant-propos .iv
Introduction .v
1 Domaine d'application . 1
2 Références normatives . 1
3 Termes et définitions . 1
4 Toilettes . 2
4.1 Généralités . 2
4.2 Types courants de toilettes . 3
4.3 Types d’usages . 3
5 Conduites d’évacuation/branchement . 3
5.1 Généralités . 3
5.2 Conditions hydrauliques de la conduite d’évacuation — écoulement intermittent . 4
5.2.1 Généralités . 4
5.2.2 Dégagement de la conduite d’évacuation — échouement . 4
5.2.3 Dégagement de la conduite d’évacuation — décantation . 4
5.2.4 Dégagement de la conduite d’évacuation — accrochage . 5
5.3 Configurations courantes des conduites d’évacuation . 5
6 Systèmes de collecte des eaux usées . 6
6.1 Généralités . 6
6.2 Durées de transit courantes dans les systèmes de collecte . 6
6.3 Conditions hydrauliques courantes dans les canalisations (nombre de Reynolds) . 6
7 Dégrilleur . 7
8 Procédés de traitement . 7
8.1 Généralités . 7
8.2 Décantation . 7
8.3 Phase liquide des stations de traitement des eaux usées . 8
8.4 Biodégradation des matériaux solides décantés . 8
9 Considérations environnementales . 8
Bibliographie . 9
Avant-propos
L’ISO (Organisation internationale de normalisation) est une fédération mondiale d’organismes
nationaux de normalisation (comités membres de l’ISO). L’élaboration des Normes internationales est
en général confiée aux comités techniques de l’ISO. Chaque comité membre intéressé par une étude
a le droit de faire partie du comité technique créé à cet effet. Les organisations internationales,
gouvernementales et non gouvernementales, en liaison avec l’ISO participent également aux travaux.
L’ISO collabore étroitement avec la Commission électrotechnique internationale (IEC) en ce qui
concerne la normalisation électrotechnique.
Les procédures utilisées pour élaborer le présent document et celles destinées à sa mise à jour sont
décrites dans les Directives ISO/IEC, Partie 1. Il convient, en particulier, de prendre note des différents
critères d’approbation requis pour les différents types de documents ISO. Le présent document a été
rédigé conformément aux règles de rédaction données dans les Directives ISO/IEC, Partie 2 (voir www
.iso .org/directives).
L’attention est attirée sur le fait que certains des éléments du présent document peuvent faire l’objet de
droits de propriété intellectuelle ou de droits analogues. L’ISO ne saurait être tenue pour responsable
de ne pas avoir identifié de tels droits de propriété et averti de leur existence. Les détails concernant
les références aux droits de propriété intellectuelle ou autres droits analogues identifiés lors de
l’élaboration du document sont indiqués dans l’Introduction et/ou dans la liste des déclarations de
brevets reçues par l’ISO (voir www .iso .org/brevets).
Les appellations commerciales éventuellement mentionnées dans le présent document sont données
pour information, par souci de commodité, à l’intention des utilisateurs et ne sauraient constituer un
engagement.
Pour une explication de la nature volontaire des normes, la signification des termes et expressions
spécifiques de l’ISO liés à l’évaluation de la conformité, ou pour toute information au sujet de l’adhésion
de l’ISO aux principes de l’Organisation mondiale du commerce (OMC) concernant les obstacles
techniques au commerce (OTC), voir le lien suivant: www .iso .org/iso/fr/avant -propos .html.
Le présent document a été élaboré par le comité technique ISO/TC 224, Activités de service relatives aux
systèmes d’alimentation en eau potable, aux systèmes d’assainissement et aux systèmes de gestion des eaux
pluviales.
Il convient que l’utilisateur adresse tout retour d’information ou toute question concernant le présent
document à l’organisme national de normalisation de son pays. Une liste exhaustive desdits organismes
se trouve à l’adresse www .iso .org/fr/members .html.
iv © ISO 2019 – Tous droits réservés

Introduction
Le présent document traite des conditions hydrauliques, mécaniques et environnementales
généralement présentes dans les systèmes de collecte et de traitement des eaux usées (qui seront
désignés collectivement par «systèmes d’assainissement» dans le reste du document) sur la base des
informations qui étaient disponibles au moment de la publication.
Les systèmes de collecte et de traitement des eaux usées ont été et sont conçus pour traiter les flux de
déchets sanitaires provenant des toilettes et des urinoirs – comprenant les matières fécales, l’urine et le
papier toilette, ainsi que d’autres flux de déchets sanitaires provenant des activités de bain, de lessive et
de cuisine. La plupart traitent aussi les rejets issus d’activités industrielles et commerciales contenant
des produits chimiques. Cependant, au cours des dernières années, un certain nombre de produits,
déclarés compatibles avec ces objectifs sanitaires, ont été introduits sur le marché. Ils ont alors été
identifiés comme étant jetables dans les toilettes. De même, de par leur emplacement d’utilisation et
leur usage, ils sont susceptibles d’être jetés dans les toilettes pour s’en débarrasser. Or, bon nombre de
ces produits ne sont pas compatibles avec les infrastructures actuelles des systèmes d’assainissement.
Les principaux objectifs des exploitants de systèmes d’assainissement sont de protéger la santé publique
et l’environnement ainsi que la santé et la sécurité au travail de leur personnel, et de promouvoir le
[1]
développement durable . Il convient également que la gestion du système d’assainissement tienne
compte des impacts sur les différents produits issus du traitement des eaux usées. De nombreux
facteurs contribuent à la performance de l’exploitation des systèmes d’assainissement, notamment
une capacité adéquate et une conception appropriée, des investissements et une maintenance adaptés
pour entretenir et agrandir les infrastructures en fonction des besoins. La prévention des obstructions
est un autre facteur contribuant à la bonne exploitation des systèmes d’assainissement. Lorsqu’une
obstruction se produit, il y a un risque inacceptable que les eaux usées débordent du système, viennent
inonder les biens et les terrains environnants, et polluer les cours d’eau et l’environnement.
Les opérateurs chargés de l’assainissement rencontrent un problème majeur qui est celui du rejet dans
[2]-[4]
les égouts de déchets inadaptés . Les obstructions du système d’assainissement et le colmatage
des pompes peuvent aussi être dus à diverses sources, notamment des débris et autres matériaux qui
créent des obstacles empêchant l’entrée ou le libre écoulement de l’eau dans le système, y compris les
branchements domestiques et les raccordements d’origine industrielle et commerciale.
Il peut en outre se produire un encrassement et un endommagement des systèmes de traitement des
eaux usées dus à des grilles et des dégrilleurs bloqués qui sont destinés à:
a) limiter le transfert de déchets solides et les collecter;
b) empêcher la détérioration d’autres équipements;
c) protéger l’exploitation des systèmes de traitement proprement dits;
d) minimiser le potentiel que des déchets non traités ou partiellement traités ne soient rejetés dans
l’environnement.
Ces problèmes peuvent conduire à:
— un risque pour la santé et une gêne des clients, notamment du fait que leurs biens peuvent être
inondés par les eaux usées;
— une atteinte à l’environnement, notamment les cours d’eau;
— des dépenses inutiles pour remédier aux problèmes survenus, afin de maintenir l’efficacité des
opérations et d’empêcher le refoulement ou le débordement des égouts;
— l’exposition des travailleurs à des risques pour la santé et la sécurité.
La présence de matériaux inadaptés peut exacerber les problèmes de vieillissement des infrastructures
et de capacité hydraulique des infrastructures d’eaux usées. Il convient de noter que les débordements
des égouts peuvent se produire pour des raisons non liées à des obstructions, par exemple: contraintes
de conception du système, défaillance des infrastructures et conditions météorologiques.
Pour protéger le système d’assainissement, il convient qu’un matériau rejeté ou tout produit évacué via
le système d’assainissement puisse:
— être chassé de la cuvette des toilettes;
— passer dans la conduite d’évacuation et dans le branchement (canalisations en partie privative
comme en domaine public);
— être transporté dans le système d’assainissement (égouts et stations de pompage);
— ne pas affecter négativement la performance prévue des systèmes de traitement des eaux usées;
— ne pas affecter négativement le milieu récepteur une fois qu’il a été désintégré.
Les caractéristiques physiques qu’un produit devrait présenter pour éviter ces problèmes sont
notamment:
— être capable de se désintégrer à un degré suffisant et dans un délai raisonnable de manière à ne pas
causer de problèmes dans la conduite d’évacuation/le branchement, le réseau d’assainissement ou
lors du passage dans les pompes;
— être transporté dans l’effluent via le système de canalisations sans décanter, mais décanter lors du
processus de décantation primaire du traitement des eaux usées;
— que les matériaux soient compatibles à la fois avec le procédé de traitement des eaux usées et le
milieu récepteur.
Les conditions énumérées dans le présent document peuvent être prises en compte lors de la conception
et de l’évaluation de la performance des produits pouvant être rejetés dans les toilettes. Ce document
peut également aider les parties prenantes à communiquer avec les consommateurs et les communautés
sur la compatibilité des matériaux rejetés dans les toilettes.
vi © ISO 2019 – Tous droits réservés

RAPPORT TECHNIQUE ISO/TR 24524:2019(F)
Activités de service relatives aux systèmes d'alimentation
en eau potable, aux systèmes d'assainissement et aux
systèmes de gestion des eaux pluviales — Conditions
hydrauliques, mécaniques et environnementales dans les
systèmes de collecte des eaux usées
1 Domaine d'application
Le présent document détaille les conditions hydrauliques, mécaniques et environnementales
généralement présentes dans les systèmes de collecte des eaux usées à partir des toilettes vers les
stations de traitement des eaux usées, les prérogatives dont disposent les services d’assainissement
pour gérer les rejets dans les égouts, et les responsabilités imposées aux services d’assainissement par
la législation locale, régionale ou nationale en vigueur.
2 Références normatives
Les documents suivants sont cités dans le texte de sorte qu’ils constituent, pour tout ou partie de leur
contenu, des exigences du présent document. Pour les références datées, seule l’édition citée s’applique.
Pour les références non datées, la dernière édition du document de référence s'applique (y compris les
éventuels amendements).
ISO 24513, Activités de service relatives aux systèmes d'alimentation en eau potable, aux systèmes
d'assainissement et aux systèmes de gestion des eaux pluviales — Vocabulaire
3 Termes et définitions
Pour les besoins du présent document, les termes et définitions donnés dans l’ISO 24513 ainsi que les
suivants, s’appliquent.
L’ISO et l’IEC tiennent à jour des bases de données terminologiques destinées à être utilisées en
normalisation, consultables aux adresses suivantes:
— ISO Online browsing platform: disponible à l’adresse https: //www .iso .org/obp
— IEC Electropedia: disponible à l’adresse http: //www .electropedia .org/
3.1
matériau rejeté
matériau évacué dans les toilettes pour s’en débarrasser
Note 1 à l'article: Certains matériaux solides qui sont rejetés seront contaminés par des excréments humains, tels
que les matières fécales, l’urine, le vomit, les menstruations, le sang, la salive et les sécrétions nasales ou de la gorge.
Note 2 à l'article: Les rejets vers les systèmes de collecte des eaux usées proviennent également d’autres
équipements sanitaires, tels que les douches, les machines à laver, les éviers et les activités industrielles et
commerciales.
3.2
grille
dispositif constitué de barres, installé à un point de sortie d’un système de collecte des eaux usées dans
l’environnement, afin de minimiser le rejet de matériaux solides dans l’environnement et d’en empêcher
l’entrée
Note 1 à l'article: Dans certaines parties du monde, les grilles sont appelées «grates».
3.3
microplastiques
petits morceaux de plastique de moins de cinq millimètres de diamètre
Note 1 à l'article: Les microplastiques peuvent se présenter sous la forme d’une sphère (microbilles) ou de fibres
ou fragments.
[SOURCE: Adapté des Rapports et études du Gesamp N° 90 – Microplastics in the Ocean (2015), p.14.]
3.4
plastique
matériau solide qui contient, comme ingrédient essentiel, un ou plusieurs hauts polymères organiques
synthétiques et qui est formé (mis en forme) lors de la fabrication du polymère ou du façonnage du
produit fini sous l’effet de la chaleur et/ou de la pression
[SOURCE: ISO 13617:2001, 3.12, modifiée — NOTE supprimée.]
3.5
nombre de Reynolds
R
e
rapport sans dimension entre les forces d’écoulement inertiel et les forces visqueuses dans un fluide
Note 1 à l'article: Un indicateur des caractéristiques d’écoulement (laminaire ou turbulent) d’un fluide en
mouvement.
[SOURCE: ISO 28520:2009, 3.4]
3.6
dégrilleur
dispositif composé de barres rigides, d’un maillage, d’un tamis ou d’autres configurations, installé dans
les systèmes d’assainissement
Note 1 à l'article: Les dégrilleurs sont utilisés pour collecter les matériaux solides provenant des systèmes
d’assainissement, par exemple pour protéger les pompes et les infrastructures en aval contre les colmatages ou
les obstructions.
3.7
toilettes
réceptacle fixe dans lequel une personne peut uriner ou déféquer, composé généralement d’une grande
cuvette reliée à un réservoir de chasse
Note 1 à l'article: Également appelées WC.
[SOURCE: Adapté du dictionnaire anglais Oxford. Oxford: OUP; 2018]
4 Toilettes
4.1 Généralités
Les toilettes ont pour but d’évacuer les excréments humains (urine, menstruations, vomit et matières
fécales) en utilisant de l’eau pour les chasser dans une conduite d’évacuation jusqu’au point de rejet vers
le système de collecte, et ainsi de fournir un moyen d’évacuation sûr et sanitaire des déchets produits
par l’homme.
2 © ISO 2019 – Tous droits réservés

Il convient que tout matériau rejeté dans les toilettes n’affecte pas négativement l’utilisation normale
des toilettes.
4.2 Types courants de toilettes
Il existe plusieurs configurations de toilettes dans les différentes parties du monde. La conception, la
configuration et l’installation des toilettes peuvent avoir un impact sur la capacité du matériau à passer
dans les toilettes et dans la conduite d’évacuation.
Le Tableau 1 indique les variantes courantes en matière de configuration des toilettes d’après une revue
réalisée en 2015 dans les différents pays cités.
Tableau 1 — Configurations courantes de conception des toilettes
dans différentes zones géographiques
Pays ou région Volume de chasse Conception de la cuvette
des toilettes
Australie/NZ 4,5 l et 6,0 l Lavage à grande eau
Canada 4,8 l et 6,0 l Siphon
Chili 4,8 l à 7,0 l Siphon
Europe (du Sud) 3,0 l à 6,0 l Lavage à grande eau
Europe (du Nord) 2,0 l à 4,0 l Lavage à grande eau
Israël 4,5 l à 6 l Lavage à grande eau
Japon 6,0 l à 10 l Lavage à grande eau/siphon
Royaume-Uni et Irlande 4,5 l à 6,0 l Lavage à grande eau
États-Unis 3,0 l à 6,0 l Siphon
Comme indiqué dans le Tableau 1, il faut tenir compte d’une plage de volumes de chasse.
Pour les considérations globales, un volume de chasse des toilettes de 4,5 l à 6,0 l peut être utilisé
comme référence.
4.3 Types d’usages
La fréquence et la nature de l’usage des toilettes varient considérablement. Certaines de ces utilisations
impliquent des matières fécales et de l’urine, avec ou sans papier toilette, d’autres impliquent de l’urine
seulement (avec ou sans papier toilette). La séquence de ces utilisations sur une journée va dépendre
de la région, du nombre, du sexe et de l’âge des personnes présentes dans le bâtiment et de la nature du
bâtiment.
5 Conduites d’évacuation/branchement
5.1 Généralités
Il existe plusieurs configurations de conduite d’évacuation dans les différentes parties du monde (voir
Tableau 2). La conception, la configuration, la construction et la maintenance de la conduite d’évacuation
peuvent avoir un impact sur la capacité des déchets à passer dans cette conduite. Généralement, le
matériau introduit dans une condui
...