ISO 24521

Drinking water, wastewater and stormwater systems and services — Management of on-site domestic wastewater services

ISO 24521:2016 provides guidance for the management of basic on-site domestic wastewater services, using appropriate technologies in their entirety at any level of development. ISO 24521:2016 supplements and is intended to be used in conjunction with ISO 24511. It includes the following: · guidelines for the management of basic on-site domestic wastewater services from the operator's perspective, including maintenance techniques, training of personnel and risk considerations; · guidelines for the management of basic on-site domestic wastewater services from the perspective of users; · guidance on the design and construction of basic on-site domestic wastewater systems; · guidance on planning, operation and maintenance, and health and safety issues. The following are outside the scope of ISO 24521:2016: · limits of acceptability for wastewater discharged into a receiving body; · analytical methods; · the management structure of sanitary waste/wastewater service activities of operation and management; · the content of contracts or subcontracts. ISO 24521:2016 is applicable to both publicly and privately operated basic on-site domestic wastewater (black and grey water) services, for one or more dwellings.

Systèmes et services relatifs à l’eau potable, à l’assainissement et à la gestion des eaux pluviales — Gestion sur site des services d’eaux usées domestiques

La présente Norme internationale donne des recommandations relatives à la gestion des services d'assainissement autonome, en utilisant les technologies appropriées dans leur intégralité à tous les niveaux de développement. La présente Norme internationale complète et est destinée à être utilisée conjointement avec l'ISO 24511. Elle comprend les éléments suivants: — des lignes directrices pour la gestion des services d'assainissement autonome du point de vue de l'exploitant, incluant les techniques de maintenance, la formation du personnel et la prise en compte des risques; — des lignes directrices pour la gestion des services d'assainissement autonome du point de vue des usagers; — des recommandations relatives à la conception et à la construction des systèmes d'assainissement autonome; — des recommandations relatives à la planification, à l'exploitation et à la maintenance ainsi qu'aux problématiques de santé et de sécurité. Les sujets suivants ne relèvent pas du domaine d'application de la présente Norme internationale: — les limites d'acceptabilité pour les eaux usées rejetées dans un milieu récepteur; — les méthodes d'analyse; — la structure de management des activités d'exploitation et de management des services de collecte de matières fécales/d'assainissement; — le contenu des contrats et contrats de sous-traitance. La présente Norme internationale s'applique aux services d'assainissement autonome (eaux noires et eaux grises) exploités aussi bien par le secteur public que privé pour une ou plusieurs habitations. NOTE 1 La gestion des services d'assainissement autonome, notamment dans les zones rurales et les zones en développement, est parfois assurée par les propriétaires des locaux où les eaux usées sont générées. Dans pareils cas, les propriétaires des locaux se chargent eux-mêmes de la gestion des eaux usées domestiques. Dans la présente Norme internationale, le terme « services » comprend les « services personnels » fournis par les propriétaires des locaux. NOTE 2 Notamment dans les zones sous-développées, les eaux usées domestiques sont collectées sous forme non diluée (à savoir, sous forme de matières fécales). Les sources de matières fécales/eaux usées citées dans la présente Norme internationale sont résidentielles, à l'exception des écoulements d'eaux pluviales. NOTE 3 L'Annexe A contient un tableau de correspondance entre des équivalences de termes en anglais, français et espagnol. NOTE 4 L'Annexe B donne quelques exemples de schémas de systèmes d'assainissement autonome et de leurs composantes.

General Information

• Status: Not Published
• ICS: 03.080.30 - Services for consumers
• ICS: 13.030.20 - Liquid wastes. Sludge
• ICS: 13.060.30 - Sewage water
• 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: 6000 - International Standard under publication
• Start Date: 07-May-2025
• Completion Date: 10-May-2025

Relations

• Revises: ISO 24521:2016 - Activities relating to drinking water and wastewater services — Guidelines for the management of basic on-site domestic wastewater services
• Effective Date: 06-Aug-2022

Standards Content (Sample)

FINAL DRAFT
International
Standard
ISO/FDIS 24521
ISO/TC 224
Drinking water, wastewater and
Secretariat: AFNOR
stormwater systems and services —
Voting begins on:
Management of on-site domestic
2025-03-11
wastewater services
Voting terminates on:
2025-05-06
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
ISO/FDIS 24521:2025(en) © ISO 2025

FINAL DRAFT
ISO/FDIS 24521:2025(en)
International
Standard
ISO/FDIS 24521
ISO/TC 224
Drinking water, wastewater and
Secretariat: AFNOR
stormwater systems and services —
Voting begins on:
Management of on-site domestic
wastewater services
Voting terminates on:
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
© ISO 2025
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ISO/FDIS 24521:2025(en) © ISO 2025

ii
ISO/FDIS 24521:2025(en)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and abbreviated terms . 2
3.1 Terms and definitions .2
3.2 Abbreviated terms .2
4 Objectives . 2
4.1 General .2
4.2 Protection of public health and safety .3
4.3 Occupational health and safety .3
4.4 Environmental protection . . .3
4.5 Sustainable development .4
4.6 Meeting the needs and expectations of users .4
4.7 Provision of services under normal and emergency situations .5
5 Components of on-site domestic wastewater systems (ODWS) . 5
5.1 General .5
5.2 User interface . .6
5.3 Collection .6
5.4 Removal and transportation .7
5.5 Treatment .7
5.6 Disposal and reuse .8
6 Management of on-site domestic wastewater systems (ODWS) . 8
6.1 General .8
6.2 External management of system function and stakeholder communication .9
6.3 Fundamental management activities .9
6.3.1 Developing objectives and establishing action plans .9
6.3.2 Financial sustainability of the system .9
6.3.3 Asset management . .9
6.3.4 Customer relations .9
6.4 Stakeholder relations .10
6.4.1 Developing plans for support of stakeholders .10
6.4.2 Education and training of stakeholders.10
6.5 Environmental management .11
6.6 Risk management .11
6.6.1 Risk management plan .11
6.6.2 Risk analysis . . 12
7 Planning and construction .13
7.1 Planning and construction of on-site domestic wastewater systems (ODWS) . 13
7.2 Criteria for selecting appropriate on-site domestic wastewater technologies . 13
7.3 User interface . .14
7.4 Collection . 15
7.5 Removal and transportation . 15
7.6 Treatment .16
7.7 Disposal and reuse .16
8 Operation and maintenance plans . . 17
8.1 General .17
8.2 Developing operational plans and instructions .17
8.3 Developing maintenance plans and instructions .18
8.4 Developing plans and instructions for collection of wastewater and sludge .18
8.5 Developing plans and instructions for removal and transportation of wastewater and
sludge .18

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ISO/FDIS 24521:2025(en)
9 Health and safety issues . 19
9.1 Health and safety measures and training .19
9.1.1 General guidance .19
9.1.2 Health risks to user and service providers .19
9.1.3 Basic hygiene practices.19
9.1.4 Personal protective equipment (PPE) . 20
9.1.5 Health and safety training . 20
9.2 Public health programmes . 20
Annex A (informative) Examples of on-site domestic wastewater systems and components .22
Bibliography .38

iv
ISO/FDIS 24521:2025(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liai
...

ISO/FDIS 24521:2025(en)
ISO/TC 224
Secretariat: AFNOR
Date: 2025-01-0802-24
Drinking water, wastewater and stormwater systems and
services — Management of on-site domestic wastewater services
Systèmes et services relatifs à l’eau potable, à l’assainissement et à la gestion des eaux pluviales — Gestion
sur site des services d'eaux usées domestiques

FDIS stage
ISO/FDIS 24521:2025(en)
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying,
or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO
at the address below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel.Phone: + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail: [e-mail]
Website: www.iso.org
Published in Switzerland.
iii
ISO/FDIS 24521:2025(en)
Contents
ISO/FDIS 24521 . 1
Foreword . vi
Introduction . vii
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and abbreviated terms . 2
3.1 Terms and definitions . 2
3.2 Abbreviated terms . 2
4 Objectives . 2
4.1 General . 2
4.2 Protection of public health and safety . 3
4.3 Occupational health and safety . 4
4.4 Environmental protection . 4
4.5 Sustainable development . 4
4.6 Meeting the needs and expectations of users . 5
4.7 Provision of services under normal and emergency situations . 5
5 Components of on-site domestic wastewater systems (ODWS) . 6
5.1 General . 6
5.2 User interface . 7
5.3 Collection . 7
5.4 Removal and transportation . 7
5.5 Treatment . 8
5.6 Disposal and reuse . 9
6 Management of on-site domestic wastewater systems (ODWS) . 9
6.1 General . 9
6.2 External management of system function and stakeholder communication . 10
6.3 Fundamental management activities . 10
6.4 Stakeholder relations . 11
6.5 Environmental management . 12
6.6 Risk management . 12
7 Planning and construction . 14
7.1 Planning and construction of on-site domestic wastewater systems (ODWS) . 14
7.2 Criteria for selecting appropriate on-site domestic wastewater technologies . 15
7.3 User interface . 16
7.4 Collection . 16
7.5 Removal and transportation . 17
7.6 Treatment . 17
7.7 Disposal and reuse . 18
8 Operation and maintenance plans . 19
8.1 General . 19
8.2 Developing operational plans and instructions . 20
8.3 Developing maintenance plans and instructions . 21
8.4 Developing plans and instructions for collection of wastewater and sludge . 21
8.5 Developing plans and instructions for removal and transportation of wastewater and
sludge . 21
9 Health and safety issues . 22
9.1 Health and safety measures and training . 22
iv
ISO/FDIS 24521:2025(en)
9.2 Public health programmes . 24
Annex A (informative) Examples of on-site domestic wastewater systems and components . 25
Bibliography . 42

v
ISO/FDIS 24521:2025(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of
ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights
in respect thereof. As of the date of publication of this document, ISO [had/had not] received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that this
may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO'sISO’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, Drinking water, wastewater and
stormwater systems and services.
This second edition cancels and replaces the first edition (ISO 24521:2016), which has been technically
revised.
The main changes are as follows:
— — the title has been changed to be in line with the title of ISO/TC 224 and with the title of
ISO 24525:2022;
— — the term “basic” has been deleted from the title and from the normative text because this document
also contains guidance and requirements for systems that are not basic;
— — the names and content of the clauses have been harmonized with those in ISO 24525:2022;
— — Annex A in ISO 24521:2016 has been deleted;
— — Annex B from the previous edition has been replaced by the new Annex AAnnex A which contains
examples for both basic and more advanced 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.
vi
ISO/FDIS 24521:2025(en)
Introduction
0.1 0.1  Water issues: global context and policies framework
st
Water constitutes a worldwide challenge for the 21 century, both in terms of the management of available
water resources and the provision of access to drinking water and sanitation for the world’s population. In
2000, the United Nations recognized that access to water is an essential human right and, in conjunction with
national governments, it set ambitious goals (the “Millennium Development Goals” MDGs) to increase access
to drinking water and wastewater services, including safe disposal or reuse of treated residues (jointly
referred to as “water services” in this document), particularly in developing countries.
The COVID-19 pandemic has demonstrated the critical importance of sanitation, hygiene and adequate access
to clean water for preventing and containing diseases. According to the World Health Organization,
handwashing is one of the most effective actions to reduce the spread of pathogens and prevent infections. Yet
billions of people still lack access to safe water and sanitation, and funding is inadequate.
Reflecting an increasing international recognition of the importance of water services, in 2010 the United
Nations General Assembly declared safe and clean water and sanitation as well to be a single human right.
In 2015, following extensive technical discussions, new international goals (the “Sustainable Development
Goals”, SDGs) were set by the United Nations Assembly. The sixth SDG aims to “ensure availability and
sustainable management of water and sanitation for all”.
In particular, its target 6.2 intends to “achieve by 2030 access to adequate and equitable sanitation and
hygiene for all” and to “end open defecation, paying special attention to the needs of womanwomen and girls
and those in vulnerable situations”. The WHO/UNICEF Joint Monitoring Programme for Water, Supply,
Sanitation and Hygiene (JMP), responsible for monitoring SDG target 6.2, concluded in its most recent
progress report (Reference [6(“Progress on household drinking water, sanitation and hygiene 2000–2022:
special focus on gender”)]) that, at current rates of progress, the world will only reach 65 % coverage by 2030,
leaving 3 billion people without safely managed sanitation services. As such, achieving universal coverage of
sanitation services by 2030 will require a fivefold increase of current rates of progress.
Another relevant remark related to SDGs is that target 6.2, contrary to precedent MDGs, goes beyo
...

PROJET FINAL
Norme
internationale
ISO/FDIS 24521
ISO/TC 224
Systèmes et services relatifs à l’eau
Secrétariat: AFNOR
potable, à l’assainissement et à
Début de vote:
la gestion des eaux pluviales —
2025-03-11
Gestion sur site des services d’eaux
Vote clos le:
usées domestiques
2025-05-06
Drinking water, wastewater and stormwater systems and
services — Management of on-site domestic wastewater services
LES DESTINATAIRES DU PRÉSENT PROJET SONT
INVITÉS À PRÉSENTER, AVEC LEURS OBSERVATIONS,
NOTIFICATION DES DROITS DE PROPRIÉTÉ DONT ILS
AURAIENT ÉVENTUELLEMENT CONNAISSANCE ET À
FOURNIR UNE DOCUMENTATION EXPLICATIVE.
OUTRE LE FAIT D’ÊTRE EXAMINÉS POUR
ÉTABLIR S’ILS SONT ACCEPTABLES À DES FINS
INDUSTRIELLES, TECHNOLOGIQUES ET COM-MERCIALES,
AINSI QUE DU POINT DE VUE DES UTILISATEURS, LES
PROJETS DE NORMES
INTERNATIONALES DOIVENT PARFOIS ÊTRE CONSIDÉRÉS
DU POINT DE VUE DE LEUR POSSI BILITÉ DE DEVENIR DES
NORMES POUVANT
SERVIR DE RÉFÉRENCE DANS LA RÉGLEMENTATION
NATIONALE.
Numéro de référence
ISO/FDIS 24521:2025(fr) © ISO 2025

PROJET FINAL
ISO/FDIS 24521:2025(fr)
Norme
internationale
ISO/FDIS 24521
ISO/TC 224
Systèmes et services relatifs à l’eau
Secrétariat: AFNOR
potable, à l’assainissement et à
Début de vote:
la gestion des eaux pluviales —
2025-03-11
Gestion sur site des services d’eaux
Vote clos le:
usées domestiques
2025-05-06
Drinking water, wastewater and stormwater systems and
services — Management of on-site domestic wastewater services
LES DESTINATAIRES DU PRÉSENT PROJET SONT
INVITÉS À PRÉSENTER, AVEC LEURS OBSERVATIONS,
NOTIFICATION DES DROITS DE PROPRIÉTÉ DONT ILS
AURAIENT ÉVENTUELLEMENT CONNAISSANCE ET À
FOURNIR UNE DOCUMENTATION EXPLICATIVE.
DOCUMENT PROTÉGÉ PAR COPYRIGHT
OUTRE LE FAIT D’ÊTRE EXAMINÉS POUR
ÉTABLIR S’ILS SONT ACCEPTABLES À DES FINS
© ISO 2025 INDUSTRIELLES, TECHNOLOGIQUES ET COM-MERCIALES,
AINSI QUE DU POINT DE VUE DES UTILISATEURS, LES
Tous droits réservés. Sauf prescription différente ou nécessité dans le contexte de sa mise en œuvre, aucune partie de cette
PROJETS DE NORMES
INTERNATIONALES DOIVENT PARFOIS ÊTRE CONSIDÉRÉS
publication ne peut être reproduite ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique,
DU POINT DE VUE DE LEUR POSSI BILITÉ DE DEVENIR DES
y compris la photocopie, ou la diffusion sur l’internet ou sur un intranet, sans autorisation écrite préalable. Une autorisation peut
NORMES POUVANT
être demandée à l’ISO à l’adresse ci-après ou au comité membre de l’ISO dans le pays du demandeur.
SERVIR DE RÉFÉRENCE DANS LA RÉGLEMENTATION
NATIONALE.
ISO copyright office
Case postale 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Genève
Tél.: [phone]
E-mail: [e-mail]
Web: www.iso.org
Publié en Suisse Numéro de référence
ISO/FDIS 24521:2025(fr) © ISO 2025

ii
ISO/FDIS 24521:2025(fr)
Sommaire Page
Avant-propos .v
Introduction .vi
1 Domaine d’application . 1
2 Références normatives . 1
3 Termes, définitions et termes abrégés . 2
3.1 Termes et définitions .2
3.2 Termes abrégés .2
4 Objectifs . 2
4.1 Généralités .2
4.2 Protection de la santé et de la sécurité du public .3
4.3 Santé et sécurité au travail .3
4.4 Protection de l’environnement .4
4.5 Développement durable .4
4.6 Satisfaction des besoins et des attentes des usagers .5
4.7 Fourniture des services dans des situations normales et d’urgence .5
5 Composantes des systèmes d’assainissement autonome (ODWS) . 6
5.1 Généralités .6
5.2 Interface utilisateur .7
5.3 Collecte .7
5.4 Vidange et transport .7
5.5 Traitement .8
5.6 Évacuation et réutilisation.8
6 Gestion des systèmes d’assainissement autonome (ODWS) . 9
6.1 Généralités .9
6.2 Gestion externe du fonctionnement du système et de la communication avec les parties
intéressées.9
6.3 Activités fondamentales de gestion .10
6.3.1 Établissement des objectifs et des plans d’action .10
6.3.2 Viabilité financière du système .10
6.3.3 Gestion d’actifs .10
6.3.4 Relations clientèle .10
6.4 Relations avec les parties intéressées .10
6.4.1 Établissement de plans de soutien des parties intéressées .10
6.4.2 Formation des parties intéressées .11
6.5 Gestion environnementale . .11
6.6 Gestion des risques . 12
6.6.1 Plan de gestion des risques . 12
6.6.2 Analyse des risques . 12
7 Planification et construction .13
7.1 Planification et construction des systèmes d’assainissement autonome (ODWS) . 13
7.2 Critères de sélection des technologies d’assainissement autonome.14
7.3 Interface utilisateur . 15
7.4 Collecte .16
7.5 Vidange et transport .16
7.6 Traitement .17
7.7 Évacuation et réutilisation.17
8 Plans d’exploitation et de maintenance .18
8.1 Généralités .18
8.2 Élaboration des plans et des instructions d’exploitation .19
8.3 Élaboration des plans et des instructions de maintenance .19
8.4 Élaboration de plans et d’instructions pour la collecte des eaux usées et des boues .19

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ISO/FDIS 24521:2025(fr)
8.5 Élaboration de plans et d’instructions pour l’extraction et le transport des eaux usées
et des boues .19
9 Problématiques de santé et de sécurité .20
9.1 Mesures et formation relatives à la santé et à la sécurité . 20
9.1.1 Recommandations générales . 20
9.1.2 Risques pour la santé des usagers et des prestataires de services . 20
9.1.3 Pratiques d’hygiène de base .21
9.1.4 Équipements de protection individuelle (EPI) .21
9.1.5 Formation relative à la santé et à la sécurité .21
9.2 Programmes de santé publique . 22
Annexe A (informative) Exemples de systèmes et de composantes d’assainissement autonome .23
Bibliographie .40

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ISO/FDIS 24521
...