National foreword

This British Standard is the UK implementation of ISO 20760‑1:2025. It supersedes BS ISO 20760‑1:2018, which is withdrawn.

The UK participation in its preparation was entrusted to Technical Committee B/505/50, Water reuse.

A list of organizations represented on this committee can be obtained on request to its committee manager.

Contractual and legal considerations

This publication has been prepared in good faith, however no representation, warranty, assurance or undertaking (express or implied) is or will be made, and no responsibility or liability is or will be accepted by BSI in relation to the adequacy, accuracy, completeness or reasonableness of this publication. All and any such responsibility and liability is expressly disclaimed to the full extent permitted by the law.

This publication is provided as is, and is to be used at the recipient’s own risk.

The recipient is advised to consider seeking professional guidance with respect to its use of this publication.

This publication is not intended to constitute a contract. Users are responsible for its correct application.

Compliance with a British Standard cannot confer immunity from legal obligations.

This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 November 2025.

Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

ISO draws attention to the possibility that the implementation of this document may involve the use of (a) patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a) patent(s) which may be required to implement this document. However, implementers are cautioned that this may not represent the latest information, which may be obtained from the patent database available at www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.

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

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISO’s adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.

This document was prepared by Technical Committee ISO/TC 282, Water reuse, Subcommittee SC 2, Water reuse in urban areas.

This second edition cancels and replaces the first edition (ISO 20760‑1:2018), which has been technically revised.

The main changes are as follows:

added information regarding the stability evaluation and corresponding evaluation parameters;
added information regarding the performance evaluation of typical treatment processes.

A list of all parts in the ISO 20760 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A complete listing of these bodies can be found at www.iso.org/members.html.

Introduction

With economic development, climate change and increases in population and rapid urbanization, water has become a strategic resource especially in arid and semi-arid regions. Water shortages are considered as one of the most serious threats to sustainable development of society. To address these shortages, reclaimed water is increasingly being used to satisfy water demands and this strategy has proven useful in increasing the reliability of long-term water supplies in many water-scarce areas.

The role of water reuse is growing for urban areas in many countries including landscape irrigation, industrial uses, toilet and urinal flushing, firefighting and fire suppression, street cleaning, environmental and recreational uses (ornamental water features, water bodies’ replenishment, etc.) and vehicle washing. These centralized water reuse systems have been developed to the degree that they are now considered as an effective component of urban water management and are used in many cities and countries.

The essential components of a reclaimed water treatment system include water sources, wastewater collection systems (sewers and pumping stations), a wastewater treatment facility, a reclaimed water distribution system, reclaimed water storage, a water quality monitoring system and operation and maintenance provided by experienced and certified operators. The variable nature and diversity in source water present a challenge to ensuring water safety and reliability in each system component. A further complication to distributing the reclaimed water is that different water reuse applications can have different levels of water quality, which would consider more complex water use patterns and system models.

This document provides design principles for centralized water reuse systems in urban areas. It considers and addresses the critical issues and factors in the design of the different system components and is intended to assist water engineers, authorities, decision-makers and stakeholders in considering feasible and cost-effective approaches for safe and reliable fit-for-purpose water reuse. For details on the management of a centralized water reuse system, see ISO 20760‑2. Additionally, for details on the design principles of decentralized or onsite water reuse systems in urban areas, see ISO 23056.

1 Scope

This document provides guidelines for the planning and design of centralized water reuse systems and water reuse applications in urban areas.

This document addresses centralized water reuse systems in their entirety and is applicable to any water reclamation system component (e.g. source water, treatment, storage, distribution, operation and maintenance and monitoring).

This document provides:

system components and possible models of a centralized water reuse system;
design principles of a centralized water reuse system;
common assessment criteria and related examples of water quality indicators, all without setting any target values or thresholds;
specific aspects for consideration and emergency response.

This document excludes design parameters and regulatory values of a centralized water reuse system.

2 Normative references

3 Terms and definitions

4 Abbreviated terms

5 Planning and design of a centralized water reuse system

5.1 General

5.2 Estimation of water demand

5.3 Site conditions

5.4 System components

5.5 Possible models of the system

5.6 Basic principles

6 Source water considerations

6.1 Type of source water

6.2 Water quality considerations for source water

6.3 Reliability considerations

6.4 Economic considerations

7 Reclaimed water treatment system

7.1 General

7.2 Centralized water reuse treatment system design principles

7.3 Possible centralized water reuse treatment system configurations

7.4 Treatment processes

8 Reclaimed water storage system

8.1 General

8.2 Storage types

8.3 Storage considerations

8.4 Size of the storage facility and turnover considerations

8.5 Control of water quality

8.6 Specific considerations for open storage reservoirs

9 Reclaimed water transmission and distribution system

9.1 General

9.2 Components and models of the distribution system

9.3 Pumping stations

9.4 Reclaimed water distribution systems

10 Monitoring system

10.1 General

10.2 Monitoring locations and facilities

10.3 Monitoring of source water

10.4 Monitoring and control of treatment facilities

10.5 Monitoring of distribution system

10.6 Monitoring of storage

10.7 Monitoring of end-user sites

11 Emergency response plan

Bibliography

BS ISO 20760-1:2025

Water reuse in urban areas — Guidelines for centralized water reuse system - Design principle of a centralized water reuse system

Current

Published:

30 Nov 2025