ISO 23446:2021

Marine technology - Product water quality of seawater reverse osmosis (RO) desalination - Guidelines for municipal water supply

This document provides guidelines for product water quality of seawater reverse osmosis (RO) desalination that is used for municipal water supply. It specifies water quality parameters and ranges, monitoring frequency and test methods to ensure the compatibility of the product water with the pipelines.

Technologie maritime — Qualité de l'eau produite par le dessalement de l'eau de mer par osmose inverse (OI) — Lignes directrices pour les réseaux municipaux d'eau potable

General Information

• Status: Published
• Publication Date: 28-Sep-2021
• ICS: 13.060.01 - Water quality in general
• Technical Committee: ISO/TC 8/SC 13 - Marine technology
• Drafting Committee: ISO/TC 8/SC 13/WG 3 - Seawater desalination
• Current Stage: 6060 - International Standard published
• Start Date: 29-Sep-2021
• Due Date: 11-Mar-2022
• Completion Date: 29-Sep-2021

Overview

ISO 23446:2021 is a global standard developed by the International Organization for Standardization (ISO) that provides comprehensive guidelines for the product water quality of seawater reverse osmosis (RO) desalination, specifically for municipal water supply. As urbanization and climate change exacerbate freshwater scarcity worldwide, seawater desalination using RO technology has become a crucial solution to ensure reliable and sustainable potable water sources.

This standard defines essential water quality parameters, testing methods, and monitoring frequencies to guarantee that the treated water is compatible with municipal distribution pipelines and infrastructure. It addresses potential issues such as water aggressiveness towards metallic materials and emphasizes post-treatment procedures to stabilize mineral content.

Key Topics

• Water Quality Parameters: The standard specifies critical parameters including pH, calcium hardness, total alkalinity, total dissolved solids (TDS), and the Langelier Saturation Index (LSI) to assess water stability and corrosiveness.

• Parameter Ranges:

  • pH: 7.5 to 8.5 (with tighter ranges recommended for specific cases)
  • Calcium hardness: 60 to 120 mg/l as CaCO₃
  • Total alkalinity: ≥ 50 mg/l as CaCO₃
  • TDS limits for desalted water vary by RO process type (single or double pass)
  • LSI: between -0.5 and 0.5 to ensure balanced scaling and corrosion potential

• Monitoring Frequency:

  • Desalted water parameters such as electrical conductivity and pH are to be monitored daily.
  • Product water quality parameters like calcium hardness and total alkalinity require weekly or monthly sampling depending on local contexts.
  • Enhanced frequency is recommended for well-equipped plants supplying primary municipal water sources.

• Test Methods:

  • pH measurement conforms to ISO 10523.
  • Electrical conductivity tests follow ISO 7888.
  • Calcium hardness determined via ISO/TS 15923-2 with specific calculation methods.
  • Total alkalinity assessed according to ISO 9963-1.
  • TDS determined by EN 15216-2007.
  • LSI calculation is detailed within the standard.

• Post-Treatment Importance: Due to the low mineral content and high corrosiveness of raw RO-desalinated water, the standard advocates mineral addition or blending to achieve balanced water chemistry.

Applications

ISO 23446:2021 serves as a critical reference for various stakeholders in the marine and municipal water supply sectors, including:

• Water Engineers and Operators: To design, monitor, and operate seawater RO desalination plants ensuring product water meets municipal supply criteria.

• Municipal Water Authorities: To develop water quality control frameworks that protect infrastructure from corrosion and scaling.

• Environmental and Public Health Agencies: To define safe deployment of desalinated water within urban water systems, considering public health and system longevity.

• Manufacturers and Suppliers: To calibrate equipment and sensors for compliance with standardized test methods and monitoring requirements.

• Policy Makers and Regulators: To set regulatory limits and water quality standards based on internationally recognized guidelines.

Implementing the guidelines can enhance the durability of water distribution pipelines, reduce maintenance costs, and assure safe drinking water quality derived from seawater RO desalination.

Related Standards

Key international standards complementing ISO 23446:2021 include:

• ISO 10523: Water quality - Determination of pH
• ISO 7888: Water quality - Electrical conductivity measurement
• ISO/TS 15923-2: Water quality - Photometric determination of selected parameters including calcium
• ISO 9963-1: Water quality - Total alkalinity determination
• EN 15216-2007: Determination of total dissolved solids (TDS) in water
• WHO Guidelines for Drinking-Water Quality: Global health recommendations impacting water treatment standards

These allied standards ensure harmonized testing procedures and coherent quality assessment methodologies relevant to water treatment and supply.

---

Keywords: ISO 23446, seawater reverse osmosis, RO desalination, municipal water supply, water quality guidelines, water parameters, desalinated water, calcium hardness, Langelier saturation index, TDS, water monitoring frequency, marine technology, post-treatment water quality, water pipeline compatibility, corrosion control in water systems.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 23446
First edition
2021-09
Marine technology — Product water
quality of seawater reverse osmosis
(RO) desalination — Guidelines for
municipal water supply
Technologie maritime — Qualité de l'eau produite par le dessalement
de l'eau de mer par osmose inverse (OI) — Lignes directrices pour les
réseaux municipaux d'eau potable
Reference number
© ISO 2021
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]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Desalted water quality . 1
5 Product water quality . 1
6 Monitoring frequency .2
7 Test methods . 2
Annex A (informative) Calculation method of calcium hardness . 3
Annex B (informative) Calculation method of the Langelier saturation index (LSI) .4
Annex C (informative) Information of product water quality of seawater RO desalination
in specific cases .5
Bibliography . 6
iii
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. 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. 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 8, Ships and marine technology,
Subcommittee SC 13, Marine technology.
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
Introduction
With population growth, urbanization, climate change impacts and increases in household and
industrial uses, fresh water scarcity will definitely affect the sustainable development of society.
Seawater desalination is an effective way to meet the water needs. In some regions, it is almost the
primary source of municipal water supply.
Because of technology and cost advantages, the reverse osmosis (RO) process has been used
increasingly for seawater desalination. However, desalted water of seawater RO desalination is low
in minerals and poorly buffered. It is usually aggressive to metallic materials used in equipment and
distribution pipelines. To solve this problem, the post-treatment of desalted water, such as the addition
of minerals and/or blending of waters, is necessary to achieve a balanced mineral content. Therefore, it
is necessary to monitor product water quality after post-treatment to confirm the safety for municipal
water supply.
Consequently, standardization of the product water quality is important and useful for the protection
of corrosive pipelines and related equipment. The key parameters are monitored to meet the related
limits and range. The product water will be compatible with municipal pipelines and related equipment.
These guidelines provide key parameters to manage the product water quality of seawater RO
desalination for municipal water supply. They are intended to assist water engineers, authorities,
decision makers and stakeholders in evaluating the compatibility of product water with pipelines and
devices.
v
INTERNATIONAL STANDARD ISO 23446:2021(E)
Marine technology — Product water quality of seawater
reverse osmosis (RO) desalination — Guidelines for
municipal water supply
1 Scope
This document provides guidelines for product water quality of seawater reverse osmosis (RO)
desalination that i
...