ISO Standards for UV Disinfection for Water Reuse Systems

By Phyllis Posy, PosyGlobal and IUVA Chair of Education Committee; and Kumiko Oguma, Department of Urban Engineering, The University of Tokyo and IUVA Asia-Pacific Vice President

Standards for UV technologies have long been a topic on the IUVA agenda, and the IUVA has issued several specific discrete measurement standards over the years. Several IUVA Task Forces also are working to establish standards that will satisfy regulators, scientists and technologists and be market relevant. However, a single industry group rarely can institute a standard for broad application, and that’s where the International Standards Organization (ISO) serves a very important market and science-driven function.

What is ISO Standardization?

ISO does not decide when to develop a new standard but instead responds to a request from industry or other stakeholders, such as consumer groups. Typically, an industry sector or group communicates the need for a standard to its national member (usually the country’s local standardization body), which then contacts ISO. ISO will determine if setting standards is appropriate, then solicit involvement of all 193 member countries and enroll both participating countries and observer countries in launching a Technical Committee to address standardization across that field.

And that’s how two general standards for UV in water reuse applications came to be developed. The UV standards are part of a broader standards setting process to address water treatment technologies for water reuse systems in the hope that clear consensus standards would make adoption easier, increase acceptance of innovative systems and facilitate international trade. Japan, China and Israel worked together to call for member countries to join. In June 2013, ISO/TC282 on water reuse was established in Geneva. The first TC282 meeting was held in Tokyo in 2014, and countries joining included Japan, Israel, China, South Korea, Canada, USA, Singapore, France, Austria and Ethiopia.

As with other TCs on other subjects, TC282 is made up of experts from each country to represent a broad portfolio of its stakeholders from the relevant industry, consumer associations, academia, NGOs and government. The TC defines its mandate, scope, how it relates to other existing TCs and what specific areas will be covered. The TC is governed by strict ISO protocols and rules of procedure, including a code of conduct that itemizes strict transparency and ethics rules and is reviewed at each meeting.

Each country has a voice and a vote on whether to move a standard from one stage to the next – from a working draft (WD) to committee draft (CD) to Draft International Standard (DIS) to Final Draft International Standard (FDIS) – until all technical issues are resolved and the standard is approved, then published. Technical and editorial changes are considered at different points in the process, but no technical changes are permitted once the FDIS stage has been completed. Further technical changes require the standard to be sent back for another FDIS review and another vote.

At each stage, the country can vote yes, no or abstain and provide line by line comments. Although each participating country only has one vote, several country experts usually will participate in the TC meetings and then bring back drafts and issues to their country’s “Mirror Committee” to be vetted by an even broader group of stakeholders and experts. Clear ISO rules require that before any formal ballot, every comment – organized and transmitted by the country representative on forms designed to describe the concern, the preferred solution and the committee’s disposition of the comment – must be taken into account, evaluated by the group and discussed until a consensus is reached to accept, change text or reject. Often specific solutions to impasses are voted upon until everyone has agreed. All issues must be resolved and agreed, with formal ballots to move to the next stage before a standard is adopted and given ISO status. Adoption requires fewer than 25% negative votes. New ISO rules strictly limit the time development is allowed and, if no consensus can be reached, the standard is abandoned.

The result is a process that gathers the top global experts to balance all sides of each issue, negotiate all aspects of the text (including its scope, key definitions and content) and develop consensus on technical issues. Since often the key technology players are represented around the table, important compromises are forged, enabling acceptance by countries that previously may have had divergent rules. The length of the development process also makes it easier for technology companies to put the new standards into practice early and facilitate transitions.

TC282 Takes on Water Reuse

TC 282 focuses on setting basic standards for various applications of water reuse, related technologies and processes. The TC is organized into Sub-Committees (SC) and Working Groups (WG), each focusing on a particular application area. Since some technologies and concepts may be relevant to several applications, the Sub-Committees coordinate between the different standards and perspectives. Technology expert representatives usually participate in more than one Sub-Committee. Before the pandemic, TC282 met twice a year and rotated locations. In compliance with ISO policy, all meetings were held on Zoom for the past several years, with the first post-pandemic, in-person meeting now scheduled for May 2023.

TC282 Sub-Committee (SC) groups include SC1 on Wastewater Reuse for Irrigation (chaired by Israel), SC2 on Water Reuse in Urban Areas (chaired by China), SC3 on Risk and Performance Evaluation of Water Reuse Systems (chaired by Japan) and Water Reuse in Industries, added in 2016 and co-chaired by Israel and China. SC1 developed a broad standard for how to effectively incorporate disinfection systems in adapting reuse water for irrigation, including chapters on chemical methods, membranes and UV, among others. In SC3, experts deliberated various unit processes – including ozonation, membrane filtration, ion exchange, advanced oxidation and UV disinfection – and how to standardize the performance evaluation methods in internationally sound ways.

SC1 developed standards that covered how to apply many technologies in various aspects of planning and implementing agricultural reuse. Concurrently, SC3 focused on how to evaluate a specific technology and its performance in a water reuse context. In some cases, standards may give one country’s method an avenue to be adopted by other countries using this process; in some, it establishes an easy model and reference to be used when a country decides to regulate. While the adopted standards are completely voluntary and members of ISO are not required to give them the force of law, once a standard is promulgated, portions often get incorporated into the legal requirements in various countries and authorities and usually are cited as references in regulation development. For example, as a consensus standard, based on the participation of many countries, this series became the foundation for the EU rules on water reuse for agriculture.

The Challenge of Setting Standards for UV

The discussion on UV disinfection kicked off at TC282/SC3 in June 2014, and it took seven years to finally complete the process and promulgate official international standards in May 2021. UV technology played a role in several of the standards under discussion in SC1, SC2 and SC3 – each requiring different considerations. Each SC focused on how to match effective UV to its application arena. Several of the participating countries already had UV specifications and rules, and these needed to be considered overall. In addition, TC282’s leadership forum decided to have a single vocabulary standard rather than changing terms to be context-specific for each standard. When it became clear that there were significant technical issues that needed to be discussed, resolved and agreed on by all of the SCs, an AdHoc Group (AHG) was chartered under the joint leadership of Japan and Israel. The AHG conferred with experts in the IUVA as well as scientists in Canada, China and Austria to assure scientific accuracy while building in flexibility for the standards to be used by engineers and regulators around the world in specifying UV systems, including in countries that already had adopted standards.

Since no previous ISO standards addressed UV, the process of achieving consistency in defining the terms and collaboration to build consensus was a seven-year effort. Thus. SC3 and SC1 each included UV treatment standards, but from different perspectives, with various issues negotiated in the AHG. UV standards were incorporated into both ISO 20468-4 (Guidelines for performance evaluation of treatment technologies for water reuse systems) and ISO 16075-5:2021 (with its catalog of technologies, including UV, for Guidelines for treated wastewater reuse for irrigation projects).

One key area the AHG resolved was the difference between performance evaluation of UV systems and validation of UV systems. Consensus was developed: Validation options were defined in the disinfection section of the standard on disinfecting treated wastewater for use in agriculture; verification options included the Japanese methodology for simulations for use in a variety of situations as part of the Performance Evaluation standard.

In this way, both simulation-based analysis for specified conditions and the conventional and well-established validation procedure testing full-scale UV reactors in certified test centers or onsite are covered.

General Disinfection Standard

Part 5, the general disinfection standard, was published in June 2021, as part of a six-part 16075 series on Guidelines for Treated Wastewater Use for Irrigation Projects. The full series is re-evaluated and revised on a regular basis, including two updated and reissued standards in 2020 on basics and project design; three standards updated and reissued in 2021 on project components, monitoring and disinfection; and a final part still under development on fertilization when using treated wastewater.

Part 5 provides general guidelines for the application of various available methods of disinfection of treated wastewater (TWW) across various irrigation purposes, across a range of water quality standards for different levels of effective inactivation/of pathogens. For each technology, it establishes the principles of operation, effective doses to be applied, possible interferences and technical guidance for design and monitoring. The standard compares the advantages and disadvantages of various disinfection methods under different circumstances. It discusses how to minimize challenges with each technology, including UV, and recommends how to use disinfection at different locations in the reuse system, (e.g., treatment plant, distribution system and at the point of use). The UV disinfection chapter focuses on system components, validation processes and standard application methodologies.

Performance Evaluation Standard

The Performance Evaluation series treats each technology separately, and Part 4 is devoted to UV. It follows the official UV certification procedure in force by Japan Water Research Center (JWRC). While reviewing various aspects of the technology so the standard can be used as a self-standing unit, it looks at how performance can be verified using a simulation-based method. There are sections on terms and definitions, the purpose and function of UV disinfection, system configuration and functional requirements, methods of monitoring UV treatment system performance and its components (flow, water quality) and diagnosis of causes for system failure.

This standard also covers aspects not specifically associated with disinfection efficacy, like environmental performance, energy efficiency, chemical consumption, safety, cost effectiveness (economic evaluation by LCC), and reliability and resilience. Annexes specify and explain experimental evaluation method for UV units, including the Japanese method for evaluation in combination with CFD-I simulation.

These valuable standards will point regulators and engineers around the world to established references and help them accept UV technology and use it properly in areas where its potential has not yet been achieved.

More information about these and related ISO standards for water reuse can be found at