In many regions, water scarcity is increasing, mainly due to climate change, population growth, urbanization and industrialization in emerging countries. To mitigate such pressing situations, the recovery and reuse of water is in many cases the only commercially, socially and environmentally sustainable solution.

The 13th IWA International Conference on Water Reclamation and Reuse was organized by the IWA Water Reuse Specialist Group and the Federation of Indian Chambers of Commerce and Industry from January 15th to 19th, 2023 at Chennai, Tamil Nadu, India. The overarching umbrella theme of the conference was ‘Water Reuse: Overcoming the Challenges of Growth and Climate Change’. The conference covered a wide range of topics which were structured in three groups: water reuse adoption, water reuse implementation and removal of water reuse bottlenecks.

  • Water reuse adoption

    • o Water reuse in developing countries

    • o Market and social acceptance

    • o Public involvement and education

    • o Risk management

    • o Regulation and governance

    • o Economic perspectives

    • o The water-energy-food nexus

    • o Integration of water reuse into existing systems

    • o The role of international collaboration and aid

    • o Improved sanitation standards and access to clean drinking water

    • o Sustainable water reuse within the context of climate change

  • Water reuse implementation

    • o Industrial reuse

    • o Agricultural reuse

    • o Urban reuse

    • o Non-potable water reuse

    • o Potable water reuse (indirect and direct)

    • o Desalination

    • o Decentralized and small-scale solutions

    • o Managing water reuse in fast-growing megacities

    • o Building resilience to water reuse

    • o The financing of water reuse projects

  • Removal of water reuse bottlenecks

    • o Innovative technologies and applications (e.g. 'green' hydrogen production)

    • o Antimicrobial resistance

    • o Concentrate and residual management

    • o Zero-liquid discharge/Minimum-liquid discharge

    • o Fecal sludge management

    • o Smart and digital water reuse

    • o SARS-CoV-2 impact on water reuse

    • o Models of adoption of water reuse

In this special issue of the Journal of Water Reuse, six very interesting contributions in various fields of water reuse (non-potable and potable reuse, risk management, cost analysis, innovation, water reuse communication and public education, etc.) have been published:

  • Potential and risks of water reuse in Brandenburg (Germany) – an interdisciplinary case study

  • How much does reclaimed wastewater cost? A comprehensive analysis for irrigation uses in the European Mediterranean context

  • Tertiary treatment using ultrafiltration in an existing sewage treatment plant for industrial reuse: a modelling approach using artificial neural network with uncertainty estimation

  • Seeded membrane distillation crystallization for hypersaline brine treatment

  • Process benefits of ozone/BAC as pretreatment to membrane-based advanced treatment for direct potable reuse

  • A communication strategy for water reuse in South Africa

The six papers exemplify the challenges of water reuse in the context of climate change in all their diversity. A regional diversity first, with cases extending from India to America, and passing by Europe and Africa, providing a critical reminder that climate change will affect our relationship with water, no matter where we live on this planet. A diversity of issues then, from the difficulty to provide safe and affordable water in sufficient quantity to a still-growing global population to the safe disposal of residual wastes generated by advanced practices and processes. Finally, a diversity of solutions both technological, illustrated by the recent leaps in artificial intelligence, advanced processes and membranes and socio-economic by being more interdisciplinary and overall better communicants to involve the society as a whole.

As underlined during the conference, water reuse is a global trend in water cycle management, which however needs specific solutions depending on local context to ensure their economic viability, sustainability and public acceptance. Nevertheless, good practices, effective tools and management strategies, as described in the presented papers, could be adapted to various climate and economic conditions. One of the most challenging issues is the cost evaluation and financing of water reuse project. As demonstrated in the paper from Spain, based on real data from several successful projects in Spain, economically viable solutions could be found, even for the low-cost reclaimed water for agricultural irrigation. Either for non-potable and potable water reuse, cost and use of recycled water should be managed within the global water cycle on a municipal or regional scale. Similarly, good examples are given for risk assessment and public education/communication.

As a rule, mature treatment technologies have been implemented in water reuse to manage technical risks and water quality compliance and public health protection. However, innovative technologies and/or new combination of proven conventional technologies are needed to improve the reliability and economic viability of wastewater treatment and polishing, as for example seeded membrane distillation crystallization for brine treatment and combination of ozonation and activated carbon membrane pretreatment for direct potable reuse.

The Guest Editors would like to acknowledge all authors and reviewers for their valuable contributions in the manuscript preparation and peer-review process.

This is an Open Access article distributed under the terms of the Creative Commons Attribution Licence (CC BY 4.0), which permits copying, adaptation and redistribution, provided the original work is properly cited (http://creativecommons.org/licenses/by/4.0/).