Overview
ISO 18997:2025 - Water reuse in urban areas: Guidelines for urban reclaimed water for landscaping uses - provides internationally harmonized guidance for the safe, sustainable use of reclaimed water in urban landscapes. The standard covers use cases where reclaimed water replenishes landscape water bodies (for example, urban stream flow, rivers, lakes, aesthetic impoundments and wetlands replenishment) to support aquatic ecosystems and enhance urban amenity. It addresses planning, design, management and maintenance while explicitly excluding irrigation of public or residential green spaces and any cultivation of aquatic plants/animals for food.
Key topics and technical requirements
ISO 18997 focuses on practical design and operation considerations rather than prescriptive numeric limits. Key technical topics include:
- General recommendations - safety, ecological rationale, public acceptability and aesthetic considerations for reclaimed water in landscape settings.
- Hydraulic design - assessment of reclaimed water quantity, hydraulic retention time (HRT), flow patterns and optimal input points to support ecosystem health and aesthetic goals.
- Water quality considerations - routine and specific monitoring parameters (microbial/pathogen risks, nutrients, suspended solids, organic load) to manage risk for incidental body contact and aquatic life.
- Supplemental treatment options - guidance on decolourisation, disinfection (UV, etc.), odour and turbidity removal, nutrient reduction and other treatments suitable for landscape reuse.
- Management and monitoring - operational controls, signage for public safety, and recommended monitoring frequency and parameters (see Annex A and B for examples).
- Emergency response planning - procedures to respond to quality or quantity failures.
- Cross-cutting topics include GHG emissions, photoreactivation risks, and interactions with local regulations.
Practical applications
ISO 18997 is intended to support projects that use reclaimed water to:
- Augment urban streams and lakes to maintain ecological flows and prevent drought impacts
- Replenish constructed or restored aesthetic wetlands and impoundments
- Improve urban aquatic habitat, visual amenity and recreational landscapes where incidental body contact may occur
Practical benefits include improved water resource resilience, ecosystem restoration, and more sustainable urban water cycles.
Who should use this standard
- Urban planners and landscape architects specifying reclaimed water systems
- Water utilities and wastewater reuse engineers designing supply points and treatment trains
- Environmental regulators and public health authorities assessing risk and permits
- Consultants and asset managers responsible for operation, monitoring and emergency response
Related standards
- ISO 20670 - Water reuse - Vocabulary (referenced)
- ISO 20469 - (referenced for water quality grading and body contact guidance)
Keywords: ISO 18997, water reuse, urban reclaimed water, landscaping uses, hydraulic retention time, reclaimed water quality, urban stream flow, aesthetic impoundments, wetlands replenishment.