Water reuse

Water reuse initiatives can be implemented at a variety of spatial scales and involve different actors. The measure is difficult to implement in countries without an adequate institutional and normative background to facilitate re-use, or where socio-cultural acceptance and conflicts may hamper the implementation of this option. Stakeholder involvement is a key component of their implementation, because this adaptation option may raise several issues of concern for the general public especially regarding the quality of reused water. Consistent communication and easily understood messages explaining the benefits of water reuse need to be delivered to the public and stakeholders. The potential risks associated with the use of wastewater should be examined and addressed in order to obtain support from the involved stakeholders. Demonstration projects and sharing successful cases can be part of participatory activities.

The JRC report "Water Reuse in Europe" (2014) lists the following main barriers for the implementation of water reuse schemes: 

• Inconsistent and unreliable methods for identifying and optimising appropriate wastewater treatment technologies for reuse applications, which are able to balance the competing demands of sustainable processes 
• Difficulties in specifying and selecting effective monitoring techniques, to ensure that water quality is compliant with the use requirements 
• Significant challenges in reliably assessing the environmental and public health risks/benefits of water reuse across a range of geographical scales 
• Poorly developed business models for water reuse schemes, and markets for reclaimed water 
• Low levels of public and government enthusiasm for water reuse 

• Limited institutional capacity to formulate and institutionalise recycling and reuse measures 
• Lack of financial incentives for reuse schemes. 

One of the key success factors is stakeholder support and involvement to avoid strong opposition to planned schemes. Interested stakeholders should receive sufficient knowledge to understand the safety and applicability of reused water. 

The possible benefits of the reuse of treated water for economy, society and the environment are numerous.. These include reducing household water demand and easing pressure on public water supply, reducing upstream energy and environmental costs. The costs of recycling water may exceed those of using fresh water directly, but are justified by the several benefits water recycling provides: it saves high quality water for drinking, it reduces the amount of polluted water released to the environment, and it may have a quality making it suitable for specific alternative uses (e.g. relative high nutrient contents may provide fertilizers through its use for irrigation). However, beyond water reuse, it is also important to implement strategies that aim to decrease the overall water demand which is one of the major causes of water scarcity. Alternative water reuse treatment technologies and other water saving solutions (see for example the adaptation options Reducing water consumption for cooling of thermal generation plants, and water restrictions and water rationing) should also be assessed. Holistic life cycle assessments can be applied in those assessments considering costs and benefits for saving water resources and reducing carbon emissions..

Prices for reused water prices should consider all those additional benefits. Public subsidies might be used to support the compensation of higher water tariffs.  In general, the allocation of costs is a political decision, which defines how they will be divided between the general taxation and fees for those interested by the benefits of water reuse.

In the 2007 “Communication on Water scarcity and Droughts”, water reuse is considered as a potential solution to alleviate the impacts of climate change across Europe. The Communication "Blueprint to safeguard Europe's water resources" emphasized this further in 2012 where the maximisation of water reuse was set as a specific objective. In 2016, an EU guidance document on “Integrating Water Reuse into Water Planning and Management in the context of the WFD” for the implementation of the Water Framework Directive was published. 

In 2020, the European Commission released a “Regulation on minimum requirements for water reuse for agricultural irrigation”. The new rules apply from 26 June 2023 and are expected to stimulate and facilitate water reuse in the EU. The Regulation sets out harmonised minimum water quality requirements for the safe reuse of treated urban wastewater in agricultural irrigation, harmonised minimum monitoring requirements, risk management provisions to assess and address potential additional health risks, and possible environmental risks, permitting requirements and provisions on transparency, whereby key information about any water reuse project is made available to the public. 

The implementation time strongly depends on the specific scope and measure adopted for water reuse. The full implementation of water reuse schemes might be in the range of 5-15 years. Some initiatives may take a longer time if the acceptance level of local communities is low.

The lifetime of water reuse schemes strictly depends on social acceptance, proper maintenance of applied solutions and evidence of real occurring benefits. Usually, the lifetime is greater than 25 years.