Water reuse

Access to an adequate supply of water is central to a sustainable future, especially considering climate change is expected to exacerbate water scarcity problems in several European regions. The reuse of water is considered as an adaptation measure as it reduces the pressure on water resources and increases water security and resilience. 

Water reuse refers to the process whereby wastewater is reclaimed from a variety of sources and treated to a standard appropriate for a second purpose. Any type of wastewater (domestic, municipal, or industrial) can be considered for reuse and, depending on its quality, can be deployed for several different secondary purposes. Secondary purposes include for example agricultural irrigation, groundwater recharge, industrial processes, potable water supply and non-potable urban applications (irrigation of parks, toilet flushing, etc.). Water reuse is increasingly applied for agricultural irrigation as it is a reliable source also during times of limited water availability. The use of nutrient-rich treated wastewater for agriculture may, in addition, lead to a reduction (or elimination) of fertilizer application or increased productivity and can also contribute to food security. Using treated wastewater can also help conserve groundwater if this is used for irrigation. A straightforward application is the use of treated wastewater for cooling purposes in industrial processes as it has lower requirements regarding water quality. Potable water reuse refers to the use of properly treated wastewater for drinking purposes; it is a valuable option for water supply in areas where water is particularly limited. Two types of potable water reuse exist: direct and indirect. Direct potable reuse is treated wastewater that is piped into a water supply system without first being diluted in a natural stream, lake or groundwater. Indirect reuse involves mixing of reclaimed wastewater with another water supply before treatment and re-use. In both case, compliance with existing drinking water regulations is necessary.  

Water reuse can serve as a dependable water source in some specific situations, contributing to a more sustainable resource utilisation and sound demand management, in particular under water scarcity conditions. This measure can reduce both overall water consumption and treatment needs, resulting in cost savings. Water reuse can also contribute to the conservation of freshwater systems and can enhance the restoration of streams, wetlands and ponds. 

IPCC categories

Structural and physical: Service options, Structural and physical: Technological options

Stakeholder participation

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 adaptation. 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 are important 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 have the support of the involved stakeholders. Demonstration projects and sharing of cases of success can be part of participatory activities. 

Success and Limiting Factors

The JRC report "Water Reuse in Europe" (2014) lists the following as 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 and technologies for the whole system 
• Significant challenges in reliably assessing the environmental and public health risk/benefit 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 social support and stakeholder involvement to avoid strong opposition to planned schemes. Knowledge and understanding about the safety and applicability of reused water needs to be ensured to the interested stakeholders. 

Costs and Benefits

he possible benefits of the reuse of treated water are numerous, including economic, social and environmental ones. These benefits include reducing household water demand and easing pressure on public water supply, reducing upstream energy and environmental costs. The cost of recycling water may exceed that of processing fresh water directly, but it is 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). Reused water prices may consider all those additional benefits and justify cheaper rates through public subsidies to encourage its use. In general, the allocation of costs is a political decision, which defines how they will be subdivided between the general taxation and fees for those interested by the benefits of re-use. 

Legal Aspects

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. This was further emphasised in the Communication "Blueprint to safeguard Europe's water resources" in 2012 where the maximisation of water reuse is set as a specific objective. In 2016 an EU CIS 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 new “Regulation on minimum requirements for water reuse for agricultural irrigation”. The new rules will 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. 

Implementation Time

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. 

Life Time

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. 

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