Advancing Sustainable Tourism through Circular Greywater Reuse
The DECIRE-WATER team in Greece has successfully completed the construction of Demo Site 1 on Lesvos Island, marking an important milestone in advancing sustainable water management in tourism-dependent regions.
Designed by the Laboratory of Water and Air Quality at the University of the Aegean, the demonstration site showcases an innovative decentralized greywater treatment and reuse system that combines nature-based solutions with a compact engineering design. Installed at the Delfinia Hotel in Molyvos, the system demonstrates how treated greywater from kitchen sinks and dishwasher facilities can serve as a valuable alternative water resource for non-potable applications, reducing freshwater consumption while supporting the transition to a circular water economy.
The need for Sustainable Water Reuse Solutions
Mediterranean islands experience increasing pressure on freshwater resources, particularly during the summer tourist season, when water demand rises dramatically. Hotels located outside centralized wastewater infrastructure often rely entirely on potable water for non-potable applications, such as irrigation and toilet flushing. At the same time, large volumes of greywater remain an underutilized resource. Demo Site 1 addresses this challenge by demonstrating a decentralized treatment and reuse system that recovers greywater and produces Class B reclaimed water in accordance with the principles of the European Water Reuse Regulation (EU) 2020/741.
From Design to Deployment
– Greywater Collection and Pre-Treatment
The pilot installation was integrated within the premises of the Delfinia Hotel, allowing the system to operate under realistic conditions while minimizing interference with the hotel’s daily activities. The construction of the system included the complete installation of the treatment train, beginning with the collection and pre-treatment of greywater. Wastewater from kitchen sinks and dishwasher facilities is first conveyed through a grease interceptor and stored in a collection tank.
The greywater then passes through a coarse filtration unit before entering the constructed wetlands. During these preliminary treatment stages, fats, oils, and large suspended solids that could interfere with downstream treatment processes are removed. This initial treatment stage protects the biological treatment units from clogging and contributes to the long-term operational stability of the system.
Constructed Wetlands: The Core Treatment Technology
The core of the installation consists of four pallet tanks arranged in parallel, operating as a vertical unsaturated subsurface-flow constructed wetland with a total treatment surface area of approximately 5 m². The wetland was engineered to operate under intensified hydraulic loading conditions while maintaining high treatment performance. Carefully designed hydraulic distribution, substrate layers, and drainage components ensure the uniform distribution of wastewater throughout the bed, promoting efficient biological degradation, filtration, and natural purification processes.
The system also supports ornamental climbing plants, creating an attractive green façade that integrates greywater treatment into the surrounding hotel environment while enhancing green space, promoting biodiversity, and improving thermal comfort.
Downstream of the constructed wetland, a chlorination unit was installed to ensure the microbiological safety of the treated effluent prior to storage and reuse. In addition, storage tanks, pumping equipment, and hydraulic control systems were installed to enable the storage, recirculation, and controlled distribution of the reclaimed water.
Operational Status and Future Research Activities
With construction now complete, Demo Site 1 is fully prepared for the operational and monitoring phase of the DECIRE-WATER project. The system will be evaluated for its ability to remove conventional pollutants, organic micropollutants (benzotriazoles and benzothiazoles), and pathogens, while assessing the long-term performance of this compact nature-based treatment technology in tourism facilities.
Beyond its scientific objectives, the demonstration highlights how decentralized water reuse systems can help hotels reduce freshwater demand, strengthen climate resilience, and contribute to more sustainable tourism across Mediterranean islands. The experience gained at the Lesvos demonstration site is expected to support the wider adoption of circular water reuse solutions in water-stressed tourist destinations throughout Europe.
Author: I. Priovolos
Images: I. Priovolos, E. Stefanatou