Nature based-solutions for water reuse: 20 years of performance evaluation of a full-scale constructed wetland system

Water reuse is becoming an important tool in water resource management in regions with recurrent droughts and water shortages, such as the Mediterranean. However, there are still obstacles preventing the multiple application of water reuse projects, such as social acceptability and financial problems. In this context, the use of green infrastructure such as constructed wetlands in combination with conventional mechanical treatments could represent a very practical alternative. In this article, we present the evaluation of the performance and the water quality obtained by a combined system over a long period of 2 decades. The water reuse system is located in Granollers, Barcelona, Spain, and consists of 3 elements: wetland, mechanical reclamation plant and distribution network. The entire system produces >10,000 m3 annually for garden irrigation, and street and sewerage cleaning, and there are plans for a substantial increase of this water reclaimed flow in the next years. The effluent meets the water reuse standards set by the water regional authority for pH, electrical conductivity, TSS, E. coli, Legionella and Nematodes eggs, either as average or as 90th percentiles. Turbidity standard is met as average but not as 90th percentile (being 10.7 NTU, while the limit 10 NTU). The combination of the green infrastructure, represented by the wetland, and the conventional mechanical system, represented by the reclamation plant, results in excellent water quality suitable for the irrigation of public gardens and the cleaning of streets. The integration of both elements increases the reliability of the system and contributes to the social acceptance of water reuse. This work presents long-term and complete evidence at a full-scale of the contribution and benefits of nature-based solutions to sustainable water management.