Some of the most critical consequences of climate change imply water scarcity and the significant reduction of its quality. Hence, one of the sectors that mainly depends on this resource, agriculture, is adversely impacted. Agriculture faces but also contributes to important treats, not only for being the most water-consuming activity in the world (accounting for 70% of the total water consumption (Shabbir, et al., 2014)) but also for remaining as a major source of water pollution. In Europe, 44% of the total water abstraction is used in agriculture. Evidence of water scarcity in Europe is borne out by research that shows increasing strain on water resources in 30% of EU member states (Stahl et al., 2016).
Therefore, it is urgent to implement strategies and technologies to reuse and recover water from different sources and thus reduce excessive consumption of this valuable resource. Current researches intend to validate the concept that water reclamation using natural engineered technologies represent a practical and eco-friendly opportunity to address the imbalances between agricultural water demand and European water resources in the long term. Currently, just 2.4% of wastewater treatment plant (WWTP) effluents are reused, and thus the water reuse potential in Europe remains high.
Nowadays, one of the most cost-effective solution for reclamation of water for irrigation purposes are the Constructed Wetlands (CW), which use ecological processes to treat wastewater by the combining action of wetland vegetation, soils and microorganisms.
CW are used to effectively remove organic, inorganic and excess nutrient contaminants in domestic sewage, municipal and industrial wastewater, among others. Furthermore, with the implementation of complementary disinfection treatments, such as UV systems, to treat microbiological parameters, CW represents one of the most reliable methods.
The system is composed by a number of processes such as: filtration, adsorption, precipitation, ion exchange, plant uptake, and microbial degradation and inactivation. They can be classified according to the flow regime into surface flow (SF or free water surface) and subsurface flow (SSF) systems. The first one is similar to natural wetlands, having a soil bottom, emergent vegetation and water surface exposed to the atmosphere. On the other hand, in the SSF the action of the soil is more important, the system is filled with porous media, such as gravel and soil and the water level is below the surface.
Treated wastewater is rich in inorganic elements and organic compounds that can increase the yield of crops, while reducing the use of fertilizers.
The results of different studies around the world (e.g. Denmark, India, Israel, Italy, Jordan and Palestine) highlighted the effectiveness in removal of organic contaminants, achieving removal efficiencies between 68-80% (Azaizeh et al., 2012) (Russo, et al., 2019). Combining CW with UV treatment shows a complete removal of E. Coli, somatic coliphages and a drastic reduction or other microbial indicators (Riva et al., 2020).
In conclusion, CW cannot only provide an optimal solution for alleviating the imbalance between water demand and water supply; it also provides plenty of alternative advantages. For instance, enhancing Biodiversity, inherent benefits of aesthetic appearance and wildlife habitats.
A sustainable and coherent approach in accordance with the nature.