Construction of the Constructed Wetland in Rayón is making great progress: Sustainable wastewater treatment for over 20,000 inhabitants.
We continue our work in the field of nature-based wastewater treatment in Mexico. Our third large-scale project is currently being implemented in Rayón, in the State of Mexico, involving the rehabilitation and expansion of an existing wastewater treatment plant. Completion is scheduled for mid-2025.
A Sustainable Concept: Since 2018, we have been implementing several large-scale Constructed Wetland (CW) projects in Mexico. These systems combine stable wastewater treatment with primary treatment, natural sludge humification, and final filtration through vertical flow CW. They are energy-efficient, easy to operate, and require minimal maintenance—key advantages for ensuring reliable operation in the region.
Beyond technical functionality, ecological and social aspects play a crucial role. The planted filter basins provide habitat for insects, birds, and reptiles, promoting biodiversity. The treated water can be reused for agriculture, contributing to regional food production.
Technical Implementation in Rayón: The project treats approximately 3.5 million liters of wastewater per day (144 m³/h) for more than 23,000 people. Existing structures, such as the sand trap, Imhoff tank, and concrete lagoons, have been largely retained and adapted to the new system. The aerated ponds were replaced with vertically-flow constructed wetlands, which purify the wastewater by breaking down organic matter, reducing nutrients, and stabilizing microbiological processes.
Sludge treatment takes place on-site in specialized humification wetlands, where solids accumulate on the surface and are transformed into fertile soil through microbial processes. The percolated water is reintegrated into the treatment process.
Biodiversity and Water Reuse: Beyond the vertical flow CW, a large polishing pond further enhances water quality while providing habitat for diverse wildlife. A biotope with an observation platform and jogging trail allows the local population to experience nature-based wastewater treatment firsthand. Particularly in arid regions, the reuse of treated water for agriculture is essential, conserving freshwater resources and strengthening ecological cycles.
Collaboration with Local Partners and Authorities: The municipality of Rayón actively supports the project and facilitates the permitting process. This initiative demonstrates how technical innovation and sustainability can work together to create long-term solutions for wastewater treatment. Another key partner in this project is ProNatura Mexico.
