New Sant Gregori WWTP: Innovation in Hydraulic Engineering and Ecological Recovery
Sanitation transformation
From a lagoon system to a state-of-the-art plant
At SOCOTEC, we consolidate our expertise in the management of hydraulic infrastructures with the completion of the works for the new Sant Gregori Waste Water Treatment Plant (WWTP). In this project, the SOCOTEC Civil Engineering team has been part of the Construction Management (DO) in a joint venture (UTE) with Enghydra, transforming the municipality's sanitation system to regenerate a natural environment of great value.
- Client: ACA
- Location: Sant Gregori, Girona
- Year: 2024 – 2026
- Joint Venture (UTE): Enghydra
Talk to our experts
Water treatment processes
Technical capacity
The work consisted of the construction of a complete conventional treatment plant, designed to manage a flow rate of 1,035 m³/day, located next to the old facilities. The new infrastructure stands out for its technical efficiency:
Pre-treatment and inlet pumping: Optimization of the incoming flow.
"Carrousel" type biological reactor: Configured in two lines to ensure maximum purification.
Secondary settling: A robust system for water clarification.
Sludge management: Dewatering by centrifuge and storage in a silo.
Deodorization: Implementation of technologies to guarantee minimum impact on the environment.
Service water system: Reuse and treatment of purified water for cleaning purposes
Photovoltaic panels: Harnessing solar energy for energy consumption optimization
For the connection with the current network, a new 163-meter gravity collector (Ø630mm corrugated HDPE) has been installed, in addition to the widening of the access road to the plant.
The work consisted of the construction of a complete conventional treatment plant, designed to manage a flow rate of 1,035 m³/day, located next to the old facilities. The new infrastructure stands out for its technical efficiency:
Pre-treatment and inlet pumping: Optimization of the incoming flow.
"Carrousel" type biological reactor: Configured in two lines to ensure maximum purification.
Secondary settling: A robust system for water clarification.
Sludge management: Dewatering by centrifuge and storage in a silo.
Deodorization: Implementation of technologies to guarantee minimum impact on the environment.
Service water system: Reuse and treatment of purified water for cleaning purposes
Photovoltaic panels: Harnessing solar energy for energy consumption optimization
For the connection with the current network, a new 163-meter gravity collector (Ø630mm corrugated HDPE) has been installed, in addition to the widening of the access road to the plant.
Gemini ha dicho
Hydraulic engineering at the service of biodiversity and the environment What defines this project is the integration of engineering with nature. Thanks to our specialization in hydraulic engineering and sanitation services, we have transformed the old sedimentation lagoons —built in 1988— into a naturalized wetland.
Naturalization of the Sant Gregori lagoons Since the commissioning of the new plant in 2025, the wastewater is treated independently and with optimal quality. Part of this reclaimed water is now diverted to the four existing lagoons before its final discharge into the Llèmena stream. This process has allowed:
To raise the ecological quality of the water present in the ponds.
To promote local biodiversity by creating a suitable habitat for migratory and resident fauna.
Educational and social use: A birdwatching point (guaita) has been installed, turning a technical facility into a space for enjoyment and environmental education fully integrated into the landscape.
"The Sant Gregori WWTP combines a capacity of 1,035 m³/day with high-efficiency carrousel-type biological purification processes. The technical success of this project lies in achieving an effluent of such quality that it allows for the naturalization of the lagoons, ensuring operational reliability and sustainability within the integrated water cycle."
SOCOTEC: Experts in the integrated water cycle and circular economy
This project in Sant Gregori is a clear example of how modern engineering acts as a driver of sustainability. Our track record allows us to offer solutions ranging from water treatment to the circular economy, including cogeneration plants for sludge drying or biomass projects for heating networks (District Heating).
With this intervention, SOCOTEC reaffirms its commitment to the development of infrastructures that not only meet the most demanding technical requirements but also bring the natural environment back to life.
