- This strategic three-year extension, with two additional renewal options, covers the management of six Wastewater Treatment Plants.
- The facilities manage a total flow of 340,000 m³/day, including the Guadalquivir WWTP, which is the largest in the network, with a capacity for 665,000 equivalent inhabitants and an advanced cogeneration system.
Spain, November 13th. 2025.
GS Inima has finalised the renewal of its Operation and Maintenance (O&M) contract for the Wastewater Treatment Plants (WWTPs) managed by the Association of Municipalities of Aljarafe, S.A. (ALJARAFESA).
The new contract has an initial term of three years, with the option of two one-year extensions. The service has been awarded for an estimated annual value of 4.5 million euros.
This renewal demonstrates ALJARAFESA’s confidence in GS Inima’s ability to manage and maintain these vital infrastructures facilities, ensuring they function properly and guaranteeing the quality of the water returned to the natural environment.
The collective facilities include six strategic treatment plants that, in total, process an approximate flow of 340.000 m³/day. The WWTPs managed are: Guadalquivir WWTP, Aznalcázar WWTP, Castilleja del Campo WWTP, Villamarnique WWTP, Aznalcóllar WWTP and Pajanosas WWTP.
“The renewal of this contract is a direct result of the trust placed by ALJARAFESA in our ability to manage complex and critical infrastructure. This trust has been earned through our proven track record of solving all issues and meeting the needs of the served population over the past years. Our highest priority is maintaining operational excellence across a network of six water treatment plants featuring the high-efficiency technology of the Guadalquivir WWTP and its cogeneration system. To this end, the contract includes implementing improvements to optimize the energy efficiency of the processes, as well as advanced sludge treatment at the Guadalquivir WWTP. These measures will enable us to enhance the system’s energy efficiency while mitigating its environmental impact. We are committed to sustainability and ensuring a top-quality sanitation service for all Aljarafe citizens, guaranteeing that every cubic meter of water treated to contributes to environmental stewardship. Our goal is to reduce our carbon footprint and gradually transition to a Net Zero GHG system.”
The Guadalquivir WWTP: a technological and energy benchmark in the region
Of all the facilities in this group, the Guadalquivir WWTP is recognized as the benchmark installation due to its size and technical complexity. Designed to serve a population equivalent of 665.000 and handle a flow of 105.000 m³/day, this WWTP is a technological and energy benchmark in the region.
The treatment process at the Guadalquivir WWTP is distinguished by its efficiency at every stage.
- Water Treatment: The process begins with high-capacity pretreatment, followed by primary clarification in four circular clarifiers. Secondary biological treatment is then carried out in seven plug-flow aeration tanks, which have anaerobic, anoxic, and oxic zones for advanced nutrient removal. This process includes the dosing of iron salt for phosphorus removal. The air supply is optimized by three state-of-the-art magnetic levitation turbocompressors.
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Sludge Treatment and Energy Recovery: Sludge management involves thickening, flotation and anaerobic digestion in six large tanks, followed by dewatering using centrifuges. Most notably, the plant features a 500kW cogeneration system which uses the biogas produced during digestion to generate energy. This system produces an average of 265,000 kWh per month, significantly contributing to the plant’s energy self-sufficiency. To improve the digestibility and methane generation of the sludge, a thermal sludge treatment system will be implemented prior to digestion, which is a complete novelty within this contract.
GS Inima has reached a significant milestone with the completion of this renewal, adding to its growing list of achievements in the water sector. This contract cements the company’s position as a leading provider of integrated water management solutions in the region, reinforcing its business model based on technological innovation and sustainability.
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