The municipality of Azeméis, located in the district of Aveiro and part of the Porto Metropolitan Area, announced the ongoing international public tender aimed at selecting a contractor is expected to conclude in time for the project to commence in January 2026. The project plans consist of three work phases, with funding from the European Regional Development Fund covering 70% of the costs.
“The remodeling of the Ossela Wastewater Treatment Plant (ETAR) is a fundamental intervention for the intermunicipal wastewater treatment system, as it will modernize an infrastructure that has been in service for over 20 years, addressing design and operational limitations that have affected its performance,” stated Joaquim Jorge Ferreira, Mayor of Oliveira de Azeméis.
By July 2027, if the project stays on schedule, the facility will be capable of “fully complying with legal discharge standards, protecting the Caima River water bodies and ensuring greater energy efficiency” in operations, “reducing odors and promoting partial reuse of treated water, all within a framework of sustainability and circular economy.”
The ETAR serves the parishes of Ossela and Pindelo in Azeméis, where the current sanitation coverage stands at 44.1% and 58.5%, respectively. It also serves the parishes of Cepelos, Codal, Macieira de Cambra, Roge, São Pedro de Castelões, Vila Chã, and Vila Cova de Perrinho in the municipality of Vale de Cambra, where coverage rates are between 65% and 70%.
The current infrastructure is designed for a population of 25,788 inhabitants, including 11,722 residents and 14,066 industrial equivalents. However, the municipalities project a significant increase in the population serviced by this ETAR, potentially reaching 35,800 by 2064.
Mayor Joaquim Jorge Ferreira noted that the project set to begin in January anticipates this growth, as with the improvement of the emissaries associated with the ETAR, “the subsystem will provide 100% coverage in the draining areas, ensuring proper treatment of all collected effluents and benefiting more than 10,000 new users.”
The ongoing public tender outlines three phases of work: Lot A for remodeling the ETAR, costing 7,070,064 euros; Lot B for improving the Ossela subsystem emissaries at 2,641,175.5 euros; and Lot C for installing an electric power production unit with 384 solar panels for self-consumption, costing 783,528.5 euros.
This 18-month intervention includes duplicating primary and secondary decantation units, constructing an emergency basin and a flow regulation chamber, completely replacing electromechanical equipment, improving the sludge treatment system, and creating a new biological treatment line enabling the removal of nitrogen and phosphorus from wastewater, and subjecting it to final disinfection via UV radiation.
The Ossela ETAR project forms part of the broader rehabilitation of the Wastewater Treatment System for the Municipalities Association of Terras de Santa Maria, which in addition to Azeméis and Vale de Cambra, also serves São João da Madeira and Santa Maria da Feira.
Initial interventions in this system “planned in 2016, were minimalistic, as costs were to be fully borne by the municipalities without access to community funding,” according to Azeméis City Council. To ensure financial viability, an operation contract was established for seven years, “enabling the municipal expense to be spread over time.”
Despite this, executing the project proved “problematic, with breaches and contractual disagreements, leading to a termination agreement in August 2022. Subsequently, in 2023, the Municipal Association commissioned HIDRA to draft execution projects for the ETAR and emissaries, with a renewed vision focused on transforming the infrastructures into ‘water factories’ aligned with circular economy and decarbonization principles.”
In early 2024, recurring alerts highlighting issues with the Ossela and Salgueiro ETARs led to their classification as major environmental liabilities under the PENSAARP 2030 – Strategic Plan for Water Supply and Wastewater and Stormwater Management 2030, ensuring priority investment. This materialized in August 2024, with funding enabled through the NORTE2030-2024-40 announcement for the Urban Water Cycle.
