Interested companies must submit their proposals by 23 October; the project has a 910-day completion timeframe, starting from the date the site is formally handed over to the contractor.

The municipality of Barcelos has highlighted that this is the “largest investment ever” to reduce pollution in the Cávado River.

The new WWTP, to be built in the parish of Barcelos, will replace the current facility—which has operated since 1999 and is described as “technically obsolete, with limited capacity to handle the municipality’s demographic, urban, and industrial growth.”

“The technical limitations of the current facility result in inadequate wastewater treatment and, consequently, pollution of local water bodies, compromising biodiversity and public health,” the municipality stated.

For this reason, the Strategic Plan for Water Supply and Wastewater and Stormwater Sanitation (PENSAARP 2030) identifies investment in a new WWTP “as a top-tier priority to resolve serious environmental liabilities.”

The new WWTP will treat not only residential wastewater but also pollution from the municipality’s textile industries.

Once operational, it is estimated that over 73,000 people will be effectively connected to the network and benefit from the service.

The municipality in the Braga district notes that one of the project’s major technical challenges is that about 35% of the influent is industrial in origin, primarily from the textile sector (dyeing facilities), and contains dyes and organic compounds that are difficult to break down and require advanced technologies.

“The chosen technology employs beneficial microorganisms to eliminate pollution from the wastewater through a prolonged process that ensures more efficient treatment. This system is capable of removing harmful compounds, such as nitrogen, without the need for additional equipment,” it explains.

After this biological phase, the water will undergo supplementary treatment, including ultra-fine filters and ozone application, to remove colour and more persistent pollutants typical of textile industry effluent.

“This ensures compliance with legal water quality standards for the Cávado River,” the municipality emphasises.

The new wastewater treatment plant was also designed to use less electricity, with efficient aerators and motors that operate only when necessary.

To achieve energy autonomy, the plant will generate its own power using solar panels and a small hydroelectric unit located at the treated water outlet.

The facility will reuse treated water, repurpose sand removed from the waste stream, and give demolition materials a new lease on life.

The clean water will be discharged back into the Cávado River within the North Coast Natural Park—a sensitive ecosystem home to protected species such as the otter.

“By significantly reducing the pollutant load discharged into the river, the new treatment plant will contribute to improved water quality and, indirectly, to the preservation of the region’s habitats and biodiversity,” the municipality adds.

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