Sea pollution can be prevented during periods of intense rainfall

For three and a half years, the cities of Bordeaux in France and Badalona in Spain have both been piloting a scheme to develop a system to reduce river and sea pollution during periods of intense rainfall as a result of untreated waste water.

Petició: David Pacheco

Most of our cities have one single urban drains network, which means that they collect waste water and rainwater jointly. This mixed water is sent to waste water treatment plants, where it is treated before being discharged into the receiving medium, typically the sea or a river. When the climate is dry or rainfall is moderate, this system works effectively.

During periods of intense rainfall, however, the capacity of the infrastructure may be overwhelmed, potentially leading to a discharge of untreated water into the receiving medium, with a negative environmental impact. Some cities have built holding tanks to avoid flooding caused by overflow from drains, and to minimise the quantity of untreated water discharged into the environment during periods of rainfall.


Research applied to urban drainage

In order to address this situation, a European research project was launched in late 2015 under the name ofLIFE Effidrain, headed by the Cetaqua Water Technology Centre. The scheme funded by the European Union’s LIFE programme involves Aquatec & Aquambiente (SUEZ) and the CSIC, and has developed an integrated and coordinated methodology for the real-time control of urban drainage networks and water treatment plants to minimise the pollution of the receiving waters during periods of intense rainfall, taking into account water system and quality data.

The La Estrella holding tank in Badalona, which is managed by Aigües de Barcelona and plays host to one of the project pilots, has capacity for 30 million litres of water stored during periods of intense rainfall in order to hold back the waste and rain water so as to avoid flooding and to prevent other infrastructure from being overwhelmed, allowing the build-up of water to be piped to the water treatment plant in a controlled manner once the rain has passed, and so avoid polluting the coastal waters.

The Badalona pilot scheme achieved a 6% reduction in the mass of pollutants released to sea, while the other pilot scheme installed in Bordeaux achieved a 30% improvement. The LIFE Effidrain project has demonstrated that the methodologies developed have considerable potential to support decision-making in water infrastructure planning and operation.

Beyond the local level, the guidelines required for replication and transferability have been drawn up, along with improvements to future EU environmental regulations.

Cetaqua Barcelona (Cornellà de Llobregat) was visited on 4 June by those attending the closing event of the European LIFE Effidrain Project: Efficient Integrated Real-Time Operation applied to Urban Drainage Networks and Wastewater Treatment Plants for Environmental Protection.