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Madrid retrofits water treatment plant

During the past 30 years Madrid’s population has soared by almost three million, putting the city’s water treatment plants under great strain. In response, the company responsible for the plants, Canal de Isabel II, decided to improve processes at the plants to meet future quality and quantity demands. 

There were two main objectives for retrofitting the Valmayor drinking water plant. The first was to double its capacity, from 6,000 liters (1,585 gallons) per second to 12,000 liters (3,170 gallons) per second, so that it could supply water for up to four million people on a daily basis. 

The other main objective was to improve the treatment process to ensure the highest water quality in the worst possible conditions for raw water, which was achieved by adding pre-ozonation (to remove algae and THM, and to improve coagulation), as well as by adding intermediate ozonation and activated carbon filters (to remove micropollutants). This €59 million project took around three years to complete, and was managed by a consortium including Acciona and Ferrovial-Cadagua. Xylem was chosen as the main technology supplier.

“We have already extended several plants using ozone followed by activated carbon for pre- and intermediate oxidation,” says Miriam Fernández Lara, responsible for the construction of treatment plants at Canal de Isabel II. “We also built a new plant, DWP at El Tajo, using ozone, ultrafiltration membranes and reverse osmosis. All these projects are part of a plan approved by Madrid’s regional government in 2005.” Of these projects, the Valmayor retrofit has been the largest.

“In all the projects for Canal de Isabel II, Xylem supplied its WEDECO ozone generators, its Leopold filters and ultrafiltration membranes from General Electric,” says Javier Carrillo de Albornoz, Sales Development Manager at Xylem for membranes in the Europe and Middle East region (EMEA) and Latin America. “Together at Valmayor we have installed the best technology available, so that Canal de Isabel II can continue to supply its customers with the highest quality water now and in the future.”

Acciona’s Jose Manuel Guinea Mairlot, General Manager of the consortium, was personally involved in the designing, purchasing, constructing and commissioning of Valmayor. “Our main concern was to fulfill our client’s water quality requirements on time without any risks or surprises, so technical feasibility was important,” he says. 

The biggest challenge during the project was that the Valmayor treatment plant needed to continue operations during the retrofit. This meant that all the improvement work needed to be carefully coordinated and planned according to the plant’s regular operations. And, as the plant is located in a protected regional park, all projects had to be conducted in a sustainable manner.

“Close collaboration of a highly qualified and experienced multidisciplinary team helped to alleviate these challenges,” says Miguel Ángel Almodóvar, Operations Manager for Xylem Spain. “Clear and regular communication was very important.” 

Because Valmayor involved the retrofitting of an old plant, the incoming and outgoing water levels were already fixed. However, adding the new step of intermediate ozonation with activated carbon filters meant that the water level needed to be increased. Five specially designed Flygt pumps from Xylem with an epoxy coating suitable for drinking water were installed before this step of the treatment – instead of in the inlet chamber – to boost the water flow. 

“We customized our standard pump to meet Canal de Isabel II’s high efficiency demands, as energy savings are important,” Almodóvar says. “We needed to pump 6,000 liters per second!”

Leopold underdrains and sludge collectors, already successfully installed in other retrofitted plants in Madrid, were used to improve the old filters and in the newly built ones. Two sets of Xylem’s Lowara-brand pumps – one for the old line, and one for the new line – were also installed to supply a steady flow of potable water to the plant for chemical preparation and to be used in drinking water, service water, irrigation and toilets. 

by Alannah Eames, Photos: Acciona, Xylem