Desalination of brackish river water using Electrodialysis Reversal (EDR): Control of the THMs formation in the Barcelona (NE Spain) area

The 4.5 million inhabitants of the Barcelona metropolitan area are mainly supplied with surface water from the Llobregat and Ter river basins. The Llobregat river water has considerable concentrations of salts, Natural Organic Matter (NOM) and high temperature (T), causing important levels of Trihalomethanes (THMs) along drinking water process.A pilot study was carried out using Electrodialysis Reversal (EDR) to assess its implementation as a new desalination step in the process of delivering drinking water. After 28 months of study, the average reduction values were for bromide > 75% and for Electrical Conductivity (EC) > 65%, while water recovery maintained a level of > 90%. Additionally, the EDR step has improved the chemical and aesthetic quality of drinking water and allows a THMs-Formation Potential (THMs-FP) that is lower than the regulated level of 100 µg/L.The final decision was the enlargement of the plant production from 3 m3/s to 4 m3/s and the inclusion of a new EDR step after Granular Activated Carbon (GAC) filtration, with a production capacity of 2.3 m3/s, which makes this plant the world's largest desalination plant using this technology, and a new example of a large scale application of a desalting technology to improve the quality of drinking water.