The experience of the Canary Islands is unique in the world. In a very limited territory, all types of technologies and combinations can be found. The tertiary treatment installed in the waste water treatment plant of Barranco Seco (Gran Canaria, Canary Islands) has been designed with an ultrafiltration membrane process as pretreatment, followed by an electrodialysis reversal desalting plant, in order to obtain a minimum of 20,000 m(3)/d of reclaimed water for irrigation.