Membrane processes for the recovery and reuse of wastewater in agriculture

Following laboratory-scale research as part of the LIFE programme, a pilot plant with a capacity of 30 m3/d was built. This plant allowed the optimization of the parameters necessary for the engineering analysis, as well as the extrapolation of results and the development of a treatment plant with a capacity of 500 m3/d. The latter includes all existing tertiary processes up to the latest generation and makes possible their sequential operation and the later integration of all the units, from the outflow onwards, into the Guía-Gáldar wastewater treatment plant in Las Palmas de Gran Canaria. The initial phase consists of treatment using reversible electrodialysis (with a production of 100 m3/d), ultrafiltration (430 m3/d) and reverse osmosis (210 m3/d). Six qualities of water are obtained which can be used for agricultural irrigation of specific crops. The feasibility of controlling both quantity and quality allows satisfying the demand. The project offers technological innovations and efficient solutions which are of special interest in areas where the water demand exceeds availability. It also has practical applications beyond those of a purely demonstration plant. Variations were introduced in order to adapt the system to the nature of the islands (type of outflows and end-use) which individualize the project.