Desalination of Morocco and presentation of design and operation of the Laayoune seawater reverse osmosis plant

Abstract Desalination is the commonly used process of exploitation of non-conventional resources in Morocco. The experience of ONEP (Office National de l'Eau Potable) in this field is more diversified because of the variability of the processes used. This experience is the subject of the first part of the paper. The second part presents the largest desalination plant currently in operation in Morocco which is Laayoune Seawater Reverse Osmosis Plant. It is operated by ONEP and has a capacity of 7000 m3/d. Pretreatment consists of chlorination, acidification (H2SO4) required for adequate coagulation, coagulation using ferric chloride, pressure filtration through a sand filter, acidification (H2SO4) to reduce the precipitation of calcium carbonate at the membrane level, injection of an antiscalant (Flocon 100) to reduce the precipitation of sulphates at the membrane level, microfiltration using 5μm cartridge filters, and dechlorination using sodium metabisulphite. The plant uses a brine staging design concept and has four trains, each with a capacity of 1750 m3/d. The RO section of the plant uses Dupont polyamide hollow fine fibre membrane. The main design features of the plant and the experience gained in the first year of operation are outlined. The third part presents the design features of the plant at the present time. It also presents the problems which occurred during five years of operation (up to now). Some solutions for the problems are presented.