Comparative design of two 60 000 m3/d desalination plants using the multi-stage flash and reverse osmosis processes

A comparison is made of the designs of two 60 000m(3)/d desalination plants that use the multi-stage flash (MSF) and reverse osmosis (RO) processes, respectively. The objective is to assess the fundamental differences between the MSF and RO technologies based on multiparametric analysis and cross-comparison of the normalized technical characteristics of the two installations. Such assessment and analysis focused on the most important comparison criteria in order to help decision making engineers and planners with the implementation of desalination projects and with the choice of the desalination process most appropriate to specific site conditions. Normalization of the plant capacity at a range of 60 000 m(3)/d for the two processes, as well as site condition normalization (the Mostaganem site, located 100 lan to the east of Oran, is the reference site for both desalination plants), allowed easier cross-comparison of the study output data and other operational parameters. The aspects covered by the comparative study included plant sizing in terms of the number of units to be installed, the specific electricity and gas consumption, the efficiency, the effectiveness, the availability and the load factor for each process. The MED process was not taken into consideration because, as yet, Algeria has no plans to introduce any large scale MED projects. The assessment included the cross-comparison of major criteria such as operation and maintenance, the influence of sea water quality on the desalination processes, the quality of the product water and the appropriate post-treatment, the need for and use of chemical products, the choice of corrosion resistant materials, the lifetime of structures and equipment and the appropriate pretreatment. Also discussed are water intake and drainage, energy efficiency and optimum coupling, the area for the installations, operation, maintenance and administration staff, the environmental impact and the construction time.