It is accepted in the world that the quality and the quantity of desalination could be improved under the hybrid desalination system

at the same time the energy cost would be decreased greatly.The superstructure model of hybrid multistage flash(MSF)/reverse osmosis(RO)desalination system is presented based on the blend note and the distribution note which aims to minimize the total annual cost.The ratio of RO and MSF product rate R is introduced as an optimum variable.The modified genetic algorithm(MGA)is adopted to solve the problem and the optimum structure and the operation condition are obtained.The results showed that the cost of water of hybrid desalination system is lower than that of the independent MSF and RO.The optimal value of R is 0.45 for the example and the optimal configuration is MSF-RO.