Membrane fouling is a key factor for the increase of operation cost and the decrease of product performance of the seawater reverse osmosis (SWRO) system. In this work

a strategy of new membrane cleaning and replacing schedule for spiral-wound SWRO system was proposed to reduce the operation cost. First

according to the solution-diffusion principle and membrane fouling characteristics

the SWRO performance model considering membrane fouling was established. Then

the total operation cost was integrated with membrane cleaning and replacing schedule to establish the optimization problem

which set minimizing the daily operation cost of the system as an objective

membrane cleaning frequency

cleaning time and replacing time as optimization variables

and the open equations as constraints. And the finite-element-based simultaneous method was applied to solve the complex optimization problem efficiently. After the case study and analysis of the SWRO system

the optimization results showed that the proposed optimization strategy can significantly reduce the operational cost

while obtaining the optimal membrane cleaning frequency and the cleaning and replacing time. It was found that the feed seawater temperature had an important effect on the membrane cleaning and replacing schedule as well as total operational cost

and thus it was not suitable to fix the membrane replacement interval. In addition

the proposed method can obtain the profile of optimal operational pressure and flow rate as well as internal status and performance of the system under different operation conditions

which was of great significance to optimize the operation of the system and the further study on the inner status of the system.