This work presents a simulation application study on the design of centralized PI controllers for a MSF desalination plant. Various design methods based on the transfer function matrix of the plant are considered. The methods include (1) the Davison method, (2) the Maciejowski method, (3) the decoupler design and (4) the Tanttu and Lieslehto method. The performance of the closed loop system for a step change in the set point is compared. The robustness of the controlled system for uncertainties in the system steady-state gains is also evaluated.