Stimela is an environment for standardized mathematical models of drinking water treatment processes. It can be used to predict the future water treatment situation which may happen or change. In water treatment plant Wim Mensink, the Stimela model train was set up to compare with other alternative water control strategies. Before starting the work of developing new water control strategies with Stimela model, Stimela model for Wim Mensink must be validated so that the model can be seen as a reliable and stable tool for the next work. Before the validation work, the current water control strategy for the treatment process needs to be investigated clearly to fulfil all the input control information is correct. Besides this, an experiment for obtaining the measured results of pellet diameters over different layers was performed in Wim Mensink. The validation work starts with single pellet softening process for three different reactors over first month from January 20th to February 20th. The fluidized bed height, pressure drop over total height of reactor, pellet diameters and porosities are validated. After that, the validation work is integrated with whole water treatment system to prove the function of pellet softening reactor and the four important water quality parameters over two important locations (after weir aerator location and final RO mixing location). The validated results of softening process are analysed by the relative error way to prove the reliability of the model results compared with measured results. The final step of the thesis work is developing the new water control strategies to optimize the current control plans of Wim Mensink. Five different water control strategies are put forward. They can be either reached separately according to their own advantages and limitations or fulfil with a step by step order as a whole optimization process. Moreover, the other water control strategies developed by engineering consultancy company DHV are evaluated here with Stimela model so that they can be proved reliable and achievable. In the future, the application of Stimela model will be spread over all the drinking water treatment plants in the Netherlands and contributes to the central automated control as a drinking water treatment operator training simulator.