This project focuses on the two separation processes used in topside oil and gas production. In depth the focus is set on control and automation of the considered processes. The first process separates a multi-phase flow in gas, oil and water components. The second process filtrates the produced water. Gravity separator system model is defined and used for control purposes of the first separation process. Hydro-cyclone separator system model is estimated for control purposes of the second separation process. The two defined separator system models are combined in order to investigate coordinated control of the two separation processes for better produced water treatment. Multi-Input Multi-Output linear quadratic regulator is defined and simulated. Further investigation and implementation is considered