Systems and methods for processing industrial process fluids including sensor devices

A method and a fluid treatment system for treating an industrial process fluid used in a system (8), the method comprising the steps of: passing a portion of the industrial process fluid used in the system (8) through a first fluid path arrangement (21) of the fluid treatment system connected to an outlet (13a) and an inlet (13b) of the system (8); measuring a concentration of an industrial process fluid concentrate in the industrial process fluid by a sensor device (25) disposed in a first fluid path arrangement (21) of the fluid treatment system; adding an amount of the industrial process fluid concentrate to the industrial process fluid used in the system (8) to maintain a predetermined concentration level, where the amount is calculated based on the measured concentration, thereby providing the industrial process fluid concentrate into the system (8) via a sensor device (25) in the fluid treatment system; the sensor device (25) is cleaned at specific time intervals by providing an industrial process fluid