A sewage treatment control device, a method and a sewage treatment system, are disclosed. In one example, the sewage treatment control device includes measuring units having sensors for inspecting specific components in water, respectively; validity verification units connected to the measuring units to determine validities for measured component values, respectively; target value setting units connected to the validity verification units to set target values for the component values measured in the measuring units, respectively; a manual setting unit for setting a target value depending on a component value inputted by an operator; a signal selection unit for allowing either one of the respective target value setting units or the manual setting unit to be connected; a proportional-integral-derivative control unit for performing proportional, integral or derivative action for the target value inputted from the signal selection unit to convert the target value into a control signal; and a manipulation unit for manipulating a sewage treatment apparatus depending on the control signal converted in the proportional-integral-derivative control unit.