A system and method for control of a gas and/or chemical for treatment of a fluid, and for monitoring the operation of such a system. In one embodiment, the system comprises a reactor for receipt of the fluid and the gas and/or chemical for dissolving, mixing, diffusing, or infusing the gas and/or chemical into the fluid, and a controller to control the flow of the fluid and the gas and/or chemical into the reactor, and to monitor the operation of the system in accordance with predetermined operating conditions. In another embodiment, the system also comprises a gas/chemical generation system for generation of the gas and/or chemical to be introduced into the reactor. The present invention permits for the control of the system based on numerous dynamic conditions to optimize operation and to minimize safety hazards.