Abstract: An air injector assembly has an input port and an output port connected by a bypass bore and tapered bore. Fitted within the tapered bore is an air injector mechanism which contains a throat and a venturi nozzle portion. The opening of the bypass bore can be varied so that the amount of water passing therethrough is controlled to regulate the pressure being received at the input port which represents the back pressure on a pump. By varying the opening of the bypass bore, the back pressure of the pump can be regulated so that the pump may operate safely. Air is injected into the air injector assembly when water is pushed through the throat and into the venturi nozzle. A cavity is formed at the junction where the throat is coupled to the venturi nozzle so that air can be drawn thereat to aerate and oxidize the water passing therethrough. By aerating and oxidizing the water, hydrogen sulfide is removed and iron is precipitated, and can be removed later.