These systems have three main components. There is an air injector and two tanks. One tank is topped with an air relief valve and is called the off air tank and the other has a control valve at the top and it's called the media tank.
The air injector is installed on the water line coming from the well before the pressure tank. The off air and media tanks are installed after the pressure tank but before the hot water heater. As the water comes from the well and passes through the air injector, air is sucked into the water, which oxidizes the iron and sulphur so that it can be filtered out. The time it takes for the water to pass through the pressure and off air tanks allows enough contact time to fully oxidize the iron and sulphur. After it's done its' job, the air is released from the top of the off air tank. The water then runs through a bed of beads called media. These beads fill about half of the media tank. As the water is passing through these beads the iron and sulphur is filtered from your water.
Eventually, the media becomes filled with the oxidized iron and sulphur and needs to be cleaned out. Typically the controller is set to clean itself every few days. The controller automatically triggers the backwashing process, which typically happens at night.
The chemical free iron/sulphur filter automatically backwashes all of the media and the iron, dirt and sediment are flushed from the beads and into the drain. Then the media is automatically rinsed to drain before the iron/sulphur filter is put back into service.
These new WS Chemical Free Sulphur/Iron Filter FOC have replaced the above Air Birm type systems, check them out!