In addition to aerating water, the activated carbon trays in a coke tray aerator filter organic contaminants out of the water. A similar method was once used to treat people who had swallowed poison. Bread was toasted in the oven until it blackened, turning into activated carbon. Then the patient ate the burnt toast. The carbon drew the poison into the carbon and out of the patient's system. Coke tray aerators work in a similar manner, drawing contaminants out of the water.