Abstract: A method of purifying water or wastewater that comprises the steps of adding a treatment agent to the water, passing the water through a mixing zone, and passing the water through a foam fractionation zone to provide purified water. The water or wastewater can be any type of water found in sewage pipes or any water discharged from domestic, commercial, industrial, agriculture or aquaculture (fresh or marine) processes, or groundwater, bore water and reservoir water. A system for purifying water, the system including a mixing zone comprising one or more mixing columns for mixing the water with a treatment agent and a foam fractionation zone for purifying the water, the foam fractionation zone in liquid communication with the mixing zone.