A method of treating water includes exposing influent comprising water desired to be treated to ozone in sufficient quantity to disrupt cell walls of undesired microorganisms therein, thereby releasing nutrients from within the microorganisms in a form amenable to bioassimilation. The ozone is further in sufficient quantity to oxidize toxic, humic substances to a form amenable to plant bioassimilation. Aquatic plants are contacted with the ozone-exposed water, the aquatic plants being adapted to remove the released and oxidized nutrients therefrom. Water emerging from the aquatic plants is then again exposed to ozone in sufficient quantity to further purify the water.