Treatment device and treatment method for river and lake water

The invention provides a treatment device and a treatment method for river and lake water. The river and lake water treatment device comprises an electric flocculation unit, an air floatation unit, a slag removal unit, an ultrasonic algae removal unit and an ecological floating island unit, wherein the electric flocculation unit is provided with a shell, the shell is provided with a reaction cavity, the reaction cavity is provided with a to-be-treated water body inlet and a purified water outlet, and a first polar plate and a second polar plate are alternately arranged in the reaction cavity; the ultrasonic algae removal unit generates ultrasonic waves to crush algae cells to obtain algae residues; the air floatation unit comprises an aeration part which is arranged in the reaction cavity; at least part of the deslagging unit is arranged at the top of the reaction cavity; the ecological floating island unit is located above the deslagging unit, the ecological floating island comprises a gel substrate layer, a