Preparation method and application method of water treatment agent

The invention relates to a preparation method and an application method of a water treatment agent. The water treatment agent is prepared from the following raw materials in percentage by mass: 75 to100 percent of acrylamide water solution with the mass fraction being 30 to 45 percent, 0 to 25 percent of dimethyl diallyl ammonium chloride, and 0 to 0.5 percent of copper sulfate pentahydrate. Thepreparation method comprises the steps of irradiating a monomer water solution, wherein the irradiation dose is 2 to 12kGy; cutting a monomer colloid obtained after irradiation into slices, stirring and cleaning; fully drying at 40 to 70 DEG C; smashing to obtain a finished product of the water treatment agent with the particle size of 0.15 to 0.60mm. During sewage treatment, the application method comprises the steps of preparing the water treatment agent into a colloid solution with the mass fraction being 5 to 10 percent; adding into the sewage according to the additive amount being 50 to 100ppm, stirring for 1 to 3h, and carrying out static settlement for 3 to 5h. The water treatment agent provided by the invention is prepared through an irradiation method, is synthesized at one step,and is simple and feasible, convenient to apply, high in flocculation ability during sewage treatment, capable of efficiently removing floating objects in the sewage, remarkably reducing sewage turbidity, improving sewage transparency and removing sewage odor, and applicable to various water.