Method for recycling waste water in production of folic acid

The invention relates to a method for recycling waste water in the production of coarse folic acid, treating folic acid waste water by using compound coagulating and decolorizing gel at each process stage and recycling the folic acid waste water. When the method is used, on one hand a folic acid production process can be optimized and yield is improved; and on the other hand, the discharge of waste water can be reduced, which is in accordance with national requirements for environment protection, and water source and cost are saved. In the invention, an acrylamide-dimethyldiallylammonium chloride copolymer serving as an additive is blended with a dicyandiamide-formaldehyde polycondensate to form compound coagulating and decolorizing gel.