The pulping and papermaking processes in the paper industry are the main sources of papermaking wastewater. Pulping is to separate the fibers from the raw materials of trees, make fiber pulp, and then bleach; papermaking is to dilute the fiber pulp, shape, press, dry, and then make paper. Both processes discharge large amounts of wastewater. The wastewater produced by pulping is seriously polluted. The pollutant concentration in the wastewater discharged during pulp washing is very high, the BOD is as high as 10-36g/L, and it contains a lot of plant fibers, inorganic salts and pigments. The wastewater discharged from the bleaching process also contains a large amount of acid and alkali substances. The wastewater discharged from the paper machine contains a large amount of fibers and fillers and sizing materials added during the production process.