How to deal with paper industry wastewater?

Papermaking wastewater mainly comes from the two production processes of pulping and papermaking in the papermaking industry. Pulping is to separate the fibers from plant raw materials to make pulp, which is then bleached; papermaking is to dilute, shape, press, and dry the pulp to make paper; both processes discharge a large amount of wastewater. Among them, the wastewater produced by pulping is the most polluted. During pulp washing, the discharged wastewater is dark brown, which is called black water. The concentration of pollutants in black water is very high, and it contains a lot of fibers, inorganic salts and pigments. The wastewater discharged from the bleaching process contains a large amount of acid and alkali substances. The wastewater discharged from the paper machine is called white water, which contains a large amount of fibers and fillers and sizing materials added during the production process.

The treatment of paper industry wastewater should focus on improving the recycling water rate, reducing water consumption and wastewater discharge, and also should actively explore various reliable, economical and can make full use of useful resources in wastewater treatment methods. For example, the flotation method can recover fibrous solid matter in white water, and the recovery rate can reach 95%; the combustion method can recover sodium hydroxide, sodium sulfide, sodium sulfate and other sodium salts combined with organic matter in black water. In addition, neutralization method can effectively adjust the pH value of papermaking wastewater; coagulation sedimentation or flotation method can remove suspended solids in wastewater; chemical sedimentation method can decolorize; biological treatment method can remove BOD, which is more effective for kraft paper wastewater; wet oxidation method The treatment of sulfite pulp wastewater is relatively successful. In addition, reverse osmosis, ultrafiltration, electrodialysis and other treatment methods are also used at home and abroad.