The paper industry wastewater is a kind of refractory organic wastewater with large water volume, high chroma, large suspended solid content, high organic matter concentration and complex composition.

There are three main sources of papermaking wastewater: pulping waste liquid, middle water, paper machine white water: pulping is to separate the fibers in the plant raw materials, make a slurry, and then bleach; papermaking is to dilute and form the slurry. , press, dry, and make paper. Both of these processes discharge large amounts of wastewater? The wastewater produced by pulping is the most polluted. The waste water discharged during washing is dark brown, called black water. The concentration of pollutants in black water is very high, and the BOD is as high as 5-40 °L, which contains a large amount of fiber, inorganic salt and pigment. The middle part of the water produced during the washing and bleaching process has the most water content, and the pollutants have higher concentrations of lignin, cellulose and resin acid salts, which are difficult to biodegrade, and the color is deep. The waste water discharged from the paper machine, called white water, contains a large amount of fibers and fillers and rubbers added during the production process.