Composition, characteristics and treatment of papermaking wastewater

High voltage electrostatic circulating water manufacturers to explain the composition, characteristics and treatment of papermaking wastewater

1. Features

Papermaking wastewater is very harmful. Black water is a huge hazard. It contains more than 90% of the total pollutant discharged from the pulp and paper industry. Because black water is alkaline, deep color, smelly and heavy foam, and a large amount of dissolved oxygen is consumed in the water, it seriously pollute the water source and brings harm to the environment and human health.

However, the serious environmental pollution of the intermediate water is the chlorine containing wastewater produced in the bleaching process, such as chlorination bleaching wastewater, hypochlorite bleaching wastewater and so on. In addition, dioxin, a highly toxic carcinogen, also poses a serious threat to the ecological environment and human health.

2. Composition

Pulping and papermaking wastewater is mainly divided into black liquor, intermediate wastewater and white water.

Black liquor: alkaline chemicals containing NaOH or NaOH + sodium sulfate are used to cook plant fibers and dissolve lignin. The discharged cooking liquor is called "black liquor" (alkali cooking is black liquor, acid boiling is red liquor, and most of them are alkali cooking). Black liquor, which contains lignin, pentose and total alkali, is a high concentration refractory wastewater.

Middle stage wastewater: the waste water produced in the process of washing, screening and bleaching of the pulp made by alkali boiling. The COD load per ton pulp is about 310kg. The BOD / cod is between 0.20 and 0.35, and the biodegradability is poor. The main pollutants are lignin, cellulose, organic acid and other soluble COD, and the most serious pollution is chlorine containing wastewater from bleaching.

White water: large amount of water, mainly contains fine fibers, fillers, coatings and dissolved wood components, mainly insoluble cod, poor biodegradability, added preservatives are toxic.

3. Treatment technology

Black liquor and middle stage wastewater: alkali recovery, acid precipitation, LB-1 alkali precipitation, membrane separation, flocculation sedimentation, biofilm process, anaerobic biological treatment, screen microfiltration, air flotation, oxidation.

White water: filtration, air flotation, precipitation, screening.