1. Features

Tanning wastewater is the wastewater discharged from the tanning production process. Usually animal skins are salted or soaked in water to swell, lime, flesh, dealkalized, and then tannin or chrome, tanned and added. The fat is softened and finally dyed to make leather. Tannery wastewater mainly comes from preparation, tanning and dyeing sections, which contain a large amount of protein, fat, inorganic salts, suspended solids, sulfides, chromium and vegetable tanning agents and other toxic and harmful substances, with high biochemical oxygen demand and high toxicity. 

2. Composition

Sulfur-containing wastewater: refers to the liming wastewater and the corresponding washing process wastewater produced by the ash-alkali dehairing process in the tanning process;

Degreasing wastewater: refers to the waste liquid and the corresponding washing process wastewater formed by the use of surfactants to treat raw hide oil in the degreasing process of tanning and fur processing.

Chromium-containing wastewater: refers to the waste chrome liquid produced in the chrome tanning and chrome retanning processes and the corresponding wastewater from the washing process.

Comprehensive wastewater: refers to the collective name of various wastewaters (such as production process wastewater, factory domestic sewage, etc.) generated by tanning and fur processing enterprises or centralized processing areas and directly or indirectly discharged into comprehensive wastewater treatment projects.

3. Integrated processing technology

a. Pretreatment system: It mainly includes treatment facilities such as grille, regulating tank, sedimentation tank, and air flotation tank. The concentration of organic matter and suspended solids in the tannery wastewater is high, and the pretreatment system is used to adjust the water quantity and water quality; remove SS and suspended solids; reduce part of the pollution load and create good conditions for subsequent biological treatment.

b. Biological treatment system: ρ(CODcr) of tannery wastewater is generally 3000-4000 mg/L, ρ(BOD5) is 1000-2000 mg/L, which belongs to high-concentration organic wastewater, m(BOD5)/m(CODcr) value It is 0.3-0.6, suitable for biological treatment. At present, oxidation ditch, SBR and biological contact oxidation methods are widely used in China, while jet aeration method, batch biofilm reactor (SBBR), fluidized bed and up-flow anaerobic sludge bed ( UASB).