What are the main components of the effluent used to make leather

Tanning production can be divided into two parts: wet operation and dry operation. Wet operation includes preparation section and tanning section; dry operation is finishing section. The tannery wastewater mainly comes from the wet operation preparation section and tanning section: soaking and degreasing and its washing water, dehairing and de-ashing and its washing water, soaking acid and chrome tanning and its washing water, dyeing and fatliquoring and its washing water, and other wastewater.

During the tanning process, most of the proteins and oils of the raw hides are discarded and enter into the waste residue and wastewater, resulting in high COD and BOD in the wastewater, which becomes the main organic pollution source of tanning wastewater. In addition to organic pollutants, tannery wastewater usually contains S2-, Cr3+ and SS. Therefore, tannery wastewater is a kind of high-concentration organic wastewater with chromaticity caused by dyestuffs and tanning agents, odor caused by added sodium sulfide and protein decomposition, and toxicity caused by sulfide and trivalent chromium. Tannery wastewater is usually chromium recovered and then combined for treatment?

The main pollutants are heavy metal chromium, soluble proteins, dander, suspended matter, tannins, lignin, inorganic salts, oils, surfactants, dyes, and resins.