The leather industry generally includes degreasing, liming and depilation, softening, tanning, dyeing, drying, finishing, etc. Many chemicals need to be added during the processing, so the wastewater contains oil, collagen, animal and plant fibers, Various pollutants and toxic substances such as dyes.

    Tannery wastewater is characterized by complex components, deep chroma, many suspended solids, high oxygen consumption, and large water volume. The composition of leather wastewater is complex and it is quite difficult to treat. Generally, the waste water is firstly subjected to physical and chemical treatment to remove fur, oil residue, meat residue, and other components in the waste water. A suitable chemical material is then added to complex heavy metals in the wastewater, such as chromium. Then add anionic polyacrylamide and polyaluminum chloride to flocculate and settle the sewage, concentrate it into sludge, and finally add cationic polyacrylamide to dewater the sludge. In this way, the sewage treated according to the steps greatly reduced the content of COD, total phosphorus, total nitrogen and heavy metals, and reached the sewage discharge standard.